Grapeseed oil and olive oil: the trials sit with olive oil

Across 13 trials with 611 mostly healthy people, virgin olive oils lowered systolic blood pressure by about 3 mmHg more than refined olive oil, at low to moderate certainty by the authors' own rating. Grapeseed oil has nothing comparable, and none of our trials put it against olive oil. In 44 overweight or obese women on an 8-week weight-loss diet, getting 15% of energy from grapeseed oil left hs-CRP, an inflammation marker, lower than sunflower oil did (p < 0.03), and the abstract gives no size for the gap. In 30 healthy adults, a week of grapeseed oil lowered platelet aggregation by 8.4%, close to the 10.4% seen with peanut oil, in a pre-post design with a tiny control group. Both oils carry 899 calories per 3.5 oz (100 g). Grapeseed oil is mostly polyunsaturated fat (68.2 g per 3.5 oz (100 g)) and olive oil mostly monounsaturated (73.0 g), by UK tables.

How much is actually in it

• Not all olive oil is the same: across 13 RCTs with 611 people, virgin olive oils lowered systolic pressure by about 3 mmHg more than refined olive oil. — 13 RCTs, 611 mainly healthy participants, at least 3 weeks (n = 611) Evidence A source
  SBP MD -2.99 to -2.87 mmHg for high- and low-phenolic (extra) virgin vs refined; LDL-C -5.4 mg/dL (-0.14 mmol/L) high vs low phenolic
• In 8 crossover RCTs with 355 people, high-phenolic olive oil lowered systolic blood pressure (SMD -0.52, measured in 69 people) versus low-phenolic oil. — 8 crossover RCTs, 355 subjects, 21-90 days (n = 355) Evidence A source
  SBP SMD -0.52 (95% CI -0.77 to -0.27, n=69); oxLDL SMD -0.25; LDL SMD -0.03 (-0.15 to 0.09)
• Both oils give 899 calories per 3.5 oz (100 g), but grapeseed oil is mostly polyunsaturated (68.2 g) while olive oil is mostly monounsaturated (73.0 g). — CoFID 2021 rows Oil, grapeseed (17-036) and Oil, olive (17-038) Evidence E source
  Grapeseed: MUFA 15.8 g, PUFA 68.2 g, SFA 11.1 g per 3.5 oz (100 g); olive: MUFA 73.0 g, PUFA 8.2 g, SFA 14.3 g; both 899 calories

What a real portion looks like

• US survey coding counts a tablespoon of olive oil as 14 g, about 126 calories, and uses the same 14 g when the amount is not stated. — FNDDS food Olive oil Evidence E source
  1 tablespoon 14 g; quantity not specified 14 g; 1 cup 224 g

What your body absorbs

• In a crossover RCT on 16 adults, eating a salad with 0.99 oz (28 g) of olive oil raised carotenoid absorption by 55% compared with the same salad and coconut oil. — 16 subjects, identical carotenoid-rich salad with 28 g of test fat, 4 conditions (n = 16) Evidence B source
  Total carotenoid iAUC 55.2% higher with olive than coconut oil; alpha-carotene +110.8%, lycopene +45.8%
• In a crossover RCT on 12 adults, hydroxytyrosol, the olive polyphenol behind the EU claim, peaked in blood 30 minutes after intake and rose with dose. — 12 healthy volunteers, single doses of 30.58 or 61.48 mg hydroxytyrosol supplements or fortified olive oil (n = 12) Evidence B source
  Plasma peak at 30 min; bioavailability increased with dose

What cooking and storage change

• A review of 23 studies found no support for the idea that frying generally raises heart disease risk, and in the large PREDIMED trial virgin olive oil was also used for frying. — 23 publications on vegetable oils, fried food and chronic disease (n = 23 studies) Evidence C source
  No general CVD risk from frying; fried food probably linked to weight gain

What it does to your health

• In 30 healthy adults, a week of grapeseed oil lowered platelet aggregation by 8.4%, close to peanut oil at 10.4%. — 30 healthy subjects plus 4 aspirin controls (n = 30) Evidence C source
  Platelet aggregation -8.4 +/- 1% with grapeseed oil, -10.4 +/- 1% with peanut oil
• Across 51 RCTs with 4,334 adults, olive oil did not significantly change blood glucose, insulin or HbA1c. — 51 RCTs, 4334 adults (n = 4334) Evidence A source
  Glucose WMD -0.04 mg/dL (95% CI -0.1 to 0.02); HbA1c WMD 0.02% (-0.01 to 0.06)
• Pooled cohorts link the highest olive oil intake, against the lowest, to a 13% lower diabetes risk. — 10 studies (4 cohorts, 6 RCTs), over 500,000 subjects (n = 10 studies) Evidence C source
  Cohorts RR 0.87 (95% CI 0.83-0.92); RCTs RR 0.78 (0.70-0.88)

