Diabetes, January 2003

Eat Fish and Veggies and Prosper

New research outlines best heart-healthy diet strategies

New research confirms what we should already know: Diets low in saturated fats, high in omega-3 fatty acids, and high in fruits, vegetables, nuts, and whole grains are the best for your heart.

"The information was scattered in various papers," says Dr. Frank Hu, lead investigator of the study and an associate professor of nutrition and epidemiology at Harvard School of Public Health. "We tried to put all the pieces together to solve the puzzle."

The study, which appears in a recent issue of the Journal of the American Medical Association (JAMA), identifies three "dietary strategies" that seem to be effective in preventing coronary heart disease (CHD).

"Such diets," the researchers write, "together with regular physical activity, avoidance of smoking, and maintaining a healthy weight, may prevent the majority of cardiovascular disease in Western populations."

"That's a huge statement by well-known researchers. That's the bottom line," says Samantha Heller, a senior clinical nutritionist at New York University Medical Center in New York City.

"What they're saying is stay away from saturated fat and cholesterol, stay away from meat, whole milk, mayonnaise, ice cream. Moving towards a plant-based diet is your best defense against not only heart disease, but obesity and diabetes as well," she adds.

The authors of the study, both professors at the Harvard School of Public Health in Boston, searched the MEDLINE database of medical literature for epidemiologic and clinical studies of dietary factors through May 2002. The authors ultimately examined 147 different studies and reviews for conclusions on diet and coronary heart disease prevention.

Three Strategies For Fighting Heart Disease

Three individual strategies emerged as the best for fighting heart disease. And they worked even better in combination.

The first is to substitute unsaturated fats for saturated and trans-fats. (Trans-fats are fats that have been altered, like those found in cookies, crackers, candy, and margarine).

What does that mean to the average person?

"That means not eating red meat, whole milk, mayonnaise, ice cream, and other whole dairy products," Heller says. "That has definitely been shown to decrease the risk of heart disease."

Eating meat or cheese interferes with the liver's ability to process fats and therefore raises cholesterol in the arteries.

The second strategy is to up your consumption of omega-3 fatty acids from fish oil or plant sources. You can get these fatty acids from eating fish regularly, and from consuming canola oil, soy bean oil, and flaxseed oil.

The third strategy is to consume a diet high in fruits, vegetables, nuts, and whole grains and low in refined grains.

The glycemic index (GI), which attempts to rank foods on how they affect blood sugar levels, is still controversial, Hu says. It may be useful to some degree in classifying starchy foods such as bread and potatoes but it is not useful for classifying other foods such as protein, fruits, and vegetables.

The Relationship Between Dietary Fat and Obesity Still Debated

Similarly, the study authors found that the relationship between dietary fat and obesity is extremely controversial.

"The conventional wisdom is that high-fat diets lead to obesity and diabetes. This hasn't been supported by the scientific evidence," Hu says.

Calories in general may lead to obesity, but not just calories from fat. In fact, Hu adds, "there's more evidence that calories from carbohydrates, especially refined carbohydrates and sugars, could be more detrimental for obesity and diabetes."

Your best bet is to combine the three dietary strategies outlined in the report. "I can be a vegetarian and still eat a lot of white flour, processed food, and white chocolate and still be overweight," Heller says. "You want the effect of all three strategies. Nuts, seeds, legumes, vegetables, fruits, whole grains, and soy products contain chemical compounds like phytochemicals, antioxidants, vitamins, and minerals that help fight disease of all kind. You're reinforcing your body's ability to stay healthy every time you eat a food like that. So why not?"

Always consult your physician for more information.

Online Resources

(These links are provided for the education and convenience of our Neighbors. AAMC is not responsible for the content of Internet sites.)

American Association of Diabetes Educators

American Diabetes Association

American Heart Association

Centers for Disease Control and Prevention (CDC)

Journal of the American Medical Association (JAMA)

National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)

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Nuts, Peanut Butter May Prevent Type 2 Diabetes 

Study finds enthusiasts at 27 percent reduced risk

If you are nuts about nuts, take heart: The more you eat them, the less likely you are to develop type 2 diabetes.

That is the conclusion of a new study finding that women who eat at least five ounces of nuts a week have a 27 percent lower risk of developing type 2 diabetes than those who rarely or never consume them. Those who eat peanut butter regularly also gain protection from the blood sugar disorder, according to the study, which appears in a recent issue of the Journal of the American Medical Association (JAMA).

Experts are not clear why nuts guard against type 2 diabetes, in which the body's cells become insensitive to the hormone insulin. However, nuts are high in healthful unsaturated fats and low in their harmful saturated cousins. They are also rich in antioxidants and other nutrients that may keep diabetes at bay.

"In our study, this [effect] was independent of known risk factors for type 2 diabetes," said Dr. Rui Jiang, a postdoctoral fellow at the Harvard School of Public Health and lead author of the study. "It's unlikely that other factors generated this inverse association."

An estimated 17 million Americans have diabetes, and 16 million have the type 2 form of the disease. Another 16 million people have "prediabetes," putting them at high risk of developing the full-blown illness.

Heart disease is the leading killer of persons with diabetes, who face two to four times the normal risk of heart attacks as a result of their condition.

Even a 27 percent reduction in the chances of getting diabetes is "pretty substantial," said Dr. David Jenkins, a specialist in the condition at the University of Toronto who studies the health benefits of nuts. "All of us living in Western society are at risk."

Nuts are not just a diabetes wonder, added Jenkins, who receives research funding from the US almond industry. They have also been shown to lower cholesterol and reduce heart disease.

The Harvard researchers studied 83,818 women participating in the Nurses' Health Study, a massive look at lifestyle and health begun in 1976.

In 1980, when the women were between 34 and 59 years old, 71 percent said they almost never or seldom at nuts. About a quarter ate them one to four times a week, and 5 percent ate at least five 1-ounce servings a week. Women who ate nuts frequently tended to weigh less than the others.

Over the next 16 years, 3,206 women developed type 2 diabetes. Being overweight is linked to the disease. But even after taking into account pounds, smoking status, exercise habits, family history of diabetes, and other risk factors, the researchers found that higher nut intake cut the chances of having diabetes years later.

Women who ate the most nuts had a 27 percent lower risk of developing diabetes than those who ate the fewest. The risk for women who ate nuts less than once a week was 8 percent lower, and it fell 16 percent for those who ate nuts between one and four times a week. Women who ate five servings a week or more of peanut butter—a substitute measure for peanut consumption—had a 21 percent lower risk of diabetes than those who ate none or almost none of the spread.

Penny Kris-Etherton, a nutrition expert at Pennsylvania State University, called the results "very interesting" but said she could not explain them. "I'm not sure what it would be in nuts, other than a favorable fat profile," she said.

Total fat and unsaturated fat intake seem to help control insulin levels, Kris-Etherton said. And perhaps there are nutrients in nuts that also afford protection against blood sugar problems.

The effect may also be due, at least in part, to the fact that when people increase their nut intake and keep their calories steady, their consumption of carbohydrates falls. Carbohydrates raise blood sugar. "Maybe that is helping control a prediabetic state," Kris-Etherton said.