The safety of nitrates in your diet is a controversial question with a parodox-laden answer. Exposure to nitrates and how they affect you depends on several variables, including source of exposure, the amount, frequency and duration of exposure and your pre-existing health condition. The majority of people unknowingly consume seemingly healthy foods with nitrates but the processed foods with added nitrates are most scrutinized as causing a health risk.
Nitrate, Environment and Plant Foods
A nitrate is a chemical compound containing a nitrogen atom joined to three oxygen atoms. Nitrates are naturally found in the soil, water and plant foods, but can have added nitrate compounds from fertilizers used in farming. In the environment, bacteria converts nitrogen to nitrate that is absorbed from soil or water into plants. Animals that eat nitrate-containing plants then return the chemical to the environment via feces. Microorganisms that grow in feces then convert the nitrate to nitrite, a similar chemical minus one oxygen atom. The concentration of nitrate and nitrite in plants generally remains low unless added nitrogen-containing fertilizers are used on crops for human consumption. According to the Ohio Department of Health, nearly 70 percent of nitrates in the human diet are found in vegetables.
Nitrate and Human Digestion
In a healthy body, nitrates consumed from foods are absorbed from the small intestine into your blood. From your blood, the nitrates then enter the large intestine, where it is processed and removed as waste. According to the Argonne National Laboratory, in a healthy person only 5 percent of the nitrate consumed is converted to nitrite, which generally poses no significant safety risk. However, if you have an acidic pH in the intestine, the nitrate will then convert into nitrite. The nitrite then absorbs back into the bloodstream where it reacts with the mineral iron to form methemoglobin, which can reduce normal oxygen transport throughout your body and cause a significant safety risk.
When Nitrates Become Unsafe
Exposure to nitrates or nitrites in significant amounts increases your risk of weakness, palpitations, coma and death because your organs cannot thrive without oxygen. Infants are at higher risk of unsafe exposure from formula made from nitrate contaminated water causing inhibited oxygen transport. However, adults are susceptible to toxicity from over-exposure. Fatal doses of nitrate in adult humans ranges between 30 g to 35 g per single dose and fatal doses of nitrite ranges from 22 g to 23 mg per kilogram of body weight, notes the University of Minnesota. The likelihood of eating that much nitrate or nitrite in one dose is unlikely; therefore, nitrate and nitrite in meat products is considered safe.
Short-Term Symptoms and Cancer Risk
Short-term symptoms of over-exposure to nitrates include diarrhea, dizziness, breathing problems or muscle paralysis. Symptoms can develop in as little as two hours from exposure or as long as 14 days later, but symptoms generally appear 18 to 36 hours after high-level consumption. Animal studies show that nitrates from food preservatives may increase the risk of cancer. However, there is insufficient evidence from human studies to conclude that dietary nitrates cause cancer.
Summary of Facts
Nitrates occur naturally in the environment. Nitrates consumed from plant foods are generally recognized as safe. Most nitrates are consumed from plant foods but also come from preserved meat products. Nitrates can convert into nitrites during digestion and impair oxygen transport to your organs if you have an acidic intestinal environment. The United States Environmental Protection Agency has established toxicity values for nitrates and nitrites to prevent unsafe consumption of products containing these chemicals.
References
- Argonne National Laboratory; Nitrate and Nitrite; August 2005
- Ohio Department of Health; Nitrates and Nitrites; November 2006
- Illinois Department of Public Health; Nitrates in Drinking Water;December 2010
- Cancer Prevention Coalition: Hot Dogs and Nitrites
- University of Minnesota Extension; Nitrite in Meat; Richard J. Epley et al; 2011
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