University of Minnesota School of Public Health (SPH) researchers who reviewed data from the CARDIA study, including 20 years of diet history and 30 years of physical and clinical measurements, have found that participants who ate walnuts early on in life showed a greater likelihood for being more physically active, having a higher quality diet and experiencing a better heart disease risk profile as they aged into middle adulthood.
Their findings, published in Nutrition, Metabolism, & Cardiovascular Diseases, note that a possible explanation for the results could be due to the unique combination of nutrients found in walnuts and their effect on health outcomes.
Walnuts are the only tree nut that is a source of omega-3 alpha-linolenic acid, which may play a role in heart health, brain health and healthy aging. Additionally, one serving of walnuts contains a variety of other important nutrients to support overall health including protein, fiber, magnesium and a variety of antioxidants.
"Nut consumers showed an advantage in relation to diet quality but walnut consumers appear to have a better heart disease risk factor profile than the other groups, even after accounting for overall diet quality," said Lyn Steffen, an associate professor in SPH and author of the study.
The study found:
- Walnut consumers had higher self-reported physical activity scores than other nut and no nut consumers.
- Compared to other nut consumers, eating walnuts was linked with a better heart disease risk profile, including lower BMI and blood pressure.
- Eating walnuts was associated with less weight gain over the study period, and fewer participants who ate walnuts were classified as obese compared to other nut and no nut consumers.
- Compared to no nut consumers, walnut consumers had significantly lower fasting blood glucose concentrations while other nut consumers had higher LDL-cholesterol.
- Including walnuts in the diet during young adulthood was linked to a higher-quality diet in middle adulthood.
"Interestingly, walnut consumers had a better cardiovascular disease risk factor profile such as lower body mass index, weight gain, waist circumference, blood pressure and triglyceride concentration compared to other nut consumers," said So-Yun Yi, a Ph.D. candidate at SPH. "Our study findings support the health claim of walnuts to be part of a healthy diet."
While these results are positive and confirm earlier work from the CARDIA study on the health benefits of walnut intake, randomized controlled clinical trials should be done in other populations and settings to confirm the observations in the current study.
Additionally, some of the outcomes for heart disease risk factors relating to cholesterol and lipids in the current study are inconsistent with previous randomized controlled trials. This could be related to differences in study design, including duration of the study or amount of nut intake. The researchers did not isolate other specific nuts in their database, so findings do not reflect benefits, or lack of benefits, related to other specific nuts.
CARDIA is supported by the National Heart, Lung, and Blood Institute and by the California Walnut Commission.
