Walnuts are round, single-seeded stone fruits that grow from the walnut tree. Walnut trees are native to eastern North America but are now commonly grown in China, Iran, and within the United States in California and Arizona.
Beneath the husk of the walnut fruit is a wrinkly, globe-shaped nut. The walnut is split into two flat segments to be sold commercially.
Walnuts are available both raw or roasted, and salted or unsalted.
This article provides a nutritional breakdown of walnuts and an in-depth look at its possible health benefits, how to incorporate more walnuts into your diet and any potential health risks of consuming walnuts.
Nutritional breakdown of walnuts
According to the U.S. Department of Agriculture National Nutrient Database, approximately 1 ounce of raw walnuts (28.35 grams) contains:
Walnuts contain high amounts of monounsaturated and polyunsaturated fats.
- 185 calories
- 3.89 grams of carbohydrate
- 0.74 grams of sugar
- 1.9 grams of fiber
- 4.32 grams of protein
One ounce of walnuts also provides the following percentages of recommended daily nutrient intake:
- 48 percent of manganese
- 22 percent of copper
- 11 percent of magnesium
- 10 percent of phosphorus
- 8 percent of vitamin B6
- 5 percent of iron
Walnuts are high in monounsaturated and polyunsaturated fats and a good source of protein. Nuts have a reputation for being a high-calorie and high-fat food. However, they are dense in nutrients and provide heart-healthy fats.
The combination of healthy fats, protein, and fiber in walnuts increase satisfaction and fullness, which makes them a great snack compared to simple carbohydrate foods like chips or crackers.
Possible health benefits of consuming walnuts
Consuming plant-based foods of all kinds has long been associated with a reduced risk of many lifestyle-related health conditions.
Many studies suggest that eating more plant-based foods like walnuts decreases the risk of obesity, diabetes, heart disease, and overall mortality. Eating these foods may also promote a healthy complexion and hair, increased energy, and overall lower weight.
Heart health
A study found that regularly eating walnuts could reduce the risk of coronary heart disease.
The monounsaturated and polyunsaturated fatty acids found in walnuts have been shown to decrease LDL (harmful) cholesterol and triglyceride levels, in turn reducing the risk of cardiovascular disease, stroke, and heart attack.
A study published in the British Journal of Nutrition showed that the risk of coronary heart disease is 37 percent lower for those consuming nuts more than four times per week compared to those who never or rarely consumed nuts.
The U.S. Food and Drug Administration (FDA) have approved the claim for food labels that "eating 1.5 ounces per day of most nuts as part of a diet low in saturated fat and cholesterol may reduce the risk of heart disease."
Weight management
According to research published in the Asia Pacific Journal of Clinical Nutrition, routine nut consumption is associated with elevated resting energy expenditure.
In trials that compare weight loss using diets that include or exclude nuts, the diets that included nuts in moderation showed greater weight loss.
A study published in the American Journal of Clinical Nutrition also found that women who reported rarely eating nuts had a greater incidence of weight gain over an 8-year period than those who consumed nuts two times a week or more.5
Gallstone disease
According to another study in the American Journal of Clinical Nutrition, frequent nut consumption is associated with a reduced risk of cholecystectomy - an operation to remove the gallbladder. In over a million people documented over 20 years, women who consumed more than 5 ounces of nuts a week had a significantly lower risk of cholecystectomy than women who ate less than 1 ounce of nuts each week.
Bone health
Walnuts are a good source of the mineral copper. Severe copper deficiency is associated with lower bone mineral density and an increased risk of osteoporosis. Osteoporosis is a condition where bones become thinner and less dense, making them easier to fracture and break.
More research is needed on the effects of marginal copper deficiency and on the potential benefits of copper supplements to prevent and manage osteoporosis.
Copper also plays an important role in the maintenance of collagen and elastin, major structural components of the body. Without sufficient copper, the body cannot replace damaged connective tissue or the collagen that makes up the building blocks for bone. This can lead to a range of issues including joint dysfunction.
Walnuts contain a high amount of manganese. Manganese has been shown to prevent osteoporosis in combination with the minerals calcium and copper.
Magnesium, another mineral in walnuts, is important for bone formation as it helps with the absorption of calcium into the bone.
