Nitrate is a salt of nitric acid and found naturally in fruits, vegetables and grains. It is also added to cured meats such as salami, bacon and hot dogs as a color preservative and to retard the growth of microorganisms. Foods that are naturally rich in nitrates can provide a variety of health benefits, but some nitrate is converted to nitrite in your body, which can form nitrosamines and cause negative effects. However, vitamin C naturally inhibits the conversion to nitrosamines, which is why fresh fruits and vegetables high in nitrates cause far fewer problems than meats artificially high in nitrates.
Nitrates in Food Crops
Nitrate is an essential plant nutrient found in soil that is taken in by all plants and used as a primary nitrogen source. As such, nitrate is a natural part of all vegetables, fruits and cereals to varying degrees. Industrial fertilizers also contain nitrates and some of their residues can be found on the outside of fruits and vegetables, but this should be removed prior to consumption because of the other potentially toxic chemicals in fertilizers, according to “Nutrition and Public Health” by Sari Edelstein. Some plants have much higher levels of nitrates than others.
Fruits High in Nitrates
In general, levels of nitrates are lower in fruits compared to vegetables, especially root vegetables, because of the distance most fruit is from the ground. In other words, the farther the fruit is away from the nitrate-rich soil, the lower the concentration of nitrate in its flesh and seeds. According to a Polish study published in a 1994 edition of “Roczniki Panstwowego Zaklapu Higieny,” the fruit with the highest nitrate content is strawberries, followed by currents, gooseberries, raspberries and cherries Apples were found to have only trace amounts of nitrates.
Vegetables High in Nitrates
Many vegetables, especially root vegetables, grow within the soil and collect high concentrations of nitrates. According to the book “Nutritional Sciences,” vegetables high in nitrates include lettuce, beets, carrots, green beans, spinach, parsley, cabbage, radishes, celery and collard greens. Obviously, the nitrate content varies depending on soil composition, so lettuce grown in California may differ greatly in nitrate content than lettuce grown in Mexico, for example. Further, the longer fresh vegetable juice sits, the greater the conversion of nitrates to nitrites, so you should drink fresh vegetable juice as quickly as you can.
Nitrate is converted to nitrite in your body almost immediately by bacteria on your tongue. As long as the nitrite is not converted to large amounts of harmful nitrosamines in your stomach, nitrite eventually becomes nitric oxide in your blood, which can relax your blood vessels. According to “Functional Biochemistry in Health and Disease,” studies done on nitrate-rich vegetables such as lettuce and beets have found that when nitric oxide is highest in the bloodstream, blood pressure is at its lowest. In addition to relaxing or vasodilating blood vessels, nitric oxide also displays anti-platelet properties, which helps to prevent inappropriate blood clotting. However, because the by-products of nitrates affect blood flow and pressure, they can also trigger migraine headaches in some people. Consult with your doctor if you suffer from migraines and ask about the connection to nitrate-rich foods.
- “Nutrition and Public Health”; Sari Edelstein; 2006
- "Roczniki Panstwowego Zaklapu Higieny"; The Content of Nitrates and Nitrites in Fruits, Vegetables and Other Foodstuffs; M. Nabrzyski et al.; March 1994
- “Nutritional Sciences”; Michelle McGuire; 2007
- “Functional Biochemistry in Health and Disease”; Eric Newsholme et al; 2010