Introduction to Bacon & the Art of Living
The story of bacon is set in the late 1800s and early 1900s when most of the important developments in bacon took place. The plotline takes place in the 2000s with each character referring to a real person and actual events. The theme is a kind of “steampunk” where modern mannerisms, speech, clothes and practices are superimposed on a historical setting. Modern people interact with old historical figures with all the historical and cultural bias that goes with this.
Finally – Nitrite is Physiologically Vital
December 1990 By Eben van Tonder (Latest review: 25 December 2022)
The overuse of nitrites or their use in poorly formulated products, including cured meat is a major concern in light of its potential effect of causing cancer. Butler (2008) adds to this, blue baby syndrome, and occasional intoxications caused by nitrite, as well as the suspected health risks related to fertilizer overuse, contributed to the negative image that inorganic nitrite and nitrate have had for decades.
Over the last few decades, an avalanche of data became available that paints a different picture which results from the molecular interaction between nitrite and heme proteins in blood and tissues. It turned out to have a key role in the quick response in our blood flow system to increased local demand for oxygen because of a change in metabolic activity, even if this is not due to disease or injury and it was found that nitrite plays a key role when we experience a restriction of blood flow and therefore also oxygen to any part of the body and also in preventing any damage to tissue that may occur as a result of such restriction of blood and oxygen to an area. All this led to a renewed look at the physiological properties of nitrite, and the long-held negative view of its toxicity has been re-evaluated.
The dietary intake of nitrite, amongst other cured meat, contributes to overall health if it is done in a balanced way and if the cured products are produced in a way that would ensure they are safe for consumption. Such companies would have programs in place to ensure the mitigation of risk factors associated with N-Nitrosamine formation, reduced sodium and fat and incorporate plant components which demonstrated an overall positive synergistic effect on human health when consumers into their cured meat formulations. In addition to these, the consumer who is regularly exercising, is not obese, does not use alcohol in excess and not exposed to cigarette smoke has a far bigger chance to enjoy cured meats with the full benefit of the dietary nitrite intake that accompany the consumption of this class of foods!
The four final chapters form a unit:
- Chapter 16.05: Finally – Nitrosamines
- Chapter 16.06: Finally – Nitrite is Physiologically Vital
- Chapter 16.07: Finally – The Human Nitrogen Cycle – Basis for Nitrite’s Physiological Value
- Chapter 16.08: Finally – Bacon, the Superfood
The Realisation of the Value of Nitrite and Nitrate
Nitrate and nitrite has been known to be present in body fluids for some time. Mitchell et al (1916) showed that the amounts of nitrate excreted in the urine are higher than those ingested with the food, pointing to the fact that our body may be producing it. Green (1981) confirmed this and provided evidence that mammals are able to synthesise it in our bodies. Griess (1878) showed that human saliva contains small quantities of nitrite. Urine is normally free from Nitrite but Cruickshank and Moyes (1914) realized it originated from bacterial reduction of urinary nitrate when high levels of nitrite were detected in the urine of a volunteer, who happened to have contracted a fever. This was the first indication that our bodies produce nitric oxide (NO) as part of the immune response.
Palmer (1988) discovered that vascular endothelial cells produce NO from L-arginine. Marletta (1988) found that the same pathway is responsible for the production of nitrite and nitrate by activated macrophages.
Gladwin (2000), on the basis of the ease with which nitrate is reduced to nitrite and nitrite, is converted into NO has shown interest in the role of blood plasma nitrite in vascular smooth muscle relaxation, and the control of blood pressure and flow. Dejam (2007) and Lundberg (2008) performed animal studies and revealed a number of possible therapeutic uses of nitrite.
Lets look at several health benefits directly assosiated with the intake of nitite and to some extent, indirectly through nitrite which is converted to nitric oxide.
-> Opening the Blood Vessels (Vasodilators)
Its role in opening the blood vessels has long been identified. Butler (2008) gives the history of its discovery. “While working at the Edinburgh Royal Infirmary in the 1860s, Brunton noted that the pain of angina could be lessened by venesection and wrongly concluded that the pain must be due to elevated blood pressure. As a treatment for angina, the reduction of circulating blood by bloodletting (venesection) was inconvenient. Therefore, he decided to try the effect on a patient of inhaling amyl nitrite, a recently synthesized compound and one that his colleague had shown lowered blood pressure in animals (A. Gamgee, unpublished observation). The result was dramatic. Pain associated with an anginal attack disappeared rapidly, and the effect lasted for several minutes, generally long enough for the patient to recover by resting. For a time, amyl nitrite was the favoured treatment for angina, but its volatility made it troublesome to administer, and it was soon replaced by chemically related compounds that had the same effect but were less volatile. The most popular replacement was glyceryl trinitrate (GTN), an organic nitrate better known as nitroglycerin. The fact that this compound is highly explosive and a component of dynamite appears not to have been a problem. In his 1894 textbook, Phillips lists a number of chemically related compounds that can be used in the treatment of angina. The list includes not only amyl nitrite but also propyl, ethyl, and isobutyl nitrites, as well as GTN. A similar list is provided by White in his 1899 textbook. GTN, a drug introduced into allopathic medicine thanks to extensive homoeopathic studies by Hahnemann, occasioned greatest favour among practising physicians, and by 1956, in a symposium on hypotensive drugs, it was the only drug of this type that was listed. GTN was first synthesized by Sobrero at the University of Torino in 1812, and considering the way in which he handled it, he was fortunate not to cause a fatal accident. He thought it too explosively violent to have any practical use. Nobel, the highly successful Swedish entrepreneur, was able to moderate its action by incorporating it into kieselguhr to form dynamite. It is largely from this invention that the Nobel family fortune is derived. Tragically, Nobel’s younger brother Emil was killed while working with GTN, a dark episode in Nobel’s life. Sobrero bitterly resented Nobel’s commercial success with what he saw as his invention, although Nobel always acknowledged his debt to Sobrero. It is a curious coincidence that by 1895 Nobel had developed angina and was prescribed GTN as treatment, but it is a happier coincidence that the 1998 Nobel Prize for Physiology or Medicine was awarded for the discovery of the role of NO as a signalling molecule in the cardiovascular system.” (Butler, 2008)
“In view of the range of organic nitrites and related compounds that act as vasodilators, it is not surprising that potassium and sodium nitrites were tested in this regard.” (Butler, 2008) The Dunhuang Medical Text that we looked at in Chapter 16.04: Finally– From Mummies to Nitrosamines was one of the earliest recorded usages where a detailed description is given for the treatment of conditions stemming from restricted blood flow using nitrate in a way that nitrite will be formed which will yield instant relief. Studying the Ariveda and ancient Chinese texts, it is certain that this effect was well-known in antiquity.