Epilepsy
Rats with manganese deficiency have been shown to be more susceptible to seizures. People with epilepsy have also been shown to have lower whole blood manganese levels than those without epilepsy.
It is uncertain if there is a possible genetic relationship between manganese deficiency and epilepsy, and whether manganese supplementation would help. More research is needed.
How to incorporate more walnuts into your diet
Nuts have a high fat content, and so they are prone to becoming rancid. Keep walnuts in a cool, dark, and dry place to improve shelf life. If properly stored, walnuts will keep for a few months at room temperature, a year in the refrigerator, or 2 years in the freezer.
Chopped walnuts can be added to salads, granola, and yogurt.
Rancid nuts are not unsafe but have a sharp flavor that people may find unpleasant.
Quick tips:
- Top salads with chopped walnuts
- Make homemade granola with a mixture of nuts, seeds, and dried fruit, using walnuts
- Make a pesto sauce using walnuts for pasta or flatbread
- Top yogurt with chopped walnuts and fruit
Try these healthy and delicious recipes developed by registered dietitians:
Cinnamon-roasted brussels sprouts with walnutsWhole-grain gnocchi alfredo with spinach and walnuts
Honey Dijon vinaigrette with arugula, pear, and walnut salad
Roasted red pepper, pomegranate, and walnut dip recipe
Risks and precautions for eating walnuts
Walnuts are dense in calories and should be consumed in moderation. A 1 ounce serving of walnuts contains about 14 half-walnut pieces.
It is the total diet or overall eating pattern that is most important in disease prevention and achieving good health. It is better to eat a diet with variety than to concentrate on individual foods as the key to good health.
References:
1. Bes-Rastrollo, M., Wedick, N.M., Martinez-Gonzalez, M.A., Li, T.Y., Sampson, L., & Hu, F.B. (2009, April 29). Prospective study of nut consumption, long-term weight change, and obesity risk in women. American Journal of Clinical Nutrition, 89(6), 1913-1919. Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2683001/.
2. Bruhn, C., Harris, L.J., Giovannia, M., & Metz, D. (2010, August). Nuts: safe methods for consumers to handle, store, and enjoy. Retrieved from http://ucfoodsafety.ucdavis.edu/files/44384.pdf.
3. Dickenson, G. (2013, September). Going nuts - for nut and seed butters, that is. Today’s Dietitian, 15(9), 64. Retrieved fromhttp://www.todaysdietitian.com/newarchives/090313p64.shtml.
4. Higdon, J., Drake, V.J., Delage, B., & Prohaska, J.R. (2014, January). Copper [Fact sheet]. Retrieved fromhttp://lpi.oregonstate.edu/mic/minerals/copper.
5. Higdon, J., Drake, V.J., & Aschner, M. (2010, March). Manganese [Fact sheet]. Retrieved fromhttp://lpi.oregonstate.edu/mic/minerals/manganese.
6. Kelly Jr, J.H., & Sabaté, J. (2006, November). Nuts and coronary heart disease: an epidemiological perspective [Abstract]. British Journal of Nutrition, 96 Suppl 2:S6,1-7. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/17125535.
7. Mattes, R.D., & Dreher, M.L. (2010). Nuts and healthy body weight maintenance mechanisms. Asia Pacific Journal of Clinical Nutrition, 19(1), 137-41. Retrieved from http://apjcn.nhri.org.tw/server/APJCN/19/1/137.pdf.
8. National diabetes fact sheet, 2011 [Fact sheet]. (2011). Retrieved from http://www.cdc.gov/diabetes/pubs/pdf/ndfs_2011.pdf.
9. Summary of qualified health claims subject to enforcement discretion [Fact sheet]. (2014, December 14). Retrieved from http://www.fda.gov/Food/IngredientsPackagingLabeling/LabelingNutrition/ucm073992.htm.
10. Tsai, C.J., Leitzmann, M.F., Hu, F.B., Willett, W.C., & Giovannucci, E.L. (2004, July). Frequent nut consumption and decreased risk of cholecystectomy in women. American Journal of Clinical Nutrition, 80(1), 76-81. Retrieved fromhttp://ajcn.nutrition.org/content/80/1/76.long.
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