What people believe that the data does not support

• Across RCTs from 52 articles, olive oil did not change body fat distribution, and olive oil capsules added no significant fat mass (0.62 lb / 0.28 kg, CI crossing zero). — adults in randomized trials comparing olive oil with other oils, 52 articles (n = 52 articles) Evidence A source
  Fat mass MD 0.62 lb (95% CI -0.6 to 1.8; metric: 0.28 kg, -0.27 to 0.83) with capsules; -0.71 lb (-2 to 0.57; metric: -0.32 kg, -0.90 to 0.26) with culinary use
• The EU authorizes one claim here: olive oil polyphenols help protect blood lipids from oxidative stress, a claim grapeseed oil cannot carry. — EU Register on nutrition and health claims, snapshot 2026-09-21 Evidence E source
  Status Authorised; per 40507112 it applies to oils with at least 5 mg hydroxytyrosol and derivatives per 20 g
• The EU refused the general claim that olive oil promotes heart health. — EU Register on nutrition and health claims, snapshot 2026-09-21 Evidence E source
  Status Non-authorized
• To carry the EU polyphenol claim, an olive oil must contain at least 5 mg of hydroxytyrosol and its derivatives per 20 g. — systematic review of 17 clinical studies on virgin olive oil and cardiovascular health (n = 17 studies) Evidence C source
  Threshold 5 mg hydroxytyrosol and derivatives per 20 g oil

Who this works differently for

• In an 8-week RCT on 44 overweight or obese women on a weight-loss diet, getting 15% of energy from grapeseed oil lowered hs-CRP more than sunflower oil. — 44 overweight or obese women, weight-loss diet, 8 weeks, 15% of energy from the test oil (n = 44) Evidence B source
  Hs-CRP lower with grapeseed than sunflower oil (p < 0.03); HOMA-IR and TNF-alpha fell within the grapeseed group

What is still unknown

• An umbrella review of 17 systematic reviews links olive oil to less heart disease, cancer, diabetes and death, but rates the evidence as heterogeneous and low quality. — 17 systematic reviews of randomized trials and observational studies (n = 17 reviews) Evidence C source
  Beneficial associations; high heterogeneity, few RCTs

The bottom line

High-phenolic olive oil lowered systolic pressure against low-phenolic oil in 8 crossover trials (standardized difference -0.52, 95% CI -0.77 to -0.27), an estimate that rests on just 69 people. The EU authorizes one claim here, that olive oil polyphenols help protect blood lipids from oxidative stress. It applies only to oils with at least 5 mg of hydroxytyrosol and its derivatives per 20 g, and grapeseed oil cannot carry it. The EU refused the general claim that olive oil promotes heart health. In 12 volunteers given hydroxytyrosol at supplement doses, as capsules or fortified olive oil, blood levels peaked 30 minutes after intake and rose with dose. Across 51 trials with 4,334 adults, olive oil did not significantly change blood glucose, insulin or HbA1c, in trials that mixed oil types and comparators. Observational data link the highest olive oil intake with a 13% lower diabetes risk in cohorts (RR 0.87, 95% CI 0.83 to 0.92), from a highest versus lowest comparison. An umbrella review of 17 systematic reviews links olive oil with less heart disease, cancer, diabetes and death. Its authors rate that evidence as heterogeneous and low quality. Olive oil did not shift body fat distribution in trials from 52 articles. Capsules showed a small rise in fat mass of 0.62 lb (0.28 kg) that did not reach significance (95% CI -0.27 to 0.83). A salad with 0.99 oz (28 g) of olive oil raised carotenoid absorption by 55% against the same salad with coconut oil in 16 people, in a single-meal trial with no grapeseed arm. A review of 23 mostly observational studies found no support for the idea that frying in general raises heart disease risk. The large randomized trial it cites told people to use virgin olive oil for frying too. US survey coding counts a tablespoon of olive oil as 14 g, about 126 calories. We hold no card on allergy, medicines, pregnancy or other cautions for either oil, so this page has no safety section. That is a gap in our evidence. It does not mean the oils were tested and cleared.

