Pumpkin seeds and walnuts: one has the trials, one has the minerals

According to a meta-analysis of 26 trials with 1059 people, walnut diets lowered LDL cholesterol by 5.5 mg/dL more than control diets (95% CI 3.3 to 7.7 mg/dL). That is a small change, and the trials differed in dose and in what walnuts were compared with. A 2026 meta-analysis of 49 trials with 4611 people found triglycerides 6.2 mg/dL lower with walnuts. An umbrella review graded the LDL effect of walnuts as small to moderate, with moderate certainty. Pumpkin seeds make their case on composition. Per 100 g raw they hold about 500 mg magnesium, 8.4 mg iron and 30 g protein, three to four times the magnesium and iron of raw walnuts and twice the protein. We found no synthesis of trials on pumpkin seeds eaten as food, and no study that compared the two foods head to head.

How much is actually in it

• Per 100 g raw, pumpkin seeds carry about 500 mg magnesium, 8.4 mg iron and 30 g protein, roughly three to four times the magnesium and iron and twice the protein of raw walnuts. — USDA Foundation Foods samples: raw pumpkin seeds (pepitas) and raw English walnut halves, 8 samples each (n = 8 + 8 samples) Evidence E source
  Pumpkin seeds: magnesium 499.7 mg (468.5-511.0), iron 8.36 mg (7.84-9.42), zinc 6.34 mg (4.34-10.0), protein 29.9 g; walnuts: magnesium 142.4 mg (125-148), iron 2.24 mg (1.99-2.54), zinc 2.76 mg (2.22-3.04), protein 14.6 g
• Raw walnuts are about 70 g fat per 3.5 oz (100 g), of which about 49 g is polyunsaturated, with little spread between samples. — USDA Foundation Foods, raw English walnut halves, 8 samples (n = 8 samples) Evidence E source
  Total fat 69.74 g (67.49-71.43, spread 6%); polyunsaturated 49.33 g (45.55-51.49); saturated 6.05 g (5.81-6.47)

What a real portion looks like

• A typical serving of either is 1 oz (28 g). A cup is 5.1 oz (144 g) of shelled pumpkin seeds or 4.2 oz (120 g) of walnuts, and one walnut weighs about 2 g. — US dietary survey portion weights Evidence E source
  Pumpkin seeds unsalted (FNDDS 43101150): 1 oz 28 g, 1 cup without shell 144 g, 1 cup in shell 46 g; walnuts (FNDDS 42116000): 1 oz 28 g, 1 cup 120 g, 1 nut 2 g

What your body absorbs

• Nuts deliver fewer calories than Atwater factors predict, and grinding or roasting releases more of their energy. — 21 human and in vitro studies of almonds, cashews, hazelnuts, pistachios, walnuts and peanuts (n = 21 studies) Evidence C source
  Metabolizable energy consistently below Atwater prediction; energy release flour > chopped > whole, butter > roasted > raw

What cooking and storage change

• By the USDA table for roasted nuts and seeds, roasting keeps all the magnesium, iron and zinc and loses about 20% of phosphorus and folate and 15% of thiamin. — USDA retention factors for the group Nut and Seed Products, roasted Evidence E source
  Retained: magnesium, iron, zinc, copper, potassium 100%; phosphorus 80%; folate 80%; thiamin 85%; riboflavin, niacin, vitamin B6 95%
• Laboratory data suggest roasting does not remove the main walnut allergens, which stay heat stable. — 32 articles, mostly in vitro, on processed tree nuts (n = 32 articles) Evidence D source
  Lipid transfer proteins and seed storage proteins of walnut and other tree nuts heat stable; roasting lowered allergenicity only for hazelnut PR-10 proteins

