Most nuts are rich in monounsaturated fat, but walnuts are mostly polyunsaturated: 47.2 g of the 65.2 g of fat in 100 g. That includes 9.08 g of alpha-linolenic acid (ALA), a plant omega-3 fat, which puts walnuts third among 110 foods on this site for omega-3.
An ounce (28 g) has 185 calories and 4.3 g of protein. It also gives 50% of the daily value of copper, and only 7 of 132 foods on this site have more copper gram for gram. Manganese comes close behind at 42% of the daily value.
Much of the research below was paid for by the California Walnut Commission, the state’s walnut industry board, and many trials are small. The papers say so, and the cards here repeat it. The English name has its own twist: the first part, wal, is an old Germanic word for foreign, so a walnut is a foreign nut.
Health benefits of walnuts
The top findings from 32 studies, strongest evidence first
What the stars mean
- Strong. Several randomized trials, pooled in a meta-analysis, point the same way, or regulators (FDA or EFSA) have approved the claim.
- Moderate. Good randomized trials support it, but there are fewer of them, or their results vary.
- Limited. Small, short or single trials, or mixed results. Promising, but it needs confirmation.
Population and lab studies get no stars: they show a link or a mechanism, not proof.
How we rate evidence →- ★★★Lower “bad” LDL cholesterolAcross 26 trials, walnut diets lowered LDL by 3.73% (5.51 mg/dL) compared with control diets, with no change in body weight. Another analysis of 13 trials found a drop of 5.68 mg/dL.
- ★★★EU allows a blood vessel elasticity claimThe EU allows a blood vessel elasticity label claim at 30 g a day; Australia and New Zealand found studies too few and varied. In people with prediabetes, pooled trials found blood vessel widening improved by 0.93%.
- ★★Fewer heart events with a mixed-nut dietAmong 7,447 adults at high heart risk, 3.4% on a Mediterranean diet with nuts had a major heart event, against 4.4% on a low-fat diet. Walnuts were only part of the mix, so it tested a whole diet.
- ★★No clear effect on blood pressureAcross 18 trials with 1,799 people, blood pressure did not change overall (0.08 mm Hg). In older adults, the top number fell 4.61 mm Hg on walnuts and 0.59 in controls over two years, a gap that just missed significance.
- ★★No clear effect on cognitive declineIn 708 healthy older adults, two years of a diet with walnuts did not change cognitive decline overall compared with a diet without walnuts.
All 32 studies, strongest evidence first
Walnut-enriched diets lowered LDL cholesterol by 5.51 mg/dL (3.73%) compared with control diets, with no change in body weight
Meta-analysis of 26 controlled trials with 1,059 people. Total cholesterol fell 6.99 mg/dL, triglycerides 4.69 mg/dL and apolipoprotein B 3.74 mg/dL. LDL fell more (8.28 mg/dL) when walnuts replaced an American or Western diet. Body weight and blood pressure did not change. Funded by a National Institutes of Health grant and the California Walnut Commission.
The EU permits the claim that walnuts contribute to the elasticity of blood vessels when 30 g a day are eaten
This is the authorized health claim for walnuts, listed in Commission Regulation (EU) No 432/2012 on the basis of this 2011 European Food Safety Authority opinion on endothelium-dependent vasodilation, the widening of blood vessels. The label must tell shoppers that the effect comes with 30 g of walnuts a day. The same opinion also assessed a claim about LDL cholesterol, which is not in the list. Australia and New Zealand reviewed the evidence in 2014, judged the studies too few and too varied to assess the link reliably, and did not add the claim to their food code.
Walnut diets ranked second best for lowering triglycerides and total cholesterol, behind pistachios, in a comparison of tree nuts
Network meta-analysis of 34 trials with 1,677 people that compared walnuts, pistachios, hazelnuts, cashews and almonds. Almonds ranked second for LDL cholesterol. The authors rate the evidence as low quality, with few and poorly reported studies.
