Could a handful of walnuts a day really keep the doctor away? For patients at risk for type 2 diabetes, perhaps.
A new study found that eating a handful of walnuts every day may be linked to better diet quality overall and improvements in certain type 2 diabetes risk factors among high-risk patients.
Patients in this study who were given walnuts every day for six months saw improvements in blood vessel function and LDL (or "bad") cholesterol levels compared to those who were not given walnuts. Poor blood vessel function and high levels of LDL cholesterol are risk factors for type 2 diabetes.
Type 2 diabetes is a chronic condition that affects how the body processes blood sugar. If left untreated, this condition can lead to long-term health problems like heart and kidney disease.
For this study — which was funded by the California Walnut Commission, making for a big potential conflict of interest — a team of researchers led by David L. Katz, MD, MPH, a nutritionist at Yale University, looked at 112 adult patients who were at high risk for developing type 2 diabetes.
These patients were randomly assigned to a diet either with or without dietary counseling to reduce calorie intake. Within the two groups, patients were also randomly assigned to either add 2 ounces of walnuts to their daily diets or to completely avoid walnuts for six months. After three months, the groups were reversed.
Height, weight, body mass index (BMI), waist circumference, blood pressure, cholesterol, and blood sugar measurements were taken at the study's start and again after three, six, 12 and 15 months.
Diet quality was also assessed at these times using the 2010 Healthy Eating Index, which looks at the relationships between food and health-related outcomes.
After accounting for potentially confounding factors, Dr. Katz and team found that the addition of walnuts to the diet was tied to improved diet quality overall. A walnut-rich diet was also tied to improved blood vessel function and lower LDL cholesterol levels in these patients — regardless of dietary counseling. No impact on blood pressure, blood sugar or HDL ("good") cholesterol levels was found.
Patients' BMIs were found to increase significantly on the walnut-rich diet in the absence of calorie restriction, but decrease significantly when combined with calorie restriction.
While walnuts are rich in essential fatty acids and other nutrients, Dr. Katz and team noted that they are also high in calories.
This study was published Nov. 23 in the journal The BMJ.
Dr. Katz disclosed compensation from the California Walnut Commission.