Ah, Nuts! Pistachios May Lower Diabetes Risk in Those With Prediabetes

Ah, Nuts! Beneficial effect of pistachio consumption on glucose metabolism, insulin resistance, inflammation, and related metabolic risk markers: a randomized clinical trial, by Hernández-Alonso and colleagues. Diabetes Care 2014;37:3098–3105

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

Before people get type 2 diabetes, they almost always have prediabetes—blood glucose levels that are higher than normal but not high enough to be diabetes. Sometimes called “impaired glucose tolerance” or “impaired fasting glucose,” prediabetes affects more than 86 million U.S. adults. Without treatment, 15 to 30 percent of people with prediabetes will get diabetes within 5 years. Taking steps to control or reverse prediabetes can lower a person’s chances of getting not only diabetes, but also heart and blood vessel diseases, and other conditions such as eye, kidney, and nerve diseases. Adopting a healthy lifestyle, including eating healthful foods, is an important part of controlling prediabetes. Studies have shown that eating various types of nuts can help to prevent heart disease. Less is known about whether eating nuts can lower a person’s chance of getting diabetes. Studies on the topic so far have had mixed results, but few have focused on pistachio nuts, and none have been done in people with prediabetes.

Why did the researchers do this particular study?

The researchers wanted to find out how regularly eating pistachio nuts as part of a healthy diet might improve the ways that glucose (sugar) and insulin (a hormone that helps the body control blood glucose levels) are processed in people with prediabetes.

Who was studied?

The study included 54 Spanish adults with prediabetes. 

How was the study done?

Participants were divided into two groups. Both groups followed a normal healthy diet for 2 weeks. Then, for the next 4 months, one group followed a diet that included 2 ounces of pistachio nuts per day, and the other group followed a similar diet without pistachio nuts. All participants then ate a normal diet for another 2 weeks. Finally, for another 4-month period, the two groups crossed over, eating the opposite diet from the one they had followed during the first 4-month period. Researchers collected health information and laboratory test results at 1) the start of the study, 2) after the first 2 weeks of the normal diet, and then 3) every month throughout the study.

What did the researchers find?

Glucose and insulin levels and other signs of insulin resistance were lower after participants followed the diet with pistachio nuts than after they followed the diet without nuts. Several other measures linked to diabetes and heart disease risk also improved after the pistachio nut diet. In addition, participants had higher levels of glucagon-like peptide1, a hormone that helps to control glucose levels, after following the diet with pistachio nuts. 

What were the limitations of the study?

This study focused on people with prediabetes, so its results may not apply to healthy people or to those individuals with diabetes.

What are the implications of the study?

Eating a handful of pistachio nuts per day as part of a healthy diet may help people with prediabetes improve their condition and avoid diabetes and other diseases. Because nuts are high in calories, people who are concerned about weight gain should adjust other parts of their diet so they can add nuts without boosting their total daily calories.

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