Walnuts are round, single-seeded stone fruits that grow from the walnut tree. They are a correct source of healthful fats, protein, and fiber. They may additionally beautify heart and bone health and help in weight management, among different benefits. Walnut bushes are native to eastern North America however are now oftentimes grown in China, Iran, and within the United States in California and Arizona.
To say that walnuts are a nutritious food is a bit of an understatement. Walnuts supply wholesome fats, fiber, vitamins, and minerals — and that’s just the starting of how they may help your health. In fact, there’s so much hobby in this one nut that for the past 50 years, scientists and industry experts have gathered annually at the University of California, Davis, for a walnut convention discussing the brand new walnut health research.
1. Rich in Antioxidants
Walnuts have higher antioxidant activity than any other common nut. This activity comes from vitamin E, melatonin and plant compounds called polyphenols, which are particularly high in the papery skin of walnuts.
A preliminary, small study in healthy adults showed that eating a walnut-rich meal prevented oxidative damage of “bad” LDL cholesterol after eating, whereas a refined-fat meal didn’t (3Trusted Source).
2. Super Plant Source of Omega-3s
Walnuts are significantly higher in omega-3 fat than any other nut, providing 2.5 grams per 1-ounce (28-gram) serving.
Omega-3 fat from plants, including walnuts, is called alpha-linolenic acid (ALA). It’s an essential fat, meaning you have to get it from your diet.
According to the Institute of Medicine, an adequate intake of ALA is 1.6 and 1.1. grams per day for men and women respectively. A single serving of walnuts meets that guideline.
Observational studies have shown that each gram of ALA you eat per day lowers your risk of dying from heart disease by 10%.
3. May Decrease Inflammation
Inflammation is at the root of many diseases, including heart disease, type 2 diabetes, Alzheimer’s disease, and cancer, and can be caused by oxidative stress.
The polyphenols in walnuts can help fight this oxidative stress and inflammation. A subgroup of polyphenols called ellagitannins may be especially involved.
Beneficial bacteria in your gut convert ellagitannins to compounds called urolithins, which have been found to protect against inflammation.
4. Promotes a Healthy Gut
Studies suggest that if your gut is rich in health-promoting bacteria and other microbes (your gut microbiota), you’re more likely to have a healthy gut and good overall health.
An unhealthy composition of your microbiota can contribute to inflammation and disease in your gut and elsewhere in your body, increasing your risk of obesity, heart disease and cancer.
What you eat can significantly influence the makeup of your microbiota. Eating walnuts may be one way to support the health of your microbiota and your gut.
When 194 healthy adults ate 1.5 ounces (43 grams) of walnuts every day for eight weeks, they had an increase in beneficial bacteria, compared to a period of not eating walnuts.
5. May Reduce Risk of Some Cancers
Test-tube, animal and human observational studies suggest that eating walnuts may reduce your risk of certain cancers, including breast, prostate and colorectal cancers.
As noted earlier, walnuts are rich in the polyphenol ellagitannins. Certain gut microbes can convert these to compounds called urolithins.
Urolithins can have anti-inflammatory properties in your gut, which may be one way that eating walnuts help protect against colorectal cancer. Urolithins’ anti-inflammatory actions could also help protect against other cancers.
What’s more, urolithins have hormone-like properties that enable them to block hormone receptors in your body. This may help reduce your risk of hormone-related cancers, specifically breast and prostate cancers.
More human studies are needed to confirm the effects of eating walnuts on decreasing the risk of these and other cancers, as well as to clarify all the ways or mechanisms by which they may help.
6. Supports Weight Control
Walnuts are calorie-dense, but studies suggest that the energy absorbed from them is 21% lower than would be expected based on their nutrients.
What’s more, eating walnuts may even help control your appetite. In a well-controlled study in 10 obese people, drinking a smoothie made with about 1.75 ounces (48 grams) of walnuts once a day for five days decreased appetite and hunger, compared to a placebo drink equal in calories and nutrients.
Additionally, after five days of consuming the walnut smoothies, brain scans showed that the participants had increased activation in a region of the brain that helped them resist highly tempting food cues, such as cake and French fries.
Even though larger and longer-term studies are needed, this provides some initial insight as to how walnuts may help control appetite and weight.
7. May Help Manage Type 2 Diabetes and Lower Your Risk
Observational studies suggest that one reason walnuts are linked to a lower risk of type 2 diabetes is that they help control weight. Excess weight increases your risk of high blood sugar and diabetes.
Yet, eating walnuts may help control blood sugar by mechanisms beyond their influence on weight control.
In a controlled study in 100 people with type 2 diabetes, consuming 1 tablespoon of cold-pressed walnut oil a day for 3 months, while continuing their usual diabetes medication and balanced diet, resulting in an 8% decrease in fasting blood sugar.
Additionally, the walnut oil users had about an 8% decrease in hemoglobin A1C (3-month average blood sugar). The control group showed no improvement in A1C or fasting blood sugar. Neither group had a change in their weight.
8. May Help Lower Blood Pressure
High blood pressure is a major risk factor for heart disease and stroke.
Some studies suggest that eating walnuts may help lower blood pressure, including in people with high blood pressure and in healthy people when under stress. Other studies did not observe this effect.
Among other diets, the four-year PREDIMED study in about 7,500 adults at high risk of heart disease tested a Mediterranean diet supplemented with 1 ounce (28 grams) of mixed nuts daily, of which half were walnuts.
At the end of the study, people on the nut-enriched Mediterranean diet had a 0.65 mmHg greater decrease in diastolic blood pressure (bottom number) than people on a similar heart-healthy control diet who weren’t given nuts.
This suggests that nuts may slightly improve the blood pressure benefits of a heart-healthy diet. This is important, as small differences in blood pressure are thought to have a big impact on your risk of heart disease death.
9. Supports Healthy Aging
As you age, good physical functioning is essential for maintaining your mobility and independence.
One thing that may help maintain your physical abilities is healthy eating habits.
In an observational study over 18 years in more than 50,000 older women, scientists found that those with the healthiest diets had a 13% lower risk of physical impairment. Walnuts were among the foods that made the strongest contribution to a healthy diet.
Though high in calories, walnuts are packed with essential vitamins, minerals, fiber, fats and plant compounds that may help support good physical functioning as you age.
10. Supports Good Brain Function
It may be just a coincidence that the shell of a walnut looks like a tiny brain, but research suggests that this nut may indeed be good for your mind.
Animal and test-tube studies found that the nutrients in walnuts, including polyunsaturated fat, polyphenols, and vitamin E, may help reduce oxidative damage and inflammation in your brain.
In a 10-month study of Alzheimer’s disease, mice fed 6–9% of their calories as walnuts (equal to 1–1.5 ounces or 28–45 grams daily in people) had significant improvements in learning skills, memory and anxiety reduction, compared to a walnut-free control group.
Observational studies in older adults have linked eating walnuts to better brain function, including faster processing speed, more mental flexibility, and better memory.
Though these results are encouraging, more studies testing the effects of walnuts on brain function in humans are needed to draw firm conclusions.
The Bottom Line
Walnuts are an exceptionally nutritious nut. They have higher antioxidant activity and significantly more healthy omega-3 fats than any other common nut.
This rich nutrient profile contributes to the many health benefits associated with walnuts, such as reduced inflammation and improved heart disease risk factors.
Scientists are still uncovering the many ways that walnuts’ fiber and plant compounds, including polyphenols, may interact with your gut microbiota and contribute to your health.
It’s likely you’ll keep hearing more about walnuts in the years to come as more studies will research their beneficial health effects.
Still, there are plenty of reasons to include them in your diet already today.