Olive oil and sunflower oil: three small trials stand between them

The largest randomized evidence on olive oil is about blood sugar, and there it found nothing. Across 51 randomized trials in 4334 adults, olive oil left blood glucose, insulin and HbA1c where they were, with a mean difference of 0.02 percent for HbA1c on an interval from -0.01 to 0.06. The one positive result, an improved insulin resistance index at 25 to 50 g a day, came out of a nonlinear dose analysis rather than the main comparison. The two oils are closer than their reputations. The UK table gives both 899 calories and 99.9 g fat per 3.5 oz (100 g), and the entire difference sits in the fatty acids. Olive oil carries 73.00 g monounsaturated against 20.50 g in sunflower oil, and sunflower oil carries slightly less saturated fat, 12.00 g against 14.30 g. Three randomized trials have compared the two head to head, the largest of them in 58 people, and two of the three disagree with each other. The single European Union claim written for olive oil itself is about its polyphenols rather than about its fat.

How much is actually in it

• By the UK composition table olive oil and sunflower oil are identical in energy and fat at 899 calories and 99.9 g per 3.5 oz (100 g), and differ almost entirely in fatty acid profile. — CoFID 2021 entries Oil olive code 17-038 and Oil sunflower code 17-045, per 3.5 oz (100 g) Evidence E source
  Olive oil monounsaturated 73.00 g, polyunsaturated 8.20 g, saturated 14.30 g; sunflower oil monounsaturated 20.50 g, polyunsaturated 63.30 g, saturated 12.00 g, n-3 0.10 g
• The one European Union claim authorized specifically for olive oil is that its polyphenols contribute to protecting blood lipids from oxidative stress. — EU Register on nutrition and health claims, snapshot of 21 September 2026, one authorized and eight refused claims found under olive oil Evidence E source
  Claim POL-HC-6431 carries the status Authorised

What a real portion looks like

• In the USDA survey food table one tablespoon of olive oil and one tablespoon of sunflower oil both weigh 14 g, so the 20 g daily amount used in label claims is about one and a half tablespoons. — USDA FNDDS survey foods Olive oil food code 82104000 and Sunflower oil food code 82108500, WWEIA category Salad dressings and vegetable oils Evidence E source
  1 tablespoon 14 g and 1 cup 224 g for both oils, quantity not specified defaults to 14 g for both

What your body absorbs

• In a crossover trial of 26 healthy young men over 2 weeks, an olive and sunflower oil mixture left circulating vitamin K1 unchanged while corn oil significantly lowered it. — 26 healthy young men, crossover between a corn oil diet and an olive and sunflower oil mixture diet for 2 weeks each, vitamin K1 intake 291 micrograms a day on both (n = 26) Evidence B source
  Fasting triacylglycerol and vitamin K1 both fell significantly on the corn oil diet and not on the olive and sunflower mixture, corn oil also raised undercarboxylated osteocalcin
• In a crossover trial of 11 healthy volunteers, adding refined olive oil to 26 oz (750 g) of tomato juice significantly raised every plasma lycopene isomer, peaking at 24 hours. — 11 healthy volunteers, single ingestion of 750 g tomato juice with 10 percent refined olive oil per 70 kg body weight versus the same juice without oil (n = 11) Evidence B source
  All lycopene isomers rose significantly with oil and peaked at 24 hours, LDL and total cholesterol fell significantly at 6 hours

What cooking and storage change

• In a crossover trial of 19 healthy men, a meal made with sunflower oil blend repeatedly heated at 180 degrees for 10 days did not impair vascular function, and it raised blood triglycerides less than the unheated blend. — 19 healthy male participants, single high-fat meals with a sunflower oil and palm olein blend heated at 180 degrees over 10 days versus unheated, 23.8 percent against 7.2 percent polar compounds, measurements over 4 hours (n = 19) Evidence B source
  Flow-mediated dilation, arterial stiffness, non-esterified fatty acids and glucose comparable between meals, postprandial triglyceride rise lower after the heated oil (p < 0.001)
• A systematic review of 23 publications concluded that the idea that frying raises cardiovascular risk is unsupported by the available evidence, while heavy consumption of fried food is probably tied to weight gain. — 23 publications on vegetable oil and fried food consumption and overweight, type 2 diabetes, metabolic syndrome, cardiovascular disease or hypertension (n = 23 publications) Evidence C source
  No support for higher cardiovascular risk from frying, virgin olive oil reduced cardiovascular clinical events in one large randomized trial, high fried food consumption probably related to weight gain

