Initial findings from the Walnuts and Healthy Aging (WAHA) study presented at Experimental Biology 2016 (EB) indicate that daily walnut consumption positively impacts blood cholesterol levels without adverse effects on body weight among older adults. The WAHA study is a dual site two-year clinical trial conducted by researchers from the Hospital Clinic of Barcelona and Loma Linda University and is aimed at determining the effect of walnuts on age-related health issues.
"Given walnuts are a high-energy food, a prevailing concern has been that their long term consumption might be associated with weight gain," said Dr. Emilio Ros, director of the Lipid Clinic, Endocrinology & Nutrition Service at the Hospital Clinic of Barcelona. "The preliminary results of the WAHA study demonstrate that daily consumption of walnuts for one year by a sizable cohort of aging free-living persons has no adverse effects on body weight. They also show that the well-known cholesterol-lowering effect of walnut diets works equally well in the elderly and is maintained in the long term. Acquiring the good fats and other nutrients from walnuts while keeping adiposity at bay and reducing blood cholesterol levels are important to overall nutritional well-being of aging adults. It's encouraging to see that eating walnuts may benefit this particular population."
Researchers instructed 707 healthy older adults to add daily doses of walnuts (~15% of caloric intake) to their typical diet or to consume their usual diet without nuts. Participants were not given advice on total calorie and macronutrient intake or food substitution for walnuts. After one year, the study found that both diets had minimal effect on body weight, triglycerides, and HDL cholesterol. However, the walnut-diet resulted in significant LDL cholesterol reductions compared to the control, nut-free diet.
"As we continue the WAHA study, we will assess how walnut consumption may affect, among other outcomes, cognitive decline and age-related macular degeneration, conditions that were major public health concerns," said Dr. Ros.
Taking place April 2-6 in San Diego, the annual EB meeting attracts an international audience of over 14,000 leading research scientists and exhibitors. Additional new research abstracts presented at EB suggest walnuts may have the potential to positively affect several important health factors, including gut health, hunger and satiety, and metabolic health. The following summaries share these findings:
- Gut Health: Food choices and the gut microbiome play an important role in human health. A recent study conducted by researchers at the Agricultural Research Service, United States Department of Agriculture (USDA) examined how the heart health benefits of walnuts may be linked to gut health among 18 healthy adults.2 Study results show that daily consumption of 1.5 ounces of walnuts significantly affects the bacteria in the human gut in a way that is favorable to decreasing inflammation and cholesterol, which are two known indicators of heart health. These results help further the understanding of the heart health benefits of consuming nuts, including walnuts.
- Hunger and Satiety: For the first time, researchers from the University of Georgia have shown that the types of fat eaten on a daily basis can alter long-term appetite responses, such as hunger and satiety.3 After consuming high-fat meals rich in saturated fat, 18 sedentary adults of normal weight were randomly assigned to consume either a diet high in polyunsaturated fat or a control diet for the next seven days. Researchers found that consuming a diet high in polyunsaturated fat after meals rich in saturated fat favorably alters hunger and satiety markers. Walnuts are a great option for getting more polyunsaturated fat, with 13 grams per ounce.
- Metabolic Health: A recent animal study conducted by researchers at Oregon State University looked at the addition of walnuts and polyphenol-rich foods to a typical high-fat Western diet to understand the impact on metabolic health in male mice.4 Results showed that a walnut-diet supplemented with polyphenol-rich foods such as raspberries, cherries or green tea may help reduce inflammation. Mice that consumed walnuts on their own or in combination with polyphenol-rich foods also demonstrated significant effects on factors related to metabolic syndrome, in addition to changes in both liver gene expression and metabolite levels consistent with an improved metabolic state. As this study was performed on animals, findings cannot yet be applied to humans.
Bioactive components or synergistic effects of walnuts may be contributing factors in providing these health benefits. Walnuts are unique among nuts in that they are primarily composed of polyunsaturated fat (13 grams per ounce), which includes alpha-linolenic acid (ALA), the plant-based omega-3 fatty acid. They are the only nut to contain a significant amount of ALA with 2.5 grams per one ounce serving.
Scientific conclusions cannot yet be drawn from abstracts presented at EB 2016, but these findings help advance the understanding of potential benefits of eating walnuts as part of a healthy diet.