Cashews and walnuts: the walnut is the one with the trials

Supermarkets sell these two as one category, and the evidence does not treat them that way. Pooling 25 randomized trials in 2155 people, walnuts lowered apolipoprotein B by a weighted mean difference of -0.06, interval -0.10 to -0.01, and left apolipoprotein A1 and blood pressure untouched. The abstract never gives the unit for that figure, and the paper disagrees with itself about how many people were in it. Cashews appear in none of those 25 trials. The wider pooling, 129 randomized trials of tree nuts and peanuts together, found lower LDL cholesterol, total cholesterol, triglycerides and apolipoprotein B, rated its own certainty moderate at best, and kept every nut inside one group. Composition splits the pair much more cleanly. Across 8 USDA samples of each, walnuts carry 69.74 g of fat per 3.5 oz (100 g) against 38.86 g in cashews, while cashews carry roughly twice the iron, zinc, magnesium and copper.

How much is actually in it

• Raw walnuts carry nearly twice the fat of raw cashews, 69.7 g against 38.9 g per 3.5 oz (100 g), while cashews carry about twice the iron, zinc and magnesium, each measured in 8 USDA samples. — USDA Foundation Foods individual sample analyses for Nuts, walnuts, English, halves, raw and Nuts, cashew nuts, raw, per 3.5 oz (100 g) (n = 8 samples of each nut) Evidence E source
  Walnut total fat 69.74 g versus cashew 38.86 g, iron 2.235 versus 5.988 mg, zinc 2.76 versus 5.071 mg, magnesium 142.4 versus 250.6 mg, copper 1.206 versus 2.218 mg, fiber 5.21 versus 4.104 g, cashew selenium 20.67 ug with a sample range of 8.22 to 54.4
• By the UK composition tables a cashew kernel is a starchy nut, 18.1 g of carbohydrate per 3.5 oz (100 g) of which 13.5 g is starch, against 3.3 g of carbohydrate in a walnut kernel. — CoFID 2021 records 14-811 Cashew nuts, kernel only, plain and 14-879 Walnuts, kernel only, per 3.5 oz (100 g) (n = 2 reference records) Evidence E source
  Cashew 573 calories, fat 48.2 g of which saturated 9.50 g and monounsaturated 27.80 g, protein 17.7 g, carbohydrate 18.1 g, starch 13.5 g; walnut 688 calories, fat 68.5 g of which saturated 7.47 g and polyunsaturated 46.76 g, protein 14.7 g, carbohydrate 3.3 g, starch 0.7 g

What a real portion looks like

• The US survey database gives both nuts the same one ounce serving of 0.99 oz (28 g), but a cup holds 4.6 oz (130 g) of cashews against 4.2 oz (120 g) of walnut halves, and a single nut is counted as 2 g either way. — USDA FNDDS household measures for Cashews, unroasted, food code 42104050, and Walnuts, excluding honey roasted, food code 42116000 (n = 5 measures for each nut) Evidence E source
  Cashews 1 nut 2 g, 1 oz 28 g, 1 package 50 g, 1 cup 130 g, quantity not specified 28 g; walnuts 1 nut 2 g, 1 oz 28 g, 1 package 50 g, 1 cup 120 g, quantity not specified 28 g

What your body absorbs

• The energy a body actually gets from cashews and walnuts is lower than food labels predict, and it moves with the form of the nut, from whole to chopped to flour. — 21 human and in vitro studies of metabolizable energy and lipid bioaccessibility in tree nuts and peanuts, adults aged 18 and over (n = 21 studies) Evidence C source
  Metabolizable energy below Atwater prediction for all nut types tested including cashews and walnuts, 22.6 kJ/g for pistachios and 18.5 kJ/g for raw almonds, rising with processing in the order whole nuts, chopped, flour and raw, roasted, butter