In 33 walnut studies published since 2017, 8 of 8 trials of blood lipids favored walnuts, while results for blood pressure, blood sugar and inflammation did not point one way
Systematic review of 23 randomized trials (1,948 people) and 10 cohort studies (about 675,928 people), counting which way each result pointed instead of pooling the numbers. Only 1 trial had a low risk of bias for any outcome, and 6 of 6 trials favored the control diet for body weight, although most effects were small. Funded by the California Walnut Commission, which the authors, who work for the British Nutrition Foundation, say had no input into the final design or conduct.
Walnut intake lowered LDL cholesterol by 5.68 mg/dL and triglycerides by 10.94 mg/dL in a meta-analysis of 13 trials
Randomized trials from the U.S., Europe and Asia. Total cholesterol fell 8.58 mg/dL, while HDL did not change. Gains were larger in people with overweight, obesity or other health conditions and in longer trials. Results varied a lot between trials, and the authors warn that bias is possible. No outside funding was reported.
A meta-analysis of 18 trials found that walnuts did not change blood pressure overall
The trials included 1,799 people. Both systolic and diastolic pressure changed by 0.08 mm Hg, which is no real change. Small drops appeared at doses of 40 g or less (0.53 mm Hg systolic) and in trials of 8 weeks or longer (1.18 mm Hg), but the authors say such tiny changes cannot be applied in practice and do not support walnuts as a way to lower blood pressure.
Eating walnuts for 2 years did not change cognitive decline overall in healthy older adults in the WAHA trial
Randomized trial of 708 people aged 63 to 79 who ate a diet with walnuts (30 to 60 g a day, about 15% of energy) or a control diet without walnuts. The global cognition score changed by -0.072 on walnuts and -0.086 without (P=0.491). A post hoc look at the Barcelona group alone found a smaller decline with walnuts (P=0.040), which the authors call encouraging but inconclusive. The trial received a grant from the California Walnut Commission.
Two years of a walnut diet lowered office systolic blood pressure by 4.61 mm Hg in older adults, a drop that just missed statistical significance against controls
Part of the WAHA trial, in 305 free-living older adults (236 finished; 60% had mild hypertension). Office pressure in controls fell 0.59 mm Hg (P=0.051 for the gap). The 24-hour systolic pressure fell 3.86 mm Hg on walnuts and 2.00 mm Hg in controls (P=0.111). In people with the highest starting pressure it fell 8.5 mm Hg versus 2.5 mm Hg. Funded by a grant from the California Walnut Commission, which the paper says had no input into the design or analysis.
In people with abnormal glucose handling, walnut trials found blood vessel dilation improved by 0.93% but no change in weight or blood sugar markers
Meta-analysis of 8 randomized trials (12 in the review) in people with impaired glucose tolerance or prediabetes. LDL tended to be lower (0.10 mmol/L, P=0.06), which was not significant. Fasting glucose, HbA1c, blood pressure and waist size did not change significantly.
Two years of walnuts did not change bone density in healthy older adults
Barcelona part of the WAHA trial, with 352 people randomized. Spine bone density changed by 0.15% with walnuts and 0.35% in controls (P=0.632), and the femoral neck by -0.90% and -0.70% (P=0.653). Markers of bone turnover did not differ either. Funding included a grant from the California Walnut Commission.
Eating tree nuts improved flow-mediated dilation, a test of blood vessel function, by 0.79% in a meta-analysis, but did not change C-reactive protein
Meta-analysis of 32 randomized trials of tree nuts and peanuts, so walnuts were one of many nuts. The dilation result came from 8 studies with 652 people. C-reactive protein and other inflammation markers showed small differences that were not significant. Funded by the International Nut and Dried Fruit Council; one author also reports grants from the California Walnut Commission.
A Mediterranean diet with mixed nuts lowered the risk of heart attack, stroke and cardiovascular death (hazard ratio 0.72) compared with a low-fat diet
PREDIMED trial of 7,447 Spanish adults aged 55 to 80 at high cardiovascular risk. Over a median of 4.8 years there were 83 major events in the nut group (3.4%) and 109 in the control group (4.4%); the 95% confidence interval was 0.54 to 0.95. Walnuts were part of the nut mix, and the trial tested a whole diet, not walnuts alone. The original 2013 report was withdrawn after randomization problems, and these are the corrected estimates.
