Walnut oil: one small trial in diabetes, and not much else yet

In a 90-day randomized trial in Iran, 100 adults aged 35 to 75 with type 2 diabetes and high blood lipids took 1 tbsp (15 mL) of Persian walnut oil a day in capsules. Their LDL cholesterol fell 30.4 more than on placebo, in a single-center trial whose water placebo carried no calories and whose abstract gives no unit for that number. Total cholesterol fell 30.0 and triglycerides 15.0 by the same comparison. HDL rose 2.3, which did not reach significance (P = 0.06). That is one trial in people with diabetes, and we found no trial of walnut oil alone on cholesterol in healthy adults. What you buy is mostly polyunsaturated fat. A single USDA record, where ALA varies with cultivar and processing, lists 63.3 g per 3.5 oz (100 g), including 10.4 g of the plant omega-3 ALA and 52.9 g of linoleic acid, with 9.1 g saturated. A 14 g tablespoon works out to about 1.5 g of ALA and 124 calories.

The numbers, per 3.5 oz (100 g)

As people eat it, per 3.5 oz (100 g)

How much is actually in it

• USDA lists walnut oil at 63.3 g polyunsaturated fat per 3.5 oz (100 g), including 10.4 g of the plant omega-3 ALA and 52.9 g of linoleic acid, with 9.1 g saturated fat. — USDA SR Legacy record Oil, walnut (n = 1 record) Evidence E source
  PUFA 63.3 g (18:3 ALA 10.4 g, 18:2 52.9 g), MUFA 22.8 g, SFA 9.1 g, vitamin E 0.4 mg, vitamin K 15 ug, 884 calories per 3.5 oz (100 g)
• The UK table gives walnut oil 69.9 g polyunsaturated, 16.5 g monounsaturated and 9.1 g saturated fat per 3.5 oz (100 g), close to the USDA figures. — CoFID 2021 record 17-047 Oil, walnut (n = 1 record) Evidence E source
  PUFA 69.9 g, MUFA 16.5 g, SFA 9.1 g, 899 calories per 3.5 oz (100 g)
• The cold-pressed walnut oil used in the trial was 64% linoleic acid and 8.5% ALA, with 13.6% palmitic acid. — Persian walnut oil analyzed for the RCT Evidence D source
  Linoleic 64%, oleic 13.3%, ALA 8.5%, palmitic 13.6%, stearic 1.3%

What a real portion looks like

• A US tablespoon of walnut oil is 14 g, which carries about 1.5 g of ALA and 124 calories by USDA composition. — FNDDS Walnut oil 82108700 portion weights Evidence E source
  1 tablespoon = 14 g; about 1.46 g ALA and 124 calories (computed from FDC 171030 per-100 g values)
• The 1 tbsp (15 mL) daily dose in the diabetes trial was chosen to match eating walnuts 4 to 5 times a week, with about 4 lb (1.8 kg) of walnuts pressed per liter of oil. — methods of a 90-day RCT in type 2 diabetes (n = 100) Evidence B source
  15 mL/day, delivered as 4 capsules of 1.25 cc three times daily

What your body absorbs

• In 15 adults with raised cholesterol, a single 51 g dose of walnut oil raised blood triglycerides after the meal but preserved endothelial function better than walnut skins. — 15 overweight and obese adults with moderate hypercholesterolemia, 4-period crossover (n = 15) Evidence B source
  Higher postprandial triglycerides after oil and whole walnuts; Framingham RHI maintained with oil
• In 25 adults, walnut fat given as oil raised the satiety hormone CCK more than the same fat as ground walnuts, in line with the fat being more available as oil. — 12 men and 13 women of normal weight, four energy-matched preloads, crossover (n = 25) Evidence B source
  Plasma CCK higher after walnut oil and safflower preloads than after ground walnuts or low-fat control; lunch energy intake unchanged