What cooking and storage change

• By the USDA retention table for nuts and seeds, roasting costs about 20 percent of folate and phosphorus and 15 percent of thiamin, while iron, magnesium, zinc and copper survive it whole. — USDA Table of Nutrient Retention Factors Release 6, food group 12 Nut and Seed Products, method NUTS,ROASTED, retention code 2203 (n = 1 retention code) Evidence E source
  Retained after roasting: folate 80%, phosphorus 80%, vitamin C 80%, thiamin 85%, sodium 95%, riboflavin 95%, niacin 95%, vitamin B6 95%, calcium 100%, iron 100%, magnesium 100%, potassium 100%, zinc 100%, copper 100%, choline 100%, vitamin B12 100%
• The safety problem the tree nut trade actually fights is aflatoxin, and across 41 studies cold plasma and UV-C cut it by 70 to 95 percent at the cost of oxidizing the fat in the nut. — 41 original studies of physical, chemical and biological aflatoxin decontamination in tree nuts, published 2005 to 2025 (n = 41 studies) Evidence D source
  Cold atmospheric plasma and UV-C reduce aflatoxin by 70 to 95 percent with rising malondialdehyde in pistachios; ozonation and organic acids approach 100 percent degradation with up to 29 percent loss of alpha-tocopherol in hazelnuts; microbial methods exceed 80 percent

What it does to your health

• Across 25 randomized trials in 2155 people, walnut supplementation lowered apolipoprotein B by a weighted mean difference of 0.06 and left apolipoprotein A1 and blood pressure unchanged. — 2155 participants in 25 randomized controlled trials with 26 intervention arms, searched to January 2025 (n = 2155) Evidence A source
  ApoB weighted mean difference -0.06, 95% CI -0.10 to -0.01, p = 0.002; ApoA1 -0.50, 95% CI -1.34 to 0.33; systolic blood pressure -1.20 mmHg, 95% CI -4.02 to 1.61; diastolic -0.44 mmHg, 95% CI -2.55 to 1.67
• Pooling 129 randomized trials of tree nuts and peanuts, nut eating lowered LDL cholesterol, total cholesterol, triglycerides and apolipoprotein B, with the certainty of that evidence rated moderate at best. — 153 articles describing 139 randomized controlled trials of tree nut or peanut consumption at any dose, 129 of them pooled (n = 129 trials) Evidence A source
  Significant reduction in LDL cholesterol, total cholesterol, triglycerides, TC to HDL ratio, LDL to HDL ratio and apoB; GRADE certainty moderate for TC:HDL, LDL:HDL and apoB, low for triglycerides, very low for LDL and total cholesterol
• Eating 1.4 oz (40 g) of walnuts at dinner for 8 weeks raised evening urinary melatonin metabolite and shortened sleep latency in 76 young adults. — 76 young adults aged 24 years, 85.5 percent women, eating 1.4 oz (40 g) of walnuts daily at dinner for 8 weeks against no nuts, crossover with a 2-week washout (n = 76) Evidence B source
  Evening urinary 6-sulfatoxymelatonin higher, p = 0.029; sleep latency improved, p = 0.001; global sleep quality improved, p = 0.002; daytime sleepiness lower, p = 0.002

Safety, limits and interactions

• A man of 78 who already had chronic kidney disease ate 3 to 4 ounces of cashews daily for a year, reached a creatinine of 6.0 mg/dL, and had a kidney biopsy full of calcium oxalate crystals. — one 78-year-old man with stable chronic kidney disease, baseline creatinine 2.05 mg/dL, eating 3 to 4 oz (85 to 113 g) of cashew nuts daily for a year (n = 1) Evidence D source
  Serum creatinine 2.05 to 6.0 mg/dL, kidney biopsy showing acute tubular injury with extensive calcium oxalate crystal deposition
• About 0.9 percent of Europeans report a tree nut allergy at some point in life, while food challenge confirms one in 0.04 percent of people at any one time. — 93 European prevalence studies published up to 2021, all age groups, pooled for the eight big food allergens (n = 93 studies) Evidence C source
  Tree nuts self-reported lifetime prevalence 0.9 percent, 95% CI 0.6 to 1.2; challenge-verified point prevalence 0.04 percent, 95% CI 0.02 to 0.1; peanut 1.5 and 0.1 percent respectively

What people believe that the data does not support

• Walnuts hold one authorized health claim in the EU, about the elasticity of blood vessels, while cashews hold none at all. — EU Register on nutrition and health claims, snapshot of 21 September 2026, 2330 claims of which 262 authorized (n = 1 authorized claim for walnuts, 0 for cashews) Evidence E source
  Claim POL-HC-6525 for Walnuts authorized; three register entries naming cashew are all non-authorized
• The best known nut claim, that 1.1 oz (30 g) of nuts a day helps keep the heart healthy, was refused in the EU, and the wording that was refused had already excluded cashews from the list of nuts. — EU Register on nutrition and health claims, claim POL-HC-7666, snapshot of 21 September 2026 (n = 1 refused claim) Evidence E source
  Status Non-authorized for the wording Eating 1.1 oz (30g) of nuts per day as part of a balanced diet helps maintain heart health, applied to peanuts and tree nuts but excluding brazil, macadamia and cashew nuts