What it does to your health

• By meta-analysis of 51 randomized trials in 4334 adults, olive oil did not change blood glucose, insulin or HbA1c, and only a daily dose of 25 to 50 g improved the insulin resistance index. — 4334 adults in 51 randomized controlled trials of any olive oil type on any glycemic outcome (n = 4334) Evidence A source
  Blood glucose WMD -0.04 mg/dL (95% CI -0.1 to 0.02), insulin WMD -0.3 microIU/mL (95% CI -0.99 to 0.38), HbA1c WMD 0.02% (95% CI -0.01 to 0.06), HOMA-IR WMD -0.09 (95% CI -0.25 to 0.06), all non-significant
• Pooled data link the highest versus the lowest olive oil consumption to 13 percent lower diabetes risk in cohorts and 22 percent lower in trials. — 10 studies, 4 cohorts and 6 randomized trials, searched to October 2024 (n = 10 studies) Evidence C source
  Cohorts RR 0.87 (95% CI 0.83 to 0.92), trials RR 0.78 (95% CI 0.70 to 0.88), benefit significant at 10 to 20 g a day and not above 20 g
• By meta-analysis of 16 controlled trials with 20 effect sizes, a Mediterranean diet supplemented with olive oil improved every inflammatory and endothelial marker measured except E-selectin, against a low-fat diet. — Adults in 16 controlled clinical trials, databases searched to 7 August 2024 (n = 16 trials) Evidence A source
  Significant improvement in all measured inflammatory and endothelial indexes except E-selectin, where the decrease was small and non-significant
• In a randomized crossover trial of 18 healthy young men on 3 week diets, olive oil lowered the peak of activated factor VII after a fatty meal by 18 percent against sunflower oil. — 18 healthy young men, diets enriched with 5 g per MJ of olive, sunflower or rapeseed oil for 3 weeks each, standardized high-fat test meals (n = 18) Evidence B source
  Nonfasting peak activated factor VII 11.3 plus or minus 5.1 U/L lower after olive oil than after sunflower oil, an 18 percent reduction (P < 0.05)
• In a randomized crossover trial of 18 healthy young men, rapeseed, olive, sunflower and palm oils and butter all raised postprandial factor VII to the same degree, and high fat meals lifted peak activated factor VII 60 percent above low fat meals. — 18 healthy young men, two meals per test day enriched with 2.5 oz (70 g) of one of five fats or isoenergetic low-fat meals, 6 test days (n = 18) Evidence B source
  Peak factor VII coagulant activity 7 percent and activated factor VII 60 percent higher after high-fat than after low-fat meals, no difference between the five fat qualities
• In a 4 week randomized trial of 58 healthy students, olive oil and sunflower oil each lowered a different set of coagulation factors, and the differences between the groups were small. — 58 healthy students on a 4 week rapeseed, olive or sunflower oil diet after a saturated fat wash-in diet (n = 58) Evidence B source
  Olive oil lowered factors VIIc, XIIc, XIIa and Xc, sunflower oil lowered factors XIIc, XIIa and IXc, while olive oil slightly raised CD62 expression and spontaneous platelet aggregation

Safety, limits and interactions

• In a systematic review of 5 human studies, Mediterranean diet components including olive oil showed a benefit against food allergy only when given during pregnancy and lactation together. — 5 human and 4 animal studies of Mediterranean diet components and food allergies, screened from 696 records (n = 5 human studies) Evidence C source
  Benefit when the intervention ran through pregnancy and lactation, no effect when it ran only to birth or was given to the infant for six months

