Know These 5 Top Health Benefits of Walnuts

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The health benefits of walnuts are due to their antioxidants, polyphenols, and omega-3 fatty acids

You may already be familiar with some of the commonly touted health benefits of walnuts, such as their association with improving brain health and cognition. What you may not know about, however, are some of the lesser-known benefits of walnuts, including their impact on gut health, heart health, weight loss, metabolic syndrome and male reproductive health. Let’s get cracking into the research! (Pun definitely intended.)

Walnuts: The Nutrition Science

Walnuts have several nutrients and compounds that make them an all-star food for improving overall health. The main beneficial components include their antioxidant and polyphenol content and their fatty acid make-up.

The most commonly studied (and eaten) type is the English walnut, also known as Juglans reglia. One of the primary polyphenols found in walnuts is ellagic acid, which has been shown to exhibit antioxidant and anti-inflammatory activities in the body. Other compounds found in the walnut, specifically in the husk, are the polyphenols catechin and epicatechin (which are also found in green tea), and quercetin, a plant flavonoid linked to reduced inflammation. 

Another prominent health benefit of walnuts is their fat content, primarily made up of polyunsaturated fat. Walnuts are one of a few plant-based sources of omega-3 fatty acids, (specifically ALA, or alpha-linolenic acid), which are crucial to include in a healthy diet.  

A small intervention study in Serbian adults found that consuming about one-half of a cup of walnuts per day (59 grams) for four weeks led to significant improvements in total omega-3 levels, ALA, and EPA (eicosapentaenoic acid; ALA gets converted into EPA in the body).

Walnuts also contain quite a few minerals, with one ounce (about 14 walnut halves) providing 50% of your daily needs for copper, 42% for manganese, and 11% for magnesium, according to the USDA. 

Walnuts have been well-studied for their beneficial impact on brain health, cognition, and reducing the risk of neurodegenerative disease (it’s no coincidence that a whole walnut looks just like a brain!). However, there’s plenty more that this brain-shaped nut has to offer.

Top 5 Lesser-Known Health Benefits of Walnuts

1. Gut Health

You likely haven’t thought much about the effect that walnuts have on your digestive health, but more and more research is showing the benefit that these nuts have on the microbes and bacteria in our gut, also known as the microbiome.

Walnuts produce beneficial gut bacteria to promote a healthy microbiome

A randomized, controlled, cross-over study of 194 individuals found that the beneficial gut bacteria Ruminococcaceae and Bifidobacteria increased significantly over an eight-week period of consuming 43 grams of walnuts daily. The Bifidobacteria species have probiotic properties, while Ruminococcaceae enhances the production of butyric acid, a short-chain fatty acid that provides energy for intestinal cells and reduces inflammation in the gut.

A recent trial from December 2019 randomized 42 adults with cardiovascular risk to one of three diets:

  1. One with walnuts
  2. One without walnuts but with the same amount of ALA and polyunsaturated fatty acids
  3. One without walnuts that substituted oleic acid (another type of fat) for the same amount of ALA found in walnuts.

Those on the walnut diet who consumed between 57 to 99 grams daily for six weeks had increases in a species of gut bacteria called Roseburia, which also produces butyric acid and protects the intestinal lining.

2. Heart Health

Although the majority of the calories in walnuts come from fat, studies have linked nut consumption to improvements in various markers of heart health. A meta-analysis of 26 clinical trials found that walnut-rich diets were associated with significant reductions in total LDL cholesterol, triglycerides, and apolipoprotein-B (a protein that mainly makes up the “bad” cholesterols, LDL and VLDL), while not leading to an increase in weight gain.

Combined results from 3 studies with over 32 years of follow-up showed that those who consumed walnuts just once or more per week had a 19% reduction in cardiovascular disease risk and a 21% reduction in risk of developing coronary heart disease compared to those who never ate nuts. For each increase in servings per week of walnuts, the incidence of these cardiovascular diseases continued to decrease. It’s worth noting that similar results were seen with the intake of peanuts and other tree nuts, too.

Other studies have linked the consumption of walnuts or walnut oil to reductions in blood pressure and arterial pressure, as well as improvements in endothelial function, a marker of atherosclerosis.

3. Weight Loss

While many people may be hesitant to eat nuts daily, thinking they will cause weight gain, the opposite has been shown to be true in several studies. A review of prospective studies concluded that a handful of nuts per day is linked to reductions in body weight, likely due to the satiating nature of the fats, fiber, and protein found in nuts.

The study mentioned earlier with Serbian adults also found that those who ate the half-cup of walnuts per day had significantly reduced BMI and body fat percentage, with an increase in lean body mass.

4. Improvements in Metabolic Syndrome

Metabolic syndrome is a combination of several risk factors, which include central obesity, high triglycerides, low HDL cholesterol or dyslipidemia, high blood pressure, and high blood sugar. Having three or more of the five risk factors leads to a diagnosis of metabolic syndrome.

