beneficial relationship between
walnuts and heart disease
(BETHESDA, MD) - Walnuts are one of the oldest known tree foods, with historical references dating back to Persia in 7000 BC. The walnut is a good source of Vitamin E, and is a high-energy and high-fat food. Some fats and fatty acids are known to increase cholesterol levels leading to an increased risk of coronary heart disease (CHD). Major studies have found that the high-fat walnut may be an exception to this rule. Is there enough evidence to support a claim that walnut consumption can reduce CHD? An exhaustive review of the data by a team of independent researchers concludes that walnuts are indeed heart friendly. These findings are published in the May 2002 supplemental edition of the Journal of Nutrition.
The results are contained in the study entitled, "The Scientific Evidence for a Beneficial Health Relationship Between Walnuts and Coronary Heart Disease." It was conducted by a panel of experts affiliated with the Life Sciences Research Office (LSRO). For nearly a half-century, the Maryland-based LSRO has been providing expert "second opinion" reports and analyses to governmental agencies and companies involved in the food, science and biomedical fields.
LSRO's Expert Panel was comprised of Elaine B. Feldman, Ph.D., Department of Medicine and Physiology and Endocrinology, Medical College of Georgia; Jacqueline DuPont, Ph.D., Department of Nutrition, Food and Exercise Studies, Florida State University; Bruce J. Holub, Ph.D., Department of Human Biology & Nutritional Sciences, University of Guelph; David M. Klurfeld, Ph.D., Department of Nutrition and Food Science, Wayne State University; and Robert H. Knopp, MD, Division of Metabolism, Endocrinology and Nutrition, University of Washington.
The panel's investigation consisted of two phases:
Interventional studies: In this phase the panel examined five controlled, peer-reviewed studies conducted in humans. These intervention studies were examined for their strength and weakness in design; the quality, consistency and magnitude of the effect; the strength and relevance of the association of walnuts with the study's outcome; and other factors.
Observational studies: Large scale observational studies were also part of the data review process. The Adventist Health Study, the Nurses' Health Study, the Iowa Women's Health Study and the Physicians Health Study were included.
Weight of Evidence
In evaluating the scientific evidence to support a health benefit claim, the reviewers used the US Food and Drug Administration's approach for significant scientific agreement standards in identifying a relationship between a food substance and a disease or health-related condition.
Based on the examination of the data and the weight of evidence guideline, the Expert Panel found that:
- walnuts, as part of a heart-healthy diet, lower blood cholesterol in humans;
- walnuts are unique compared to other nuts because the predominant fatty acids they contain are n-6 (linoleate) and n-3 (linolenate) polyunsaturated compounds, rather than the monosaturated fatty acids present in most nuts. Walnuts, like other nuts, have a high fat content but are low in saturated fatty acids;
- the clinical dietary intervention studies show that consuming walnuts does not cause a net gain in body weight when eaten as a replacement food;
- intervention studies suggest reduced relative risk of coronary heart disease but are currently inconclusive since only five studies with a limited number of human subjects has been published thus far; and
- the observational studies demonstrate a dose response-related inverse association of the relative risk of coronary heart disease with frequent daily consumption of walnuts and other nuts.
The review panel concluded that the scientific claim about the beneficial relationship between walnuts and CHD is valid. At the same time, they recommend that further studies be undertaken to confirm the b trend lines in the data.
Editor's Note: To schedule an interview with a member of the Expert Panel, please contact Donna Krupa at 703.527.7357 (office), 703.967.2751 (cell) or