Q: Various pamphlets I have collected over the years show conflicting information about the cholesterol content of shellfish. Can you provide the correct information?

A: Some of your materials must be outdated, and therein lies the conflict. Because laboratory techniques used in the past did not separate cholesterol from chemically similar compounds, the first published values were too high.

Analyses using newer methods indicate that a 3-ounce portion of clams, oysters, mussels or scallops has between 30 and 50 milligrams (mg.) of cholesterol, while the same amount of lobster or crab provides 90 mg. Values for shrimp vary widely, from just 60 mg. in Japanese prawns to as much as 180 mg. in Atlantic varieties.

And squid, which is actually a mollusk with the shell inside, contains an average of 215 mg. in a 3-ounce serving. However, values can range anywhere from 130 to 385 mg. To put those figures into perspective, 3 ounces of lean beef, veal or chicken contain an average of 80 mg. of cholesterol.

Q: I am retired and live in the South. Recently my doctor said I have borderline diabetes, and told me to watch my diet. I have tried getting information that would be helpful, but so far all the literature seems far too stringent. What do you advise?

A: Without knowing details of your condition, it is impossible to provide specific guidance. But whether or not you are among the majority of older individuals with recently discovered diabetes who are overweight or you are at normal weight, sound diet and regular exercise are the cornerstones for managing your condition.

We suggest that you would benefit from professional nutrition counseling, and the development of a plan that addresses not only your condition, but food preferences and life style habits as well. Ask your doctor to recommend a registered dietician to provide you with this type of guidance. If your physician does not know of anyone in your area, contact your State Dietetic Association or the nutrition office in the state health department. They will be able to help identify sources of professional help.

Q: Reading your column about inappropriate nutritional supplements directed toward people 65 or over made me wonder whether this age group is the heaviest user of supplements. Is it?

A: Data from a nationally representative sample of almost 3,000 adults, aged 16 and over, did not find that the elderly were overrepresented among "very heavy" users of vitamin and mineral supplements.

That study found that 42.5 percent of all adults in the United States take nutrition supplements. Usage was classified into four levels. Of those who take supplements, 42 percent were light users, getting, on average, 70 percent of the RDA per nutrient from a supplement; 16 percent were moderate users, getting about 128 percent of the RDA per nutrient; 28 percent were heavy users, getting an average of 400 percent of the RDA per nutrient, and finally, 14 percent were very heavy users, averaging an outrageous 777 percent of the RDA per nutrient.

Those in the light and moderate groups tended to take one broad-spectrum vitamin-mineral supplement, while those in the heavy supplement groups typically took two or more specialized vitamin and mineral products, as part of a "personalized" health regimen. This later group tended to make more visits to health-food stores and to rely less on physicians for advice.

In general, adults age 41-64 and those living in the western part of the country were more conspicuously represented in the heavy and very-heavy-user groups. But usage dropped a little after age 65. For example, of all those 41-64 surveyed, 16.4 percent were heavy users and 7.2 percent were very heavy users, while among those 65 and over, 12.6 percent fell into the former group and 6.9 percent into the latter. In contrast, among those 16-24, only 9.8 percent were heavy users and 3.7 very heavy users.

Do physiological changes related to the aging process or interactions between drugs and nutrients provided in these supplements make it more dangerous for the elderly to consume such huge amounts? Only additional research will tell. Meanwhile, the use of vitamins and minerals in amounts well beyond the level of the RDA is a poor idea at any age.

1987, Washington Post Writers Group