For people who may be headed for Type 2 diabetes, regularly eating pistachios might help turn the tide, according to a new trial from Spain.
People with so-called prediabetes have blood sugar levels higher than normal but not yet in the diabetes range. If they do nothing, 15 to 30 percent will develop diabetes within five years, according to the U.S. Centers for Disease Control and Prevention.
In the new Spanish study, people with prediabetes who ate about two ounces of pistachios daily showed significant drops in blood sugar and insulin levels and improvements in insulin and glucose processing. Some signs of inflammation also dropped dramatically.
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Although the trial specifically involved pistachios, many previous studies have found encouraging evidence that eating nuts may be linked to a lower risk of heart disease and lower cholesterol, the authors write in Diabetes Care.
The study team divided 54 prediabetic adults into two groups. Both groups were instructed to keep to a calorie-regulated diet with 50 percent of energy from carbohydrates, 35 percent from fat and 15 percent from protein, using provided menus and seasonal recipes.
One group was given 57 grams of pistachios, about two ounces, daily to add to their diets. To match those calories, the comparison group added olive oil and other fats for the four months of the study.
By the end of the study, fasting blood sugar levels, insulin and hormonal markers of insulin resistance had decreased in the pistachio group while they rose in the comparison group.
Participants’ weight did not significantly change by the end of the study in either group. But glucose-use by immune cells involved in inflammation, as well as circulating inflammatory signaling molecules both dropped in the pistachio group, the authors note.
“Although pistachios were examined in this work, I believe that any beneficial effects on glucose metabolism are shared by all nuts, as they have a general composition with lots of bioactive compounds liable to beneficially affect biological pathways leading to insulin resistance and diabetes,” said Dr. Emilio Ros, director of the Lipid Clinic of the Endocrinology and Nutrition Service at Hospital Clínic in Barcelona. He was not part of the new study.
Researchers from the Universitari Hospital of Sant Joan de Reus, in Reus, and the Instituto de Salud Carlos III in Madrid collaborated on the trial, which was funded by American Pistachio Growers and Paramount Farms.
“The nut industry always supports clinical or experimental studies with their nuts, otherwise no such studies would be carried out,” Ros said by email.
He believes the evidence is strong enough for people with prediabetes to add pistachios, or other nuts like peanuts, to their diet, and recommends about "a handful" per day, or around one serving.
“This particular study builds on previous research on pistachios,” said Dr. Joan Sabate, professor of nutrition and epidemiology at the School of Public Health at Loma Linda University in California.
Sabate has also researched nuts, principally walnuts, but was not involved in the new study.
“There are some indications that eating pistachios on a regular basis lowers fasting glucose and lowers insulin and hormone ratio, which is particularly relevant in prediabetic subjects because unless they do a change in lifestyle they will end up being diabetic,” he said by phone.
“So the fact that eating nuts on a regular basis seems to improve some of the critical parameters is very relevant.”
Results with almonds and walnuts have been similar, he said.
Pistachio allergies are rare, but nut allergies generally would be the only deterrent to adding them to the diet, Ros said.
Pistachios are very rich in energy, he noted, so it would be better to incorporate the nuts into the diet without increasing your total calorie intake.
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