" "Patients often ask me, 'Why does nutrition advice flip-flop all the time?' " Thayer says. They may have a point. Take the recent dustup over fat recommendations, for example. In 2005, the USDA's Dietary Guidelines for Americans recommended limiting the amount of fat you consume each day to 20 to 35 percent of total calories. But in a year later, the front page of The New York Times declared: "Low-Fat Diet Does Not Cut Health Risks." No wonder Thayer's patients -- and many others -- are confused. What should the average person make of these mixed messages?"

" Thayer's answer: Take the long view. "One study isn't going to determine what we should be eating," she says. "Nutrition is a complex science -- what appears to some as flip-flopping is actually defining and refining some of the recommendations we make.""

" Nowhere is the evolving nature of nutrition science clearer than in the fight against heart disease, the No. 1 cause of death among Americans. Some foods that were once considered to increase the risk of disease, like fats and alcohol, now don't seem so bad -- in fact, limited amounts may play an active role in helping ward off heart disease. As nutrition knowledge has grown, so has scientific understanding of heart disease, a maze of cholesterol levels, blood pressure, arterial inflammation, and lifestyle factors, such as diet, stress, and fitness levels."

" This is why prevention requires a multipronged approach -- but what you eat is certainly key. "Just eating certain foods isn't going to completely prevent heart disease, but they can take the fight to the next level," says Mikelle McCoin, R.D., M.P.H., senior nutrition educator at the Gladstone Institute of Cardiovascular Disease in San Francisco, California. To identify those foods, we spoke to Thayer, McCoin, and three other leading nutrition researchers. The result is a guide to the nutritional architecture that supports a heart-healthy diet. "

" Soluble fiber acts like a scouring pad for your circulatory system, clearing out harmful low-density lipoprotein (LDL) cholesterol before it has a chance to stick to artery walls, where it forms thick, hard deposits that block blood flow. "Soluble fiber is potent in lowering ldl," says Wahida Karmally, Dr.P.H., M.S., R.D., director of nutrition at the Irving Center for Clinical Research at Columbia University Medical Center. According to a study Karmally co-wrote in the Journal of the American Dietetic Association, people who add just 3 grams of soluble fiber to their diets each day (the research team used three-fourths of a cup of whole-grain oat cereal, three times daily) can lower their LDL levels by 5 percent in six weeks. While that might sound small, consider this: The National Heart, Lung, and Blood Institute has found that each 1 percent reduction in a person's LDL cholesterol levels can be expected to reduce his or her overall heart disease risk by 2 percent. The other form of fiber, insoluble, also has a scouring effect, but in a different way; it helps move food through your digestive system."

" Whole grains, such as oatmeal, bran, and barley, as well as fruits, vegetables, and legumes are great sources. Some of these foods also contain other compounds, such as phytochemicals, vitamins, and trace minerals, that may help fight heart disease -- another reason fruits, vegetables, and whole grains frequently top nutritionists' lists of recommended foods. "

" Although conventional wisdom once held that the heart-healthiest diets were practically fat-free, that notion has changed in recent years. "You want a diet that's moderate in fat," says Alice H. Lichtenstein, D.Sc., chairperson of the American Heart Association's nutrition committee and director of the Cardiovascular Nutrition Laboratory at Tufts University in Boston, Massachusetts. The best way to achieve it: Restrict the two types of fat that don't benefit your heart -- saturated and trans-fatty acids -- and substitute two "good" fats, monounsaturated and polyunsaturated. "

" Monounsaturated fats help raise levels of helpful high-density lipoprotein (HDL) cholesterol. These HDL molecules act like bodyguards, capturing "bad" LDL molecules in the arteries and escorting them to your liver, where they are filtered out of the body. According to the results of a study in the Journal of the American Medical Association, people who increased their intake of monounsaturated fats in place of saturated fats and high-sugar carbohydrates over three years reduced their risk of heart disease by 20 percent."

" Vegetable oils, nuts, olives, avocados, and fish are all good sources of mono- and polyunsaturated fats. Just remember that any source of fat -- whether it's olive oil or butter -- is calorie dense. "One gram of fat contains nine calories, compared to only four calories for carbohydrates and protein," Thayer says. That's why substitution is crucial; you want to add healthful fats to your diet while subtracting not-so-healthful ones to keep daily calorie intake on an even keel."

" The 2005 Dietary Guidelines for Americans suggest that 20 to 35 percent of your total daily calories should come from fat. Of that amount, no more than 10 percent should come from saturated fat. For someone on a 2,000-calorie per day diet, that translates to 65 grams of unsaturated fats."

" Polyunsaturated fats are helpful in their own right, but a subset of polys, called omega 3 fatty acids, are amazing multi-taskers, simultaneously combating several heart disease risk factors. Omega 3s permeate the cells that line your circulatory system. They make your arteries more supple, which helps reduce blood pressure and prevent arterial inflammation. They also help regulate the electrical impulses that keep your heart beating steadily, preventing arrhythmia. But omega 3s' neatest trick is changing the quality of LDL cholesterol molecules. "Omega 3s help reduce the rate of plaque buildup by making LDL cholesterol lighter and fluffier, so blood vessels can't take it up as easily," says Marguerite M. Engler, Ph.D., a cardiovascular researcher
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