Although walnuts were considered a valuable source of calories and nutrients for thousands of years, nuts generally fell out of favor with health-conscious Americans during the low-fat diet craze of the 1980s. Today, walnuts are recognized as a nutrient-dense source of beneficial fatty acids, protein, dietary fiber and antioxidants. According to the U.S. Food and Drug Administration, eating a handful of nuts every day can help protect against heart disease.
A 1-ounce portion of shelled walnuts constitutes a single serving. This is also the standard amount for an individual serving of other kinds of nuts and edible seeds, including almonds, pistachios and sunflower seeds. According to the U.S. Department of Agriculture, it takes about seven whole walnut kernels, or 14 halves, to make a 1-ounce serving of walnuts. One cup of shelled walnut halves contains about 50 pieces, meaning a 1-ounce serving of halved walnuts is just over 1/4 cup by volume. An ounce of chopped walnuts is slightly less than 1/4 cup by volume, while an ounce of ground walnuts is slightly more than 1/3 cup.
A 1-ounce serving of walnuts contains 185 calories, just over 4 grams of protein, 18.5 grams of fat and just under 4 grams of carbohydrates, of which about 2 grams are fiber. Like other nuts, walnuts contain mostly unsaturated fatty acids -- more than 70 percent of a walnut’s fat is the polyunsaturated type, according to the USDA. One serving of walnuts also delivers 11 percent and 10 percent of the daily values for magnesium and phosphorus, respectively, as well as about 7 percent each of the daily values for vitamin B-6 and folate and 6 percent each of the daily values for thiamine and zinc.
The kind of unsaturated fatty acids found in walnuts are believed to reduce high cholesterol levels when included in a diet that’s low in saturated fat. Roughly 20 percent of the polyunsaturated fat in walnuts is in the form of alpha-linolenic acid, a type of omega-3 fatty acid. Omega-3s are integral to many basic processes in your body, including normal heart and kidney function. The protein in walnuts is a significant source of arginine, an essential amino acid that reduces the risk of blood clots by keeping arteries and veins smooth and relaxed. As a good source of magnesium and phosphorus, walnuts contribute to healthy teeth and bones. Nearly 70 percent of the fiber in walnuts is insoluble, the kind that promotes efficient digestion and helps prevent constipation.
Since walnuts are a concentrated source of fat and calories -- and because most people miscalculate how many nuts are in one serving -- the U.S. Food and Drug Administration suggests limiting individual portions to the amount of nuts you can comfortably fit in the palm of one hand. A handful of nuts is loosely defined a 1.5-ounce serving, which amounts to just under 1/2 cup of walnut halves or about 1/3 cup of chopped walnuts. While the FDA recommends eating a handful of nuts every day to help reduce your risk of heart disease, the American Heart Association suggests consuming a small handful of nuts just four times per week.
- USDA Nutrient Data Laboratory: Nuts, Walnuts, English
- California Walnut Commission: Alpha-Linolenic Acid
- Harvard University Health Services: Fiber Content of Foods in Common Portions
- MayoClinic.com: Nuts and Your Heart: Eating Nuts For Heart Health
- American Heart Association: Be Nutty (But Just a Little)
- Wellness Foods A to Z; Sheldon Margen, M.D., et al.
Based just outside Chicago, Meg Campbell has worked in the fitness industry since 1997. She’s been writing health-related articles since 2010, focusing primarily on diet and nutrition. Campbell divides her time between her hometown and Buenos Aires, Argentina.