Proven health benefits of walnuts

Each year, National Walnut Day is celebrated on May 17. And believe it or not, there is a lot to celebrate about this ‘lowly’ little nut.

Healthy fats, fiber, vitamins, and minerals are just some of the great components Mother Nature has packed into the wonderful walnut. And these components have become the fodder for a multitude of studies that have documented the numerous health benefits walnuts proffer to those who eat them.

So, with no further ado, let’s take a look at some of the scientifically-proven benefits of walnuts:

Higher antioxidant activity. Because vitamin E, melatonin, and polyphenols are found in high concentrations in the papery skin of the walnut, walnuts have a higher antioxidant activity than any other common nut, as validated by several studies. 

Decreased inflammation. The polyphenols found in walnuts can help reduce oxidative stress and the ensuing inflammation it causes. Inflammation plays a vital role in the development of many diseases, including cancer, heart disease, type 2 diabetes, and Alzheimer’s disease. Of particular note is pedunculagin, the primary polyphenol walnuts contain. Pedunculagin is an ellagitannin, a subgroup of polyphenols. Ellagitannins have known activities against disease initiation and progression, including cancer, cardiovascular, and neurodegenerative diseases. In addition, walnuts contain ALA omega-3 fat, magnesium, and arginine, which may also serve to decrease inflammation.

Improved metabolic status in patients with metabolic syndrome. In a two-arm, randomized, controlled crossover study, researchers found that daily consumption of walnuts (45 g) for 16 weeks improved metabolic syndrome status in patients with metabolic syndrome. In addition, this intervention significantly increased HDL cholesterol levels (P=0.028), fasting glucose (P=0.013), HbA1c (P=0,021), and adiponectin (P=0.019).

Improved cardiometabolic profile. In a randomized, double-blind, placebo-controlled, cross-over trial, subjects who consumed a smoothie containing 48 grams of walnuts during two 5-day inpatients stays spaced 1 month apart had reduced fasting small and dense LDL particles (P < 0.02), and increased large HDL (P < 0.01), compared with placebo patients. Researchers also found that walnut smoothie-drinking patients had significantly decreased lipoprotein insulin resistance scores (P < 0.01), glucose AUC (P < 0.02), and insulin AUC (P < 0.04).

Decreased depression. Walnut consumers, especially women, may have lower depression scores than non-nut consumers, according to the results of a recent study published in Nutrients. This association was seen in a gamut of depressive states. Researchers used data from the National Health and Nutrition Examination Survey (NHANES) for 26,656 participants who ate 1) walnuts with high certainty, 2) walnuts with other nuts, 3) other types of nuts, or 4) zero nuts.

The mean depression score of participants who ate walnuts with high certainty was 26% lower than non-nut consumers (P < 0.0001), with the correlation stronger among women (32%, P < 0.0001) vs men (21%, P=0.05). Of note, women in the study more frequently reported higher depression scores. Specifically, when compared with walnut eaters, those who didn’t partake were more likely to have trouble concentrating, feel that they were moving or speaking abnormally, and think that they were better off dead.

Good gut health. In a study published in Nutrients, researchers found that healthy adults who ate 1.5 oz (43 g) of walnuts daily for 8 weeks had significantly increased probiotic- and butyric acid-producing species in the gut. Butyrate is a fat that nourishes the gut and promotes good gut health.

Reduced risk of some cancers. Results from several pre-clinical, clinical, and observational studies suggest that eating walnuts may reduce the risk of certain cancers, including breast, prostate, and colorectal cancers. Again, the ellagitannins in walnuts play a role. They are converted in the gut into urolithins, which have anti-inflammatory properties there and elsewhere. Urolithins also have hormone-like properties, which may block hormone receptors, and thus reduce the risk of hormone-related cancers, such as breast and prostate cancers.

It’s clear that the walnut, with all of its proven health benefits, deserves a day of recognition. So, the next time someone offers you walnuts—raw, roasted, or sprinkled on a salad—please partake of them, for your continued good health!