A walnut is the nut of any tree of the genus Juglans (family Juglandaceae), particularly the Persian or English walnut, Juglans regia.
A walnut is the edible seed of a drupe, and thus not a true botanical nut. It is commonly consumed as a nut. After full ripening for its edible seed when the shell has been discarded, it is used as a garnish or a snack.
Nuts of the eastern black walnut (Juglans nigra) and butternuts (Juglans cinerea) are less commonly consumed
Walnuts provide healthy fats, fiber, vitamins and minerals – and that’s just the beginning of how they may support your health.
In fact, there’s so much interest 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 conference discussing the latest walnut health research.
The most common variety of walnut is the English walnut, which is also most studied type
SCIENCE-BASED HEALTH BENEFITS OF WALNUTS.
■ 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.
That’s beneficial because oxidized LDL is prone to build up in your arteries, causing atherosclerosis.
Walnuts are an excellent source of antioxidants that can help fight oxidative damage in your body, including damage due to “bad” LDL cholesterol, which promotes atherosclerosis.
■ 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, 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 guidelines.
Observational studies have shown that each gram of ALA you eat per day lowers your risk of dying from heart disease by 10%.
Walnuts are a good source of the plant form of omega-3 fat, which may help reduce heart disease risk.
■ MAY DECREASE INFLAMMATION
Inflammation is at the root of many diseases, including heart diseases, 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.
ALA omega-3 fat, magnesium and amino acid arginine in walnuts may also decrease inflammation.
Several plant compounds and nutrients in walnuts may help decrease inflammation, which is a key culprit in many chronic diseases.
■ 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 health and cancer.
What you eat can significantly influence the makeup of your microbiota. Eating walnuts may be one way to suport the health of your microbiota and your gut.
When 194 healthy adults ate 1.5 ounces (143 grams) of walnuts every day for eight weeks, they had an increase in beneficial bacteria, compared to a period of not eating walnuts.
This include an increase in bacteria that produce butyrate, a fat that nourishes your gut and promotes gut health.
Eating walnuts not only nourishes you but also the beneficial bacteria that live in your gut. This promotes the health of your gut and may help reduce disease risk.
■ 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 cancers.
What’ 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 mechanism by which they may help.
The polyphenol in walnuts may reduce your risk of certain cancers, including breast, prostate and colorectal cancers. However, more human studies are needed to confirm this.
Walnuts are calorie dense, but studies suggest that the energy absorbed from them is 21% lower than would be expected based on their nutrients.
■ SUPPORTS WEIGHT CONTROL
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 qual in calories and nutrients.
Additionally, after five days of consuming the walnut smoothies brain scan 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.
Though they’re calorie-dense, you may not absorb all of the calories in walnuts. Additionally, they may even help you control appetite and hunger.
■ 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 mechanism 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, resulted in an 8% decrease in fasting blood sugar.
Additionally, the walnut oil users had aboutman 8% decrease in hemoglobin A1C (3-month avarage blood sugar). The control group showed no improvement in A1C or fasting blood sugar. Neither group had a change in their weight.
Eating walnuts may help control type 2 diabetes and reduce your risk of the disease, as the nut may help control your weight. Walnut might have more direct effects on sugar control as well.
■ 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 improved the blood pressure benefits of a heart-healthy diet. This is importan,t, as small differences in blood pressure are thought to have a big impact on risk of heart disease death.
Some studies suggest that eating 1 ounce (28 grams) of nuts daily, including walnuts, as part of a heart healthy diet may help improve blood pressure.
■ 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 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.
A healthy diet that includes walnuts may help preserve physical function, such as walking and self-care abilities as you age
■ 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 nutrient s inmwalnuts, including polyunsaturated fat, polyphenols and vitamin E, may reduce oxidative damage and inflammation in your brain.
In a 10-month study of Alzheimer’s disease, a 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 in humans are needed to draw firm conclusion.
Walnuts contain nutrients that may help protect your brain from damaging inflammation and support good brain function as you age.
■ SUPPORTS MALE REPRODUCTIVE HEALTH
Typical Western diets – high in processed foods, sugar and refined grains – have been linked to reduced sperm function.
Eating walnuts may help support sperm health and male fertility.
When 117 helthy young men included 2.5 ounces (75 grams) of walnuts daily in their Western-style diet for three months, they had improved sperm shape, vitality and mobility, compared to men not eating nuts.
Animal research suggests that eating walnuts may protect sperm by reducing oxidative damage in their membranes.
Eating walnuts regularly may help counteract potential harmful effects of less-than-ideal eating habits on sperm health.
■ IMPROVES BLOOD FATS
Elevated levels of “bad” LDL cholesterol and triglycerides have long been linked to an increase heart disease risk.
Regularly eating walnuts has been consistently shown to decrease cholesterol levels..
In a recent study in 194 healthy adults, eating 1.5 ounces (43 grams) of walnuts daily for eight weeks produced 5% decrease in total cholesterol, 5% decrease in triglycerides, compared to not eating walnuts.
The walnut easters also had nearly a 6% decrease in apolipoprotein -B which is an indicator of how many LDL particles are in your blood. When elevated, apolipoprotein-B is a major risk factor for heart disease.
A daily 1.5-ounce (43-gram) serving of walnuts may help lower harmful cholesterol and triglycerides levels, which contribute to disease risk.
Walnut are easy to add to your diet since they’re widely available in stores and a great addition to countries dishes.
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
The 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 interacts 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.