This book shows the link between foods and mental activity isn't quite that direct. But evidence exists, say Arthur Winter, a neurosurgeon, and Ruth Winter, a veteran science writer, that specific types of foods or components of foods can alter the amount or activity of chemical messengers in the brain that affect behavior.

If you want to be as sharp as possible and use your memory, or if you plan to participate in an athletic competition, they suggest, eat foods rich in protein, such as turkey, fish, and cheese. If you want to calm yourself or fall asleep more easily, they say, eat a meal high in carbohydrates and low in protein. High carb foods include pasta, breads, potatoes, and fruits.

Timing may be important, too. The authors report a study showing that some Parkinson's patients had fewer adverse side effects from levodopa medication when they ate only carbohydrates in the daytime and consumed proteins only in the evening.

For anyone who has ever wandered the aisles of a health food store bewildered by the variety of offerings with unfamiliar chemical names and claims that strain credulity, this book provides a state-of-the-art guide to what food supplements purportedly do, and how well they work.

The best brain food of all, however, may be a steady diet of sufficient sleep. The ability to do useful mental work, the authors report, falls by 25 percent for each additional 24-hour day people go without this 100 percent natural, easy-to-use, doctor-approved, safe and effective home remedy.