What it does to your health

• According to a meta-analysis of 26 trials with 1059 people, walnut diets lowered LDL cholesterol by 5.5 mg/dL more than control diets. — 26 clinical trials, 1059 participants (n = 1059) Evidence A source
  LDL -5.51 mg/dL (95% CI -7.72 to -3.29); total cholesterol -6.99 mg/dL (-9.39 to -4.58); no difference in body weight or blood pressure
• According to a meta-analysis of 25 trials with 2155 people, walnuts lowered apolipoprotein B slightly and did not lower blood pressure. — 25 RCTs, 26 arms, 2155 patients (n = 2155) Evidence A source
  ApoB -0.06 (95% CI -0.10 to -0.01); systolic -1.20 mmHg (-4.02 to 1.61), not significant
• According to a 2026 meta-analysis of 49 trials with 4611 people, walnuts lowered LDL cholesterol by 5.7 mg/dL and triglycerides by 6.2 mg/dL. — 49 RCTs, 57 effect sizes, 4611 adults (n = 4611) Evidence A source
  TG -6.24 mg/dL (95% CI -9.49 to -2.99); TC -6.39 (-8.54 to -4.23); LDL -5.68 (-7.89 to -3.47); no effect on HDL or apolipoproteins
• An umbrella review of 108 systematic reviews graded walnuts as lowering LDL cholesterol by a small to moderate amount, with moderate certainty. — 37 guidelines, 108 systematic reviews and 20 RCTs on foods and LDL (n = 108 reviews) Evidence A source
  Walnuts: small to moderate LDL reduction, moderate GRADE evidence

Safety, limits and interactions

• Pumpkin seed allergy is reported mostly as single cases, and seed allergy is managed by avoidance. — literature 1930-2016 on six edible seeds Evidence C source
  Sesame allergy prevalence 0.1-0.2%; other seeds mainly case reports
• The US levothyroxine label warns that walnuts may bind the drug in the gut and reduce its absorption. — people taking levothyroxine Evidence E source
  Possible reduced absorption; size not given

What people believe that the data does not support

• Walnut diets did not change body weight in a meta-analysis of 26 trials, against the belief that nuts are fattening. — 26 clinical trials, 1059 participants (n = 1059) Evidence A source
  Weight change -0.26 lb (95% CI -4.7 to 4.1; metric: -0.12 kg, -2.12 to 1.88), not significant
• The EU authorizes the claim that walnuts improve the elasticity of blood vessels. — — Evidence E source
  Authorized claim; condition of use not in this snapshot
• The EU did not authorize the broader claim that walnuts support cardiovascular health. — — Evidence E source
  Non-authorized claim

Who this works differently for

• In a trial in 20 boys aged 2 to 7 in a bladder stone area of Thailand, pumpkin seeds at 60 mg per kg body weight daily lowered calcium oxalate crystals in urine compared with orthophosphate supplementation. — 20 boys aged 2-7 years, Ubon province, Thailand (n = 20) Evidence B source
  Lower calcium oxalate crystal occurrence and urinary calcium, higher phosphorus, pyrophosphate and potassium versus orthophosphate
• Challenge-confirmed tree nut allergy affects under 2% of people, and walnut is among the most common tree nut allergies in the USA and UK. — 36 prevalence studies, mostly children, Europe, UK, USA (n = 36 studies) Evidence C source
  Challenge-confirmed prevalence < 2%; probable 0.05-4.9%
• In 25 children with pumpkin seed allergy at one Turkish clinic, 64% had anaphylaxis and all tolerated pumpkin flesh. — 25 children, median age 2.98 years, tertiary clinic in Turkey, 2016-2024 (n = 25) Evidence C source
  Anaphylaxis 64%; tree nut co-allergy 76%; pumpkin pulp tolerated in all

What is still unknown

• Whether walnuts specifically affect prostate cancer risk is unknown, as data were too sparse for a meta-analysis. — 11 observational studies, 287,786 participants, 32,213 prostate cancer cases (n = 287786) Evidence C source
  Total nuts RR 0.94 (95% CI 0.85-1.04), not significant