What people believe that the data does not support

• The European Union allows the label claim that replacing saturated fats with unsaturated fats maintains normal blood cholesterol, and names oleic acid as such an unsaturated fat. — EU Register on nutrition and health claims, snapshot of 21 September 2026, 2330 claims of which 262 authorized Evidence E source
  Claim POL-HC-6430 carries the status Authorised
• The European Union refused the right to say on a label that olive oil promotes your heart health. — EU Register on nutrition and health claims, snapshot of 21 September 2026 Evidence E source
  Claim POL-HC-7679 carries the status Non-authorized
• By the Nordic Nutrition Recommendations scoping review, olive oil may have no differential effect on LDL cholesterol against other fats and oils, while canola oil may lower LDL below both olive oil and sunflower oil. — Scoping review of systematic reviews and meta-analyses on fats and oils at the food level, PubMed search 2011 to 2021 updated January 2022 Evidence E source
  Canola oil may decrease LDL cholesterol compared with olive oil, sunflower oil and saturated fat sources, olive oil may decrease some inflammation markers without a differential LDL effect

Who this works differently for

• By meta-analysis of randomized trials in 2348 pregnant women, a Mediterranean diet supplemented with extra virgin olive oil and pistachios cut gestational diabetes incidence by 29 percent. — 2348 pregnant women across 3 eligible randomized controlled trials, two of them comparing Mediterranean diet with extra virgin olive oil and pistachios against Mediterranean diet alone (n = 2348) Evidence A source
  Risk ratio 0.71 (95% CI 0.57 to 0.88) for gestational diabetes

What is still unknown

• An umbrella review of 17 systematic reviews found a beneficial association of olive oil with cardiovascular disease, cancer, type 2 diabetes and all cause mortality, and weaker evidence for blood lipids and inflammation. — 17 systematic reviews of randomized trials and observational studies in adults, searched to 6 February 2023 (n = 17 systematic reviews) Evidence C source
  Beneficial association for cardiovascular disease, cancer, type 2 diabetes and all-cause mortality, less definitive for inflammatory markers, oxidative stress, glucose metabolism and blood lipids
• Almost all evidence about cooking oils is reported at the fatty acid level rather than at the oil level, and every systematic review found at the oil level was of low methodological quality. — Nordic Nutrition Recommendations 2023 scoping review of fats and oils Evidence E source
  Few systematic reviews exist at food level, all identified reviews and meta-analyses of low methodological quality

