THE NITRITE QUESTION: WHAT CAN YOU EAT?

By MARIAN BURROS

THE controversy surrounding nitrites, which began in the early 70's with reports that the chemicals, used to cure processed meats, might cause cancer, was rekindled by a recent report of the National Academy of Sciences. The report said that nitrites in cured meats account for ''only a small proportion of the total exposure to nitrosamines,'' a suspected cancer-causing agent, and that eliminating them ''would not have a major effect on the risk'' of cancer during a lifetime.

What's more, the report said that nitrites and nitrates from other sources, such as vegetables, baked goods and cereals, might present more of a hazard than those in cured meats.

The 550-page study, entitled ''The Health Effects of Nitrate, Nitrite and N-Nitroso Compounds,'' is a comprehensive accumulation of all the literature on nitrites. Its conclusions appeared to change public perceptions about what is, and isn't, safe to eat: meats cured with sodium nitrite are not so hazardous, it seemed to say, and vegetables took on the role of villains.

The fact is, the report offered no new information. In the opinion of some scientists, including one former member of the committee that prepared the report, cured meats are as potentially dangerous as ever. The high nitrate level of certain vegetables has long been known. Whether vegetables and baked goods and cereals contain significant levels of nitrites appears to be a matter of debate.

In other words, the report has by no means cleared the air for health-conscious consumers trying to cope with what seem to be everincreasing sources of nitrites, nitrates and nitrosamines, all of which may be carcinogenic.

There is still much that is unknown about these chemicals and how they act in the body. For instance, some vegetables are a rich source of nitrates, but vegetables also contain ascorbic acid, which is an inhibitor of nitrosamine formation. No one knows whether the vegetables' ascorbic acid completely counteracts the nitrosamine formation. (Vegetables high in nitrates include beets, celery, endive, lettuce, parsley, radishes, rhubarb and turnip greens.) A disagreement also exists over the necessity for nitrite as a preventative against the formation of botulinus toxins in processed meats.

There is general agreement, however, that nitrosamines are potent animal carcinogens and are likely to be human carcinogens as well. Even the report, while suggesting that nitrites in cured meat are not a major risk, said an alternative to them should be found. (Another academy report, on alternative curing agents, is expected next year.) It also pointed to nitrosamines in the work environment, in tobacco smoke and possibly from certain cosmetics and drugs as being more dangerous than those in cured meats.

It is the report's downplaying of the relative dangers of nitrites in cured meat that has stirred the most debate. The report estimated that only six to 138 cases of cancer could be prevented annually if nitrites were removed from cured meats; it further said that there was no way to estimate the risks of botulism if nitrites were not used. Meat industry officials and some members of the scientific community have vociferously approved of these conclusions; others have not.

Dr. Philip Hartman, a former committee member and professor of biology at Johns Hopkins University, said in a telephone interview last week: ''I personally feel cured meat is 9 or 10 percent of the problem of gastric cancer, and that is not insignificant.'' Based on the annual number of cases, Dr. Hartman estimated that ''perhaps 250 cases of gastric cancer a year are from nitrite in cured meat.''

Dr. Hartman left the committee earlier this year but remained as an adviser. He said he felt that the report ''was put out in too much of a hurry and didn't allow enough time for the members to discuss the recommendations.'' The committee of 14 scientists, convened at the request of the Food and Drug Administration and the Department of Agriculture, was given 15 months in which to complete the project.

Dr. William Lijinsky, director of the National Cancer Institute's chemical carcinogenesis program in Frederick, Md., who was not a committee member, took exception to the report's statement that total exposure to nitrosamines is not of major significance.

He said: ''You cannot add up total nitrite exposure because the amount of nitrosamines formed depends on nitrite concentration, not total intake. And the concentration of nitrites in cured meats is much higher than in anything else.''

During the last five years the Federal Government has tried to lessen public exposure to nitrites, nitrates and nitrosamines. The levels of nitrite used in cured meats has been reduced, and, with a few exceptions, the use of nitrate in cured meats has been banned. Nitrosamines in beer and bacon have been reduced significantly. The manufacture and sale of nitrite-free processed meats has gained limited acceptance. Americans have reduced their consumption of meats cured with nitrites from 50 grams per person a day in the 1950's to 30 grams in the 1970's.

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