Vitamin A has made a great deal of news recently, and it has been good news.

For one thing, there is growing evidence that Vitamin A itself, or synthetic derivatives called retinoids, or beta-carotene, a provitamin from which the body manufactures Vitamin A, may have a protective influence against some forms of cancer. The results are so encouraging that the National Cancer Institute and the American Cancer Society are launching programs to support basic research and clinical trials on the effect of Vitamin A in cancer prevention.

In another series of investigations, it's been shown that oral doses of closely related synthetic forms of Vitamin A appear to be very effective against cases of severe cystic acne and psoriasis.

With good news often comes bad news: Many investigators fear that some rash people may try self-treatment with large doses of Vitamin A and wind up with a case of Vitamin A toxicity.

We think there is cause for concern. Today, many people are aware that vitamins A and D, which are fat soluble and can be stored in the body, can prove toxic. In adults, toxic symptoms may appear after daily intakes of more than 50,000 International Units for long periods. That's 10 times the Recommended Dietary Allowance for adult men and boys over the age of 11. Infants, young children and pregnant women are even more intolerant to large doses.

There are also individual differences in sensitivity to large doses of Vitamin A, just as there are individual differences in reactions to other drugs. Infants, for example, have shown severe symptoms, including bulging of the head from intracranial pressure, after doses of 25,000 I.U. for only a month.

Hypervitaminosis A, as it is called, is not too uncommon in children and adults. A report published in 1980 by the International Vitamin A Consultative Group listed 579 known cases of acute or chronic overdosage of Vitamin A and suggested that some other cases may have been diagnosed as "pseudotumor cerebri," a condition that produces symptoms like those of a brain tumor.

Most often, toxicity occurs in young people -- particularly young women -- with acne or a similar skin problem who decide to up their dermatologist's short-term prescription of, say, 50,000 I.U. a day to as much as 400,000 units plus eating raw carrots during the day in the hope of achieving a quick, radical improvement in their complexion.

Ironically, one of the earliest symptoms of Vitamin A overdosage is dry skin, lip fissures and a scaly dermatitis.

Generally, recovery from hypervitaminosis A is rapid, once the individual is taken off the vitamin. But in severe cases it can require strong treatment and several months before getting back to normal.

In short, a little Vitamin A goes a long way and a lot can be harmful unless it is professionally prescribed and carefully monitored.

We'll have to see what develops in the exciting research attempts to probe the relationship and use of Vitamin A against cancer. Meantime, if you want to plan menus with added servings of dark green and deep yellow fruits and vegetables, because of their high content of beta-carotene, that's fine. But if you feel that you may not always be able to eat a good diet, don't take a Vitamin A supplement. Instead, one multi-vitamin-mineral tablet a day is all right to take as nutritional insurance as long as it contains 100 percent of the USRDA -- but not more -- of each nutrient, including Vitamin A, your body needs every day.

Q. Could you please bring me up to date on the effort to reduce the amount of lead that gets into our food supply from solder on cans?

A. Happily, we can report that considerable progress has been made. The canning industry, the makers of cans and the FDA -- all of whom have been working on the problem -- are optimistic that they will meet the FDA's goal to reduce lead intake from food by half by 1984.

Because very young children are much more vulnerable to lead exposure than older people (they absorb approximately 40 to 50 percent of dietary lead, while adults absorb only 5 to 10 percent, it was obviously important to place primary emphasis on reducing the lead content in their diets.

Ten years ago, the first focus of effort centered on evaporated milk. Not only was it more commonly used for infant feeding than it is today, but it contained more lead than other foods. That was because the seams of the cans were soldered with lead, and a vent hole closed with a solder plug after the can was filled.

As a result of manufacturing changes, the lead level of evaporated milk has been cut 85 percent -- from 0.5 parts per million (ppm) in 1972 to a current low of .08 ppm.

Ironically, during the same period the use of evaporated milk formula declined to a point where it is now being fed to only 1 percent of the young babies in this country.

At the same time, lead levels have been greatly reduced in commercial liquid infant formulas, from 0.10 ppm in 1974 to 0.02 ppm today. Some of this occurred when manufacturers switched production from lead-soldered to welded steel or seamless two-piece cans. It is expected that by the end of this year all infant formulas will be packed by either of these two methods. Choosing a different alternative, manufacturers of infant juices have switched from cans to glass, dropping the amount of lead from that source by 90 percent.

More recently, with all the progress in reducing lead in foods produced specifically for infants, attention has been turned toward reducing lead in regular canned foods commonly eaten by young children. The FDA is analyzing lead levels in 10 such foods, including tuna, apple juice, orange juice, string beans, baked beans, tomatoes, applesauce, chicken noodle soup, vegetable soup and fruit punch.

Progress in decreasing lead levels has not been limited to foods for infants and children. Results of FDA surveys for lead in 13 popular canned adult foods showed a drop from 0.38 ppm in 1974 to 0.21 ppm in 1980.

An increasing number of canners are packing food in seamless two-piece cans, and their use is expected to increase. In addition, more cans are being made with electric welded side seams which require no lead solder. According to the American Iron and Steel Institute, it will not be long before welded cans will eliminate soldered cans.

Copyright (c) 1982, The Washington Post Company