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Department of nutrition publishes walnut and fish research
School of Public Health nutrition professors published research this spring in the American Journal of Clinical Nutrition comparing the effects of walnuts and fatty fish in the fight against heart disease. The research demonstrates that in healthy individuals, walnuts lower cholesterol more than fish, while fatty fish lower triglycerides. Both can reduce the overall risk of coronary heart disease, with results appearing after only four weeks.
“The practical significance of the study is that eating an easy-to-incorporate amount of walnuts and fatty fish can cause meaningful decreases in blood cholesterol and triglyceride even in healthy individuals,” says lead author and co-principal investigator Sujatha Rajaram, PhD, associate professor of nutrition.
Following the qualified health claim issued by the Food and Drug Administration, the researchers found that incorporating approximately 1.5 ounces of walnuts (42 grams, a handful of whole nuts or about three tablespoons of chopped nuts) into the daily diet lowered serum total cholesterol by 5.4 percent and LDL (bad) cholesterol by 9.3 percent compared to a control diet based on USDA recommendations.
Using American Heart Association guidelines, the researchers also found that a diet including two servings of fatty fish per week (roughly four ounces each as recommended by the AHA for individuals without heart disease) decreased triglyceride levels by 11.4 percent. Additionally, it increased HDL (good) cholesterol by 4 percent, but also slightly increased LDL (bad) cholesterol compared to the control diet. The fish used in this study was salmon.
Associate professor Ella Hasso Haddad, DrPH, was co-principal investigator of the study. Nutrition department chair Joan Sabaté, MD, DrPH, and Alfredo Mejia, DrPH, formerly of the department of nutrition, were also authors of the study publication.
“Both plant- and marine-derived omega-3 fats are cardioprotective, and since they seem to be effective for lowering different risk factors, it would be prudent to include both in the diet,” says Dr. Sabaté.
Dr. Rajaram adds, “Individuals should strive to include a plant source of omega-3 fat in their diet, like walnuts, and also a marine source of omega-3 fat. If fatty fish is not a preferred option for marine-derived omega-3 fat, other options include microalgae oil or DHA-enriched eggs.”
Dr. Rajaram presented this research during LLU’s Fifth International Congress on Vegetarian Nutrition, held in March 2008.
Miriam Yvanovich and her husband, Anthony, were two the study participants. She says the experience was extremely positive.
“My husband and I still eat walnuts and salmon on a weekly basis because the effects of fish and walnut consumption on our health were so compellingly positive,” she says. “We’re thrilled that the results of the study are finally going public so that more people are aware of these amazing health benefits.”
The department of nutrition has significant experience conducting tightly controlled feeding studies among varying populations. This one, conducted with a healthy population, is the fifth study testing the health and nutrition properties of walnuts. This study differs from the previous studies in that it compared a plant source of the omega-3 fatty acid with a marine source, the first study to make this comparison. Subjects were randomly assigned to each of the three diets for four weeks over a 13-week feeding schedule. This gave the researchers a chance to compare the effect of each diet on each participant.
To access the American Journal of Clinical Nutrition manuscript reference doi: 10.3945/ajcn.2009.26736S on the Internet.