Eating a handful of pecans every day for four weeks improved certain markers of cardiometabolic disease risk, including insulin sensitivity, among a group of overweight and obese adults with excess abdominal fat, according to a new study from researchers at Tufts University published in the peer-reviewed scientific journal Nutrients.
 
Cardiometabolic risk is a relatively new term that refers to the chances of developing cardiovascular and metabolic diseases, including type 2 diabetes and metabolic syndrome. Collectively, these conditions are the leading cause of preventable deaths worldwide.
 
Previous studies on pecans examined blood lipids changes. In addition to those markers, researchers claimed this is the first study to assess the effects of pecan consumption on other markers of cardiometabolic risk, including insulin resistance, glucose, insulin levels, and beta cell function, which is a measure of the pancreas' ability to produce and secrete insulin to help control blood sugar levels.
 
"Pecans are naturally high in unsaturated fats, including oleic and linoleic acids, so replacing a portion of the saturated fat in the diet with these more beneficial fats may explain some of the changes we observed, but bioactive compounds might also have contributed," said lead researcher Diane L. McKay, PhD. "Obesity, coupled with insulin resistance increases insulin demand and hyperfunction of pancreatic beta cells resulting in eventual dysfunction. Our results suggest nutrients in pecans may play a role in supporting normal insulin responses in adults who are overweight or obese, although we do not know the mechanism."
 
In addition to the monounsaturated and polyunsaturated fats, pecans also contain fiber and essential minerals (copper, magnesium, and zinc), and have bioactive compounds, such as flavonoids (10 mg per ounce) and plant sterols (36 mg per ounce), that may play a role.
 
Methodology
In this randomized, placebo-controlled feeding study of 26 overweight or obese men and women (21 men and 5 women, ages 45 and older), the research team compared the effects of a pecan-rich diet to a control diet that contained the same amount of calories, fat, and fiber, but without the pecans. The control diet resembled the average American diet—low in fruit, vegetables, fiber and omega-3 fatty acids, and high in nutrient-poor, calorie-dense foods.
 
All meals were provided to the subjects, including the pecans (about 1.5 ounces a day or 15% of total calories), which were ground and incorporated into various recipes, such as muffins, meatballs and coating for chicken.
 
A double-blind, crossover study design was used for the intervention. The study participants followed either the pecan diet or the control diet for four weeks. A two-week washout period took place before the groups switched to the opposite diet for four weeks. Evaluations were conducted at the start of the study and at the end of each four-week feeding period.   
 
Results
After four weeks on the pecan-rich diet, overall outcomes showed the study participants had statistically significant greater reductions in serum insulin, insulin resistance and pancreatic beta cell function, compared to the control diet. Although both total and LDL cholesterol were lower following the pecan diet, their magnitude of change compared with the control diet was not statistically significant—which the authors said may be due to the lower dose of pecans compared with other tree nut studies or the higher prevalence of obesity among the participants. Other markers of cardiometabolic risk, including serum glucose, systolic blood pressure, and diastolic blood pressure also had greater reductions among participants on the pecan diet compared to the control diet, but these results did not reach statistical significance.
 
The researchers also simultaneously assessed five clinically relevant markers of cardiometabolic risk (including blood lipids, glucoregulation, and insulin), and found that the pecan diet had a statistically significant effect on insulin related markers associated with cardiometabolic risk. Additionally, there were subgroup differences noted by gender and glucose levels that modified the effects of the pecan diet.
 
"Our study suggests that making one small change, such as eating a handful of pecans daily and displacing saturated fat in the typical American diet has the potential to make a difference," said McKay. "The limitation of our study is its small size and duration. We found that consuming pecans improved certain markers in some at-risk individuals, but larger and longer studies are needed to determine whether pecans could reduce risk for cardiovascular disease and type 2 diabetes. More research could also reveal the specific effects of bioactive compounds in pecans and their potential mechanisms of action."