The bottom line

A serving of either is 1 oz, or 28 g, and one walnut weighs about 2 g. Walnuts are about 70 g fat per 3.5 oz (100 g), 49 g of it polyunsaturated, and that fat is the main compositional difference from pumpkin seeds. Zinc in pumpkin seeds ran from 4.3 to 10 mg per 3.5 oz (100 g) across eight USDA samples, so a single label value can be far off. The belief that walnuts make you fat does not hold up in the trials. In the same 26 trials body weight did not change significantly (difference -0.26 lb (95% CI -4.7 to 4.1; metric: -0.12 kg, -2.12 to 1.88)), though weight was a secondary outcome and many trials matched calories. Roasting leaves the minerals alone. By the USDA retention table for roasted nuts and seeds, magnesium, iron and zinc stay at 100% while about 20% of phosphorus and folate and 15% of thiamin are lost. That group factor dates from 1975 and was never measured on these two foods. A review of 21 studies found that nuts deliver fewer calories than Atwater factors predict, and that grinding or roasting releases more of their energy. It had no pumpkin seed data. Allergy is the main caution. Walnut is among the most commonly reported tree nut allergies in the USA and the UK. Laboratory data suggest roasting does not break down the main walnut allergens, and the review behind that had no challenge tests of roasted walnuts in allergic people. Pumpkin seed allergy appears in the literature mostly as single case reports. In one Turkish clinic series of 25 children with pumpkin seed allergy, 64% had anaphylaxis, 76% were also allergic to tree nuts, and all of them tolerated pumpkin flesh. The US levothyroxine label warns that walnuts may bind the drug in the gut and reduce its absorption, without saying by how much. If you take it, the person who prescribes it is the one to ask. The EU authorizes one health claim for walnuts, that they improve the elasticity of blood vessels, which is a marker of vessel function. The broader claim that walnuts support cardiovascular health was not authorized, meaning the evidence fell short at assessment. Whether walnuts change prostate cancer risk is unknown. A meta-analysis of 11 observational studies found no significant link for total nuts (RR 0.94, 95% CI 0.85 to 1.04), and walnut data were too sparse to analyze. In 20 boys aged 2 to 7 in a bladder stone area of Thailand, pumpkin seeds lowered calcium oxalate crystals in urine compared with an orthophosphate supplement. That trial dates from 1987, and its abstract gives no effect size.