What it does to your health

• In 20 adults with high cholesterol, 6-week diets rich in walnuts, walnut oil and flax oil lowered diastolic pressure by 2 to 3 mmHg against an average American diet. — 20 hypercholesterolemic adults, 3-period controlled-feeding crossover, 6 weeks per diet (n = 20) Evidence B source
  Diastolic BP -2 to -3 mmHg; total peripheral resistance -4%; FMD +34% on the higher-ALA diet
• In 212 overweight Germans, a 12-week Mediterranean-style diet built on canola oil, walnuts and walnut oil led to 11 lb (5.2 kg) weight loss versus 0.88 lb (0.4 kg) in waiting controls. — 212 overweight or grade 1 obese adults, 100 intervention and 112 waiting-list controls, 12 months (n = 212) Evidence B source
  Weight -11 vs -0.88 lb (-5.2 vs -0.4 kg) at 12 weeks; -9.3 lb (-4.2 kg) at 12 months (pooled)
• In young adults, a milkshake with walnut oil (12% ALA) led to faster extinction of a learned fear response than one with cream or no added fat. — young adults, between-subject laboratory study with walnut oil, cream or no-fat milkshake Evidence B source
  Walnut oil group extinguished the fear prediction most rapidly; acquisition similar across groups

Safety, limits and interactions

• Over 90 days of 1 tbsp (15 mL) walnut oil a day, the only side effects were 2 cases of mild gut intolerance, and nobody stopped. — walnut oil and placebo groups of a 90-day RCT in type 2 diabetes (n = 90) Evidence B source
  2 mild gastrointestinal oil intolerance cases, no discontinuation

Who this works differently for

• In 100 adults with type 2 diabetes and high lipids, 1 tbsp (15 mL) of walnut oil a day for 90 days cut LDL by 30.4 units more than placebo. — 100 hyperlipidemic type 2 diabetic patients aged 35-75, 15 cc walnut oil daily for 90 days (n = 100) Evidence B source
  LDL treatment difference -30.44 (P<0.001); total cholesterol -30.04; triglycerides -15.04; HDL +2.28 (P=0.06)

The bottom line

The UK food table puts polyunsaturated fat higher, at 69.9 g per 3.5 oz (100 g) against USDA's 63.3 g, a gap that reflects different samples. The one batch of cold-pressed oil analyzed for the Iranian trial was 64% linoleic acid and 8.5% ALA, below the USDA figure. The trial authors chose 1 tbsp (15 mL) to match eating walnuts four to five times a week, an equivalence they stated and did not measure. About 4 lb (1.8 kg) of walnuts went into each liter of oil. Other trials put walnut oil into a mixed diet, so its own effect cannot be separated out. In a controlled-feeding crossover on 20 adults with high cholesterol, six-week diets built on walnuts, walnut oil and flax oil lowered diastolic pressure by 2 to 3 mmHg against an average American diet. In 212 overweight German adults, a Mediterranean-style diet using canola oil, walnuts and walnut oil brought 11 lb (5.2 kg) of weight loss at 12 weeks against 0.88 lb (0.4 kg) on the waiting list, in a trial with high dropout where walnut oil was one fat among several. The single-meal studies are small. In 25 normal-weight adults, walnut fat taken as oil raised the fullness hormone CCK more than the same fat eaten as ground walnuts, most clearly in men, and they ate no less at lunch. In 15 overweight adults with raised cholesterol, one meal with walnut oil raised blood triglycerides after eating and kept a measure of blood vessel function steady compared with walnut skins or whole walnuts. A laboratory study in young adults found faster unlearning of a fear response after a milkshake with walnut oil than after one with cream. That was one session, the sample size is not in the abstract, and its meaning for health is unknown. On safety, the Iranian trial recorded two cases of mild gut intolerance over 90 days and nobody stopped, in a trial too small to be built for safety. We have no carded data on nut allergy and walnut oil, or on pregnancy, children, kidney disease or medicines. The oil is pressed from walnuts, so anyone with a walnut allergy should not assume it is safe. We also found no study of heating, frying or storing walnut oil.

