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QUESTION: Do dietary habits influence the risk of developing gallstone disease?

ANSWER: You've posed a thorny question. Various studies have examined the relationship between dietary factors and risk of gallstone disease, which, incidentally, is far more common among women than men. Findings have been inconsistent, partly because of limitations in the way the studies were designed.Recently, however, researchers from the National Institutes of Health studied data of a prospective investigation using diets of women 25-74 years old. The data were collected as part of the First National Health and Examination Survey (NHANES I). The women's dietary intakes were scrutinized in relation to information about hospitalizations for gallstone disease. The information was obtained about 10 years after the hospitalizations as part of a follow-up study.

The researchers kept in mind the conflicting results of previous studies as they weighed factors that could be linked to gallstone disease. The one that emerged as most important came as a surprise: The number of hours between the last meal or snack at night and the first one the next day surfaced as the factor most strongly associated with risk of gallstones. Risk was greatest among women whose overnight fast was 14 hours and least for those who fasted less than eight hours. Dieters were also more likely to have experienced gallstone disease.

Increased fiber intake, which had been found in some but not all studies to be linked to lowered risk, also had a small protective effect. And lower calorie consumption increased risk but only among women under 50 years old.

It's not known why longer overnight fasting and dieting raise gallstone risk. One possibility is that they may slow gall bladder motion, and/or result in changes in the bile. Both these factors could increase risk. More studies may shed light on the matter.

Meanwhile, the current findings provide yet another reason not to skip breakfast.

QUESTION: Are fluoride drops as effective as water fluoridation in protecting children's teeth against decay?

ANSWER: Unfortunately they are not, not even when used in amounts equivalent to what would be ingested if fluoridated water was consumed. Two reasons have been suggested for the lesser effectiveness of drops. One, a single dose once a day doesn't provide the continuous exposure that children would derive from getting the mineral throughout the day if they drank fluoridated water and consumed beverages and foods prepared with it. The other relates to the practical issue of following the regimen. It's relatively easy to remember to include fluoride drops at a particular feeding each day for a young infant, but it becomes more difficult as children grow older. It's thought that for maximum effectiveness the use of fluoride should continue until the child reaches 16, when the second molars are fully erupted.

If you do rely on fluoride drops, it may help to ensure consistent practice if you bring the kids into the act. While very young children shouldn't be allowed to mete out their own dose, they're often very good at reminding adults about the issues of importance to them. They can be enlisted to help remember to make fluoride drops a regular part of the morning routine.

QUESTION: I'm in the 65+ age group and was raised to shop economically. I'm curious about whether younger shoppers today are careful with their food dollars. Has anyone ever studied this and if so what were the results?

ANSWER: The Food Marketing Institute addresses the question of frugal shopping as part of its annual nationwide survey of consumer attitudes related to food purchases. Eight items are included in their list of economical practices, including use of price-off coupons; newspaper advertisements; stocking up on bargains; comparing prices at different markets; buying store or lower price brands; buying products on special even if you had not planned to; going to supermarkets other than your principal one for advertised specials; and shopping at discount or warehouse stores for groceries.

The highest percentage of "heavy economizers" were in the youngest age group in the survey, women and men between 18 and 26 years old. And the proportion declined steadily with increasing age. Among those 65 and over, only 15 percent fell into the "heavy economizer" category. In part, this probably reflects the fact that some money-saving measures, such as quantity buying and using supermarkets farther away, simply aren't feasible for older households. Older households used several measures, including newspaper ads and price-off coupons, most consistently.

QUESTION: I know that too much vitamin A is toxic. But if the body converts beta carotene to vitamin A, why isn't it toxic, too, especially when used in amounts that turn the skin orange?

ANSWER: There are people who insist on consuming enough carrots and other carotene-rich foods that they turn themselves into walking carrot sticks. There's no evidence that getting this excessive amount has any benefit to health. These people remain protected against toxicity for two reasons: The conversion of carotenes to vitamin A is a relatively slow process, and as carotene consumption increases, the body absorbs less of it.

The orange skin tint characteristic of excess carotene consumption occurs as the carotenes are stored in the fatty tissue just beneath the skin.

Washington Post Writers Group