There’s plenty of research to back up health claims about walnuts. But defining a specific “dose” associated with benefits is less clear.
“There’s not enough evidence to recommend any specific dose to prevent a specific disease per se, but based on all the research on overall health effects of nuts, a daily 1 to 2 oz serving of walnuts or other mixed nuts is advisable for good health,” says Dariush Mozaffarian, MD, the director of the Food Is Medicine Institute at Tufts University in Medford, Massachusetts.
Substantial evidence suggests that a daily serving of nuts is beneficial for cardiovascular and metabolic health, and might also improve cognitive function and reduce the risk of other diseases.
Walnuts — like any healthy food — should be part of a well-rounded, nutrient-rich diet, says Sharon Palmer, RDN, the author of The Plant-Powered Plan to Beat Diabetes Now, who is based in Ojai, California. “Including walnuts in a nutritionally balanced diet that includes healthful protein and fat sources, vegetables, fruits, and whole grains is key to gaining these health benefits,” she says, adding that it’s also good to let your doctor know before you make major dietary changes.
Support Heart Health
“Walnuts’ unsaturated fat content, as well as their unique and abundant presence of omega-3 fatty acids and specific phytochemicals, appear to be behind these benefits,” Palmer says. How many should you eat? According to Cleveland Clinic, a 1 oz serving of walnuts is about 12 to 14 halves or ¼ cup of nuts, roughly the amount that fits in your palm. Eating just five servings per week may help lower the risk of heart disease.
A systematic review and meta-analysis indicates that walnut consumption is significantly associated with lower total cholesterol, LDL (“bad” cholesterol), and triglyceride levels. That’s partly because of how the polyunsaturated fats in walnuts, including alpha-linolenic acid (ALA), a plant-based omega-3 fatty acid, influence fat metabolism. In addition, dietary fiber and plant sterols in walnuts can help block cholesterol absorption in the gut.
Help Fight Inflammation
Persistent, systemic inflammation may contribute to several chronic health conditions, including arthritis, diabetes, hypertension, ischemic stroke, Alzheimer’s, seizures, and certain cancers, according to a recent review published in the Journal of Functional Foods.
Thanks to their anti-inflammatory compounds, such as polyphenols, flavonoids, and polyunsaturated fatty acids, walnuts may help decrease inflammation and, in turn, help prevent some of these diseases.
“Walnuts contain powerful polyphenol ellagitannins, which impact the gut microbiome and lower inflammation,” Retelny says. The gut microbiome — the community of organisms that live in your digestive tract — plays many important roles in the body, such as supporting immune function (including the inflammatory response), hormone regulation, nutrient absorption, and more.
When the gut metabolizes nutrients from walnuts, including phytochemicals such as pedunculagin (an egallitannin), the process produces molecules that help reduce inflammation throughout the body, including in the colon. In turn, it may help lower the risk of colon cancer, according to a recent small study of 39 participants published in Cancer Prevention Research.
In another long-term randomized trial of healthy older adults, researchers found participants who ate 30 to 60 g of raw walnuts (one to two ounces) daily for two years had significantly lower levels of inflammatory markers in their blood than those who didn’t eat walnuts. Of the 10 inflammatory markers measured, 6 — including the pro‑inflammatory cytokine interleukin‑1β — were reduced by up to about 11.5 percent in the walnut-eating group. The study authors concluded that this may, in turn, help reduce the chances of developing cardiovascular disease with age.
May Support Brain Health
“The link between eating walnuts and having strong brain health has been studied extensively,” Retelny says, noting that the nuts’ healthy fats (like ALA) and various other plant compounds contribute to this.
A review article in the Journal of Nutrition summarized the potential effects of walnut consumption on the brain and cognition.
Here, researchers concluded that daily servings of walnuts may improve cognition and reduce the risk of cardiovascular disease, depression, and type 2 diabetes, which are risk factors for dementia. “Substantial evidence from animal and human studies suggests that dietary consumption of walnuts (1 to 2 oz per day) can improve cognitive function and also reduce the risk of other diseases,” the study authors wrote.
Possibly Help Stabilize Blood Sugar
In a review of 32 randomized controlled trials (RCTs), researchers found that walnut intake significantly reduced Homeostatic Model Assessment of Insulin Resistance (HOMA‑IR), a measure of how well your body responds to the hormone insulin.
It also modestly reduced body weight (more on that below). But the study found no significant effect of walnut intake on fasting blood sugar, insulin, or HbA1C (a measure of average blood glucose over the past two to three months). “Based on this meta-analysis, I would say that eating walnuts helps reduce insulin resistance,” Dr. Mozaffarian says. This is primarily due to their fiber, healthy fat, and protein content, which help regulate blood sugar levels.
That said, Retelney points out that walnuts are just one component in a blood sugar management plan, noting that healthy foods often work in “synergy” with others.
May Help Support a Healthy Weight
If you’re looking to lose or maintain weight, walnuts might be a good addition to your diet, Mozaffarian says. “Eating nuts does not cause weight gain for most people, and in fact may help cut central body fat,” he notes.
For example, in a study published in Nutrition, Metabolism, and Cardiovascular Diseases, researchers found that participants who ate nuts, especially walnuts, had better health markers, including lower BMI, waist circumference, blood pressure, triglycerides, and fasting blood sugar.
In part, this may be because — thanks to their protein, healthy fat, and fiber content — nuts can help you feel fuller for longer and consume fewer calories throughout the day. “Walnut consumption has been associated with increased satiation, which can help people to eat less,” says Jamie Lhungay, MD, an internal medicine physician with medical offices in New York City.
Again, there’s no specific, universal recommendation for how many walnuts to eat to experience the benefits. But Dr. Lhungay says about 1 to 1.5 ounces daily, as part of a balanced eating plan, is a good rule of thumb for most people.
Keep in mind that walnuts — like most nuts — are high in calories, so eating too many could cause you to go over your calorie budget.