An expert committee assessing the safety of nitrites and nitrates as food additives reported today that eliminating them from cured meats would probably not have a major impact on human health.
The committee concluded that cured meats accounted for only a small proportion of human exposure to cancer-causing nitrosamines, which can be formed by nitrites and nitrates. A far larger amount of nitrosamines may reach the average consumer through cigarette smoke, baked goods, vegetables, cosmetics, automobile interiors and drinking water, according to the committee chairman, Dr. Maclyn McCarty, a bacteriologist at The Rockefeller University in New York City.
Nonetheless, the committee, convened by the National Academy of Sciences at the request of the Food and Drug Administration and the United States Department of Agriculture, urged at a news conference that the use of nitrites and nitrates in meat products be reduced ''to the extent that protection against botulism is not compromised.''
Different Curing Agent Urged
In its 550-page report, the committee also recommended that alternative curing agents be sought. A separate report, dealing with such alternatives, is due next spring.
Nitrites and, to a lesser extent, nitrates are used in such products as ham, bacon, frankfurters and salami to help prevent the growth of deadly botulism spores. Nitrates also flavor the meat and give it a pink color. The safety of these additives, which have been used to preserve food for at least 2,000 years, has been challenged in recent decades after studies showed they could be converted to nitrosamines in the body.Continue reading the main story
Although the committee found that neither nitrates nor nitrites directly caused cancer in animals, nearly 200 types of nitrosamines are known carcinogens in animals and are therefore suspect as agents causing human cancer. The committee found some evidence to suggest that high exposure to nitrates and nitrites might be associated with an increased risk of cancers of the stomach and esophagus. Vitamins Can Block Nitrosamines
The committee also noted that vitamin C included in the diet or added to foods could help block the formation of nitrosamines. Vitamin E has a similar effect. But Dr. McCarty told reporters that the possible value of supplementing the diet with vitamin C was not yet known and would require a separate study.
By far the greatest exposure to nitrosamines occurs among people who work in such industries as rocket fuel, leather-tanning and rubber manufacture. Their average exposure is about 250 micrograms per day, 200 times more than the 1.3 micrograms the average person would derive from a typical day's diet, which includes 0.17 micrograms from bacon and other cured meats. Outside of occupational exposures, the committee reported, cigarette smoke is the main source of nitrosamines. A person who smokes one pack of filtered cigarettes a day would inhale 17 micrograms of nitrosamines.
Cosmetics such as facial creams, shampoos and soaps are also sources of nitrosamines, which can be absorbed through the skin and into the bloodstream, according to a committee member, Dr. David Fine, a chemist at the New England Institute for Life Sciences. The committee estimated that the average person absorbed 0.41 micrograms of nitrosamines a day from cosmetics. Volatile chemicals released from automobile interiors account for an average exposure of 0.20 micrograms of nitrosamines a day, more than is derived from bacon, the committee said. Levels High in Beets and Lettuce
The committee said the typical American diet contained many potential sources of nitrosamines besides meats cured with nitrates or nitrites. Nitrate levels are naturally high in several vegetables, including beets, spinach, celery, lettuce and turnip greens. The amount of nitrates in such foods varies widely according to the soil in which they are grown, harvesting and storage conditions, and the amount of fertilizer used, whether synthetic or natural.
Baked goods, cereals and fruit juices also contain nitrates. Drinking water may contain large amounts of nitrates in areas where the water supply is affected by agricultural runoff. Nitrites are present in significant quantities in baked goods and cereals, vegetables and fresh meats.
Nitrites can be changed to nitrosamines in the digestive tract by combining with amines or amides, substances commonly found in foods such as meats and cheeses, and in drugs, agricultural chemicals, cosmetics and tobacco. Nitrates, on the other hand, do not directly form nitrosamines, but after passing through the stomach they can reach the saliva where about 5 percent of the total amount ingested is converted to nitrites, Dr. Fine said in an interview. These nitrites, in turn, can be changed to nitrosamines.
The nitrosamines that enter the body from drugs, cosmetics, agricultural chemicals, tobacco smoke, new car interiors and occupational exposures are already in that chemical form. Beer and Scotch whiskey had been cited as sources of preformed nitrosamines, but recent changes in processing have reduced the amounts to levels considered inconsequential by regulatory agencies. Bacon Curing Process Changed
Nitrosamines had also been shown to form when bacon was fried. However, processing changes that included a reduction in the amount of nitrite used to cure bacon and the addition of sodium ascorbate (a form of vitamin C) are making it possible to reduce nitrosamine levels in cooked bacon to undetectable amounts, according to the Department of Agriculture.
The committee estimated that eliminating meats cured with nitrates and nitrites from the average diet would reduce nitrosamine exposure by 13 percent in non-smokers and by 2 percent in smokers. The committee assumed that the cancer risk from nitrosamines would be reduced proportionately.
The committee's findings illustrate the complexity that can enter the scientific process when many factors and processes must be considered. For example, although vegetarian diets contain large amounts of nitrates, vegetables are also rich sources of vitamins C and E, which may significantly reduce the amount of nitrosamines formed in the body.
Nitrates, the committee noted, have no direct preservative action but can be a continuing source of preserving nitrites during lengthy curing. The committee thus recommended that nitrates not be used to process poultry and meat products, except for meats involved in a lengthy curing process such as dried beef, jerky, salami and pepperoni.Continue reading the main story