Q. Does beer provide anything besides calories?

A. As produced in this and other developed countries, where it is filtered to make it clear, beer provides mainly calories. A 12-ounce glass of regular beer containing 150 calories has just over a gram of protein, accounting for slightly less than 3 percent of the calories, while 37 percent comes from carbohydrate and the rest from alcohol. The beer would also provide some thiamin and riboflavin, and a significant amount of niacin -- about 12 percent of the adult male and 17 percent of the adult female Recommended Daily Allowance.

Beers made in some of the developing countries contain greater amounts of B-complex vitamins than the grains from which they are produced. The vitamins are actually made by the yeast used in beer production. The beers tend to be quite cloudy, and some of the nutrients are found in the sediment that settles out of the liquid.

Q. Please explain to me why so many packaged foods have emulsifiers added to them? A Versatility is probably the best word to explain why they are used in everything from bread to sausages. Emulsifiers alter the surface properties of other ingredients, thereby lowering their resistance to combining with each other. And while they are perhaps most widely used to mix oil and water, they are also helpful in other ways.

In bakery products, they improve volume, moisture retention, uniformity and fineness of grain. They also retard staling and are used as conditioners to increase the strength of the dough. They enhance the texture of pasta and inhibit clumping, a particular problem when pasta is used commercially to produce canned and frozen foods.

In both dairy products and nondairy substitutes, such as coffee whiteners, they provide stability to emulsion and help maintain the starch and protein complexes in these foods. In manufacturing ice cream, emulsifiers are used to ensure proper texture. And in processed cheese, they are responsible for keeping the fat (which holds the flavor) evenly dispersed and for preventing the cheese from "weeping" as it melts.

The importance of emulsifiers obviously goes well beyond the role of the egg yolk in making mayonnaise.

Q. I have a friend who insists that when she is emotionally stressed, she feels better if she takes vitamin C. Is there any scientific evidence that it may work or is this another case of what you often refer to as "the placebo effect?"

A. There is a rationale for suggesting that vitamin-C requirements may increase with stress: The highest concentrations of the vitamin are found in stress-responsive body organs, the pituitary and the adrenal glands, and the concentration of vitamin C in the adrenals seems to decrease in response to stress.

But the only report of increased vitamin-C excretion associated with stress was part of an incomplete study. It was made as a secondary observation, and other factors that could have explained the observed effect were not controlled. This hardly represents a solid foundation for claiming that vitamin-C requirements go up during periods of emotional stress.

Indeed, there is no well-documented evidence that any nutrient requirements change with emotional stress. Experiments to quantify and compare the effects of stress are extremely difficult to design. One study, nearly 20 years ago, did find that college students excreted more nitrogen in the pre-exam period, an indication that they might have been using more protein. However, the change was not considered of significant enough magnitude or duration to warrant a change in recommendations for protein requirements.

In short, there is little reason to believe that a diet that meets the Recommended Dietary Allowances will fail to provide adequate amounts of vitamin C to meet any demand caused by emotional stress. Perhaps it is more important to recognize that during such periods people's eating habits can change dramatically. In the short term this is of little consequence. If, however, it is a chronic problem, nutrition intervention is indicated. That intervention should focus on skilled nutrition counseling, not on self-medication with vitamin C or any other nutrient.