A new study published in the Journal of Nutrition suggests that consuming 1-2 servings of walnuts per week (1/4 cup per serving) was associated with reduced risk of developing impairments in physical function, which helps enable older women to maintain independence throughout the aging process.
This paper emphasized that overall diet quality, rather than individual foods, may have a greater impact on reducing risk of physical function impairments. Specifically, diet quality traits most associated with reduced rates of incident physical impairment were higher intake of fruits and vegetables; lower intake of sugar-sweetened beverages, trans fat, and sodium; and moderate alcohol intake. Among food components, the strongest relations were found for increased intakes of oranges, orange juice, apples, pears, romaine or leaf lettuce, and walnuts.
"There's a lot of research that looks at specific health conditions in aging, such as diabetes and heart disease, but less attention to research on quality of life and ability to maintain independence with aging," said Dr. Francine Grodstein, ScD, professor of medicine at Brigham and Women's Hospital and Harvard Medical School. "The simple message from this study is that eating an overall healthy diet, including certain foods, such as walnuts and other whole foods, may help women with the ability to do key everyday tasks as they age, like carrying groceries or dressing themselves."
The researchers looked at data from 54,762 women in the Nurses' Health Study, which tracked women for over 30 years. Between 1992 and 2008, the women were asked questions about their physical function, including their ability to perform basic activities of daily living. This new paper prospectively examined the association between the dietary habits of the participants and subsequent impairment in physical function. Diet was assessed using the Alternative Healthy Eating Index (AHEI-2010), a measure of diet quality that incorporates foods and nutrients predictive of chronic disease risk based on scientific evidence.
"These results add to the large body of evidence that outline the many benefits of a healthy diet for women. Additional research is needed to better understand how diet and lifestyle choices can help maintain our health and well-being as we age," said Dr. Grodstein.
There are numerous possible active properties in walnuts that may be contributing factors in providing 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.
Some study limitations should be considered. The sample only included women, so these results may not be generalizable to men. Additionally, participants were not assigned to eat walnuts or other foods, and were just asked about their dietary choices. It is also possible that subjects may have misreported their dietary intake since this information was collected by questionnaires. In addition, because this is an observational study, residual confounding cannot be ruled out (i.e. that other lifestyle habits which are more common in adults who eat walnuts could contribute to the study findings); and, thus, the results should be interpreted with caution.