Sources

1. psw-r3-01 · USDA FoodData Central Foundation Foods, dataset
   Seeds, pumpkin seeds (pepitas), raw: Magnesium 499.7 MG range 468.5-511.0 n=8; Iron 8.363 MG range 7.84-9.42 n=8; Zinc 6.341 MG range 4.34-10.0 n=8; Protein 29.9079 G range 28.355-31.058 | Nuts, walnuts, English, halves, raw: Magnesium 142.4 MG range 125.0-148.0 n=8; Iron 2.235 MG range 1.99-2.54 n=8; Zinc 2.76 MG range 2.22-3.04 n=8; Protein 14.5644 G range 12.932-16.324
   USDA FoodData Central, Foundation Foods, release 2026-04-30 · checked 2026-10-01
2. psw-r3-02 · USDA FoodData Central Foundation Foods, dataset
   Nuts, walnuts, English, halves, raw: Total lipid (fat) 69.74 G range 67.49-71.43 n=8; Fatty acids, total polyunsaturated 49.331 G range 45.55-51.49 n=8; Fatty acids, total saturated 6.054 G range 5.81-6.47 n=8
   USDA FoodData Central, Foundation Foods, release 2026-04-30 · checked 2026-10-01
3. psw-r3-03 · USDA FNDDS, dataset
   Pumpkin seeds, unsalted (FNDDS 43101150): 1 oz, without shell 28 g; 1 cup, without shell 144 g; 1 cup, in shell, yields 46 g | Walnuts, excluding honey roasted (FNDDS 42116000): 1 oz 28 g; 1 cup 120 g; 1 nut 2 g
   USDA FNDDS, codes 43101150 and 42116000 · checked 2026-10-01
4. psw-r3-04 · systematic review
   The ME of nuts was consistently lower than that predicted by Atwater factors for investigated nut types (almonds, cashews, hazelnuts, pistachios, walnuts, and peanuts).
   Adv Nutr, 2023 · checked 2026-10-01
5. psw-r3-05 · USDA Nutrient Retention Factors, Release 6, dataset
   USDA-RETN-R6:2203 NUTS,ROASTED (Nut and Seed Products): phosphorus_mg 80%; folate_total_ug 80%; thiamin_mg 85%; magnesium_mg 100%; iron_mg 100%; zinc_mg 100%
   USDA Table of Nutrient Retention Factors, Release 6 (2007), code 2203 · checked 2026-10-01
6. psw-r3-06 · systematic review
   The majority of the in vitro studies investigating the allergenicity of nonspecific lipid transfer proteins (nsLTPs) and seed storage proteins in hazelnut, almond, cashew nut, Brazil nut, walnut, pecan nut and pistachio nut show heat stability towards different thermal processing methods.
   Allergy, 2013 · checked 2026-10-01
7. psw-r3-07 · systematic review and meta-analysis
   -5.51 mg/dL (95% CI: -7.72, -3.29 mg/dL; P < 0.001) (3.73% greater reduction) for low-density lipoprotein (LDL) cholesterol
   Am J Clin Nutr, 2018 · checked 2026-10-01
8. psw-r3-09 · systematic review and meta-analysis
   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)
   Endocrinol Diabetes Metab, 2026 · checked 2026-10-01
9. psw-r3-10 · systematic review and meta-analysis
   The pooled analysis of 49 RCTs (57 effect sizes; 4611 participants) showed that Walnut consumption significantly reduced and TG (WMD: -6.24 mg/dL, 95% CI: [-9.49, -2.99], p < 0.001)
   Food Sci Nutr, 2026 · checked 2026-10-01
10. psw-r3-11 · umbrella review
    Pulses, hazelnuts, walnuts, high-fiber/wholegrain foods, and green tea caused small to moderate reductions, whereas sugar caused a small increase.
    Nutr Metab Cardiovasc Dis, 2021 · checked 2026-10-01
11. psw-r3-15 · review
    Considering the worldwide consumption of those seeds, the number of published articles on the subject was relatively small and was mainly as case reports rather than large series.
    Allergy, 2016 · checked 2026-10-01
12. psw-r3-16 · drug label
    Soybean flour, cottonseed meal, walnuts, and dietary fiber may bind and decrease the absorption of levothyroxine sodium from the gastrointestinal tract.
    Levothyroxine sodium, FDA-approved label (DailyMed), effective 2026-03-24 · checked 2026-10-01
13. psw-r3-08 · systematic review and meta-analysis
    Walnut-enriched diets did not lead to significant differences in weight change (kg) compared with control diets [WMD = -0.12 (95% CI: -2.12, 1.88); P = 0.90]
    Am J Clin Nutr, 2018 · checked 2026-10-01
14. psw-r3-17 · regulatory 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 2026-10-01
15. psw-r3-18 · regulatory register entry
    POL-HC-8134 Walnuts Walnuts support cardiovascular health. Non-authorised
    EU Register on nutrition and health claims, claim POL-HC-8134, snapshot 2026-09-21 · checked 2026-10-01
16. psw-r3-12 · randomized controlled trial
    Pumpkin seeds lowered calcium-oxalate crystal occurrence and calcium level but increased phosphorus, pyrophosphate, glycosaminoglycans, and potassium values in urine as compared with orthophosphate supplementation.
    Am J Clin Nutr, 1987 · checked 2026-10-01
17. psw-r3-13 · systematic review
    Prevalence of individual tree nut allergies varied significantly by region with hazelnut the most common tree nut allergy in Europe, walnut and cashew in the USA and Brazil nut, almond and walnut most commonly reported in the UK.
    Curr Allergy Asthma Rep, 2015 · checked 2026-10-01
18. psw-r3-14 · case series
    Immediate reactions were universal, and anaphylaxis occurred in 64%.
    Allergy Asthma Proc, 2026 · checked 2026-10-01
19. psw-r3-19 · systematic review and meta-analysis
    Data on other types of nuts, including walnut, tree nuts, peanut, and peanut butter, were not sufficient for performing a meta-analysis.
    Nutr Metab Cardiovasc Dis, 2023 · checked 2026-10-01