The bottom line

A tablespoon of either oil weighs 14 g in the USDA survey table, which is about 126 calories, and the 20 g a day used in label claims is around one and a half tablespoons. Both oils sit in the same survey category, so the identical measures are a property of the table rather than a measurement of each oil. There is no USDA composition entry for this pair, and the UK table does not separate ordinary sunflower oil from the high oleic kind, whose fatty acid profile is closer to olive oil. European labeling law splits these oils along a line most shoppers do not expect. The authorized claim that replacing saturated fats with unsaturated fats helps maintain normal blood cholesterol is written for oleic acid, so it covers high oleic sunflower oil exactly as it covers olive oil. The claim is about replacement rather than about adding oil to what you already eat. The second authorized claim belongs to olive oil polyphenols and their protection of blood lipids from oxidative stress. That ties the claim to a component of the oil rather than to its fat. Nothing on this page measures how much of that component a given bottle holds. The wording that olive oil promotes your heart health was submitted three times and refused three times, and a refusal means the evidence fell short when it was assessed. The head to head trials are small, old and about clotting markers. In 18 healthy young men on three week background diets, olive oil left the peak of activated factor VII after a fatty meal 11.3 U/L lower than sunflower oil, an 18 percent reduction. From the same research tradition, a trial in 18 young men fed single meals found rapeseed, olive, sunflower and palm oils and butter all raised factor VII to the same degree. A high fat meal of any kind lifted activated factor VII 60 percent above a low fat one. Read together, the amount of fat in a meal mattered and the choice of oil showed up only against a three week background. The third trial, 58 healthy students over 4 weeks, had each oil lowering a different set of clotting factors, with small differences between groups, and spontaneous platelet aggregation slightly higher on olive oil. Factor VII is a marker on the way to a clot, not a heart attack, and all three trials ran in young people. At the level of whole diets the evidence favors olive oil, and the comparison is usually against a low fat diet rather than against another oil. An umbrella review of 17 systematic reviews reports a beneficial association with cardiovascular disease, cancer, type 2 diabetes and all cause mortality, and calls the evidence less definitive for blood lipids, inflammation and glucose, with high heterogeneity, wide intervals and few randomized trials. A meta-analysis of 16 controlled trials found a Mediterranean diet supplemented with olive oil improved every inflammatory and endothelial marker except E-selectin against a low fat diet, without separating the oil from the rest of the diet. Pooled data link the highest olive oil intake to 13 percent lower diabetes risk in cohorts and 22 percent in trials. The curve is not a straight line: the benefit is significant at 10 to 20 g a day and not significant above 20 g. The Nordic Nutrition Recommendations scoping review is the one agency answer that does not put olive oil first. It reports that olive oil may have no differential effect on LDL cholesterol against other fats and oils, and that canola oil may lower LDL below olive oil, sunflower oil and saturated fat sources. Its authors add that every review they found at the level of oils was of low methodological quality. Only one review on this page looked at frying. Across 23 publications it concluded that the idea of frying raising cardiovascular risk is unsupported by the available evidence, and that heavy consumption of fried food is probably tied to weight gain. The trial behind its olive oil finding recommended high amounts of the oil as part of a wider intervention. In 19 healthy men, a meal made with a sunflower and palm olein blend heated at 180 degrees over 10 days, to 23.8 percent polar compounds, left vascular function unchanged and raised blood triglycerides less than the unheated blend. That is one meal, and it says nothing about eating that way for years. Some fat in the meal earns its place for absorption. Adding refined olive oil to tomato juice raised every plasma lycopene isomer in 11 volunteers, peaking at 24 hours, and any oil would serve that purpose. In 26 young men, a two week olive and sunflower oil mixture left circulating vitamin K1 unchanged while corn oil lowered it. The safety shelf here is close to bare, and that is worth saying plainly. The only card we have found is a review of 5 human studies in which Mediterranean diet components including olive oil showed a benefit against food allergy, and only when the intervention ran through pregnancy and lactation together. There was no effect when it ran to birth or was given to the infant for six months, and the authors call five studies too few to conclude from. We found no records on poisoning, allergy or tolerance for either oil under this pair, no data on interactions with medicines, and no separate data on sunflower oil allergy even though sunflower seed is a recognized allergen. For pregnancy the one strong number is borrowed. A meta-analysis of 3 randomized trials in 2348 pregnant women found a Mediterranean diet supplemented with extra virgin olive oil and pistachios cut gestational diabetes by 29 percent, with the oil and the nuts given together. This base holds nothing at all on sunflower oil in pregnancy.