A review of 5 trials found no significant effect of walnuts on overall cognition, although 3 found gains in some subdomains or subgroups
Systematic review of 32 randomized trials and 7 observational studies of walnuts. All 7 observational studies linked walnut intake to better cognition outcomes in a dose-response way, but a meta-analysis of cognition was not possible because the tests differed. Meta-analyses of 27 trials found no significant effect on blood sugar or inflammation. Funded by the California Walnut Commission.
A Mediterranean diet with mixed nuts raised a memory score by 0.09, while controls fell by 0.17 over a median of 4.1 years
Barcelona arm of the PREDIMED trial, with 447 cognitively healthy volunteers (mean age 66.9) and 334 retested. The memory gain on the nut diet was significant against controls (P=0.04), but the frontal and global scores did not clearly separate the nut group from controls, while the olive oil group did better on both. The nuts were mixed nuts at 30 g a day, not only walnuts.
Replacing saturated fat with walnuts lowered central diastolic blood pressure by 1.78 mm Hg compared with a diet that swapped the walnuts’ omega-3 for oleic acid
Controlled-feeding crossover trial in 45 adults at risk for cardiovascular disease, with 6 weeks on each diet. The main outcome, central systolic pressure, did not change. All the lower-saturated-fat diets cut total, LDL and HDL cholesterol, so that benefit was not special to walnuts. Funded by the California Walnut Commission.
A walnut diet improved endothelium-dependent vasodilation compared with a Mediterranean diet in people with high cholesterol, and lowered LDL by 6.4%
Crossover trial in which 21 men and women with high cholesterol ate each diet for 4 weeks, and 18 had usable ultrasound scans. On the walnut diet, walnuts replaced about 32% of the energy from monounsaturated fat. Total cholesterol fell 4.4%. Levels of C-reactive protein and homocysteine did not differ. The trial was small and short.
In 46 overweight adults, 56 g of walnuts a day for 8 weeks raised flow-mediated dilation by 1.4%, against 0.3% on the control diet
Crossover trial in adults averaging 57.4 years with a large waist and at least one other sign of metabolic syndrome, with a 4-week break between diets. Weight stayed the same and other measures did not change. Funded by the California Walnut Commission.
In 24 adults with type 2 diabetes, 56 g of walnuts a day for 8 weeks improved blood vessel dilation (2.2% against 1.2%)
Single-blind crossover trial. From baseline, fasting glucose rose 10.0 mg/dL and LDL fell 7.7 mg/dL on walnuts, but the cholesterol changes were not significant against the diet without walnuts. HbA1c and insulin sensitivity did not change.
Eating 42 g of walnuts a day for 3 weeks lowered LDL cholesterol by 7% and shifted gut bacteria
Controlled-feeding crossover trial in 18 adults. Bacteria that make butyrate, such as Faecalibacterium and Roseburia, were 49 to 160% more abundant, and fecal secondary bile acids were 25% and 45% lower. Small and short. Supported by the USDA Agricultural Research Service and the California Walnut Commission.
In 194 healthy adults, 43 g of walnuts a day for 8 weeks changed the make-up of gut bacteria, with more Ruminococcaceae and bifidobacteria
Crossover trial with stool samples from 135 people. Some Clostridium cluster XIVa species (Blautia and Anaerostipes) fell. Whether these shifts matter for health is not known. Funded by a grant from the California Walnut Commission, which the paper says had no role in the study.
Adding 75 g of walnuts a day for 12 weeks improved sperm vitality, motility and shape in healthy young men
Randomized trial in 117 men aged 21 to 35 who ate a Western-style diet: 59 ate walnuts and 58 avoided tree nuts. The gaps against controls were P=0.003 for vitality, P=0.009 for motility and P=0.04 for normal shape. It measured semen quality, not pregnancies. Funded by the California Walnut Commission and UCLA.
In 64 college students, 8 weeks of walnuts raised inferential verbal reasoning by 11.2% but did not change memory, mood or non-verbal reasoning
Crossover trial with a 6-week break between diets. The effect on reasoning was of medium size (P=0.009). The authors conclude that walnuts do not appear to improve memory, mood or non-verbal reasoning in young, healthy adults.
