I've read that the FDA has proposed banning the use of guar gum in diet products. It appears on a number of ingredient lists, and I'd like to know why the ban relates only to diet products.

ANSWER - The amount of guar gum used as an additive in foods is small and doesn't represent a health risk. By contrast, the doses in weight-loss preparations are much heftier. The FDA has received 17 reports of obstruction of the esophagus resulting from use of an over-the-counter (OTC) drug containing guar gum, 16 of them between June 1988 and August 1989. Of these, 10 people required hospitalization, and one eventually died as a result of open-heart surgery.Beyond the danger, we also have the question of effectiveness. There's insufficient data to show the usefulness of guar gum as an ingredient in OTC weight-reducing aids. Indeed, the FDA has on numerous occasions invited manufacturers to provide evidence of effectiveness. But to date, it has received none.

Reports of drawbacks linked to taking water-soluble gum for laxative purposes date back to the 1930s.

Given the potential for serious problems, using guar preparations, for which there is no demonstrated effectiveness, certainly seems an unwise approach to weight loss. Where the use of these compounds is warranted, it's crucial to take them with ample amounts of water.

QUESTION - As the weather gets colder, my hair goes completely limp and my nails dry, split and break. Are there nutritional remedies for these problems?

ANSWER - Many hair- and nail-care products are fortified with vitamins, minerals, protein and even substances not considered to be essential dietary nutrients. But the plain fact is that, regardless of the claims, they really don't improve the condition of your hair or nails.

It's true that in order to produce hair and nails, an adequate supply of nutrients must be available. When they're lacking, both hair and nails suffer. However, the nutrients needed for the body to grow hair and nails are obtained from the blood supply, not by applying them topically.

It's also true that some of the products, whether or not they are "nutrient fortified," can coat both hair and nails to give them a healthier, shinier and even stronger appearance. But once they are removed, so is the effect. Similarly, there's no evidence that swallowing protein supplements, mineral and vitamin preparations or gelatin in the hope of healthier hair or nails will result in any improvement.

1990, Washington Post Writers Group