“In 1880, Reichert and Mitchell published a very full account of the biological action of potassium nitrite on humans and animals. At that time, the value of amyl nitrite in the treatment of angina was severely compromised by the short duration of its effect, so the search for an improved drug had begun. The effect of potassium nitrite on the nervous system, brain, spinal cord, pulse, arterial blood pressure, and respiration of healthy human volunteers was noted, as was the variability between individuals. The most significant observation was that even a small dose of <0.5 grains (≈30 mg) given by mouth caused, at first, an increase in arterial blood pressure, followed by a moderate decrease. With larger doses, pronounced hypotension ensued. They also noted that potassium nitrite, however, administered, had a profound effect on the appearance and oxygen-carrying capacity of the blood. They compared the biological action of potassium nitrite with that of amyl and ethyl nitrites and concluded, rather interestingly, that the similarity of action depends on the conversion of organic nitrites to nitrous acid.” (Butler, 2008) It is astounding that even despite these findings, it would be another 150 years before these observations, from studies following the 1980s would enter mainstream thought.
Observations similar to those of Reichert and Mitchell were made by Atkinson (1888) and Densham (1927). Practising physicians, including Hay (1883) and Leech (1885), examined the therapeutic value of inorganic nitrites as hypotensive drugs and noted that, although of slower onset, their therapeutic effect lasts much longer, and they might be seen as superior drugs. They soon appeared in the Materia Medica of the time. In 1906, the drug supplier Squibb sold a 1-lb bottle of sodium nitrite for $1, and by the mid-1920s, an injectable solution of sodium nitrite became available (Nitroskleran, E. Tosse & Co, Hamburg, Germany) for the treatment of hypertension and vasospasm. Instructions for using sodium nitrite to treat angina are given in Martindale’s Additional Pharmacopoeia and in the US National Standard Dispensatory of 1905. A textbook on Materia Medica for medical students in 1921 gives details of the appropriate dose, but by the middle of the 20th century, its medicinal use had essentially ceased, largely because of adverse side effects. Blumgarten noted that sodium and potassium nitrites often caused nausea, belching, stomachache, and diarrhoea. Although these side effects may have caused physicians to hesitate in prescribing sodium nitrite for angina, another event precipitated the fall of inorganic nitrite from favour.
Interest in the vasodilator properties of nitrite enjoyed a renaissance with the notion that nitrite may be involved in the regulation of local blood flow after conversion to NO by nonenzymatic mechanisms (Modin, 2001 and Zweier, 1995) and an oxygen-sensitive nitrite-reductase (Cosby, 2003) and S-nitrosothiol–synthase (Angelo, 2006 ) function of haemoglobin. Like NO, inhaled nebulized nitrite has been shown to be an effective pulmonary vasodilator (Hunter, 2003) and, along with organic nitrites (Moya, 2002), suggested for potential use in neonatal pulmonary hypertension. Although there is no doubt that appropriate pharmacological doses of nitrite can normalize elevated blood pressure (Beier, 1995), the question of whether physiological concentrations of nitrite are vasodilator active is still a matter of debate. (Lauer, 2001 and Dalsgaard , 2007)
Conversion of Nitrite Into NO and NO-Related Products as Vasodilators
According to Butler (2008), one should not only think of the value of nitrite in terms of it being an intermediary product to Nitric Oxide production. He writes, “In view of the close chemical connection between nitrite and NO, it is tempting to assume that nitrite acts as a source of NO when functioning as a vasodilator. However, such conversion requires either strongly acidic conditions or enzymatic catalysis. At low pH, nitrous acid can give rise to the spontaneous generation of NO: 2HNO2→H2O+N2O3 and N2O3→NO+NO2.” (Butler, 2008)
“Solutions of acidified nitrite have been used successfully to generate NO and to induce vasorelaxation in isolated blood vessel studies, (Furchgott, 1953) and the same reaction mechanism has been proposed to explain the biological action of nitrite (Farrari, 1996 and Samlouilov, 1998). However, pHs at which this occurs are generally not found within living systems (Butler, 2004), with the exceptions mentioned above. On the other hand, the enzyme xanthine oxidoreductase converts nitrite into NO when oxygen levels are low, and this is a more likely course of action (Webb, 2004) in the vascular system, at least under ischemic conditions. In fact, recent data suggest that hypoxic NO formation from nitrite is carried out by multiple enzyme systems (Lundberg, 2003) and occurs in virtually all tissues and organs (Feelisch et al, unpublished data, 2006). Independently of its reduction to NO, nitrite is converted into NO-related products, including S-nitrosothiols and NO-heme species, at normal physiological pH and oxygen levels (Bryan, 2005). Although it cannot be excluded that some of the biological effects of nitrite may be mediated by nitrite itself, it is fair to assume that most of the physiological and therapeutic actions of nitrite that require conversion into NO and NO-related products involve enzymatic catalysis.
Cardiac Ischemia /Reperfusion Injury
Cardiac ischemia is when the heart is not getting enough blood and a reperfusion injury is damage to tissue when blood supply returns to tissue after a period of ischemia or lack of oxygen.
