Daily Handful of Walnuts Linked to Better Diet and Improvements in Some Health Risk Factors

Walnut ingestion in adults at risk for diabetes: effects on body composition, diet quality, and cardiac risk measures. BMJ Open Diab Res Care 2015;3:e000115 doi: 10.1136/bmjdrc-2015-000115

What is the problem and what is known about it so far?

Walnuts are a rich source of essential fatty acids and other nutrients, such as folate and vitamin E. And they have been associated with various health benefits. But, they're high in calories.

Why did the researchers do this particular study?

Researchers wanted to study the effects of walnut intake on weight gain and overall diet quality in people at risk for diabetes.

Who was studied?

Included in the study were 31 men and 81 women, who were aged between 25 and 75 years, all at high risk of developing diabetes.

How was the study done?

The researchers randomly assigned 112 people to either following a diet with dietary counseling designed to curb calorie intake, or to one without. Within these two groupings, participants were randomly assigned to the daily inclusion of 56 g (2 oz) of walnuts in their diet or the complete avoidance of walnuts for a period of six months. Their height, weight, BMI, waist circumference, blood pressure, cholesterol, fasting blood glucose, and HbA1c (glycated haemoglobin), which gives an indication of average blood glucose levels over time, were assessed at the start of the trial, and then again after 3, 6, 12 and 15 months. Dietary intake was similarly assessed at these time points.

What did the researchers find?

After taking account of influential factors, such as age, calorie and fatty acid intakes, and the amount of regular exercise, the analysis indicated that adding walnuts to the daily diet was associated with improved diet quality. Total and "bad" (LDL) cholesterol also fell significantly among those who ate walnuts every day. Body fat significantly increased on the walnut-rich diet, when eaten in the absence of calorie restriction, but waist circumference fell significantly when combined with calorie restriction. The addition of walnuts to the diet had no impact on blood pressure, fasting blood glucose, or "good" (HDL) cholesterol, and HbA1c increased on both types of diet, regardless of dietary counseling.

What were the limitations of the study?

The group studied was not very diverse in terms of race/ethnicity, and there were many more women than men. More study is needed in diverse groups of people, including an equal amount of men and women, to see if the results are the same.

What are the implications of the study?

Eating a daily handful of walnuts is linked to better overall diet quality and an improvement in certain diabetes risk factors among people at high risk of diabetes.