Can Walnuts Reduce the Risk of Heart Disease?

Want to reduce your risk of heart disease? The California Walnut Commission makes it simple. Eat Walnuts. And the U.S. Food and Drug Administration agrees. Sort of. The following claim is allowed on packages of walnuts. "Supportive but not conclusive research shows that eating 1.5 oz of walnuts per day, as part of a low saturated fat and low cholesterol diet, and not resulting in increased caloric intake may reduce the risk of
coronary heart disease." How do walnuts do this? They are rich in many healthful ingredients such as polyunsaturated fats, antioxidants, fiber and folic acid. It has even been demonstrated that blood levels of total cholesterol, the so-called bad or LDL cholesterol, and triglycerides decrease when walnuts are added to the diet, while levels of the beneficial HDL cholesterol increase. Seems simple. But science is never that simple.

The studies cited by the walnut industry have been largely critiqued for their small numbers or short duration. A typical example is a study conducted in Spain at the Lipid Clinic in Barcelona, where researchers substituted walnuts for about one-third of the calories from olives, olive oil, and other monounsaturated fats in a Mediterranean diet. For the first time Spanish scientists found that a whole food, not its isolated components, demonstrated a beneficial effect on heart health. Walnuts were found to increase the elasticity of arteries by 64 per cent, and to reduce cell adhesion molecules associated with hardening of the arteries by 20 per cent.

And so, many public health professionals are concerned that the new guidelines for claims will prove to be misleading. So where does all this leave the consumer- other than scratching his head in the produce aisle? Well, nuts have notoriously been prey to the mistaken perception that all fatty foods are bad. Health claims on packaging can help clarify that and educate consumers so that they may make informed choices at the supermarket as nutrition science unfolds. But there is still concern. Food producers touting their products’ benefits all over the packaging may result in consumers paying more attention to health claims and less to calories. It is worthwhile noting that despite the many advertisements promoting the genuine benefits of increased fiber consumption, fiber intake has remained static since 1990. What has increased since then is calorie consumption. The consumption of 4000 calories a day, not unusual for many people, is not healthy, no matter what their source! Additionally, many health claims placed on produce packaging are presented as “quick fixes”. Be very wary. One food isn’t going to make a significant difference. In the end, it’s everything you eat that really counts. But given that food labeling remains under the control of the FDA in the U.S., consumers can rest assured that producers will be restricted to making claims that are, at minimum, scientifically qualified.

In Canada, we are more restrictive and such claims are not allowed. The clever consumer will however recognize that health claims are most often used as marketing tools and that good health cannot come wrapped neatly in any one package.

Joe Schwarcz, McGill, Office for Science & Society