When the heart is not getting enough oxygen, ATP is progressively depleted in cardiac muscle cells, which impairs ion pumps, leads to the accumulation of calcium ions, and consequently damages the cell membrane stability. When the blood flow returns, the cardiac muscle cells are further injured. During these conditions, the availability of NO through the network carrying blood is impaired due to the reduced Nitric Oxide Sythase activity which is the process by which Nitric Oxide is produced from the amino acid, L-Arginine during the period of restricted blood flow and the fact that when the blood flow returns, consumption of the nitric oxide takes place by superoxides, resulting in severe injory when the flow of blood and therefore oxygen is restricted and when the flow or availability is restored, (Kobayashi, 2015)
“Nitrite, nitrate, and NO-related compounds (e.g., S-nitrosothiols) are inherently present in blood and tissues. The nitrite level in cardiac tissue is a couple of times higher than that in blood plasma due to an unknown form of active transport from blood to tissues or due to the oxidation of Nitric Oxide which is generated by the body (endogenously generated-NO) to nitrite by, and serves as a significant pool for NO during restricted blood flow and therefore also oxygen in the tissues (tissue hypoxia) from outside the vascular system.” (Kobayashi, 2015)
Most relevant to our discussion, “Carlström et al., showed that dietary nitrate increased the tissue levels of nitrite and S-nitrosothiols in the heart, and reduces oxidative stress and prevented cardiac injury in Sprague-Dawley rats. Shiva et al., recently showed that the nitrite stored in the heart and liver via systemic and oral routes augmented the tolerance to ischemia/reperfusion injury in the mouse heart and liver.” (Kobayashi, 2015)
“. . .in general, the protective effects of NO on cardiac ischemia/reperfusion injury depend on the local stock of nitrite and its subsequent reduction to NO at the critical moment when NOS activity is lacking under hypoxic conditions. Indeed, the tissue levels of S-nitrosothiols (NO-mediated signalling molecules) are enhanced through the nitrite reduction due to NOS inhibition, hypoxia, and acidosis, suggesting that the tissue nitrite stores can be regarded as a backup and on-demand NO donor. There are a number of factors that have been demonstrated to reduce nitrite in the tissues, including deoxyhemoglobin, deoxymyoglobin, xanthine oxidoreductase, heme-based enzymes in the mitochondria and acidosis during ischemia. In patients with coronary heart disease, the different consequences of myocardial infarction may depend on the patient’s daily intake of nitrate/nitrite. Indeed, Bryan et al., showed that dietary nitrite (50 mg/L) or nitrate (1 g/L) supplementation in drinking water for seven days maintained higher steady-state levels of nitrite and nitroso compounds, as well as nitrosyl-heme, in mouse cardiac muscle, and these mice exhibited a smaller cardiac infarct size after ischemia/reperfusion injury compared with control mice fed a diet deficient in nitrate/nitrite for seven days. These findings suggest that this protective nitrate/nitrite may be derived at least in part from dietary sources.” (Kobayashi, 2015)
“Intriguingly, recent large-scale epidemiological studies reported the preventive effects of antioxidant supplementations including vitamins E, C, and beta carotene rich in fruits and vegetables on cardiovascular disease, whereas no beneficial effects were shown in other studies, and in some cases, a decrease in cardiovascular protection with these supplementations was observed. On the other hand, a number of epidemiological studies”, which are done through tracking the prevalence of the disease, characterizing the natural history, and identifying determinants or causes of the disease, “have shown the preventive effects of fruits and vegetables on coronary heart disease. It should be noted that the consumption of an appropriate amount of fruits and vegetables, which might contain balanced doses of nitrate/nitrite and vitamins, might be more effective with regard to health maintenance and improvement than antioxidant supplementation alone.” (Kobayashi, 2015)
It is this finding in particular that gives direction to my work with my collaborator Richard Bosman. Whether we will succeed in our quest, time will tell but we have some impressive early breakthoughs and with solid support of scientists, industry professionals and inventors of new technology which has the potential to unluck the application of these fruits and vegetables to meat, we are hopeful and extremely motivated!
-> Antimicrobial properties of Nitrite and Novel Treatments Based on it.
Butler (2008) asserts that since acidification is a prerequisite for nitrite to act as an antimicrobial agent it suggests (albeit not proving) that the active principle is NO. “It has been known for some time that the nitrite found in human saliva originates from nitrate that is actively secreted into the oral cavity and gets partially reduced there by the local commensal bacterial flora. After swallowing, nitrite ends up in the acidic environment of the stomach, and the NO thus produced is thought to contribute to the antibacterial effects of gastric juice. Similarly, the nitrite produced from nitrate in sweat is believed to exert antimicrobial effects on the surface of the skin. Thus, acidified nitrite may be a component of innate immunity at several locations on and within the body. Some attempts to capitalize on this insight point in potentially promising therapeutic directions, although few of these findings have made their way into the clinic.” (Butler, 2008)
“The effectiveness of acidified nitrite in killing antibiotic-resistant Pseudomonas bacteria might offer a possibility to eradicate a major cause for chronic lung infections in cystic fibrosis patients provided a safe mode of administration can be found. The antimicrobial properties of NO can be exploited by dermal application of creams containing nitrite and an acidifying agent, eg, ascorbic acid, to treat a number of skin diseases. The same concept has been demonstrated to increase microcirculatory blood flow in Raynaud patients and to accelerate wound healing. Although the effects of acidified nitrite are typically ascribed to the generation of NO, the possibility that part of the nitrite applied is absorbed and converted into NO-related products in the tissue cannot be excluded.” (Butler, 2008)
-> Treatment for Asthma and Bronchitis.
For a time, amyl nitrite was used for relieving patients suffering from asthma attacks. Butler (2008), references Pearse (1891), suggests other nitrites, including sodium nitrite, suggested for this purpose. “The author remarks that the use of nitrites is not the treatment of choice but that it is said to be beneficial, probably by virtue of its smooth muscle–relaxing effects. However, relief could be delivered even better by a procedure using nitrate rather than nitrite. Blotting paper was soaked in a solution of niter and allowed to dry. Squares of the paper were burnt in a jar, and the patient inhaled the fumes. Apparently, this procedure was frequently successful in relaxing a bronchial spasm. It was first published as a patent in 1867 (Cassan, 1868)” (Butler, 2008)
Saul Cassan: relieving affections of the lungs or chest
by Cassan, Saul
Publication date 1868
“The procedure is described in detail in the Encyclopedia Britannica of 1911 and occurred as recently as 1926 in the US Dispensatory. The products of thermal decomposition of niter include NO, NO2, and O2 (Oza, 1945). Because NO is a poor bronchodilator and NO2 is toxic, it is difficult to see how inhalation of this mixture brings relief. The combination possibly has an effect that is greater than the sum of its parts.” (Butler, 2008)
This remedy is personal. My maternal great-grandfather passed away from astha in the hospital that he helped establish in the southern Free State town of Windburg. My Uncle, Jan Kok who was named after him tells me the following story. He reminds me that his memory goes back to when he was 4 or 5. Because there were many people in the house, he had to sleep on the couch in the living room. He remembers that his grandfather took a small pill and burned it in an ashtray. He then inhaled the fumes created He would wake up due to the fact that his grandfather inhaled “loudly.”
“In addition to its use in asthma, sodium nitrate was given orally to treat chronic bronchitis. (Ziment, 1991) It is unclear whether the apparent effectiveness of this treatment was secondary to its conversion to nitrite causing bronchial relaxation and antibacterial effects or due to an effect of nitrate itself.” (Butler, 2008)
The anecdotal evidence from my family continues here. My Uncle, Oom Jan (Kokkie Kok) told me the following story. I translate from Afrikaans, “I (Jan Kok) remember a time when Sannie (my mom) and I had whooping cough ()it may even have been bronchitis). Every morning my dad (my Grandfather, Eben) took us to the horse stables and we had to smell the horses and this prevented us from bad fits of coughing.
I think the actual issue was the smelling the fresh horse manure and urine. We had to be in the stables very early in the morning before they were cleaned and the horses were taken out to the fields. I remember how my dad picked us up so that we could smell the back of the horse where he sweated under the saddle when he was last ridden.
