Benefits of walnuts: what they do for your heart, and what’s still unproven

The short answer: the main benefit of walnuts is for your heart. They have more plant omega-3 (ALA) than any other common nut, about 2.5 grams an ounce, and in controlled trials they lowered LDL cholesterol by about 4 to 6 mg/dL compared with diets without them. An ounce is about 14 halves and 183 calories. Evidence that they protect memory is still weak.

That LDL drop is modest, and it adds up when walnuts are one of several good swaps. Our guide to foods that lower cholesterol shows how nuts fit with oats, beans and the rest. Here we look closely at walnuts alone.

What are the benefits of walnuts?

The best-supported benefit of walnuts is a small, steady drop in LDL cholesterol. A 2018 Harvard-led review pooled 26 trials with 1,059 people. Walnut diets lowered total cholesterol by about 7 mg/dL, LDL by about 5.5 mg/dL and triglycerides by about 4.7 mg/dL more than the comparison diets. Apolipoprotein B, a count of the particles that carry LDL, fell too.

Other claims are less certain. The same review found no effect on blood pressure. Harvard’s Nutrition Source says the omega-3 in walnuts may help prevent erratic heart rhythms and may reduce blood clotting, and it notes that nuts also carry fiber, vitamin E, folate and potassium. Large studies that followed people for decades link walnuts with less heart disease, though those studies show a link and can’t prove cause.

How many walnuts are in an ounce?

An ounce of walnuts is about 14 halves, by USDA’s count, or a small handful. Here’s what that ounce holds:

Source: USDA FoodData Central, SR Legacy (English walnuts and dried black walnuts). Most walnuts sold in stores are English walnuts. Black walnuts have more protein but less than a third of the omega-3. Glazed and salted walnuts add sugar or sodium, so plain is the version the research used.

Walnuts vs almonds: which is healthier?

Neither nut wins on everything: walnuts lead for omega-3, while almonds have more protein, fiber and magnesium. Here’s how an ounce of each common nut compares in USDA data:

Source: USDA FoodData Central, SR Legacy, raw or plain nuts. Walnuts have about nine times the ALA of the next nut on the list. That’s why they show up next to flaxseed and chia in our list of foods high in omega-3. ALA is the plant form of omega-3, and that guide explains how it differs from the EPA and DHA in fish. If magnesium is your goal, cashews and almonds do more, and our guide to foods high in magnesium lists better sources still.

Do walnuts lower cholesterol?

Yes, walnuts lower LDL cholesterol a little when you eat them most days. The longest test was the Walnuts and Healthy Aging (WAHA) trial in Barcelona and Loma Linda, California. It assigned 708 healthy older adults either to eat walnuts every day for two years or to avoid them.

Source: Rajaram and colleagues, Circulation, 2021. The 628 people with full results started with an average LDL of 117 mg/dL, and the results were similar at both sites. If those terms are new, our guide to good vs bad cholesterol explains them.

The pooled trials point the same way, with a bigger drop when the comparison diet was a typical American or Western diet. The FDA lets walnut packages carry a qualified claim: supportive but not conclusive research shows that 1.5 ounces a day, as part of a diet low in saturated fat and without adding calories, may reduce the risk of coronary heart disease.

Walnuts work best as a swap. Use them in place of chips, cookies or processed meat, not on top of them. If you take a cholesterol medicine, keep taking it as prescribed. Food changes work alongside it.

Are walnuts good for your brain?

Walnuts haven’t been shown to protect memory in a large trial. WAHA tested this as its main goal. After two years, thinking scores in the walnut group and the no-walnut group declined by about the same amount, and the authors concluded walnuts had no effect on cognition in healthy older adults.

There was a hint worth watching. In an extra analysis of the Barcelona group, who started with lower test scores, the walnut eaters declined less, and brain scans in a small subgroup also differed. The researchers called this encouraging but inconclusive. So eat walnuts for your heart, and treat any brain benefit as unproven for now. If your memory is worrying you, talk with your doctor, since many treatable things can affect it.

How many walnuts should I eat a day?

Most studies used 1 to 2 ounces of walnuts a day, which is roughly 14 to 28 halves. These are the amounts behind the evidence:

• WAHA trial: 30 to 60 grams a day (about 1 to 2 ounces), set at around 15% of each person’s calories, for two years. Walnuts were well tolerated.
• FDA qualified claim: 1.5 ounces a day, as part of a diet low in saturated fat.
• Harvard’s analysis of more than 210,000 health professionals: benefits were seen with walnuts once a week or more, and for all nuts the lowest risk was at five or more 1-ounce servings a week.

