Nuts about health

People who regularly eat peanut butter or nuts can significantly reduce their risk of developing type 2 diabetes, according to researchers at the Harvard School of Public Health.

In a new study researchers found that consuming one tablespoon of peanut butter or 28g of peanuts or other nuts five or more times a week is associated with a 20-30 per cent reduced risk of developing the disease.

The study involved over 83,000 female nurses who were followed for an average of 16 years in the Brigham and Women's Hospital-based Nurses' Health Study. The women in the study completed food frequency questionnaires approximately every four years between 1980 and 1996, and had no history of diabetes, cardiovascular disease, or cancer.

The team concluded that women who eat five tablespoons of peanut butter each week can reduce their risk of developing type 2 diabetes by almost 20 per cent. Further, the relationship between consuming peanut butter, peanuts and other nuts and type 2 diabetes is linear - higher consumption provided a greater protective effect. The group of women consuming a half serving of peanut butter or a full serving of peanuts and other nuts one to four times per week had a 16 per cent reduced risk of developing the disease.

Dr Frank Hu, associate professor of Nutrition and Epidemiology at Harvard School of Public Health and an author of the study, said: "Given the observed inverse association between nuts and risk of coronary heart disease as well as type 2 diabetes, it is advisable to recommend regular peanut butter and nut consumption as a replacement for refined grain products or red or processed meats, which would avoid increasing caloric intake."​

Rates of type 2 diabetes have tripled in the US in the last 30 years and in Europe incidence of the disease is growing rapidly. A growing database of clinical studies indicates that part of the beneficial effect of nuts may be due to their fatty acid composition, particularly when they replace food sources of saturated fatty acids, as well as refined carbohydrates, in the diet.

Peanuts contain mainly good unsaturated fat and are low in saturated fat, characteristics which are associated with lower risk of type 2 diabetes. Many peanut butters contain a high percentage of peanuts, have a very small amount of salt and sugar for taste, and have undetectable levels of trans fats even though labels list partially hydrogenated oil as a minor ingredient.

Nuts also contain fibre and magnesium which decrease insulin resistance and have been inversely associated with risk of type 2 diabetes. Peanuts have more plant protein than any other nut. They are also rich in vitamin E, folate, potassium, zinc, phytosterols and antioxidants, which are thought to be important to health.

The study is published in the 27 November issue of the Journal of the American Medical Association​.