I heard a similar story from a woman in Cape Town. I suffer from asthma and have been buying my medication for years from a pharmacy in the Riverside Mall in Rondebosch. One of the pharmacy assistants, who, as a young girl, grew up in Cape Town, was sent to the horse stables where she had to sit between the manure with a blanket over her head to ensure that the inhalation of the gasses is maximised. According to her, she was developing asthma, and after one winter of following this routine every morning between 5 and 6, she stopped showing any symptoms of asthma. Again, I suspect that low dosages of hydrogen sulphide and possibly nitric oxide (even nitrite) may have played a role.
Several gasses are released by manure. Hydrogen sulphide, carbon dioxide, methane and ammonia. In high dosages, these gasses are dangerous, but in low dosages, “over the past 2 years, a number of independent groups have reported the beneficial effects of hydrogen sulphide.” One of the mechanisms identified related to it is an anti-inflammatory response.
Related to the smelling of the horse’s sweat, a close link exists between its action and nitric oxide, released from the sweat of the horse through the reduction of saltpetre and nitrite. Nitric Oxide and hydrogen sulphide have been shown to be the key and independent regulators of many physiological functions in mammals, including in the cardiovascular, nervous, respiratory, and immune systems. (Nagpure BV and Bian JS.; 2010) The fact that they had to inhale hydrogen sulphide and NO (if this was still being released, 12 hours after the horse was ridden) is interesting. If these gasses were both inhaled in low quantities, they could have been responsible for some therapeutic effects.
The death certificate of my great grandfather, JW Kok on 27 June 1950, when he passed away from Asthma in the hospital that he helped found.
-> Contribute to protection against UV-induced cell damage.
The presence of nitrite, but not nitrate, reduced the extent of apoptosis, or the death of cells which occurs as a normal and controlled part of an organism’s growth or development, in cultured endothelial cells during UVA-irradiation in a concentration-dependent manner by inhibiting lipid peroxidation. (Rassaf, 2014) Endothelial cells form the inner lining of a blood vessel and provide an anticoagulant barrier between the vessel wall and blood.
The protective effect described above was abolished by simultaneous administration of a NO scavenger (Suschek et al., 2003) suggesting that nitrite-derived NO may contribute to protection against UV-induced cell damage (Suschek et al., 2006). (Rassaf, 2014)
-> Protection of gastric mucosa from hazardous stress.
Nitrite, generated from nitrate by oral bacteria, is converted to NO in the stomach was also suggested to play an important role in the protection of gastric mucosa from hazardous stress (Miyoshi et al., 2003). (Rassaf, 2014 and Kobayashi (2015)
-> Cardiovascular Benefits
“Since the rate of NO generation from nitrite depends on the reduction in oxygen and pH, nitrite could be reduced to NO in ischaemic tissue or tissue lacking oxygen and exert protective effects (for review, see van Faassen et al., 2009). Nitrite-mediated protection was independent of endothelial nitric oxide synthase” (Webb et al., 2004; Duranski et al., 2005).
-> The Brain
“Depending on the timing of application nitrite might not only reduce irreversible brain injury following ischaemia/reperfusion but also vasospasm following cerebral haemorrhage.” (Rassaf, 2014) Ischaemia/ reperfusion refers to the paradoxical exacerbation of cellular dysfunction and death, following restoration of blood flow to previously ischaemic tissues which refers to the demand of tissue for energy, for example, from oxygen, and this demand is not matched by supply mostly due to to a lack of blood flow.
-> Protection of the Liver
“Nitrite exerted profound dose-dependent protective effects on cellular necrosis, which refers to the loss of cell membrane integrity as a result of exposure to a noxious stimulus and apoptosis, which refers to a form of programmed cell death that occurs in multicellular organisms. Nitrite has a highly significant protective effect observed at near-physiological nitrite concentrations.” (Rassaf, 2014)
-> Protection of the Lungs
“In a mouse model of pulmonary arterial hypertension, inhaled nebulized nitrite has been demonstrated to be a potent pulmonary vasodilator that can effectively prevent or reverse pulmonary arterial hypertension.” (Rassaf, 2014)
> Protection of the kidneys
In rats subjected to 60 min of bilateral renal ischaemia and 6 h of reperfusion sodium nitrite administered topically 1 min before reperfusion significantly attenuated renal dysfunction and injury. (Rassaf, 2014)
Renal ischemia associated with renal artery stenosis (RAS) which is the narrowing of one or more arteries that carry blood to your kidneys is the most frequent condition occurring with renin-dependent hypertension. Renovascular hypertension (RVH) results from occlusion (the blockage or closing of a blood vessel or hollow organ) of blood flow to either kidney, which stimulates renin release. Increased renin leads to a series of actions that rapidly leads to increased systemic blood pressure or hypertension or abnormally high blood pressure. (Rassaf, 2014)
Similarly, in mice subjected to bilateral renal ischaemia for 30 min and 24 h reperfusion, renal dysfunction, damage and inflammation were increased; these effects were all reduced following nitrite treatment 1 min prior to reperfusion. (Rassaf, 2014)
-> Crush syndrome and shock
Limb muscle compression and subsequent reperfusion are the causative factors in developing a crush syndrome. In rats subjected to bilateral hind limb compression for 5 h followed by reperfusion for 0 to 6 h, nitrite administration reduced the extent of rhabdomyolysis markers such as potassium, lactate dehydrogenase and creatine phosphokinase. Nitrite treatment also reduced the inflammatory activities in muscle and lung tissues, finally resulting in a dose-dependent improvement of survival rate. (Rassaf, 2014)
Similarly, in a mouse shock model induced by a lethal tumour necrosis factor challenge, nitrite treatment significantly attenuated hypothermia, mitochondrial damage, oxidative stress and dysfunction, tissue infarction and mortality. Rassaf, 2014)
-> Protection Against Lipopolysaccharide
Nitrite could also provide protection against toxicity induced by Gram-negative lipopolysaccharide. are large molecules consisting of a lipid and a polysaccharide that are bacterial toxins. (Rassaf, 2014)
-> Protective Effects of Dietary Nitrate/Nitrite on Lifestyle-Related Diseases
Kobayashi (2015) reviewed nitrites’ protective effect on lifestyle-related diseases. They write: “Lifestyle-related disease is a chronic disease characterized by oxidative and proinflammatory state with reduced NO bioavailability. The cellular redox balance in these patients shifts toward a more oxidizing state which affects a number of protein functions at the transcriptional and posttranslational levels, consequently disrupting the cellular homeostasis. However, increased NO bioavailability can improve the intracellular redox environment by S-nitrosylation-mediated modulation of most classes of proteins present in all cells. Recently, accumulating evidence has suggested that dietary nitrate/nitrite improves the features of lifestyle-related diseases by enhancing NO availability and thus provides potential options for prevention and therapy for these patients. Based on the recent evidence, the beneficial effects of a diet rich in these components are discussed below, focusing on insulin resistance, hypertension, cardiac ischemia/reperfusion injury, chronic obstructive pulmonary disease (COPD), cancer, and osteoporosis.”
