Nitrates occur naturally in the environment and are produced by living organisms. It aids in the growth of fruits and vegetables. Nitrates are also added to some foods to help preserve them and maintain color. They are also found in water, although in varying amounts. Certain vegetables contain different amounts of nitrates, especially green leafy ones. The amount present is determined by many factors, like the environment the plant is grown in, how it is stored and how it is processed. All of these things affect the metabolic processes of the plant.
Although nitrates help plants to grow, there are some negative effects when ingested by humans. It is not the nitrates that cause damage; your body metabolizes and converts them into nitrites. In adults, the conversion takes place in the saliva. In infants, it takes place in the gastrointestinal tract. Nitrites have been linked to cancer and other health complications. Most adults are not affected by the amounts of nitrates that are in the food we eat. The Expert Committee on Food Additives has assigned a system of values to determine the of certain foods. It is deemed safe to have an intake of up to 5 mg of sodium nitrate per kg of body weight or up to 3.7 mg of nitrate ion per kg of body weight.
Infants are the age group most likely to be effected by nitrates. The conversion rate of nitrates to nitrites is double that of adults. This is especially true of bottle-fed babies. If the water mixed in with the formula is high in nitrates, it is converted into nitrites in the body and causes a condition called methaemoglobinaemia. The nitrites cause the body to carry less oxygen through the blood and results in oxygen deficiency. This condition is also known as "blue baby syndrome" for the color that oxygen-starved skin takes on. In some rare instances, the oxygen deprivation can cause death or brain damage. Babies under the age of 6 months should be given limited quantities of vegetables like spinach and beets and should eat limited quantities of food that contains additives like cheese and cured meats.
Some scientists believe that there is a correlation between nitrates and some. Studies showed that when nitrites in the body react with amine in food, they form nitrosamines. Nitrosamines have been linked to cancers of the lung, liver and esophagus. Although some studies claim that nitrates in drinking water can cause stomach cancer, even more studies exist that proves that untrue. Currently, the National Academy of Science's stand on the issue is that it is unlikely to cause any kind of cancer.