Adding walnuts to a weight-loss diet gave a similar weight loss to a standard diet (8.9% against 9.4%) over 6 months
Randomized trial in 100 overweight or obese adults in a behavioral weight-loss program. Only the walnut group lowered LDL, from 121 to 112 mg/dL, and kept a lower systolic blood pressure at 6 months. Self-rated fullness was similar. Funded by the American Institute for Cancer Research and the California Walnut Commission.
Supplements of ALA, the omega-3 in walnuts, raised blood EPA and DPA but not DHA in healthy adults
Review by the International Society for the Study of Fatty Acids and Lipids of human studies on how the body converts ALA. Only preformed DHA raised blood DHA. This is why a plant omega-3 does not stand in for fish or algae oil when the goal is DHA.
Women who ate 2 or more servings of walnuts a week had a 33% lower risk of type 2 diabetes, or 24% lower after adjusting for body mass index
Two cohorts, 58,063 women in the Nurses’ Health Study and 79,893 in its younger sister study, followed for about 10 years with 5,930 new cases of diabetes. One serving was 28 g. The hazard ratio was 0.67, and 0.76 after adjusting for body mass index, so weight explains part of the link. Supported by the National Institutes of Health and an unrestricted educational grant from the California Walnut Commission.
Each extra half serving (14 g) of walnuts a day was linked to 0.37 kg less weight gain per 4 years in 3 US cohorts
The cohorts were 27,521 men, 61,680 women and 55,684 younger women who were followed for 20 to 24 years. The link for other tree nuts was similar (0.36 kg), and a half serving a day of walnuts went with a 15% lower risk of obesity (RR 0.85). The participants were mostly white health professionals. One author was partly funded by the California Walnut Commission and another by the Peanut Institute.
People who ate nuts 7 or more times a week had a 20% lower risk of death than people who never ate them (hazard ratio 0.80)
This covers nuts as a group, not walnuts alone. It followed 76,464 women in the Nurses’ Health Study and 42,498 men in the Health Professionals Follow-up Study for up to 30 years, with 16,200 women and 11,229 men dying. Deaths from cancer, heart disease and respiratory disease were also lower. Funded by the National Institutes of Health and the International Tree Nut Council Nutrition Research and Education Foundation.
Each extra 1 g a day of ALA, about the amount in half an ounce of walnuts, was linked to a 5% lower risk of death from any cause
Meta-analysis of 41 cohort studies with 1,197,564 people. ALA is the omega-3 in walnuts, but this covers ALA from all foods. The highest intake went with 10% lower all-cause mortality (RR 0.90) and a slightly higher risk of cancer death (RR 1.06). The authors equate 1 g of ALA with 0.5 ounces of walnut.
US adults who ate walnuts scored 26% lower on a depression questionnaire than adults who ate no nuts
Cross-sectional analysis of 26,656 NHANES participants from 2005 to 2014, using a 24-hour food recall. The gap was 32% in women and 21% in men. A snapshot like this cannot show that walnuts caused the difference. The analysis was supported by the California Walnut Commission.
In mice, walnut-containing diets slowed the growth of implanted human breast cancers by about 80%
Review of mouse and cell studies by one lab. A walnut diet cut mammary gland tumors by about 60% in a transgenic mouse model and slowed prostate, colon and kidney tumors. Whole walnuts did better than the same amount of omega-3 fat alone. This is animal work, not a trial in people.
Mice bred to develop Alzheimer’s-like disease and fed a 6 or 9% walnut diet did as well on memory tests as normal mice
The diets matched 1 or 1.5 ounces of walnuts a day in people and began at 4 months of age, with tests at 13 to 14 months. It is a mouse study and does not show that walnuts prevent Alzheimer’s disease in people.
Male mice on a Western-style diet with 7% walnuts developed 2.3 times fewer colon tumors after a cancer-causing chemical
On a standard diet with 9.4% walnuts the drop was a modest 1.3-fold. Higher walnut levels did not help, especially in females, which hints that there may be a best amount. Gut bacteria also changed. Mouse study.