a. Insulin Resistance
Insulin resistance strongly associates with decreased nitric oxide (NO) bioavailability and endothelial dysfunction. In the vasculature, NO mediates multiple processes that affect insulin delivery, including dilating both resistance and terminal arterioles in skeletal muscle in vivo.(Hong Wang, 2013) Note 1
b. Chronic Obstructive Pulmonary Disease (COPD)
“COPD is considered to be a lifestyle-related disease because long-term tobacco smoking and subsequent chronic bronchitis are causally associated with this disease. Varraso et al., recently reported the importance of a healthy diet in multi-interventional programs to prevent COPD. They showed that high intake of whole grains, polyunsaturated fatty acids, nuts, and long-chain omega-3 fats, and low intake of red/processed meats, refined grains and sugar-sweetened drinks, was associated with a lower risk of COPD in both women and men.” (Kobayashi, 2015)
“Because cured meats such as bacon, sausage and ham contain high doses of nitrite for preservation, antimicrobial and colour fixation, epidemiological studies have demonstrated that the consumption of cured meats is positively linked to the risk of newly diagnosed COPD. Nitrite generates reactive nitrogen species, which may cause nitrosative damage to the lungs, eventually leading to structural changes like emphysema. This is supported by an animal study in which rats chronically exposed to 2000 and 3000 mg/L of sodium nitrite in their drinking water for two years showed distinct lung emphysema. However, the dose of nitrite used in that study was 250–350 mg/kg/day, which was too high to compare with those achieved in standard human diets.
In fact, cured meats have been reported to generally comprise only 4.8% of the daily nitrite intake, and 93% of the total ingestion of nitrite is derived from saliva, suggesting that cured meats provide minimal contributions to the human intake of nitrite, even if they are frequently consumed. In addition, the recent nitrite levels in processed meats have been approximately 80% lower than those in the mid-1970s in the US. Therefore, discussions encompassing all ingested sources of nitrite should consider whether or not the nitrite derived only from the consumption of cured meats might be responsible for the development of COPD.” (Kobayashi, 2015)
“On the other hand, a number of epidemiological studies have shown the beneficial effects of n-3 fatty acids, vitamins, fruits and vegetables on lung functions and the risk of COPD. Although it may be difficult to isolate the specific effects of these dietary nutrients, as discussed above, the nitrate and nitrite derived from vegetables and fruits are reduced to NO, which is followed by the formation of S-nitrosothiols, rather than the formation of nitrosamines especially in the presence of reducing agents such as vitamin C and E in the stomach. It has been shown that high dietary nitrate intake does not cause the expected elevation of the gastric nitrite concentrations or appreciable changes in the serum nitrite concentrations.” (Kobayashi, 2015) These findings should do not cause the industry to relax and have an attitude that says “you see, consumption of cured meat is safe” even though the validation is encouraging – in the case of me and my collaborators it energises us to do even better and work to turn cured meat into a superfood.
“As mentioned above, different from the effects of the direct elevation of nitrite concentration in the plasma, the entero-salivary route of dietary nitrate/nitrite might enhance the availability of NO through the formation of S-nitrosothiols and its transnitrosylation to the other thiol residues of proteins, suggesting that, depending on the tissues and organs, separate metabolic pathways might exist for NO availability in this entero-salivary route. Consistent with this idea, Larsen et al., recently demonstrated that acute intravenous infusion of nitrite enhanced the plasma levels of nitrite, whereas it did not affect the oxygen consumption (VO2) or the resting metabolic rate (RMR) in humans. Instead, dietary nitrate significantly reduced the VO2 and RMR by improving the mitochondrial respiratory chain function and enhancing efficient O2 consumption, suggesting that rather than direct nitrite infusion to enhance the plasma nitrite levels, biologically active nitrogen oxide (including the S-nitrosothiols produced in the stomach) might be an important molecule for the transfer of biological NO activity for cardiopulmonary function. Because COPD is a state of protein-energy malnutrition due to an increased resting metabolic rate and VO2, the effects of dietary nitrate on the reduction of the RMR and VO2 might be advantageous for patients with COPD.” (Kobayashi, 2015)
“Whether the role of NO in COPD is protective or pathogenic depends on the origin and concentration range of NO. NO activity derived from dietary nitrate and constitutive NOS might be protective against COPD largely through the S-nitrosothiol-mediated mechanism including inhibition of the noncholinergic nonadrenergic nerve activity, bronchial smooth muscle relaxation, reduction of airway hyperresponsiveness, downregulation of the proinflammatory activity of T lymphocytes, and antimicrobial defence. However, the deleterious effects of NO on the development of COPD might be derived from iNOS-mediated pro-inflammatory signalling, which is consequently (not causally) reflected by the huge amount of NO in the exhaled air of patients with COPD.” (Kobayashi, 2015)
“Recent human studies have demonstrated that dietary nitrate (beetroot juice containing approximately 200–400 mg of nitrate) improved exercise performance and reduced blood pressure in COPD patients. However, large-scale epidemiological evidence of the impact of nitrate is still lacking.” (Kobayashi, 2015)
c. Lowering Blood Pressure
An obvious benefit of nitrite is its role as a reservoir of Nitric Oxide, which is a key molecule which blood pressure. The blood pressure-lowering and performance-enhancing effects of nitrites have been known for many years. (Keller, 2017) This is due to the fact that the nitrite anion (NO2–) acts as an endogenous nitric oxide source. (Keszler, 2008) Nitrite is reduced to nitric oxide (NO). “One major mechanism of nitrite reduction is the direct reaction between this anion and the ferrous heme group of deoxygenated haemoglobin.” The oxidation reaction of nitrite with oxyhemoglobin (oxyHb) which is formed by the combination of haemoglobin with oxygen, is also well established and generates nitrate and methemoglobin (metHb). (Keszler, 2008)
“Increased consumption of fruits and vegetables is associated with a reduction of the risk of cardiovascular disease. The DASH studies recommended the consumption of diets rich in vegetables and low-fat dairy products to lower blood pressure, and these effects are thought to be attributable to the high calcium, potassium, polyphenols and fibre and low sodium content in these food items. However, vegetable diets containing high nitrate levels increase the plasma levels of nitrate and nitrite, which are the physiological substrates for NO production. Accumulating evidence has recently indicated that the nitrate/nitrite content of the fruits and vegetables could contribute to their cardiovascular health benefits in animals and humans.” (Kobayashi, 2015)
“A number of publications have demonstrated that dietary nitrate reduces blood pressure in humans. Larsen et al., reported that the diastolic blood pressure (the second number in a blood pressure reading which measures the pressure in your arteries when your heart rests between beats) in healthy volunteers was reduced by dietary sodium nitrate (at a dose of 0.1 mmol/kg body weight per day) corresponding to the amount normally found in 150 to 250 g of a nitrate-rich vegetable, such as spinach, beetroot, or lettuce. Webb et al., studied the blood pressure and flow-mediated dilation of healthy volunteers, and showed the protecting effect on the blood vessels by dietary nitrate (a single dose of 500 mL of beetroot juice containing 45.0 ± 2.6 mmol/L nitrate), was attributable to the activity of nitrite converted from the ingested nitrate. Kapil et al., also showed a similar finding that consuming 250 mL of beetroot juice (5.5 mmol nitrate) enhanced the blood plasma levels of nitrite. (Kobayashi, 2015)
They later presented the effects of dietary nitrate on high blood pressure and showed the first evidence that daily dietary nitrate supplementation (250 mL of beetroot juice daily) for four weeks reduced the blood pressure, with improvements in the endothelial function and arterial stiffness in patients with high blood pressure.
