In its first-ever single-topic special issue, the Harvard Heart Letter focuses on nutrition. The November 2007 issue offers advice aimed at unscrambling the mixed messages about what constitutes healthy eating. Based on the latest research on nutrition, its recommendations include:

• You can’t go wrong with fruits and vegetables. Along with exercise, fruits and vegetables are the closest thing we have to a magic bullet against heart disease. To get the most phytonutrients, choose foods in all colors of the rainbow. The Harvard Heart Letter notes that an ever-growing variety of frozen fruits and vegetables makes it easier to tap into the power of produce.

• Choose healthful sources of fat, carbohydrate, and protein. When it comes to fats, carbs, and protein, many people are in the dark, confused by widely promoted diet claims and flip-flops from research. The Harvard Heart Letter debunks the myths and tells you how to make smart choices. The bottom line: Emphasize unsaturated fats and choose carbs with a low glycemic index.

• Check out four diets that have been tested in clinical trials. Four diets forged in rigorous clinical trials offer real benefits for the entire cardiovascular system. These are the DASH diet, a higher-protein diet called the OmniHeart diet, the cholesterol-lowering "portfolio" diet created by University of Toronto researchers, and a Mediterranean-type diet. These four diets are much better for the heart than the average American diet, and each has its own subtle effects on various heart disease risk factors. The November Harvard Heart Letter describes the diets and how they stack up against heart disease.

• “Healthy eating” and “holiday season” needn’t be mutually exclusive. By practicing the 12 tips for holiday eating presented in the Harvard Heart Letter, you can come through the holidays without making “go on a diet” one of your New Year’s resolutions.