Know These Top 5 Lesser-Known Health Benefits of Walnuts

Updated on 12/13/22 by Cambria Glosz, MS, RD 

With the holiday season upon us, many people tend to increase their nut consumption—especially walnuts, which are delicious additions to both sweet and savory dishes. Although nuts are found in grocery stores year round, the harvest season for walnuts is typically from November to June, making the holiday season the perfect time to stock up on these nutritious nuts. 

You may already be familiar with some of the commonly touted health benefits of walnuts, such as their association with brain health and cognition. However, there are many lesser-known benefits of walnuts, including their impact on longevity, gut function, heart health, weight management, 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 snack for supporting both lifespan and healthspan, including antioxidants, polyphenols, and healthy fats.  

One of the primary polyphenols found in walnuts is ellagic acid, which exhibits antioxidant action 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 healthier inflammatory responses. 

As with all nuts, walnuts are high in healthy fats—especially polyunsaturated fat. Walnuts are one of a few plant-based sources of omega-3 fats, in the form of alpha-linolenic acid (ALA), which is essential for brain, skin, and heart health. 

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. 

Walnuts have been well-studied for their beneficial impact on brain health and cognition—it's no surprise that walnuts are known as "brain food," considering whole walnuts look 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. Linked to Longer Lifespan

Recent research has suggested that eating walnuts regularly is linked to longevity. A 20-year study from Harvard University found that 60-year-old adults who ate five or more 1-ounce servings of walnuts per week lived approximately 1.3 years longer than people who never ate walnuts. Plus, the heavy walnut-eaters also had a 14% lower risk of death during that time period. 

A lesser consumption of walnuts—just two to four servings per week—also led to longevity benefits, including a one-year increase in lifespan and a 13% reduced risk of mortality over 20 years. 

2. 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 makeup of bacteria in our gut—also known as the microbiome.

A study of 194 people found that consuming 43 grams of walnuts per day (about one-third of a cup) for eight weeks increased the beneficial gut bacteria Ruminococcaceae and Bifidobacteria. 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.

Similarly, a trial randomized 42 adults with cardiovascular risk to consume one of three diets—daily intake of 57-99 grams of walnuts; a diet without walnuts but with similar amounts of ALA; and a diet without walnuts but with a fat called oleic acid. The researchers found that those on the walnut diet 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 study that combined data from 26 clinical trials found that walnut-rich diets were associated with significant reductions in total and 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-relate risk factors compared to those who never ate nuts. 

Other studies have linked the consumption of walnuts or walnut oil to reductions in blood pressure and arterial pressure, which are strong markers of cardiovascular health with age.

3. Weight Management 

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 several studies concluded that eating 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.

Similarly, a study published in Nutrients 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. 

5. Male Reproductive Health

Lastly, an uncommonly known health benefit of walnuts is the effect they have on male reproductive 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.

Health Benefits of Walnuts: Key Takeaways

• While the cognitive benefits of walnuts have been well-studied, there are several other lesser-known health benefits of walnuts that contribute to longer lifespan and healthspan. 
• Regular consumption of walnuts—even an ounce or so per day—may extend lifespan by a year or more. 
• 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 management and improvements in cardiovascular 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.
  

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.

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. 

Liu X, Guasch-Ferré M, Tobias DK, Li Y. Association of Walnut Consumption with Total and Cause-Specific Mortality and Life Expectancy in U.S. Adults. Nutrients. 2021;13(8):2699. Published 2021 Aug 4. 

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.

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. 

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. 

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. J Nutr. 2019;nxz289.