Sources

1. wnol-r5-01 · USDA FoodData Central SR Legacy, dataset
   Oil, walnut (FDC 171030, SR Legacy, Fats and Oils): Total lipid 100 g; Fatty acids, total polyunsaturated 63.3 g; PUFA 18:3 10.4 g; PUFA 18:2 52.9 g; Fatty acids, total monounsaturated 22.8 g; Fatty acids, total saturated 9.1 g; Vitamin E 0.4 mg; Vitamin K 15 ug; Energy 884 kcal per 100 g
   USDA FoodData Central, SR Legacy, FDC 171030 · checked 2026-09-29
2. wnol-r5-02 · CoFID 2021, dataset
   Oil, walnut (CoFID 17-047, group OC): Fat 99.9 g; Poly FA 69.90 g; Mono FA 16.50 g; Satd FA 9.10 g; Energy 899 kcal per 100 g
   CoFID 2021 (Public Health England), code 17-047, OGL v3.0 · checked 2026-09-29
3. wnol-r5-06 · food analysis
   It contained linoleic (64%), oleic acid (13.3%), α-linolenic acid (8.5%) and palmitoleic acid (0.2%). On the other hand, it contained some saturated fatty acids including palmitic acid (13.6%) and stearic acid (1.3%).
   Nutr Diabetes, 2017 · checked 2026-09-29
4. wnol-r5-03 · USDA FNDDS, dataset
   Walnut oil (FNDDS 82108700): 1 tablespoon 14 g; 1 cup 224 g; Quantity not specified 14 g
   USDA FNDDS, FDC 2710193 · checked 2026-09-29
5. wnol-r5-12 · randomized controlled trial
   Approximately 4 pounds (1.8 kg) of walnut was needed to make 1 liter of the oil. Both capsules were made by Shiraz Pharmacology School. We chose 15 ml of oil as its consumption corresponds to high amounts of walnut consumption (4–5 servings in a week).
   Nutr Diabetes, 2017 · checked 2026-09-29
6. wnol-r5-07 · randomized controlled trial
   There was a treatment × time point interaction for triglycerides (P < 0.01) and increased postprandial concentrations were observed for the oil and whole walnut treatments (P < 0.01). ... The Framingham RHI was maintained with the oil treatment compared with the skins and whole nut (P < 0.05).
   J Nutr, 2013 · checked 2026-09-29
7. wnol-r5-08 · randomized controlled trial
   Plasma cholecystokinin (CCK) concentrations reflected preload fat content and availability, particularly among men; CCK was higher after WOL and SAFF preloads than after LFC or WNT preloads.
   J Nutr, 2005 · checked 2026-09-29
8. wnol-r5-09 · randomized controlled trial
   RESULTS: The ALA and LA diets significantly reduced diastolic blood pressure (-2 to -3 mm Hg) and total peripheral resistance (-4%), and this effect was evident at rest and during stress (main effect of diet, p < 0.02).
   J Am Coll Nutr, 2010 · checked 2026-09-29
9. wnol-r5-10 · randomized controlled trial
   Per-protocol weight loss after 12 weeks was 5.2 kg in IG vs 0.4 kg in CG (P ⩽ 0.0001), BMI -1.8 vs -0.1 kg/m(2) (P ⩽ 0.0001), waist circumference -4.7 vs -0.9 cm (P ⩽ 0.0001).
   Eur J Clin Nutr, 2015 · checked 2026-09-29
10. wnol-r5-11 · randomized controlled trial
    For this reason, the present laboratory work examined the effects of adding walnut oil (12% ALA) to a chocolate milkshake on the acquisition, generalization, and extinction of a fear-based prediction in young adults. ... However, those who consumed walnut oil extinguished most rapidly and profoundly.
    Appetite, 2018 · checked 2026-09-29
11. wnol-r5-05 · randomized controlled trial
    There were two cases of mild gastrointestinal oil intolerance, none of whom discontinued the intervention. No other side effects were noticed.
    Nutr Diabetes, 2017 · checked 2026-09-29
12. wnol-r5-04 · randomized controlled trial
    In a randomized, double-blind, placebo-controlled clinical trial, 100 hyperlipidemic type 2 diabetic patients aged 35-75 years were assigned to receive 15 cc Persian walnut oil or placebo every day for 90 days. ... Consumption of walnut oil by type 2 hyperlipidemic diabetic patients resulted in a significant decrease in total cholesterol levels (treatment difference (TD)=-30.04, P<0.001), triglyceride (TG) level (TD=-15.04, P=0.021), low-density lipoprotein (LDL) level (TD=-30.44, P<0.001)
    Nutr Diabetes, 2017 · checked 2026-09-29