Who should be careful with walnuts
Most people can eat walnuts freely. Take a little care if one of these applies:
- Tree nut allergy. Walnuts are a major allergen in US and EU labeling law, so packaged foods must name them. About 1.2% of US adults report a tree nut allergy, and a review notes it is outgrown in fewer than 10% of cases and that walnut and pecan are highly cross-reactive. With a diagnosed allergy, avoid walnuts and ask an allergist about other nuts.
- Young children. The NHS advises that whole nuts should not be given to children under 5 because they can choke. Crushed or ground nuts mixed into food are the safer form.
- Calories. Walnuts hold 185 calories in 1 oz (28 g). Trials found no weight gain on average when walnuts were added to a diet, so this is a small concern that comes down to portion size.
How to choose, store and eat walnuts
- Plain walnuts: the nutrition numbers on this page are for plain English walnuts, 185 calories in 1 oz (28 g), so salted, candied or coated ones will differ.
- Daily amount: the EU claim uses 30 g a day. Trials used 42 g, 43 g and 56 g a day, and the cohort link to less weight gain was for a half serving (14 g) a day.
- Part of a plan: in a 100-person weight-loss trial, a diet with walnuts gave similar weight loss to a standard diet (8.9% against 9.4%), and only the walnut group lowered LDL.
Shelled walnuts keep about 3 months at room temperature, 6 to 9 months in the fridge and over a year in the freezer, because the fat in nuts turns rancid. Buy small bags you will use soon and keep them cold in a tight container.
Sources
- Food allergies. US Food and Drug Administration.
- Regulation (EU) No 1169/2011 on the provision of food information to consumers, Annex II. European Union. 2011.
- Gupta RS, Warren CM, Smith BM, et al. Prevalence and severity of food allergies among US adults. JAMA Netw Open. 2019.
- Smeekens JM, Bagley K, Kulis M. Tree nut allergies: allergen homology, cross-reactivity, and implications for therapy. Clin Exp Allergy. 2018.
- Foods to avoid giving babies and young children. NHS.
- Qualified health claims: letter of enforcement discretion, walnuts and coronary heart disease. US Food and Drug Administration. March 9, 2004.
- Commission Regulation (EU) No 432/2012 establishing a list of permitted health claims made on foods. European Union. 2012.
- Consideration of European Union authorised health claims. Food Standards Australia New Zealand.
- Drying, preserving, and storing walnuts and almonds at home. UCCE Master Food Preservers of El Dorado County. University of California Agriculture and Natural Resources.
- FoodData Central: Nuts, walnuts, english. US Department of Agriculture. (Nutrition numbers as shown on this site.)
History of walnuts
The common walnut, Juglans regia, is also called the Persian or English walnut. It is native somewhere in Eurasia, from southwest and central Asia to southeast Europe, but long cultivation has blurred its natural range. Ancient DNA from walnut remains of the Tang Dynasty in Xinjiang, China, fits the idea that Central Asia and its neighbors are the center of origin, because walnuts there show the most genetic diversity.
In Europe the walnut did not need people to survive. Genetic data show it lived through the last ice age in refuges in the Balkans and western Europe. People then moved it around: mixing between walnuts from Anatolia and the Balkans began in the Early Bronze Age, and between western Europe and the Balkans under the Roman Empire. The walnut range in Europe today reflects both natural recovery and about 5,000 years of human use.
The names carry history. Juglans comes from the Latin for Jupiter’s nut, and regia means royal. The Germanic wal in walnut means foreign, as in Wales, and in the Ottoman and Byzantine era the nut was also called the royal nut. Walnuts reached China from Central Asia about 2,000 years ago and the Americas with European colonists in the 17th century.
In California, Franciscan missionaries introduced English walnuts around the 1770s. Joseph Sexton planted the first known commercial orchard near Goleta in 1869, and in 1871 Felix Gillet set up an orchard in Nevada City with French varieties such as Franquette and Mayette. Between 1879 and 1885 Luther Burbank crossed walnut species and named a hybrid of northern California black walnut and English walnut Paradox, which growers found more vigorous and resistant to root disease.
