Nuts and oats may build a strong heart.

Heart-healthy components in oats may help lower high cholesterol levels, and a nutrient in nuts may help prevent death from heart disease, according to preliminary research from two studies presented at last month's American Heart Association's 71st Scientific Session. In a 12-year study of 22,071 doctors participating in the Physicians Health Study, men whose diets contained high quantities of nuts had a decreased risk of dying from heart disease, says the study's lead author, Christine M. Albert, M.D., an instructor at the Harvard Medical School (Boston, MA). Nuts contain unsaturated fats including alpha-linolenic acid, which may help prevent fatal disturbances in the heart's rhythm.

Meanwhile, in a study funded by Quaker Oats at Tufts University (Boston, MA), another group of researchers examined 43 men and women eating a diet rich in oats. People on this diet had lower blood pressure and reduced blood levels of cholesterol at the end of the study. High blood pressure and high cholesterol are risk factors for heart attack and stroke.

The oat diet lowered total blood levels of cholesterol by 34 mg per deciliter (mg/dL), while study participants who ate a diet that substituted wheat for oats lowered their cholesterol only 13 mg/dL. The individuals' blood levels of low-density lipoprotein cholesterol (LDL or bad cholesterol), which can accumulate in blood vessels and increase risk of a heart attack or stroke, followed the same pattern. The oat group's LDL was 23 mg/dL lower and the wheat group's LDL was 8 mg/dL lower.

Also, those in the oat group reduced their systolic blood pressure by 7 mm of mercury (mm/Hg) at the end of the six-week study, compared with 2 mm/Hg for the wheat group. Researchers attribute the benefits of oats to its soluble fiber. There are several reasons why foods that contain soluble fiber, or soluble fiber itself, could have beneficial effects on blood pressure or cholesterol. The presence of soluble fiber in foods slows the rate of digestion and absorption. The slower digestion causes a more gradual rise in insulin levels. Insulin is a hormone that helps regulate blood sugar, but it may raise blood pressure in some individuals. There may be other as-yet unidentified factors in oats that affect the way the blood vessels react, we're told.

The men and women in the study ate one of two calorie-controlled diets. Researchers determined their individual maintenance caloric needs, then gave each 1,000 calories less than the maintenance level each day. The study group was given an oat-rich diet. The control group ate a diet that substituted wheat for oats. The two diets differed mainly in the amount of soluble fiber. Oats contain more of this fiber than the same quantity of wheat. Other foods high in soluble fiber are barley, lentils, pinto beans, black beans and citrus fruits.

Researchers stress the study is very preliminary, and that more research is needed to determine if an oat-rich diet would have the same effects in a long-term study. The diet needs to be strictly followed for results to be significant.

In the Harvard investigation linking nut consumption to a reduced risk of heart disease, researchers believe that alpha-linolenic acid, a component of nuts, may protect the heart by preventing a rhythm disturbance called ventricular fibrillation that causes sudden death. Other sources of alpha-linolenic acid include unhydrogenated canola and soybean oils used in most full-fat commercial salad dressings, flaxseed, flaxseed oil and a leafy vegetable called smooth purslane, which is eaten mostly in Greece.

Further information. Brian Henry, American Heart Association, 7272 Greenville Ave., Dallas, TX 75231; phone: [phone]; email: [e-mail].