Grape Seed Extract Benefits: What Human Studies Show

Grape seed extract is a supplement made from the seeds of wine grapes. Human studies are strongest for blood pressure and cholesterol, but the effects are small, results are mixed, and the studies are often small with products that differ from one to the next. For skin, teeth, arteries, kidneys and most other uses you may have heard about, there is little or no good human evidence yet.

Quick facts

What does human evidence show?

The studies are listed with the strongest evidence first. Many of the outcomes are lab numbers such as cholesterol or blood pressure, not heart attacks or strokes. Our guide to surrogate outcomes explains why that difference matters, and our guide to meta-analyses explains how pooled results are built.

Does grape seed extract lower cholesterol?

Possibly a little, and the picture is mixed.

• Meta-analysis of 50 randomized trials (Phytotherapy Research, 2020): pooled results showed lower total cholesterol, LDL cholesterol and triglycerides, but no change in HDL cholesterol. The paper has a published erratum.
• Review of 11 studies, 536 participants (2020, summarized by NCCIH): LDL cholesterol and triglycerides may improve, but total and HDL cholesterol did not. NCCIH says the conclusions are not definite because the studies were small and the products varied.
• Systematic review of 24 intervention studies, 20 of them on grape seed extract (Nutrients, 2021): grape seed extract may lower total and LDL cholesterol in some groups, such as people with high cholesterol, type 2 diabetes or metabolic syndrome. Age, dose and study length did not explain why groups responded differently.

Memorial Sloan Kettering describes the meta-analyses as mixed on lipid, glucose and inflammation markers.

Does it lower blood pressure?

It may, by a small amount, but studies disagree.

• Review of 19 studies, 1,080 participants (2022, summarized by NCCIH): diastolic pressure (the lower number) fell, systolic (the higher number) did not. Individual studies differed, possibly because of dose, duration and who was studied.
• Systematic review (Nutrients, 2021, linked above): grape seed extract may lower both numbers in people with hypertension or metabolic syndrome.
• One 16-week randomized trial in 80 adults aged 40 to 70 with mild hypertension (trade-press report): participants took two 150 mg tablets a day or a placebo. The report says systolic pressure changes were comparable between the groups, with no improvement from the extract. The authors saw a reduction in worry scores and a better mental-health score, which they called unexpected and worth testing again.

Memorial Sloan Kettering says meta-analyses suggest a lower systolic pressure and heart rate. That conflicts with NCCIH’s summary, which is one reason to treat the blood pressure effect as unsettled.

What about blood sugar, inflammation and oxidative stress?

• Blood sugar: the 50-trial meta-analysis found lower fasting glucose but no change in HbA1c, the longer-term sugar measure.
• Oxidative stress and inflammation: a meta-analysis of 19 trials found lower malondialdehyde (a marker of fat oxidation), lower oxidized LDL and lower high-sensitivity C-reactive protein. Total antioxidant capacity rose only marginally, and standard C-reactive protein and white blood cell count did not change significantly. The authors describe the effect on inflammation as neutral or mildly beneficial.
• Body weight: the 50-trial meta-analysis found no effect on body measurements. A separate review of research on grape seed proanthocyanidin and obesity covers mechanisms and research progress, not proof of weight loss in people.

Does it remove plaque from arteries?

No human study listed here shows that. Memorial Sloan Kettering lists atherosclerosis as a use people promote, and says preliminary human studies suggest lower LDL, higher antioxidant activity, and a possible benefit in people having coronary bypass surgery. Those are indirect markers and early studies, not scans showing plaque shrinking. If you have heart disease, plaque is something to discuss with your clinician, not something to treat with this supplement.

Does it improve exercise performance or blood vessel function?

One small trial suggests it might. Twelve elite college basketball players took a 300 mg capsule or a placebo for 14 days in a randomized, double-blind crossover design, with a one-week gap between. After the extract, oxygen use at 80% and 120% of peak effort was lower, time to exhaustion at the hardest effort was longer, and flow-mediated dilation (a test of artery widening) rose from 14.4% to 17.6%. The authors list limits: they did not measure nitric oxide, and they did not compare before-and-after values within each condition. Twelve healthy athletes tells you little about the general public.

Benefits for skin and wound healing

NCCIH says experimental-model studies suggest skin application may promote wound healing, but very little research has been done in people, so there is not enough evidence to say it helps. No human trial listed here tests it for acne, wrinkles or skin tone.

