Walnut

Studies in people

• Open question

  Brain function and memory³

  Walnuts did not clearly improve memory or thinking in studies, and scientists still cannot say whether they help.

• Benefit

  Diet and autism case⁵

  A boy with autism improved on a diet high in pumpkin and walnuts, but this is just one case.

• No harm found

  Weight and waist size⁶

  Eating walnuts did not change body weight, waist size, or fat mass in these studies.

• Benefit

  Blood fat levels⁷

  In people with high blood fats, walnut oil capsules lowered triglycerides, but scientists still need to study this more.

• Benefit

  Sleep quality⁹

  In a study of young adults, eating walnuts daily helped people fall asleep faster and feel less sleepy in the day.

• Benefit

  Heart and diabetes risk¹⁰

  In people, 19 blood substances linked to eating walnuts tracked with lower risk of type 2 diabetes and heart disease.

• Benefit

  Lifespan and heart health¹¹

  People who ate walnuts five or more times a week tended to live longer and die less often from heart disease.

• Open question

  Diet quality and nutrient intake¹³

  In healthy adults, a daily walnut supplement raised fiber, minerals and some fats, and lowered some others.

• Benefit

  Heart relaxation¹⁴

  In people, walnut eaters had better heart relaxation readings than non-eaters, though systolic function was the same.

Animal and lab studies only

• Benefit

  Stomach protection from painkillers²¹

  In animal studies, eating walnuts helped protect the stomach from damage caused by painkillers like indomethacin.

• Benefit

  Gut inflammation in mice²²

  In mice with gut inflammation, walnut oil eased swelling and shifted gut bacteria toward helpful kinds.

• Benefit

  Blood sugar spikes²³

  Walnut extracts slowed the enzymes that break down carbs and cut glucose movement across gut cells.

Study type not stated

• Benefit

  Heart and cell health¹⁶

  Walnuts and their nutrients may help the heart and protect cells, though scientists are still learning how.

• Benefit

  Heart and brain health¹⁷

  Walnut polyphenols may help protect against heart disease, cancer and brain decline, but scientists do not yet know for sure.

• Benefit

  Heart and cholesterol health¹⁸

  Walnut oil is rich in fatty acids and other compounds that may help with cholesterol and heart health.

• Benefit

  Heart and blood vessel health¹⁹

  Eating walnuts often may help your heart and blood vessels, though scientists still have questions.

• Concern

  Nut allergy testing²⁰

  Walnut allergy tests can miss nuts in cooked foods, and heating may make walnuts less allergenic for some people.

Allergies and intolerances

These are about people with an allergy, an intolerance or coeliac disease. The signal is about the ingredient itself, and these are about the person eating it, so the signal does not count them.

• Nut allergy in children⁴

  Walnut is one of the tree nuts most often causing allergy in US children.

• Nut allergy reaction levels⁸

  Scientists studied how much walnut protein triggers a reaction in allergic people, but the exact amount is still not settled.

• Nut protein reaction¹⁵

  Some adults allergic to walnuts react to a walnut protein called Jug r 4.

How it’s made and used

• Gut bacteria and urine compounds¹²

  Eating walnuts daily for three weeks changed gut bacteria and raised urolithin levels in people's urine.

The signal at the top counts the findings in people and in animal and lab studies. A concern in studies of people outranks animal and lab studies, and “No concerns” needs at least one finding in people. When most findings in people point one way, the page leans that way (“Mostly”), and every finding is still shown. Findings whose study type is not stated are shown but not counted. This page is a reference, not medical advice. It describes what regulators and published research say. Talk to a doctor or dietitian about your own diet.