Walnut consumption can reduce the risk of type 2 diabetes

With the prevalence of type 2 diabetes skyrocketing in recent years, a focus on reducing blood sugar is important. Combined results from two large cohort studies of nurses found that those who consumed walnuts had a reduction in the risk of type 2 diabetes in a dose-dependent manner, reducing the severity of metabolic syndrome.

In this study, women who consumed between one to three servings of walnuts per month had a 7% reduction in type 2 diabetes risk, while women who consumed one serving per week had a 19% reduction, and those who had two or more weekly walnut servings saw a 33% reduction, compared to those who never or rarely ate walnuts. Considering that a serving is just 12 to 14 walnut halves, it would be wise to include a twice-weekly walnut snack to benefit your risk of developing type 2 diabetes.

5. Male Reproductive Health

Lastly, an uncommonly known health benefit of walnuts is the effect they have on male reproductive and sexual health. In a randomized controlled trial of healthy men age 21-35, those who added 75 grams of walnuts daily to their typical Western diet had improvements in sperm vitality, motility, and morphology (meaning sperm with normal form). As infertility is increasingly common in developed countries, a simple addition of walnuts — even despite eating the unhealthy foods associated with the Western diet — may help to improve sperm quality and improve fertility.

As you can see, research on the benefits of walnuts goes far beyond the brain!

Health Benefits of Walnuts: A Recap

  • While the cognitive benefits of walnuts have been well-studied, there are several other lesser-known health benefits of walnuts that are more recently researched.
  • The research shows that consumption of walnuts leads to improvements in gut health by promoting beneficial bacteria and reducing intestinal inflammation.
  • Regular walnut intake is also linked to weight loss, reductions in metabolic syndrome risk, and improvements in cardiovascular markers and male reproductive health.
  • While the amount of walnuts varies study by study, it seems that a daily 1-ounce serving (about 14 walnut halves) could be enough to produce health benefits.

Show references

Bamberger C, Rossmeier A, Lechner K, et al. A Walnut-Enriched Diet Affects Gut Microbiome in Healthy Caucasian Subjects: A Randomized, Controlled Trial. Nutrients. 2018;10(2):244. doi:10.3390/nu10020244

Guasch-Ferré M, Li J, Hu FB, Salas-Salvadó J, Tobias DK. Effects of walnut consumption on blood lipids and other cardiovascular risk factors: an updated meta-analysis and systematic review of controlled trials. Am J Clin Nutr. 2018;108(1):174–187. doi:10.1093/ajcn/nqy091

Guasch-Ferré M, Liu X, Malik VS, et al. Nut Consumption and Risk of Cardiovascular Disease. J Am Coll Cardiol. 2017;70(20):2519–2532. doi:10.1016/j.jacc.2017.09.035

Jackson CL, Hu FB. Long-term associations of nut consumption with body weight and obesity. Am J Clin Nutr. 2014;100 Suppl 1(1):408S–11S. doi:10.3945/ajcn.113.071332

Kang I, Buckner T, Shay NF, Gu L, Chung S. Improvements in Metabolic Health with Consumption of Ellagic Acid and Subsequent Conversion into Urolithins: Evidence and Mechanisms. Adv Nutr. 2016;7(5):961–972. doi:10.3945/an.116.012575

Pan A, Sun Q, Manson JE, Willett WC, Hu FB. Walnut Consumption Is Associated with Lower Risk of Type 2 Diabetes in Women, The Journal of Nutrition, 2013; 143(4): 512–518 doi: 10.3945/jn.112.172171

Petrović-Oggiano G, Debeljak-Martačić J, Ranković S, et al. The Effect of Walnut Consumption on n-3 Fatty Acid Profile of Healthy People Living in a Non-Mediterranean West Balkan Country, a Small Scale Randomized Study. Nutrients. 2020;12(1):E192. doi:10.3390/nu12010192

Poulose SM, Miller MG, Shukitt-Hale B. Role of Walnuts in Maintaining Brain Health with Age, The Journal of Nutrition. 2015;144(4):561S–566S. doi:10.3945/jn.113.184838

Robbins WA, Xun L, FitzGerald LZ, Esguerra S, Henning SM, Carpenter CL. Walnuts Improve Semen Quality in Men Consuming a Western-Style Diet: Randomized Control Dietary Intervention Trial. Biology of Reproduction. 2012; 87(4): 101, 1–8. doi: 10.1095/biolreprod.112.101634

Tindall AM, McLimans CJ, Petersen KS, Kris-Etherton PM, Lamendella R. Walnuts and Vegetable Oils Containing Oleic Acid Differentially Affect the Gut Microbiota and Associations with Cardiovascular Risk Factors: Follow-up of a Randomized, Controlled, Feeding Trial in Adults at Risk for Cardiovascular Disease. J Nutr. 2019;nxz289. doi:10.1093/jn/nxz289

Walnuts. My Food Data website.

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