As one gets older, there is a change in the structure of resistance vessels contributing to elevating the total force exerted on the flow of blood. This leads to high blood pressure. When these aging cells are studied under the microscope, you see that these vascular structural changes represent is due to the formation of fibrous scar tissue on the walls of the vascular system with increased collagen deposits and reduced elastin fibres, which result in arterial stiffening and subsequent high blood pressure in elderly patients. Sindler et al., recently demonstrated that dietary nitrite (50 mg/L in drinking water) was effective in the treatment of vascular ageing in mice, which was evidenced by a reduction of aortic pulse wave velocity and normalization of NO-mediated endothelium-dependent dilation. They showed that these improvements were mediated by reduction of oxidative stress and inflammation, which were linked to mitochondrial biogenesis and health as a result of increased dietary nitrite. These beneficial effects were also evident with dietary nitrate in their study, suggesting that dietary nitrate/nitrite may be useful for the prevention and treatment of chronic age-associated hypertension.” (Kobayashi, 2015)
In addition, hypertension is also a major cause of restricted blood flow to the heart and changes in the heart muscle, which leads to heart failure. Bhushan et al., reported that dietary nitrite supplementation in drinking water (50 mg/L sodium nitrite, for nine weeks) increased the cardiac nitrite, nitrosothiol, and cGMP levels, which improved the left ventricular function during heart failure in mice with high blood pressure produced by transverse aortic constriction. They also showed that dietary nitrite improved the cardiac fibrosis associated with pressure-overloaded left ventricular hypertrophy through the protective effect given by NO-mediated signalling. Although a number of studies on the acute effects of dietary nitrate have been conducted using animal models and healthy humans, more evidence in patients with high blood pressure as well as additional studies on the long-term effects of dietary nitrate, will be needed in the future.” (Kobayashi, 2015)
“In the stomach, swallowed nitrite is decomposed to form a variety of nitrogen compounds, including N-nitrosamines. In the 1950s, Magree et al., first reported that N-nitrosodimethylamine caused malignant primary hepatic tumours in rats. After this report, a number of studies followed in relation to the carcinogenic effects of N-nitroso compounds in animal models. In particular, the dietary intake of red and cured meats was found to be associated with an increased risk of certain types of cancer due to the relatively large amounts of nitrite added. However, the methodological aspects have been challenged concerning the high dose of nitrosatable amines and the physiological difference between animals and humans.” (Kobayashi, 2015)
“In the stomach, the nitrosonium ion (NO+) derived from nitrite can bind to thiol compounds (R-SH) and amines (especially secondary amines: R1-NH-R2), forming S-nitrosothiol and N-nitrosamine, respectively. However, while N-nitrosamine formation occurs even at neutral or basic pH, S-nitrosothiol formation tends to occur only under acidic conditions. In addition, this reaction kinetically occurs much more easily than N-nitrosamine formation, particularly in the presence of vitamins C and E and polyphenols, which are highly present in fruits and vegetables, which also eliminate potent nitrosating agents such as the N2O3 formed from nitrite by decomposing them to NO. This might partly explain why patients with achlorhydria and non-vegetarians eating large amounts of cured meats are at risk of developing gastric cancer.” (Kobayashi, 2015) Epidemiological studies mostly indicate that abundant consumption of vegetables reduces the risk of cancer (Block et al., 1992; Terry et al., 2001). (Rassaf, 2014)
“However, this idea appears to be inconsistent with the belief that dietary nitrite is a major cause of cancer. This is because, according to the average nitrate/nitrite intake of adults in the US, most of the daily nitrate intake (around 90%) comes from vegetables, and the nitrite intake is primarily derived from recycled nitrate in the saliva (5.2–8.6 mg/day nitrite), with very little coming from cured meats (0.05–0.6 mg/day nitrite in 50g/day cured meats) and other dietary sources (0–0.7 mg/day nitrite), suggesting that the entero-salivary route may be the more important source of nitrosamine exposure than exogenous intake including cured meats, that is, spitting out saliva all day long might prevent cancer development more effectively than cutting cured meats. However, recent experimental and epidemiological studies could not demonstrate a positive relationship between nitrate consumption and the risk of cancer.” (Kobayashi, 2015) These epidemiologic studies include Van Loon et al., 1998; Pannala et al., 2003; Hord et al., 2009; Tang et al., 2011. “The Joint Food and Agriculture Organization/World Health Organization Expert Committee on Food Additives concluded in 2008 that there was no evidence that nitrate was carcinogenic in humans. Consistent with this, recent studies have found no link between dietary nitrate and cancer.” (Kobayashi, 2015)
“Bradbury et al., reported a large-scale study (>500,000 participants) of the associations between fruit, vegetable, or fibre consumption and the risk of cancer at 14 different sites. They showed that there was an inverse association between fruit intake and the risk of upper gastrointestinal tract and lung cancer, as well as an inverse association between fibre intake and liver cancer. The dietary intake of vegetables, as well as fruits and fibre, was inversely associated with the risk of colorectal cancer, suggesting that there is little evidence that vegetable intake is associated with the risk of any of the individual cancer sites reviewed.” (Kobayashi, 2015)
“However, chronic inflammation, including inflammatory bowel disease and Helicobacter pylori-induced gastritis induce inducible NOS (iNOS) and generate large quantities of NO, forming nitrosating and oxidant species such as N2O3 and peroxynitrite, which might cause mutagenesis through deamination, nitration of DNA, or inhibition of the DNA repair system. Depending on the sites and amounts of NO generation, NO might represent a double-edged sword in the sense that it confers both protective and deleterious effects on cancer development.” (Kobayashi, 2015)
“Meta-analyses of primary and secondary cancer prevention trials of dietary antioxidant supplements, such as beta carotene, vitamins A, C, and E, showed a lack of efficacy, and on the contrary, an increased risk of mortality. Although the general role of NO in carcinogenesis is complicated, and many unknown mechanisms remain to be resolved, the dietary nitrate/nitrite (at least that obtained from plant-based foods such as fruits and vegetables) has obvious inhibitory effects on cancer risk by playing some synergistic role with other nutrients in these foods.” (Kobayashi, 2015) It is again findings like these that give direction to our product developments.
