Pecans can cut cardiometabolic risk factors in older overweight adults

A study conducted at the Antioxidants Research Laboratory at Tufts University showed that pecan nuts can reduce cardiometabolic risk factors in older and overweight individuals.

The team carried out tests on 24 overweight or obese adults over 45 years old. The subjects were chosen for their high waist-to-hip ratio, with a high level of abdominal fat. The participants were placed on one of two diets with slightly different ratios, and whole nuts were used as the primary source of energy in an otherwise typical low-fibre, high-fat US diet.

The diets were then standardised to ensure each participant received the same level of fibre, as well as maintaining the levels of all other macronutrient levels, such as protein and carbohydrates. Each participant consumed just over 2,000 calories a day.

The meals consisted of 47%-48% of carbohydrates, 15%-16% protein and 35%-36% fat. Both diets included 1.1 servings of fruit and 2.3 servings of vegetables.

While tree nuts like pecans are high in fibre, the fibre intake of the trial diets was around 18g, which is less than the recommended amount of 25g-30g but is representative of typical US consumption.

The study was designed to be double-blind and placebo-controlled, meaning the presence of pecans was disguised. They were often blended into the meals prepared for the test subjects and participants could only eat food prepared at the Tufts clinic.

The experiment consisted of two four-week feeding periods, with a two week washout phase in between.  Participants were asked to continue with the high-fat, low-fibre diet during the washout period to maintain a fair test.

The team found significant improvements across several parameters under the pecan diet, writing: “After four weeks on a pecan-rich diet, changes in subjects​’​ serum insulin, insulin resistance (HOMA-IR) and beta cell function (HOMA-​β​) were significantly greater than on the control diet.”

The pecan diet also reduced total and LDL cholesterol levels in the participants.

The researchers added: “Other bioactive compounds present in nuts, including micronutrients, fibre, and phytochemicals, may also contribute to their cardio-protective effect by reducing inflammation, improving vascular reactivity as well as fasting glucose and insulin sensitivity, and by lowering oxidative stress status.

“Therefore, well-controlled studies focusing on the additive and/or synergistic effects of the nut constituents present in the whole food matrix, and the degree to which they confer a health benefit and prevent chronic disease, are warranted.”

In a previous study, Tufts University researchers found that pecans can reduce cardiometabolic risks when substituted into a high-fibre, low-fat diet.

Lead author Dr Diane McKay said: “Pecans are naturally high in monounsaturated and polyunsaturated fats, so replacing a portion of the saturated fat in the diet with these healthier fats can explain some of the cardio-protective effects we observed.”

“But pecans also contain a number of bioactive plant compounds as well as vitamins and essential minerals that all likely contributed to this benefit. What’s really interesting is that just one small change–eating a handful of pecans daily–may have a large impact on the health of these at-risk adults.”