Walnuts: a Nutritional Powerhouse

The key components of highly satisfying foods are protein and fiber, and with 4 grams of protein and 2 grams of fiber in a 1-oz serving, walnuts are filled with nutrients and will leave a person feeling satisfied and full. With a serving of walnuts equaling only one ounce (oz.), (i.e., 28gm, ¼ cup, or 12–14 walnut halves), they are high on the list of very healthy foods to consume.

In the nut family, walnuts have the highest source of alpha-linolenic acid (ALA), which is a plant-based omega-3 fatty acid needed by our bodies for optimal functioning. In fact, walnuts are one of the best plant-based sources for omega-3 fatty acids, with a 1-oz serving of walnuts providing 2.5gm ALA, while pecans have 0.5gm ALA per 1-oz serving and almonds, peanuts, and pistachios have 0gm ALA per 1-oz serving. Walnuts also contain a number of other potential neuroprotective compounds such as vitamin E, folate, melatonin, magnesium, phosphorus, flavonoids, and phenolic acid. 1-7 In fact, when 1,113 different foods were analyzed for antioxidant content, walnuts ranked second, behind blackberries.7 It has even been reported that walnuts have more antioxidant phenols per ounce (802mg)  than a milk chocolate bar (205mg), a glass of apple juice (117mg), or a glass of red wine (372mg).3

In March 2004, the U.S. Food and Drug Administration approved this qualified health claim for walnuts because of the strength of the evidence supporting their relationship to cardiovascular health, “Supportive but not conclusive research shows that eating 1.5 ounces 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.”8

Researchers fed mice the human equivalent of a control diet, 1-oz walnuts, or 1.5-oz of walnuts per day. Supplementing their diet with walnuts reversed the cognitive deficits of ‘Alzheimer’s mice’ (transgenic mice with Alzheimer’s-like features, known as AD-tg mice). Normally these mice perform more poorly than their normal (‘wild-type’) counterparts in cognitive tests including various skill tests, but walnut supplementation reversed these differences. The mice exhibited improved learning skills, memory, and motor development and reduced anxiety after eating a diet including walnuts. The researchers concluded that dietary supplementation with walnuts may have a beneficial effect in reducing the risk of, or slowing the progressing of, Alzheimer’s disease.9

There is also ongoing research looking at possible associations between walnut consumption, body composition, and cognition. The preliminary findings from the first year of a two-year clinical trial presented at Experimental Biology 2016 are promising.10 Researchers from the Hospital Clinic of Barcelona and Loma Linda University, as part of the Walnuts and Healthy Aging study, instructed 707 older adults to add walnuts (approximately 15% of their daily intake of calories) to their diet or to consume their usual diet without nuts. Those eating walnuts were not given instructions about total calorie, macronutrient (carbohydrate, protein, and fat), or food substitution for the walnuts. The initial results show that consuming walnuts daily is associated with a significant reduction in LDL- cholesterol levels without adversely affecting the body weight among the older adults in the study. This is good news because researchers were concerned that increased walnut consumption would lead to weight gain due to their high energy nature. Results from other studies have shown that improving cholesterol is associated with reducing risk for Alzheimer’s disease, so these preliminary findings are promising. As the trial progresses, the researchers will continue to evaluate the impact that walnut consumption has on the health of these older adults, including looking for possible relationships to cognitive function.

Overall, the research on the nutrient density and health benefits of walnuts is quite compelling. Walnuts are a nutritional powerhouse that fuel your body with many vital nutrients, and leave you feeling full and satisfied. Their consumption is also associated with a decreased risk of cardiovascular disease and improved physical functioning in humans, and reduced agitation and improved cognition in mice models.  Hence, the next logical question is, “How do you get more walnuts into your diet?” Check back later in the week for a list of great recipes using walnuts in our Walnuts: Food 4 Thought recipe postings.

Written by Marci L. Hardy, PhD

  1. Jurd L. Plant phenols: The polyphenolic constituents of the walnut (Juglans regia). Journal of the American Chemical Society. 1958; 80: 2249-2252.
  2. Lavedrine F, Ravel A, Poupard A, Alary J. Effect of geographic origin, variety and storage on tocopherol concentrations in walnuts by HPLC. Food Chemistry. 1997; 58: 135-140.
  3. Anderson KJ, Teuber SS, Gobeille A, Cremin P, Waterhouse AL, Steinberg FM. Walnut polyphenolics inhibit in vitro human plasma and LDL oxidation. Journal of Nutrition. 2001; 131: 2837- 2842.
  4. Fukuda T, Ito H, Yoshida T. Antioxidative polyphenols from walnuts (Juglans regia L.). Phytochemistry. 2003; 63: 795-801.
  5. Crews C, Hough P, Godward J, Brereton P, Lees M, Guiet S, Winkelmann W. Study of the main constituents of some authentic walnut oils. Journal of Agricultural and Food Chemistry. 2005; 53: 4853-4860.
  6. Reiter RJ, Manchester LC, Tan DX (2005) Melatonin in walnuts: Influence on levels of melatonin and total antioxidant capacity of blood. Nutrition. 2005; 21: 920-924.
  7. Halvorsen BL, Carlsen MH, Phillips KM, Bohn SK, Holte K, Jacobs DR, Jr., Blomhoff R. Content of redox-active compounds (i.e., antioxidants) in foods consumed in the United States. American Journal of Clinical Nutrition. 2006 July; 84(1): 95-135.
  8. California Walnuts Scientific Summary. www.walnuts.org. Accessed on February 22, 2017.
  9. Muthaiyah B., Essa MM., Lee M., Chauhan V., Kaur K, Chauhan K. Dietary Supplementation of Walnuts Improves Memory Deficits and Learning Skills in Transgenic Mouse Model of Alzheimer’s Disease. Journal of Alzheimer’s Disease. 2014; 42(4):1397-1405.
  10. Ros E, Rajaram S, Sala-Vila A, et al. Effect of a 1-Year Walnut Supplementation on Blood Lipids among Older Individuals: Findings from the Walnuts and Healthy Aging (WAHA) study. The FASEB Journal. April 2016; 30(1): Supplement 293.4.

 

 

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