“Lifestyle habits, such as smoking, alcohol intake, little or no exercise, and an inadequate amount of calcium intake all influence the calcium-vitamin D metabolism and bone mineral density, in some cases leading to osteoporosis, particularly in postmenopausal women. The implications of NOS-mediated NO in the regulation of bone cell function have been well described in a number of publications. For example, iNOS-induced NO production following stimulation with proinflammatory cytokines, such as interleukin 1 (IL-1) and tumour necrosis factor-α (TNF-α), inhibits bone resorption and formation, resulting in osteoporosis in patients with inflammatory diseases such as rheumatoid arthritis. On the other hand, eNOS, a constitutive NO synthase, plays an important role in regulating osteoblast activity and bone formation, because eNOS knockout mice exhibit osteoporosis due to defective bone formation, and eNOS gene polymorphisms were reported to be causally linked to osteoporosis in postmenopausal women.” (Kobayashi, 2015)
“In addition, Wimalawansa et al., showed that some of the beneficial effects of estrogen on bone metabolism are mediated through a NO-cGMP-mediated pathway, suggesting that NO donor therapy might provide a promising alternative to estrogen therapy. In this context, it has been shown that organic nitrate NO donors, such as glycerol trinitrate, isosorbide dinitrate and mononitrate all have beneficial effects on experimental and clinical osteoporosis, and a number of epidemiological studies also indicated that a high fruit and vegetable intake appears to have a protective effect against osteoporosis in men and pre- and postmenopausal women. However, few studies have been conducted to evaluate the detailed mechanism by which inorganic nitrate/nitrite prevents osteoporosis at the molecular level, and thus further basic research will be needed for this purpose.” (Kobayashi, 2015)
f. Methemoglobinemia (MetHb)
A negative effect of nitrite in the body relates to its link with methemoglobinemia. It is historically this link which contributed to casting nitrite in a negative light, and day plays a dominant role in establishing what the WHO regards as safe levels of ingested nitrites. For a detailed treatment of the subject, see What is N-nitrosamines and when did it become an issue? in Finally – Nitrosamines.
“Methemoglobinemia (MetHb) is a blood disorder which the US National Institute of Health defines as occurring when “an abnormal amount of methemoglobin is produced.” They explain that “haemoglobin is the protein in red blood cells (RBCs) that carries and distributes oxygen to the body. Methemoglobin is a form of haemoglobin. Inherited (congenital) methemoglobin occurs when the disorder “is passed down through families.” Our interest is in what is referred to as acquired MetHb, which is “more common than inherited forms and occurs in some people after they are exposed to certain chemicals and medicines.” One such chemical is nitrites. (National Libary of medecine) “Elevated levels of nitrite in the blood can trigger the oxidation of haemoglobin, leading to methemoglobinemia.” Keszler (2008) suggests a simplified model of the kinetics involved where the end products of the reaction are methemoglobin (metHb) and nitrate.
The “World Health Organization (WHO) used data based on the risk of methemoglobinemia to set an acceptable daily intake (ADI) for nitrate of 3.7 mg/kg body weight per day, equivalent to 222 mg nitrate per day for a 60-kg adult, and nitrite of 0.07 mg/kg body weight per day, equivalent to 4.2 mg nitrite per day for a 60-kg adult. (Keller, 2017)
The upper limit represented by the WHO ADI corresponds to the concentration of dietary nitrate that lowers blood pressure in normotensive and hypertensive adults. (Keller, 2017)
Very high concentrations of nitrate in drinking water may cause methemoglobinemia, particularly in infants (blue baby syndrome). “In the 1940s, Comly first reported cases of cyanotic infants who received formula prepared with well water containing a high nitrate content. Based on the subsequent analyses of the infantile cases of methemoglobinemia, the US Environmental Protection Agency (EPA) set a Maximum Contaminant Level (MCL) for nitrate of 44 mg/L (equal to 10 mg/L nitrogen in nitrate). However, it is now thought that methemoglobinemia per se was not caused by nitrate itself, but by faecal bacteria that infected infants and produced NO in their gut. A recent report by Avery has argued that it is unlikely that nitrate causes methemoglobinemia without bacterial contamination, and also that the 40–50 mg/L limit on nitrate in drinking water is not necessary.” (Kobayashi, 2015)
However, there are now legal limits to the concentrations of nitrate and nitrite in both food and drinking water. The WHO showed that the Acceptable Daily Intake for humans (ADI) for nitrate and nitrite were 3.7 and 0.07 mg/kg body weight/day, respectively, which were based on the calculations from the doses of <500 mg of sodium nitrate/kg body weight that were harmless to rats and dogs. The international estimates of nitrate intake from food are 31–185 mg/day in Europe and 40–100 mg/day in the United States. However, the Ministry of Health, Labour and Welfare of Japan reported that the average intake of nitrate in the Japanese population is around 200–300 mg/day, which is one and a half times to two times the ADI. Furthermore, according to a report by Hord, in which the daily nitrate and nitrite intakes were calculated based on the variations using the vegetable and fruit components of the DASH (Dietary Approaches to Stop Hypertension) dietary pattern, the level easily exceeds 1,200 mg/day nitrate. This is more than five-fold higher than the WHO’s ADI of 3.7 mg nitrate/kg body weight/day, and more than two-fold the US Environmental Protection Agency’s level of 7.0 mg nitrate/kg body weight/day for a 60 kg individual. Furthermore, as indicated in Figure 2, approximately 25% of the ingested nitrate is secreted in saliva, and 20% of the secreted nitrate in the saliva is converted to nitrite by commensal bacteria on the tongue, indicating that about 5% of the originally ingested nitrate is swallowed into the stomach. Therefore, for a DASH diet containing 1200 mg nitrate, an individual would be expected to swallow approximately 45 mg of nitrite a day, which easily exceeds the ADI of nitrite. Therefore, a comprehensive reevaluation of the health effects of dietary sources of nitrate/nitrite might be required in the near future.” (Kobayashi, 2015)
A court case from Hamilton, Scotland, was reported on by the Hamilton Advertiser, 01 Jun 1912. It related to the prosecution of the Uddington Cooperative Society by the Lanark Public Health Authority for selling bleached flour. During the bleaching, process, nitrites are produced. The journalist quotes a miner from Hamilton who had this to say about the matter that in the course of the proceedings they were told that there are ” nitrites in the air we breath, nitrites in the water he drinks, nitrites in his very mouth swarming around in the saliva, nitrites in his smoked ham and beef and bacon. With it all he will live, and move, and have his being quite undisturbed.” We are learning that the anonomous miner quoted from the 1912s was right in more ways than anyone could have imagined. He meant his words that he lives his life unidsturbed despite nitrites being all around us including in our bodies. It turns out that not just despite of nitrites, but rather becasue of nitrites we continue to ive, and move, and have his being quite undisturbed even into old age.