University of California, Davis professors Eugene Serr and Harold Forde released 10 new English walnut varieties in 1968, and later releases included Chandler, which growers still plant widely. The California Walnut Commission was created in 1987. In 2023 the world grew 4 million tonnes of walnuts in the shell, with China producing 35% of them, followed by the United States, Iran and Turkey.
Sources
- Zhang B, Hu X, Li C, et al. Revisiting the dispersal history of walnut by analyzing the ancient DNA of walnut remains in Xinjiang, China. Cell Rep. 2025.
- Pollegioni P, Woeste K, Chiocchini F, et al. Rethinking the history of common walnut (Juglans regia L.) in Europe: its origins and human interactions. PLoS One. 2017.
- Juglans regia. Wikipedia.
- Walnut. Wikipedia.
- Walnuts in California. Wikipedia.
Frequently asked questions about walnuts
Are walnuts good for you?
For most people, yes. One ounce (28 g) has 185 calories, 4.3 g of protein, 1.9 g of fiber and 50% of the daily value for copper. A meta-analysis of 26 trials found walnut diets lowered LDL cholesterol by 5.51 mg/dL, and women who ate 2 or more servings a week had a lower risk of type 2 diabetes in a cohort study, though that is a link, not proof. Tree nut allergy is the main reason to avoid them.
How many walnuts should you eat a day?
No study here proves an ideal amount. The EU claim uses 30 g a day, about an ounce, and the US FDA wording uses 1.5 ounces (about 42 g). Trials used 42 g to 56 g a day. An ounce has 185 calories, so count walnuts as part of the day’s food rather than an extra.
Do walnuts lower cholesterol?
Yes, modestly. A meta-analysis of 26 trials found LDL fell 5.51 mg/dL (3.73%), and another of 13 trials found 5.68 mg/dL. In a feeding trial where every diet cut saturated fat, all of them lowered LDL, so part of the effect comes from replacing saturated fat. Many trials were funded by the California Walnut Commission.
Are walnuts good for your brain?
Not proven. A 2-year trial gave 708 older adults walnuts and found no overall change in cognitive decline, though the Barcelona group alone did better in a post hoc look. A review of 5 trials also found no significant overall effect, while all 7 observational studies in it found links. Mice fed walnuts held up on memory tests, which is not evidence for people.
Do walnuts make you gain weight?
Not on average in trials. The meta-analysis of 26 trials found no weight change, and in a 100-person weight-loss trial both diets lost similar weight (8.9% with walnuts, 9.4% without). Walnuts are calorie-dense at 185 calories an ounce, and one review found 6 of 6 trials leaned toward the control diet for body weight, though most effects were small. In 3 US cohorts, a half serving a day went with 0.37 kg less weight gain per 4 years, which is a link only.
Are walnuts a good source of omega-3?
Yes, of the plant kind, ALA: 2.57 g per ounce and 9.08 g per 100 g, third among 110 foods on this site. A review found ALA supplements raised blood EPA and DPA but not DHA, so walnuts do not replace fish or algae oil for DHA. In a cohort meta-analysis, each extra gram of ALA a day went with a 5% lower risk of death, but that covers ALA from all foods.
Do walnuts lower blood pressure?
Probably very little. A meta-analysis of 18 trials found a 0.08 mm Hg change in both systolic and diastolic pressure. In the 2-year WAHA trial, office systolic pressure fell 4.61 mm Hg on walnuts, a gap that just missed significance, and the 24-hour drop was bigger (8.5 mm Hg against 2.5 mm Hg in controls) in people who started with the highest pressure. Do not change blood pressure medicine based on this.
Are walnuts good for people with diabetes?
They can fit, but the evidence is limited. In a cohort of women, 2 or more servings a week went with a lower risk of developing type 2 diabetes (hazard ratio 0.67, or 0.76 after adjusting for weight). In a meta-analysis of people with abnormal glucose handling, walnuts did not change fasting glucose or HbA1c, and in a small diabetes trial fasting glucose rose 10.0 mg/dL from baseline on walnuts. Check portions with your care team.