An ounce adds about 183 calories, so it helps to make room for them. Easy ways to start today:

• Stir a tablespoon of chopped walnuts into oatmeal or yogurt, as in our high-protein breakfast ideas.
• Swap croutons for walnuts on a salad.
• Keep 1-ounce bags for snacks. Pair them with a cheese stick or an egg for more protein, using our high-protein snacks table.
• Toast them in a dry pan for more flavor, with no added oil or salt.

Comparing nut butters too? Our sister guide asks is peanut butter healthy and looks at natural vs regular jars.

Are walnuts tree nuts?

Yes, walnuts are tree nuts, one of the nine major food allergens in the US. The American College of Allergy, Asthma and Immunology (ACAAI) says tree nut allergy usually lasts a lifetime, with fewer than 10% of people outgrowing it, and that tree nuts are among the foods most often linked to anaphylaxis. Between 25% and 40% of people with a peanut allergy also react to at least one tree nut.

The FDA requires labels to name the exact tree nut, so look for "walnuts" in the ingredients or a "Contains" line. Symptoms can include hives, tingling or swelling of the mouth, lips or tongue, vomiting, wheezing and dizziness. Use epinephrine if it’s been prescribed, and call 911 for trouble breathing, throat swelling or fainting. If you’ve reacted to any nut before, see an allergist before trying walnuts.

Your next step

Pick one place walnuts can replace something less useful this week, like the chips at lunch or the croutons at dinner. Walnuts and banana are a natural pair in oatmeal, muffins and smoothies, and The Banana Book has simple recipes that use them.

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Quick questions

Do walnuts have omega-3?

Walnuts have more omega-3 than any other common nut. One ounce of English walnuts has about 2.5 grams of ALA, the plant form of omega-3, in USDA data, about nine times as much as pecans. ALA isn’t the same as the EPA and DHA in fish, so walnuts don’t replace oily fish.

Do walnuts have protein?

Walnuts have some protein, about 4.3 grams per ounce, or 14 halves, in USDA data. That’s less than almonds, at 5.9 grams, or peanuts, at 7.2 grams. Black walnuts have more, about 6.7 grams an ounce. To make a filling snack, pair walnuts with yogurt, cheese or an egg.

Are walnuts or pecans healthier?

Walnuts and pecans are both healthy, but walnuts have more omega-3, protein and magnesium. An ounce of walnuts has about 2.5 grams of ALA omega-3 and 4.3 grams of protein, while pecans have 0.3 grams and 2.6 grams, USDA data shows. Pecans have slightly more fiber and calories. Either one fits a heart-healthy diet.

What is the difference between black walnuts and English walnuts?

English walnuts are the mild, common walnuts sold in most stores. Black walnuts have a stronger flavor, more protein and less omega-3. An ounce of black walnuts has about 6.7 grams of protein and 0.75 grams of ALA, compared with 4.3 grams and 2.5 grams for English walnuts, in USDA data. Most research used English walnuts.

Is it OK to eat walnuts every day?

Eating walnuts every day is fine for most people without a nut allergy. In the two-year WAHA trial, older adults ate 1 to 2 ounces a day, walnuts were well tolerated and LDL cholesterol fell slightly. An ounce has about 183 calories, so use walnuts in place of another snack or topping rather than on top of everything else.

Do walnuts have magnesium?

Walnuts have a moderate amount of magnesium, about 44 milligrams per ounce in USDA data. That’s similar to hazelnuts and peanuts. Almonds have about 76 milligrams, cashews about 82 and Brazil nuts about 105, so those nuts are better choices if you’re trying to get more magnesium from food.

This article is general information, not medical advice. If you have a nut allergy, high cholesterol or heart disease, talk with your doctor or an allergist about what’s right for you, and don’t change any medicine without their advice. If someone has trouble breathing or swelling after eating nuts, call 911.

Sources

• Rajaram S, et al. Effects of Walnut Consumption for 2 Years on Lipoprotein Subclasses Among Healthy Elders: the WAHA Randomized Controlled Trial. Circulation, 2021
• Guasch-Ferré M, et al. Effects of walnut consumption on blood lipids and other cardiovascular risk factors: an updated meta-analysis. Am J Clin Nutr, 2018
• Sala-Vila A, et al. Effect of a 2-year diet intervention with walnuts on cognitive decline: the WAHA study. Am J Clin Nutr, 2020
• Harvard T.H. Chan School of Public Health, The Nutrition Source. Nuts for the heart
• FDA. Qualified Health Claims: Letter of Enforcement Discretion, Walnuts and Coronary Heart Disease (2004)
• FDA. Food Allergies: What You Need to Know
• American College of Allergy, Asthma and Immunology. Tree Nut Allergy
• USDA FoodData Central. SR Legacy: walnuts (English and black), almonds, pecans, pistachios, cashews, hazelnuts, macadamias, Brazil nuts, peanuts