Pecans vs cardiometabolic disease

Pecans are a common ingredient, adding a health component, along with a nice crunch, to baked goods, on-the-go salads, and confectionery. In Asia, the biggest markets for pecans (sourced mostly from the US which dominates global production) are China and Vietnam.

Food manufacturers can highlight their use of pecans in light of a recent study.

According to Tufts University researchers, consuming a handful of pecans daily for four weeks goes a long way in improving some markers of cardiometabolic disease risk, as they have shown in a study of overweight and obese adults with excess abdominal fat. Their findings are published in the peer-reviewed scientific journal Nutrients.

Previous research on pecans examined blood lipid changes alone. Tufts scientists took it further by studying the effects of pecan consumption on 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.

American diet vs pecan-rich meals

Subjects, 26 obese men and women, 45 years and older underwent a randomized, placebo-controlled feeding study comparing a pecan-rich diet to a control diet that contained the same amount of calories, fat, and fibre, 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.  

A small change makes a big impact

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 say 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 lead researcher Diane L. McKay, Ph.D. “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.”

What is in pecans?

“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 Dr McKay. “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 fibre and essential minerals (copper, manganese, 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.

Source McKay DL, Eliasziw M, Oliver Chen CY, Blumberg JB. A pecan-rich diet improves cardiometabolic risk factors in overweight and obese adults: a randomized controlled trial. Nutrients. 2018; 10:339. 

The study was supported by the U.S. Department of Agriculture (USDA), Agricultural Research Service and the National Pecan Shellers Association (NPSA). NPSA also provided the pecans for the intervention, yet had no role in the design of the study, or in the collection, analyses or interpretation of the data.