Who this works differently for

• In 38 postmenopausal women with high cholesterol, 1.4 oz (40 g) of walnuts a day for 4 weeks improved microvascular function against a 5 g dose while leaving total, LDL and HDL cholesterol unchanged. — 38 hypercholesterolemic postmenopausal women randomized to 5 g or 1.4 oz (40 g) of daily walnut intake for 4 weeks (n = 38) Evidence B source
  Reactive hyperemia index and Framingham reactive hyperemia index higher on 40 g than on 5 g; no significant change in total, LDL or HDL cholesterol; change in index correlated with the sum of plasma epoxides, r = 0.65, P = .002
• For people with chronic kidney disease the whole evidence base on nuts is four studies in 1270 patients, and walnuts were the nut that lowered LDL cholesterol and blood pressure without upsetting electrolytes. — four studies, three trials and one cohort, involving 1270 patients with chronic kidney disease, searched to February 2025 (n = 1270) Evidence C source
  Walnuts lowered LDL cholesterol and blood pressure with no electrolyte disturbance; Brazil nuts and baru almond oil improved oxidative stress and inflammation markers; total nut intake was associated with lower all-cause mortality

The bottom line

The difference that shows up on a plate is what surrounds the fat. By the UK tables a cashew kernel is a starchy nut, 18.1 g of carbohydrate per 3.5 oz (100 g) of which 13.5 g is starch, against 3.3 g of carbohydrate in a walnut kernel. The walnut is the denser of the two at 688 calories against 573. One ounce is 0.99 oz (28 g) of either in the US survey database, a cup holds 4.6 oz (130 g) of cashews against 4.2 oz (120 g) of walnut halves, and counting in pieces is unreliable, because a walnut counted as one nut in that dataset is a half kernel. Not all of the labeled energy arrives either. A review of 21 studies found metabolizable energy below the Atwater prediction for every nut type tested, falling as the nut moves from flour to chopped to whole, with no separate figure for cashews or for walnuts. Roasting costs about 20 percent of folate and phosphorus and 15 percent of thiamin, while iron, magnesium, zinc and copper come through intact. That USDA factor is set for the whole nut and seed group rather than for these two nuts, and the table carries no vitamin E at all. The walnut also has two small trials of its own. In 76 young adults, 85.5 percent of them women, 1.4 oz (40 g) of walnuts at dinner for 8 weeks raised the evening urinary melatonin metabolite and shortened sleep latency, in an open study with no placebo where sleep was measured by questionnaire. In 38 postmenopausal women with high cholesterol, 40 g a day for 4 weeks improved microvascular function against a 5 g dose and left total, LDL and HDL cholesterol where they were, which 38 women over 4 weeks cannot settle in either direction. On who should be careful, nothing here is trial-grade. About 0.9 percent of Europeans report a tree nut allergy at some point in life, and food challenge confirms one in 0.04 percent at any one time, which are two numbers counted in different ways rather than a gap between belief and fact, from a pooling of 93 European studies that does not separate cashew from walnut. One man of 78 who already had chronic kidney disease ate 3 to 4 ounces of cashews daily for a year and went from a creatinine of 2.05 to 6.0 mg/dL, with a biopsy full of calcium oxalate crystals. That is one case in a kidney that was already damaged, it says nothing about how often this happens, and no source here gives the oxalate content of either nut, so it is not evidence that the walnut is the safer of the two on oxalate. For kidney disease the whole literature is four studies in 1270 patients, where walnuts lowered LDL cholesterol and blood pressure without disturbing electrolytes and cashews do not appear at all. In the EU one claim stands, that walnuts contribute to the elasticity of blood vessels. The familiar claim that 1.1 oz (30 g) of nuts a day helps maintain heart health was refused, and its wording had already left cashews out.