Sources

1. olsf-daily-r2-01 · reference dataset
   Oil, olive | CoFID 17-038 | Energy 899 kcal | Fat 99.9 g | Mono FA /100g food 73.00 g | Poly FA /100g food 8.20 g | Satd FA /100g fd 14.30 g || Oil, sunflower | CoFID 17-045 | Energy 899 kcal | Fat 99.9 g | Mono FA /100g food 20.50 g | Poly FA /100g food 63.30 g | Satd FA /100g fd 12.00 g | n-3 poly /100g food 0.10 g
   CoFID 2021, Public Health England, codes 17-038 and 17-045 · checked 2026-09-25
2. olsf-daily-r2-04 · regulatory 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 2026-09-25
3. olsf-daily-r2-02 · reference dataset
   Olive oil | FNDDS 82104000 | fdc_id 2710186 | 1 cup 10205 = 224 g | 1 tablespoon 21000 = 14 g || Sunflower oil | FNDDS 82108500 | fdc_id 2710192 | 1 cup 10205 = 224 g | 1 tablespoon 21000 = 14 g
   USDA FNDDS, Olive oil food code 82104000 and Sunflower oil food code 82108500 · checked 2026-09-25
4. olsf-daily-r2-15 · randomized crossover trial
   Mean fasting levels of TAG and K1 were both significantly reduced by the CO diet, but not by the O/SO diet.
   J Lipid Res, 2002 · checked 2026-09-25
5. olsf-daily-r2-16 · randomized crossover trial
   All lycopene isomers increased significantly in subjects consuming TJ with oil, reaching the maximum concentration at 24h.
   Food Chem, 2015 · checked 2026-09-25
6. olsf-daily-r2-17 · randomized crossover trial
   The postprandial TAG increase was lower after heated versus unheated oil (p < 0.001).
   Lipids, 2026 · checked 2026-09-25
7. olsf-daily-r2-18 · 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; and (3) high consumption of fried foods is probably related to a higher risk of weight gain, though the type of oil may perhaps modify this association.
   Br J Nutr, 2015 · checked 2026-09-25
8. olsf-daily-r2-06 · meta-analysis of RCTs
   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%) and Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) (WMD = -0.09; 95% CI, -0.25 to 0.06; P = .26; I2 = 73.13%).
   Nutr Rev, 2026 · checked 2026-09-25
9. olsf-daily-r2-07 · 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 2026-09-25
10. olsf-daily-r2-08 · meta-analysis
    This meta-analysis revealed that the MED diet supplemented with olive oil significantly improved all of the indicators of the study compared with the LFD, except in the case of E-selectin, in which a low and nonsignificant decrease was reported.
    Nutr Rev, 2025 · checked 2026-09-25
11. olsf-daily-r2-12 · randomized crossover trial
    Mean (+/-SEM) nonfasting peak concentrations of activated FVII (FVIIa) were 11.3 +/- 5.1 U/L lower after olive oil than after sunflower oil, an 18% reduction (P < 0.05).
    Am J Clin Nutr, 1999 · checked 2026-09-25
12. olsf-daily-r2-13 · randomized crossover trial
    The five different fat qualities caused similar postprandial increases in plasma triglycerides, FVIIc, and FVIIa. These findings indicate that high-fat meals may be prothrombotic, irrespective of their fatty acid composition.
    Arterioscler Thromb Vasc Biol, 1997 · checked 2026-09-25
13. olsf-daily-r2-14 · randomized trial
    With the olive oil diet, a reduction of coagulation factors VIIc, XIIc, XIIa, and Xc was found, whereas sunflower oil led to lower values of coagulation factors XIIc, XIIa, and IXc.
    Thromb Haemost, 2001 · checked 2026-09-25
14. olsf-daily-r2-20 · systematic review
    In human studies, when the intervention was given during pregnancy and lactation, a beneficial effect was observed. When the intervention was given during pregnancy and until birth or to the infant for six months, no effect was observed.
    Nutrients, 2023 · checked 2026-09-25
15. olsf-daily-r2-03 · regulatory register
    POL-HC-6430 Oleic acid Replacing saturated fats in the diet with unsaturated fats contributes to the maintenance of normal blood cholesterol levels. Oleic acid is an unsaturated fat. Authorised
    EU Register on nutrition and health claims, claim POL-HC-6430, snapshot 2026-09-21 · checked 2026-09-25
16. olsf-daily-r2-05 · regulatory 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 2026-09-25
17. olsf-daily-r2-10 · scoping review
    Canola/rapeseed oil may decrease LDL-cholesterol compared to olive oil, sunflower oil and sources of SFA and may also reduce body weight compared to other oils. Olive oil may decrease some inflammation markers but may not have a differential effect on LDL-cholesterol compared to other fats and oils.
    Food Nutr Res, 2024 · checked 2026-09-25
18. olsf-daily-r2-19 · meta-analysis of RCTs
    Meta-analysis of these trials found a significant reduction in the incidence of gestational diabetes in the intervention group compared to the control group (risk ratio=0.71, 95% confidence interval=(0.57, 0.88)).
    Eur J Obstet Gynecol Reprod Biol, 2024 · checked 2026-09-25
19. olsf-daily-r2-09 · umbrella review
    The evidence suggests a beneficial association between olive oil consumption and cardiovascular diseases, cancer, type 2 diabetes, and all-cause mortality. However, the evidence was less definitive for inflammatory markers, oxidative stress, glucose metabolism, and blood lipid outcomes. Several meta-analyses revealed high heterogeneity and wide confidence intervals, along with a limited number of randomized clinical trials.
    Nutr Rev, 2025 · checked 2026-09-25
20. olsf-daily-r2-11 · scoping review
    There are few SRs and meta-analyses available that investigate the association between fats and oils (food level) and health outcomes; the majority report associations at the nutrient level (fatty acid classes). All identified SRs and meta-analyses were of low methodological quality, thus the findings and conclusions presented within this scoping review should be interpreted cautiously.
    Food Nutr Res, 2024 · checked 2026-09-25