Sources

1. gsoo-daily-r1-04 · network meta-analysis
   Both, HP(E)VOO and LP(E)VOO reduces SBP compared to ROO (range of MD: -2.99 to -2.87 mmHg), and HP(E)VOO may improve oxidized LDL-cholesterol (oxLDL-C) compared to ROO (standardized MD: -0.68, 95%-CI: -1.31, -0.04).
   Nutr Metab Cardiovasc Dis, 2019 · checked 2026-10-02
2. gsoo-daily-r1-05 · meta-analysis
   There were medium effects for lowering systolic blood pressure (n = 69; SMD -0.52; CI -0.77/-0.27; p < 0.01) and small effects for lowering oxLDL (n = 300; SMD -0.25; CI [-0.50/0.00]; p = 0.05).
   Phytomedicine, 2015 · checked 2026-10-02
3. gsoo-daily-r1-12 · CoFID 2021, dataset
   Oil, grapeseed (CoFID 17-036): Energy 899 kcal, Fat 99.9 g, Mono FA 15.80 g, Poly FA 68.20 g, Satd FA 11.10 g per 100 g; Oil, olive (CoFID 17-038): Energy 899 kcal, Fat 99.9 g, Mono FA 73.00 g, Poly FA 8.20 g, Satd FA 14.30 g per 100 g
   CoFID 2021, Public Health England / OGL v3.0, codes 17-036 and 17-038 · checked 2026-10-02
4. gsoo-daily-r1-13 · USDA FNDDS, dataset
   Olive oil (FNDDS 82104000, FDC 2710186): 1 cup 224 g; 1 tablespoon 14 g; Quantity not specified 14 g
   USDA FNDDS, food code 82104000 (FDC 2710186) · checked 2026-10-02
5. gsoo-daily-r1-07 · RCT, crossover
   Similarly, the positive iAUC1-10h of TC, α-carotene, and lycopene were 55.2%, 110.8%, and 45.8%, respectively, higher with olive oil than with coconut oil.
   Am J Clin Nutr, 2023 · checked 2026-10-02
6. gsoo-daily-r1-08 · RCT, crossover
   Pharmacokinetic results showed that dietary HT administered through the food supplements is bioavailable and bioavailability increases with the administered dose...The maximum concentrations in plasma peaked 30 min after intake.
   Nutrients, 2023 · checked 2026-10-02
7. gsoo-daily-r1-09 · systematic review
   Based on the results of the studies included in the present systematic review, we conclude that (1) the myth that frying foods is generally associated with a higher risk of CVD is not supported by the available evidence; (2) virgin olive oil significantly reduces the risk of CVD clinical events, based on the results of a large randomised trial that included as part of the intervention the recommendation to use high amounts of virgin olive oil, also for frying foods
   Br J Nutr, 2015 · checked 2026-10-02
8. gsoo-daily-r1-02 · controlled trial
   Grape seed oil showed a decrease of 8.4 ± 1% in aggregation, compared with peanut oil, which decreased aggregation by 10.4 ± 1%.
   Am J Ther, 2016 · checked 2026-10-02
9. gsoo-daily-r1-03 · meta-analysis
   We found the consumption of olive oil was not associated with statistically significant changes in blood glucose (WMD = -0.04 mg dL-1; 95% CI, -0.1 to 0.02; P = .18; I2 = 27.05%), insulin (WMD = -0.3 µIU mL-1; 95% CI, -0.99 to 0.38; P = .39; I2 = 91.49%), hemoglobin A1c (HbA1c) (WMD = 0.02%, 95% CI, -0.01 to 0.06; P = .21; I2 = 0%)
   Nutr Rev, 2026 · checked 2026-10-02
10. gsoo-daily-r1-10 · meta-analysis
    A 13% (RR = 0.87, 95%CI = 0.83 - 0.92, P < 0.01) decreased risk of diabetes was shown in Cohort study and 22% (RR = 0.78, 95%CI = 0.70 - 0.88, P < 0.01) decreased risk in RCT study for the highest vs. lowest olive oil consumption.
    J Health Popul Nutr, 2025 · checked 2026-10-02
11. gsoo-daily-r1-06 · meta-analysis
    The results indicate that the consumption of olive oil does not seem to alter the distribution of body fat, despite a small indication that supplementation in capsules can increase adipose mass (Mean Difference = 0.28 kg, 95% CI [-0.27, 0.83]; between-groups difference p = 0.59)
    Food Funct, 2023 · checked 2026-10-02
12. gsoo-daily-r1-14 · EU claim register
    POL-HC-6431 Olive oil polyphenols Olive oil polyphenols contribute to the protection of blood lipids from oxidative stress Authorised
    EU Register on nutrition and health claims, claim POL-HC-6431, snapshot 2026-09-21 · checked 2026-10-02
13. gsoo-daily-r1-15 · EU claim register
    POL-HC-7679 Olive Oil Olive Oil promotes your heart health Non-authorised
    EU Register on nutrition and health claims, claim POL-HC-7679, snapshot 2026-09-21 · checked 2026-10-02
14. gsoo-daily-r1-16 · systematic review
    Olive oils must contain at least 5 mg of Hydroxytyrosol (HYTY) and its derivatives (oleuropein and Tyrosol (TY)) per 20 g to qualify for the EFSA-approved health claim.
    Nutrients, 2025 · checked 2026-10-02
15. gsoo-daily-r1-01 · RCT
    The subjects (n = 44) were randomly assigned into intervention group as "GSO" (consuming 15% of energy from GSO) and control group as sunflower oil "SFO" (consuming 15% of energy from SFO) through a weight loss diet for 8 weeks...The hs-CRP was lower in GSO than the SFO group (p < 0.03).
    Int J Food Sci Nutr, 2013 · checked 2026-10-02
16. gsoo-daily-r1-11 · umbrella review
    Given the high heterogeneity and low quality of evidence, further studies involving randomized trials are imperative.
    Nutr Rev, 2025 · checked 2026-10-02