(c) Eben van Tonder
(c) eben van tonder
Part of my series, the Truth About Meat Curing: What the popular media do NOT want you to know!
1. Insulin Resistance
“The insulin receptor shares a signalling pathway with the activation of endothelial NOS (eNOS) to regulate the postprandial blood flow and efficient nutrient disposition to peripheral tissues. Therefore, insulin resistance is always associated with impaired NO availability, suggesting that a reciprocal relationship exists between insulin activation and endothelial function. Insulin resistance is improved by NO at various levels including insulin secretion, mitochondrial function, modulation of inflammation, insulin signalling and glucose uptake. For example, insulin-stimulated NO production has physiological consequences resulting in capillary recruitment and increased blood flow in skeletal muscle, leading to efficient glucose disposal.” (Kobayashi, 2015)
However, the most important mechanism to improve insulin resistance might be at the post-receptor level of insulin signalling. In diabetic states, increased adiposity releases free fatty acids and produces excessive reactive oxygen species (ROS) through a toll-like receptor 4 (TLR4)-mediated mechanism, which activates a number of kinases and phosphatases, and then disrupts the balance of protein phosphorylation/dephosphorylation associated with insulin signalling. The mechanisms underlying the NO-mediated beneficial effects on insulin resistance are as follows: First, NO suppresses the TLR4-mediated inflammation and ROS production by inactivating IkB kinase-β/nuclear factor-κB (IκκB/NF-κβ), the main trigger for the induction of a number of proinflammatory cytokines. Second, Wang et al., indicated that NO mediates the S-nitrosylation of protein-tyrosine phosphatase 1B (PTPB1) and enhances the effects of insulin. Because PTPB1 dephosphorylates the insulin receptor and its substrates, attenuating the insulin effect, its phosphatase activity tends to be suppressed by eNOS-mediated S-nitrosylation. In contrast, when the vascular eNOS activity is impaired, PTPB1 suppresses the downstream signalling to PI3K/Akt, leading to insulin resistance. Therefore, NO might act as a key regulatory mediator for the downstream signalling linking glucose transporter 4 (GLUT4) translocation and glucose uptake. Third, Jiang recently reported that NO-dependent nitrosylation of GLUT4 facilitates GLUT4 translocation to the membrane for glucose uptake, and improves insulin resistance. Fourth, excess nutrients also overproduce superoxide in the mitochondrial respiratory chain, leading to the subsequent formation of ROS. NO can inhibit mitochondrial ROS production through the S-nitrosylation of mitochondrial respiratory chain complex 1 enzyme and by improving the efficiency of oxidative phosphorylation in the mitochondria.” (Kobayashi, 2015)
“Indeed, the therapeutic potential of dietary nitrate/nitrite has been supported by recent studies demonstrating the improvements of insulin resistance in humans and animals as a result of its enhancing the NO availability in plasma and tissues. As mentioned above, insulin resistance always accompanies metabolic and endothelial dysfunction, which leads to hypertension and atherosclerosis. Enhancement of the availability of NO might therefore be a promising strategy for the prevention and treatment of patients with not only insulin resistance but also endothelial dysfunction.” (Kobayashi, 2015)
Butler AR, Ridd JH. Formation of nitric oxide from nitrous acid in ischemic tissue and skin. Nitric Oxide. 2004; 10: 20–24
Butler, RA and Feelisch, (2008) Therapeutic Uses of Inorganic Nitrite and Nitrate M. Volume 117, Issue 16, 22 April 2008; Pages 2151-2159; https://doi.org/10.1161/CIRCULATIONAHA.107.753814
Duranski MR, Greer JJ, Dejam A, Jaganmohan S, Hogg N, Langston W, et al. Cytoprotective effects of nitrite during in vivo ischemia-reperfusion of the heart and liver. J Clin Invest. 2005;115:1232–1240.
Dispensatory of the United States of America. 21st ed. Philadelphia, Pa: JB Lippincott; 1926.
Encyclopædia Britannica. Vol. XXIV, 11th ed. Cambridge, UK: CUP; 1911: 94.
Kobayashi, J. (2015) NO-Rich Diet for Lifestyle-Related Diseases, Article in Nutrients, June 2015, DOI: 10.3390/nu7064911
Oza TM. Thermal decomposition of sodium and potassium nitrites. J Indian Chem Soc. 1945; 22: 173–180.
Pearse F. The treatment of paroxysmal nerve disorders. Practitioner. 1891; 46: 29–32.
Rassaf T, Ferdinandy P, Schulz R. Nitrite in organ protection. Br J Pharmacol. 2014 Jan;171(1):1-11. doi: 10.1111/bph.12291. PMID: 23826831; PMCID: PMC3874691.
Suschek CV, Schroeder P, Aust O, Sies H, Mahotka C, Horstjann M, et al. The presence of nitrite during UVA irradiation protects from apoptosis. FASEB J. 2003;17:2342–2344.
Suschek CV, Schewe T, Sies H, Kroncke KD. Nitrite, a naturally occurring precursor of nitric oxide that acts like a ‘prodrug’ Biol Chem. 2006;387:499–506.
van Faassen EE, Bahrami S, Feelisch M, Hogg N, Kelm M, Kim-Shapiro DB, et al. Nitrite as regulator of hypoxic signaling in mammalian physiology. Med Res Rev. 2009;29:683–741.
Hong Wang, Aileen X. Wang, Kevin Aylor, Eugene J. Barrett; Nitric Oxide Directly Promotes Vascular Endothelial Insulin Transport. Diabetes 1 December 2013; 62 (12): 4030–4042.
Webb A, Bond R, McLean P, Uppal R, Benjamin N, Ahluwalia A. Reduction of nitrite to nitric oxide during ischemia protects against myocardial ischemia-reperfusion damage. Proc Natl Acad Sci U S A. 2004;101:13683–13688.
Ziment I. History of the treatment of chronic bronchitis. Respiration. 1991; 58 (suppl 1): 37–42.