Walnuts May Protect Against Diabetes and Heart Disease in Those at Risk

Walnuts and Diabetes

Researchers are becoming more convinced that the walnut is a nutritional powerhouse that can protect the body against disease. A new finding, from a team at Yale-Griffin Prevention Research Center, suggest that adding walnuts to the diet can protect the blood vessels in those who are overweight, perhaps preventing the development of diabetes and heart disease.

The endothelium is a thin layer of cells that lines the interior surface of blood and lymphatic vessels. They provide many important functions, including assisting with the control of blood pressure and preventing blood clotting. Endothelial dysfunction, or the loss of proper endothelial function, is a hallmark for vascular disease and is considered a key early event in the development of atherosclerosis, a risk factor for heart attack.

Impaired endothelial function is often seen in those with coronary artery disease, diabetes, hypertension, hypercholesterolemia, and in smokers.

Dr. David Katz, Director of the Yale-Griffin Prevention Research Center, and colleagues studied the effects of walnuts on a sample of 46 adults aged 30-75 who had a BMI of greater than 25 – considered overweight – and a waist circumference exceeding 40 inches in men and 35 inches in women, suggesting abdominal obesity. All were non-smokers, but had at least one additional risk factor for metabolic syndrome, a precursor of diabetes and cardiovascular disease.


One group was assigned to a walnut-enriched diet while the other maintained a control diet void of walnuts. Those chosen for the walnut diet consumed 56grams of shelled, unroasted English walnuts per day as a snack or with a meal. This is approximately ½ cup, or about 2 servings.

The walnut-eaters did not experience weight gain, a concern because of the high caloric content of nuts. They did note several improvements to endothelia function, including improved flow-mediated vasodilatation (FMD) which decreases blood pressure. They also noted improvements to serum lipids (cholesterol levels), fasting glucose and insulin.

"We know that improving diets tends to be hard, but adding a single food is easy," says Dr. Katz. "Our theory is that if a highly nutritious, satiating food like walnuts is added to the diet, there are dual benefits: the benefits of that nutrient rich addition and removal of the less nutritious foods."

Here are a few ideas for adding walnuts to your diet:
• Mix crushed walnuts into plain yogurt and top with maple syrup.
• Add walnuts to salads or healthy sautéed vegetables.
• Purée walnuts, cooked lentils and your favorite herbs and spices in a food processor. Add enough olive or flax oil so that it achieves a dip-like consistency.
• Add walnuts to your favorite poultry stuffing recipe.
• To roast walnuts at home, do so gently—in a 160-170°F oven for 15-20 minutes—to preserve the healthy oils.
• Make homemade walnut granola: Mix together approximately 1/2 cup of honey, 3 to 4 tablespoons of blackstrap molasses, a tablespoon of vanilla, a dash of salt, and a teaspoon each of your favorite spices, such as cinnamon, ginger and/or nutmeg. Place 6-8 cups of rolled oats in a large bowl and toss to coat with the honey-blackstrap mixture. Then spread on a cookie sheet and bake at 275°F (135°C) for 45 minutes. Cool and mix in 1/2 to 1 cup of walnuts.

Journal Reference:
David L Katz, et al. Effects of Walnuts on Endothelial Function in Overweight Adults with Visceral Obesity: A Randomized, Controlled, Crossover Trial. Journal of the American College of Nutrition, 2012; 31 (6): 415 DOI: 10.1080/07315724.2012.10720468