Benefits for teeth

Lab studies only. A review of 22 in vitro studies found that grape seed extract (0.5 to 250 mg/mL) reduced growth and biofilm formation of Streptococcus mutans, a bacterium linked to tooth decay. Those were test-tube concentrations, not what a supplement does in a mouth. NCCIH says there has not been enough research in people to judge whether it prevents tooth decay.

Benefits for the kidneys

There is no human evidence on kidneys in the sources here. One rat study gave rats cadmium, a toxic metal, with or without 200 mg a day of grape seed extract. Cadmium levels in the kidneys were lower with the extract, and the rise in creatinine was slower. Urea still rose almost as much. In rats given the extract alone, creatinine and urea stayed normal. Each group had six rats, and the results do not transfer to people. If you have kidney disease, ask your clinician before using it.

Other uses: cancer care, eyes, memory, ADHD, women’s health

• Memorial Sloan Kettering says oral extract did not improve radiation-related breast hardness, pain or tenderness in a placebo-controlled randomized trial of breast cancer patients. Data on diabetic retinopathy are described as suggesting a possible add-on benefit, and the benefits are preliminary.
• Memorial Sloan Kettering also notes a study linking grape seed supplement use to lower risk of blood cancers; that was an observational study and cannot show cause.
• No human trials on ADHD, or on benefits specific to women, appear in these sources. NCCIH says not much is known about effects on conditions other than cholesterol and blood pressure.

What about grapeseed oil?

The studies above test the extract, not the oil. Memorial Sloan Kettering notes that seeds are ground to make grape seed oil, but the research it summarizes is about the extract. Do not assume that findings on the extract apply to cooking oil or skin oil.

What doses did studies use?

This is what researchers used, not a recommendation.

No study listed here compared morning with night, so nothing shows that timing matters. Your clinician or pharmacist is the right person to ask about when to take any supplement alongside your medicines.

Is grape seed extract safe? Side effects and interactions

NCCIH says grape seed extract is generally well tolerated when taken by mouth or used on the skin. Memorial Sloan Kettering lists gastrointestinal upset as an adverse reaction, although another line on the same page says side effects have not been reported.

NCCIH adds that some herbs and medicines interact in harmful ways, so tell your provider about any supplement you use. NCCIH also says supplements are not approved by the FDA before they are sold. Its page Know the Science: How Medications and Supplements Can Interact is a good next read.

Who should talk to a clinician first?

• Anyone taking a blood thinner, antiplatelet drug, or any medicine for blood pressure, cholesterol or diabetes.
• Anyone with a bleeding disorder or planning surgery.
• People who are pregnant or breastfeeding.
• People with kidney or liver disease.
• Anyone with cancer being treated with chemotherapy or radiation.

Grape seed extract is not a substitute for a prescribed medicine, and these studies do not test it as one. Do not change a medicine without your prescriber.

What is still unknown?

• Whether it prevents heart attacks, strokes or other outcomes, rather than nudging lab numbers.
• Why results differ: products vary in composition, doses differ, and groups studied differ.
• Long-term safety, and safety in pregnancy and breastfeeding.
• Whether the lab-based drug interactions matter in people.
• Whether the animal and lab findings on wounds, teeth and kidneys hold in people.

For help judging study strength, see our guides on evaluating evidence quality and ingredient evidence versus marketing claims.

How do you read a label that lists grape seed extract?

• Check the exact ingredient. It should say grape seed extract (Vitis vinifera), not grapefruit seed extract.
• Look for the amount per serving. Studies used 300 mg a day, but NCCIH notes that product composition varied between studies, so a milligram figure on one label may not match another product or a study’s extract.
• Check the form. Capsules and tablets, liquid extracts and tinctures differ; Memorial Sloan Kettering says extracts are stronger and contain less alcohol than tinctures.
• Watch for proprietary blends. If grape seed extract sits inside a blend with only a total weight, you cannot tell how much you would get or compare it with study doses.
• Ask about standardization. The studies describe active compounds as proanthocyanidins and other polyphenols. Ask the maker what the extract contains and whether independent testing is available.
• Ignore ranking claims. The studies here do not compare brands, so none can be called best; the human evidence is for the ingredient in general, not a product.

Before you decide

• Ask your clinician whether it fits with your medicines and conditions.
• Ask the seller for the full label, amount of extract per serving and any testing information.
• Be skeptical of claims that go beyond blood pressure and cholesterol markers.

By ClinicalStudyConnect.com Research Desk