Tree Nuts May Reduce Metabolic Syndrome Risk

Diets rich in tree nuts lowered blood sugar and blood fat levels in recent studies

(RxWiki News) Tree nuts are full of various nutrients, including protein, fatty acids, fiber and vitamins, and new research suggests that they may actually help fight disease.

Two recent studies found that eating approximately 50 grams of tree nuts per day decreased and stabilized levels of blood fats and blood sugar.

The researchers concluded that a diet rich in tree nuts could help people with diabetes or metabolic syndrome control their conditions.

"Ask your dietitian if you should eat more tree nuts."

The lead author of both studies was John L. Sievenpiper, MD, of the Clinical Nutrition and Risk Factor Modification Centre at St. Michael's Hospital in Toronto, Ontario, Canada.

Dr. Sievenpiper and team explained that tree nuts include almonds, Brazil nuts, cashews, hazelnuts, macadamia nuts, pecans, pine nuts, pistachios, walnuts and chestnuts. They are high in unsaturated fats (known as "good" or "healthy" fats).

One of the reviews included 12 studies published through April 2014 with 450 participants total. These studies compared HbA1c and fasting blood sugar levels in patients with diabetes who ate diets rich in tree nuts versus diets without tree nuts.

HbA1c is a test that measures a person’s average blood sugar level over the course of three months, and fasting blood sugar measures a person’s blood sugar level after not eating anything for eight hours.

The average amount of tree nuts in the diets in this first study was 56 grams, and the average follow-up time in each study was eight weeks.

The findings showed that the participants who ate the diets rich in tree nuts were able to significantly lower their HbA1c and fasting blood sugar levels compared to the participants who ate diets without tree nuts.

The researchers said these findings suggest that people with diabetes could help control and stabilize their condition (through controlling and stabilizing their blood sugar level) by including tree nuts in their diets.

The second review included 49 studies published through April 2014 that compared the effects of diets rich in tree nuts versus diets without tree nuts on any of the criteria associated with metabolic syndrome.

Metabolic syndrome describes a group of risk factors that increase a person’s risk for heart disease, diabetes, stroke and other health problems. Patients are considered to have metabolic syndrome if they present three of the following risk factors: large waist size, high levels of fats in the blood, low levels of "good" cholesterol, high blood pressure or high fasting blood sugar.

The second study included 2,226 participants who were either healthy or had dyslipidemia (abnormal amount of fats in the blood), metabolic syndrome or diabetes.

The average amount of tree nuts included in the tree nut-rich diets was 50 grams per day.

The findings showed that a diet rich in tree nuts significantly lowered participants’ HbA1c, fasting blood sugar and blood fat levels.

The researchers discovered that eating tree nuts did not have an effect on the participants’ control of their waist size, levels of "good" cholesterol or blood pressure.

In the second study, Dr. Sievenpiper and team determined that the participants saw the best results when they replaced refined carbohydrates (carbs that digest very quickly and lead to surges in blood sugar) with tree nuts, rather than saturated fats.

The study participants in both reviews ate approximately 1 1/2 servings of tree nuts per day on average. The researchers recommended that people who have or are at risk for diabetes or metabolic syndrome include this amount of tree nuts in their daily diet.

The authors mentioned that one serving of tree nuts is about 1/4 cup, or 30 grams, and that people in North America typically do not eat even one serving per day on average.

"Fifty grams of nuts can be easily integrated into a diet as a snack or as a substitute for animal fats or refined carbohydrates," Dr. Sievenpiper said in a press release.

Dr. Sievenpiper said that, despite tree nuts’ high fat content, their healthy unsaturated fats did not cause participants to gain weight.

"Tree nuts are another way people can maintain healthy blood sugar levels in the context of a healthy dietary pattern," he said.

According to the authors, the US Food and Drug Administration determined that tree nuts help reduce the risk for heart disease as well.

These studies were limited by short follow-up periods, different study factors and the overall inability to account for outside factors that may have not been apparent in each data set, the study authors reported.

These studies were published July 29 and 30 in BMJ Open and PLOS ONE, respectively.

Funding for both studies was provided by the International Tree Nut Council Nutrition Research and Education Foundation and the Canadian Institutes of Health Research.

Review Date: 
July 30, 2014