Nuts are well known for their ability to pack a lot protein and other nutrients into a tiny space. But isn't all that goodness outweighed by all the fat they also come loaded with? A new study published by the British Medical Journal — which can be found online in BMJ Open Diabetes Research & Care — suggests that eating a handful of walnuts a day could improve overall diet quality and can help those at high risk of diabetes.
Walnuts are a rich source of essential fatty acids, folate and vitamin E. They also come with a healthy dose of omega-3 fatty acids. Just one cup can provide around a quarter of the recommended daily value of protein and a fifth of the dietary fiber you need. However, they are also high in calories — that one cup also supplies 80% of the fat you need — and in the past this has meant concern over the contribution they make to weight gain if not balanced out by a calorie controlled diet.
Researchers took a group of 112 participants and divided them randomly into two groups. The first group followed a meal plan with dietary counseling — designed to curb calorie intake — while the second went without the guidance. Throughout the trial, random participants in each group were given either a daily treat of 2 ounces (or one quarter of a cup) of walnuts in their diet or were made to have none for a period of six months.
The 31 men and 81 women included in the research were aged between 25 and 75 and were all known to be at high risk of developing diabetes. Measurements of height, weight, BMI, waist circumference, blood pressure, cholesterol as well as fasting blood glucose and glycated hemoglobin levels were all taken at the start of the trial, and then again after 3, 6, 12 and 15 months. The team also looked at each of the participants' dietary intake at these time points.
After taking account of factors such as age, calorie and fatty acid intakes as well as the amount of regular exercise taken, the study seems to show that adding walnuts to a daily diet can result in an improvement in diet quality. Doctors know that better diets mean a healthier forecast for the cardiovascular system and a lower risk of developing problems with long-term health problems.
The researchers found, after six months, an improvement in blood vessel cell wall function and better "bad" (or LDL) cholesterol levels in those with the walnut enhanced diet, though no change in blood pressure or blood glucose levels. The walnut-rich diet was also found to be associated with "significantly improved" endothelial cell function. These cells line the walls of all blood vessels and form a permeable barrier between the blood and other body tissues, enabling certain chemicals and blood gases to pass through.
The scientists also found, however, that endothelial function and cholesterol levels also improved among those following the diet that excluded walnuts. This may be due, they say, to the placebo effect. The overall level of cholesterol (including "bad" LDL cholesterol) also dropped for those who ate walnuts every day and, though body fat significantly increased for those who ate walnuts but were given no dietary counseling, measurements of waist circumference fell significantly when combined with calorie restriction.
The team says there saw little or no impact on blood pressure, fasting blood glucose or "good" HDL cholesterol levels whereas glycated hemoglobin increased on both types of diet, irrespective of any dietary counseling. Although this initial study was relatively small, the researchers say it may warrant further investigation with more diverse groups of people
"Our data suggest that inclusion of walnuts in the diet, with or without dietary counseling to adjust caloric intake, improved diet quality and may also improve [endothelial function], and reduce total and LDL cholesterol in this sample of adults at risk for diabetes," the researchers conclude.
It's only fair we point out that the study — by academics from the Yale University Prevention Research Center and Griffin Hospital in Derby, Connecticut — was funded by the California Walnut Commission but for those who want to pursue a healthy diet, adding nuts (in moderation, as the study suggests) is never a bad idea. It still sounds like promising news. We're big fans of the humble walnut whether it's for breakfast, lunch or dinner.