Sources

1. cawn-daily-r2-01 · reference dataset
   Nuts, walnuts, English, halves, raw: Total lipid (fat) 69.74 G range 67.49-71.43 n=8 spread 6% | Iron, Fe 2.235 MG range 1.99-2.54 n=8 spread 25% | Zinc, Zn 2.76 MG range 2.22-3.04 n=8 spread 30% | Magnesium, Mg 142.4 MG range 125.0-148.0 n=8 spread 16% | Copper, Cu 1.206 MG range 1.02-1.39 n=8 spread 31% | Fiber, total dietary 5.21 G range 4.3-7.38 n=8 spread 59% || Nuts, cashew nuts, raw: Total lipid (fat) 38.86 G range 36.39-42.17 n=8 spread 15% | Iron, Fe 5.988 MG range 5.46-6.84 n=8 spread 23% | Zinc, Zn 5.071 MG range 4.56-5.44 n=8 spread 17% | Magnesium, Mg 250.6 MG range 222.0-265.0 n=8 spread 17% | Copper, Cu 2.218 MG range 1.97-2.49 n=8 spread 23% | Fiber, total dietary 4.104 G range 3.63-5.55 n=8 spread 47% | Selenium, Se 20.67 UG range 8.22-54.4 n=8 spread 223%
   USDA FoodData Central, Foundation Foods, release 2026-04-30 · checked 2026-09-25
2. cawn-daily-r2-02 · reference dataset
   CoFID 14-811 Cashew nuts, kernel only, plain: Energy 573 kcal, Fat 48.2 g, Satd FA /100g fd 9.50 g, Mono FA /100g food 27.80 g, Poly FA /100g food 8.80 g, Protein 17.7 g, Carbohydrate 18.1 g, Starch 13.5 g, Total sugars 4.6 g, NSP 3.2 g, Water 4.4 g | CoFID 14-879 Walnuts, kernel only: Energy 688 kcal, Fat 68.5 g, Satd FA /100g fd 7.47 g, Mono FA /100g food 10.67 g, Poly FA /100g food 46.76 g, Protein 14.7 g, Carbohydrate 3.3 g, Starch 0.7 g, Total sugars 2.6 g, NSP 3.5 g
   CoFID 2021, Public Health England, records 14-811 and 14-879 · checked 2026-09-25
3. cawn-daily-r2-03 · USDA FNDDS portion dataset
   Cashews, unroasted (FNDDS 42104050, fdc_id 2707494): 1 nut 2 g, 1 cup 130 g, 1 package 50 g, 1 oz 28 g, Quantity not specified 28 g | Walnuts, excluding honey roasted (FNDDS 42116000, fdc_id 2707531): 1 nut 2 g, 1 cup 120 g, 1 package 50 g, 1 oz 28 g, Quantity not specified 28 g
   USDA FNDDS, food codes 42104050 and 42116000 · checked 2026-09-25
4. cawn-daily-r2-05 · systematic review of human and in vitro studies
   The ME of nuts was consistently lower than that predicted by Atwater factors for investigated nut types (almonds, cashews, hazelnuts, pistachios, walnuts, and peanuts). ... ME was influenced by nut type (ME = 22.6 kJ/g for pistachios; ME = 18.5 kJ/g for raw almonds), physical form (flour > chopped > whole nuts), heat processing (butter > roasted > raw) and dose of consumption.
   Adv Nutr, 2023 · checked 2026-09-25
5. cawn-daily-r2-04 · USDA retention factor dataset
   USDA-RETN-R6:2203 NUTS,ROASTED, group 12 Nut and Seed Products: phosphorus_mg 80%, vitamin_c_mg 80%, folate_total_ug 80%, thiamin_mg 85%, sodium_mg 95%, riboflavin_mg 95%, niacin_mg 95%, vitamin_b6_mg 95%, calcium_mg 100%, iron_mg 100%, magnesium_mg 100%, potassium_mg 100%, zinc_mg 100%, copper_mg 100%, choline_mg 100%, vitamin_b12_ug 100%
   USDA Table of Nutrient Retention Factors, Release 6, 2007, retention code 2203 · checked 2026-09-25
6. cawn-daily-r2-12 · scoping review of in vitro and processing studies
   Physical approaches, particularly cold atmospheric plasma and UV-C radiation, achieved robust reduction rates ranging from 70% to 95%; however, these highly energetic treatments often induced lipid oxidation, evidenced by linear increases in malondialdehyde (MDA) levels in matrices such as pistachios.
   Mycotoxin Res, 2026 · checked 2026-09-25
7. cawn-daily-r2-06 · meta-analysis of RCTs
   Twenty-five RCTs comprising 26 intervention arms with 2155 patients were included. Walnut significantly decreased ApoB (WMD = -0.06; 95% CI: -0.10, -0.01, p = 0.002), but did not affect ApoA1 (WMD = -0.50; 95% CI: -1.34, 0.33, p = 0.249), systolic blood pressure (SBP) (WMD = -1.20; 95% CI: -4.02, 1.61, p = 0.401) and diastolic blood pressure (DBP) (WMD = -0.44; 95% CI: -2.55, 1.67, p = 0.682).
