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By Peter Gorner
Tribune science reporter
Published November 27, 2002

Just when you thought that everything you liked to eat was bad for you, scientists at Harvard University have found that peanut butter sandwiches may prevent diabetes.

In a study published Wednesday, researchers at the Harvard School of Public Health reported that women who consumed an ounce of nuts or peanut butter five times a week reduced their risk of type 2 diabetes by 21 percent.

"Although we studied women, the same thing should hold true for men," said Dr. Rui Jiang, co-author of the study and a specialist in nutrition and epidemiology.

"Nuts contain lots of fat, but most fats are in the mono or polyunsaturated form, which are good for insulin sensitivity and serum cholesterol," Jiang said. "Nuts are also rich in antioxidant vitamins, minerals, plant protein and dietary fiber."

Type 2 diabetes usually occurs after age 40 when people do not produce adequate amounts of insulin for the needs of the body or it can no longer be used effectively. Secreted by the pancreas, the hormone triggers cells to accept and use sugar (glucose) from food.

Consequently, excessive amounts of sugar float in the bloodstream, slowly destroying the kidneys, eyes, blood vessels and nerves.

Obesity is closely associated with fat cells becoming resistant to insulin and is one of the leading risk factors for type 2 diabetes. Both combined affect more than 50 percent of the U.S. population, the Harvard researchers said.

Little is known about the molecular mechanisms of these two metabolic disorders, although both are associated with inflammatory activity in fatty tissue.

The advice offered by the Harvard researchers, whose work was reported in this week's Journal of the American Medical Association, is not merely to replace one kind of fat with another. You must also consider your total caloric intake.

"To avoid increasing calories, people should not simply add nuts to their diet, but substitute them for less healthy foods such as refined carbohydrates like white bread and red meats," Jiang said.

"Given the inverse association between nuts and the risk of coronary heart disease as well as type 2 diabetes, it is advisable to recommend regular nut consumption as a replacement to refined grain products or red or processed meats, which would avoid increasing caloric intake," Jiang said.

"The most important thing you can do to prevent type 2 diabetes is to have an energy balance--you should burn the same amount of calories you take in," said Dr. Francine Kaufman, president of the American Diabetes Association and head of endocrinology at Children's Hospital in Los Angeles.

"If you're overweight, you should expend more calories than you take in until you reach your ideal body weight."

In the Harvard study, researchers compared nut consumption and type 2 diabetes among 83,818 women ages 34 to 59 who were enrolled in the Nurses' Health Study. Established in 1976, the study has provided many highly publicized reports that challenged some deeply held beliefs about diet and health.

Women participating in the Nurses' Health Study completed questionnaires about their eating habits between 1980 and 1996, including how often they consumed certain foods.

Nut and peanut butter consumption was divided into categories ranging from "never/almost never" to "five or more times a week."

The women had no history of diabetes, cardiovascular disease or cancer. During the 16 years that they were tracked, they also provided information about their body weight, smoking and drinking habits, family health history, physical activity and multivitamin use.

The researchers documented 3,206 new cases of type 2 diabetes among the women. After adjusting for the influence of body weight, smoking, alcohol use and other diabetes risk factors, Jiang found that the risk of type 2 diabetes steadily went down as the frequency of nut and peanut butter consumption went up.

Women in the study who reported eating nuts at least five times per week reduced their risk of type 2 diabetes by almost 30 percent.

Women who ate peanut butter five or more times a week (approximately 5 ounces of peanuts per week) reduced their risk 21 percent, compared with those in the study who rarely ate it.

The researchers wrote: "There have been concerns that frequent nut consumption may result in weight gain and increased risk of coronary heart disease because of the high fat content. However, in our cohort, we did not find an appreciable association between nut consumption and weight change."

Other physicians viewed the latest Nurses' Health Study as good news, though hardly surprising.

"The peanut butter consumption may reflect a well-balanced diet," said Dr. Jeanette Newton Keith, a gastroenterologist at the University of Chicago who specializes in nutrition.

"Thirty years ago, a peanut butter and jelly sandwich on whole-grain bread and a glass of low-fat milk was considered an excellent meal. It was well-balanced.

"Studies like this show it's important not to restrict any food group, but to eat a well-balanced diet, including nuts, dairy products, fruits and vegetables and whole grains.

"We need to go back to that kind of thinking."

Copyright © 2002, Chicago Tribune