DEAR DR. DONOHUE - After smoking for about 16 years I quit a year ago. Now I run three miles three times a week and lift weights. I have lost the 20 pounds I put on when I quit cigarettes. Now my question has to do with diet. I read your column all the time. If I have it right, protein is used by muscles to grow and carbohydrates are used by muscles to provide energy. So a low-carb diet makes the body use its fat for energy. So if all this is true, a low-fat, low-carb, high-protein diet is best to gain muscle and lose fat. But how much and how little of each is best? - M.W.

ANSWER - Wait a minute. My head's spinning. The first part of your syllogism is true. Your conclusion is false, maybe even dangerous.First off, you have to store carbohydrates for energy. You won't be able to move a muscle unless you have carbohydrate energy. A low-carb diet, therefore, translates into weakness.

Now fat. You use fat for energy only when carb stores are depleted. Then you are approaching fatigue limits anyway, so it's moot. In long-distance events, it's true, you do burn fat, but this is somewhat of an exception to the rule. And you see how exhausted marathoners are at the finish line. If they didn't have carbohydrate stores, they wouldn't be able to start, much less finish the race. So again, a low-carb diet is not good for an athlete.

Now, protein. You don't need much protein to build muscle. Even though muscle is made of protein, you can't leap to the conclusion that more protein intake means more muscle. It doesn't. Any protein taken over and above what little the muscles use for growth is either burned for last-resort energy or eliminated. A normal American diet supplies all the protein the muscles will ever use for growth.

The best diet? For the athlete and non-athlete alike, it is one high in complex carbohydrates (50 percent to 60 percent of total calories), low in fat (less than 30 percent) and the rest in protein (10-15 percent).

Congratulations on quitting.

DEAR DR. DONOHUE - Is there such a thing as "eyedness" (like handedness, left or right)? Does it bear on athletic performance? - J.O.

ANSWER - Sure. Most people have a dominant eye, and some have no preference, seeing as though they had a single Cyclops-like vision. Special vision tests show this.

Recently, varsity baseball players at a major college were studied for both eye and hand dominance as it related to their statistical performances.

The researchers found that players with crossed dominance (left eye/right hand or vice versa) were better hitters than those with uncrossed dominance (right eye/right hand, etc.). It was not thus with pitchers. Those with uncrossed dominance had better earned run averages than other pitchers. What about Cyclops vision? Those people fared better in both hitting and pitching.

You can say, then, that vision and hand coordination are of obvious importance in baseball, but how much of a factor it is in other sports is not certain.

DEAR DR. DONOHUE - Can you answer this for a group of granny golfers (70ish), who keep in good shape? Is there any hope of getting rid of flabby, wrinkly skin inside the upper arms? A set of exercises has been suggested with light weights. Will this work? - Mrs. T.

ANSWER - Exercise might increase muscles and fill in a bit of the slack. But it won't get rid of redundant skin. The only way that will happen is by way of the scalpel.

DEAR DR. DONOHUE - I am a frequent user of diet drinks, the labels of which contain the warning, "Phenylketonurics: Contains phenylalanine." There is no further information. What does this mean? Is continuous use dangerous? - F.A.

ANSWER - That warning is for people who have an inherited diseasee done for it routinely) the person must avoid the substance. Otherwise, mental retardation can develop. Have you been told you are a phenylketonuric? If not, you should have no concern. The warning is not for you.

DEAR DOCTOR - If a person is allergic to penicillin and has sex with someone who has just had a penicillin shot, can the allergic person get a reaction? - J.C.S.

ANSWER - No.

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