   Endocrinol Diabetes Metab, 2026 · checked 2026-09-25
8. cawn-daily-r2-07 · meta-analysis of RCTs
   A total of 153 articles describing 139 studies (81 parallel design and 58 cross-over design) were included in the systematic review, with 129 studies in the meta-analysis. The meta-analysis showed a significant decrease for low-density lipoprotein (LDL) cholesterol, total cholesterol (TC), triglycerides (TG), TC:high-density lipoprotein (HDL) cholesterol, LDL cholesterol:HDL cholesterol, and apolipoprotein B (apoB) following nut consumption.
   Adv Nutr, 2023 · checked 2026-09-25
9. cawn-daily-r2-08 · randomized crossover trial in humans
   The 8-week walnut intervention significantly increased evening urinary 6-SMT concentrations (p = 0.029) and improved sleep latency (p = 0.001), while no differences were found between the baseline and control conditions. ... Specifically, we demonstrated that a daily serving of 40 g of walnuts increases urinary 6-SMT levels, reduces sleep latency, and improves global sleep quality.
   Food Funct, 2025 · checked 2026-09-25
10. cawn-daily-r2-10 · case report
    He underwent a kidney biopsy, which showed acute tubular injury associated with extensive calcium oxalate crystal deposition. On revisiting his history, it was discovered that the patient had been consuming 3-4 oz of cashew nuts daily for the last 1 year.
    Kidney Med, 2026 · checked 2026-09-25
11. cawn-daily-r2-11 · meta-analysis of prevalence studies
    The overall pooled estimates for all age groups of self-reported lifetime prevalence were as follows: cow's milk (5.7%, 95% confidence interval 4.4-6.9), egg (2.4%, 1.8-3.0), wheat (1.6%, 0.9-2.3), soy (0.5%, 0.3-0.7), peanut (1.5%, 1.0-2.1), tree nuts (0.9%, 0.6-1.2), fish (1.4%, 0.8-2.0) and shellfish (0.4%, 0.3-0.6).
    Allergy, 2023 · checked 2026-09-25
12. cawn-daily-r2-14 · EU health claim register entry
    POL-HC-6525 Walnuts Walnuts contribute to the improvement of the elasticity of blood vessels Authorised
    EU Register on nutrition and health claims, claim POL-HC-6525, snapshot 2026-09-21 · checked 2026-09-25
13. cawn-daily-r2-15 · EU health claim register entry
    POL-HC-7666 Nuts - peanuts and tree nuts (almonds, hazelnuts, pecans, pistachios and walnuts), excluding brazil, macadamia and cashew nuts Eating 30g of nuts per day as part of a balanced diet helps maintain heart health. Non-authorised
    EU Register on nutrition and health claims, claim POL-HC-7666, snapshot 2026-09-21 · checked 2026-09-25
14. cawn-daily-r2-09 · randomized trial in humans
    Thirty-eight hypercholesterolemic postmenopausal women were randomized to 4 weeks of 5 g or 40 g of daily walnut intake. ... Compared to 5 g of daily walnut intake, consuming 40 g/d of walnuts for 4 weeks increased the RHI and Framingham RHI. Total cholesterol and low- and high-density cholesterol did not significantly change after walnut intake.
    J Nutr Biochem, 2015 · checked 2026-09-25
15. cawn-daily-r2-13 · systematic review in humans
    The search identified 2,521 records, with four studies (three trials, one cohort) involving 1,270 CKD patients meeting the inclusion criteria. ... Overall the findings indicate positive effects of Brazil nuts and baru almond oil on oxidative stress and inflammation markers, while walnuts reduced LDL cholesterol and blood pressure while posing no risk regarding electrolytes balance.
    Front Nutr, 2025 · checked 2026-09-25