Grapeseed oil: six small studies and no long view

Grapeseed oil has almost nothing behind it. Our corpus holds eight cards drawn from six studies: five small randomised crossover trials and one set of case reports from 1987. Most of them fed people a single meal and drew blood for the next four hours. The biggest had 20 people in it. Everything on this page is therefore about one meal in a healthy young adult. What happens to someone who cooks with this oil for a year has never been measured. The one comparative result we hold is this. A mixed meal built on 40 g of grapeseed oil produced a lower four hour triglyceride rise than the same meal built on olive oil, in 20 healthy Chinese men. How much lower was never reported in a form we can quote, so read it as a direction and not as a size. That is one afternoon of blood samples, and it tells you nothing about cholesterol after a month. The trial people bring up on the other side, from 1999, used a spread that was 90 percent butter and 10 percent grapeseed oil. It measured dairy fat with a splash of this oil in it. The safety section further down holds one set of case reports from 1987 and nothing else. We hold no card on an upper limit, on interactions with medicines, on pregnancy or on children, and empty there means unstudied rather than safe.

The numbers, per 100 g

What your body absorbs

• Refined grapeseed oil fortified with 5 mg of hydroxytyrosol delivered 0.33 ug/mg creatinine in urine over the study period in 20 volunteers, the lowest of the four oily matrices tested. — 20 healthy volunteers, double-blind, single 5 mg dose of hydroxytyrosol in different food matrices (n = 20) Evidence B source
  Urinary hydroxytyrosol 0.33 ug/mg creatinine for grapeseed oil vs 0.86 for extra virgin olive oil

What cooking and storage change

• Bread baked with grapeseed oil formed less amylose-lipid complex than bread baked with coconut or olive oil across 5 test breads eaten by healthy men. — healthy men, randomised order of 5 test breads (control, butter, coconut oil, grapeseed oil, olive oil) Evidence B source
  Complexing index significantly higher for coconut and olive oil breads than for butter and grapeseed oil breads (P<0.05)
• Across 5 breads baked with different fats, glycaemic response differed overall (P=0.002) but no significant difference was seen between the fat types themselves, so swapping in grapeseed oil did not change the blood glucose curve. — healthy men, 5 test breads in random order, postprandial glucose and insulin Evidence B source
  Overall difference P=0.002 driven by coconut oil vs control (P=0.016); no significant difference between fat types

What it does to your health

• A mixed meal built on 40 g of grapeseed oil gave a lower 4-hour triglyceride response than the same meal built on olive oil in 20 healthy men. — 20 healthy Chinese men, randomised crossover, six isocaloric meals, 4-hour postprandial sampling (n = 20) Evidence B source
  Triglyceride iAUC significantly lower after the PUFA (grapeseed oil) and SFA meals than after the MUFA (olive oil) meal
• A meal carrying 7.4 g of grapeseed oil as omega-6 fat did not raise postprandial serum endotoxin above the olive oil control meal in 20 healthy adults. — 20 healthy adults, mean age 25 years, single-blind randomised crossover, four isoenergetic meals (n = 20) Evidence B source
  No difference in postprandial serum endotoxin between the omega-6 (grapeseed oil) meal and the control meal (p > 0.05)
• In the same 20-adult trial postprandial serum endotoxin was not associated with systemic inflammation. — 20 healthy adults, four isoenergetic meals, inflammatory markers measured alongside endotoxin (n = 20) Evidence B source
  Postprandial endotoxin not associated with systemic inflammation in vivo
• Replacing 65 g of habitual dietary fat with a 90:10 butter and grapeseed oil spread for 3 weeks left total and LDL cholesterol higher than rapeseed-based spreads in 13 healthy young men. — 13 healthy free-living men aged 21 to 26 years, randomised crossover, 3-week periods with 3-week washout (n = 13) Evidence B source
  Total and LDL cholesterol significantly lower after both rapeseed blends than after the butter and grapeseed blend (P < 0.05); apo B increased after the butter and grapeseed blend

Safety, limits and interactions

• The only harm recorded in the corpus under the name grapeseed oil is the 1981 Spanish toxic oil syndrome, and the oil was traced to one refinery that processed both rapeseed and grapeseed oils. — three patients in two families in Sevilla investigated during the 1981 Spanish epidemic (n = 3) Evidence D source
  Three cases fitting the clinical picture of toxic oil syndrome traced to oil from one refinery that handled both oils

