The study, led by Carol E. O’Neil, PhD, MPH, RD, of Louisiana State University in Baton Rouge, included 13,292 adults participating in the 1999-2004 National Health and Nutrition Examination Survey. For the study, individuals who ate at least one quarter of an ounce of nuts per day were considered nut consumers. Those who ate less than this were considered nonconsumers of nuts.
The prevalence of nut consumers was 18.6% and 21% among subjects aged 19-50 years and 51 years or older, respectively. Nut consumers had a significantly decreased mean body mass index (27.7 vs. 28.1 kg/m2), mean waist circumference (95.6 vs. 96.4 cm), and mean systolic blood pressure (121.9 vs. 123.2 mm Hg) compared with nonconsumers, the investigators reported in the Journal of the American College of Nutrition (2012;30:502-510). In addition, nut consumers had a lower percentage of individuals with two risk factors for metabolic syndrome: hypertension (31.5% vs. 34.2%) and low HDL (29.6% vs. 34.8%).
Tree nut consumers had a significantly lower prevalence of four risk factors for metabolic syndrome: abdominal obesity (43.6% vs. 49.5%), hypertension (31.4% vs. 33.9%), low HDL (27.9% vs. 34.5%), and high fasting glucose (11.4% vs. 15%). They also had a significantly lower prevalence of metabolic syndrome (21.2% vs. 26.6%).
The investigators defined nuts as peanuts, peanut butter, tree nuts (almonds, Brazil nuts, cashews, walnuts, pecans, pistachios, macadamias, pine nuts, and hazelnuts), or tree nut butters. All nuts are low in saturated fatty acids and are rich sources of monounsaturated fatty acids, the authors observed. Nuts are high in dietary fiber, vitamin E, folate, magnesium, copper, selenium, and potassium. They also provide phytonutrients, including resveratrol, flavonoids, proanthocyanidins, and phenols.
Although nut consumption in the study population was low, it was associated with better health risk parameters and, for consumers of tree nuts, a lower prevalence of metabolic syndrome compared with nonconsumers, the authors noted. “On a population basis, these lower risk factors could lead to better health and lower long-term health care costs,” they concluded.
Their study, along with the preponderance of other evidence, suggests that consumption of peanuts and tree nuts, and tree nuts alone, should be encouraged by health professionals, especially registered dietitians, the author noted.
“This study also raises the possibility that future dietary recommendations should consider a separate nut category to encourage consumption.”