The bottom line

Our cards give no reason to reach for this oil over another, and none to put it back on the shelf. That is a statement about how little has been measured, not a verdict on the oil. Baking is the single place it behaved differently. In bread, grapeseed oil formed less of the starch and fat complex that slows starch digestion than coconut or olive oil did (P<0.05). The blood glucose curves after those same breads showed no significant difference between the fat types, so that laboratory difference never reached the person eating. If you have read that grapeseed oil carries polyphenols, look at what was in the bottle. The trial behind that idea used refined oil which the researchers then fortified with 5 mg of hydroxytyrosol. It delivered 0.33 ug/mg creatinine in urine, the lowest of four oils tested, against 0.86 for extra virgin olive oil. The absorption section on this page is about that added compound, not about anything plain grapeseed oil carries on its own, and plain oil off a supermarket shelf was never in that study. The omega-6 worry has been tested once, and narrowly. A meal carrying 7.4 g of grapeseed oil did not push serum endotoxin above the olive oil control meal in 20 healthy adults, and the endotoxin that did rise showed no link to any inflammation marker the researchers measured. One meal. Twenty young people. One afternoon. Two things have to be said about what is missing. The only harm in our corpus filed under the name of this oil is the 1981 Spanish toxic oil syndrome. The record we hold is three patients in two families in Sevilla, and it traces their oil to one refinery that processed both rapeseed and grapeseed oils. It does not say which of the two carried the agent. That is a case report from 1987, not a measurement of this oil, and it is also not a clean record, because nobody has since looked. We hold no card at all on an upper limit, on interactions with medicines, on pregnancy, on children, or on anyone with liver or kidney disease. The part of this page where those answers belong is empty, and empty here means unstudied rather than safe. If you are asking because of a medicine you take, that is a question for whoever prescribed it.

Sources

1. gseo-r3-01 · double-blind crossover trial, 20 volunteers
   Regarding the hydroxytyrosol bioavailability, the intake of extra virgin olive oil, as well as fortified refined olive, flax, and grapeseed oils provided significantly higher urinary contents (0.86, 0.63, 0.55, and 0.33 µg/mg creatinine, respectively) compared with basal urine, whereas hydroxytyrosol metabolites showed no significant changes.
   Eur J Nutr, 2021 · checked 2026-09-23
2. gseo-r3-03 · randomised crossover feeding trial, 5 test breads
   The complexing index (CI), a measure of ALC formation, was significantly higher for COC and OLV compared with BTR and GRP (P<0·05).
   Br J Nutr, 2016 · checked 2026-09-23
3. gseo-r3-04 · randomised crossover feeding trial, 5 test breads
   There was a significant difference in glycaemic response between the different test breads (P=0·002), primarily due to COC having a lower response than CTR (P=0·016), but no significant differences between fat types were observed.
   Br J Nutr, 2016 · checked 2026-09-23
4. gseo-r3-02 · randomised crossover trial, 20 healthy men
   The incremental area under the curve (iAUC) for TG was significantly lower after the SFA and PUFA meals compared with the MUFA meal, irrespective of GI.
   Eur J Nutr, 2018 · checked 2026-09-23
5. gseo-r3-05 · single-blind randomised crossover trial, 20 healthy adults
   The n-6 meal did not effect a different outcome in participant postprandial serum endotoxin concentration from that of the control meal (p > 0.05).
   Lipids Health Dis, 2016 · checked 2026-09-23
6. gseo-r3-06 · single-blind randomised crossover trial, 20 healthy adults
   However, postprandial endotoxin was not associated with systemic inflammation in vivo.
   Lipids Health Dis, 2016 · checked 2026-09-23
7. gseo-r3-07 · randomised crossover trial, 13 young men
   Significantly (P < 0.05) lower total and LDL-cholesterol concentrations were observed after the BR and BS period, compared to BG.
   Eur J Clin Nutr, 1999 · checked 2026-09-23
8. gseo-r3-08 · case reports, 3 patients
   Illness apparently occurred as a result of ingestion of oil taken from the ITH oil refinery in Sevilla, a plant in which rapeseed and grapeseed oils were refined for the distributing firm through which oil bearing the causative agent of TOS is thought to have entered the market.
   Food Chem Toxicol, 1987 · checked 2026-09-23