Grape Seed Extract Side Effects

There isn’t enough evidence to support this statement. Some small studies have suggested that phlebotonics (including GSE) may help reduce leg swelling associated with venous insufficiency. However, larger clinical trials are needed to confirm these findings before recommending the use of GSE. Additionally, only one of the 53 studies looked into GSE.

What Is Grape Seed Extract?

Jennifer Lefton, MS, RD/N-AP, CNSC, FAND is a Registered Dietitian/Nutritionist and writer with over 20 year of experience in clinical nutrition.

Updated on January 27, 2023

Elizabeth Barnes, RDN, is a registered dietitian nutritionist who specializes in eating disorders, type 2 diabetes, and heart health.

Verywell / Anastasia Tretiak

Table of Contents
Table of Contents

Grape seed extract (Vitis vinifera) is a natural substance available in capsule and tablet form. It is usually sourced from grape seeds provided by wine manufacturers.

Grapes and grape seed extract (GSE) have a long history of culinary and medicinal use. However, there is limited scientific evidence to support supplementing with GSE for any health condition.

Dietary supplements are not regulated like drugs in the United States, meaning the Food and Drug Administration (FDA) does not approve them for safety and effectiveness before products are marketed. When possible, choose a supplement that has been tested by a trusted third party, such as USP, ConsumerLab, or SNF.

However, even if supplements are third-party tested, it doesn’t mean they are necessarily safe for all or effective in general. Therefore, it is important to talk to your healthcare provider about any supplements you plan to take and to check in about any potential interactions with other supplements or medications.

Supplement Facts

Active ingredient(s): Oligomeric procyanidins
Alternate name(s): GSE, OPC, oligomeric procyanidins, procyanidin
Suggested dose: insufficient data to recommend a standard dose
Safety considerations: Avoid if pregnant or breastfeeding due to lack of safety data; do not combine with blood thinners; avoid taking before surgery

Uses of Grape Seed Extract

Supplement use should be individualized and vetted by a healthcare professional, such as a registered dietitian (RD), pharmacist, or healthcare provider. No supplement is intended to treat, cure, or prevent disease.

Today, we know that grape seed extract contains oligomeric proanthocyanidin (OPC), an antioxidant believed to improve certain health conditions. Limited—and sometimes conflicting—scientific evidence suggests GSE may have benefits for the following:

Chronic venous insufficiency and edema
Wound healing
Skin (antiaging and ultraviolet, or UV, protection)
Eye stress due to glare
Age-related macular degeneration
Viral infection
High cholesterol
Atherosclerosis
Heart disease
Metabolism

However, scientific support for the potential benefits of GSE is very limited. There is insufficient evidence to determine if GSE can improve any of these conditions. Most research focuses on cardiovascular health, blood pressure, and risk factor modification.

Heart Health

Grape seed extract may have heart-health benefits. Some studies have suggested it may modestly improve blood pressure, cholesterol, and C-reactive protein (CRP) levels. However, evidence is conflicting—other studies have shown no effect on the same measures.

Grape seed extract may be more beneficial for those who are obese. One small study of 40 people showed improvement in several heart disease risk factors—including cholesterol levels—when they took GSE supplements and followed a calorie-restricted diet for 12 weeks. However, in this case, it would be hard to know if the diet or the GSE led to the improvement in risk factors.

Another small trial by the same authors showed that taking 300 milligrams (mg) a day of GSE reduced waist circumference and several inflammatory markers in those who were obese.

Further research is still needed before recommending GSE supplementation. For now, following a heart-healthy diet and maintaining a healthy weight are known to reduce risk factors for heart disease.

High Blood Pressure

As with other cardiovascular indicators, evidence regarding grape seed extract’s effects on blood pressure is conflicting.

A meta-analysis from 2011 found that GSE significantly lowered systolic blood pressure and heart rate.

A 2016 meta-analysis of 16 small clinical trials found GSE lowered blood pressure somewhat overall, but had a more pronounced effect in people who are younger (under 50) or experiencing obesity, as well as for people who already had a metabolic condition, such as metabolic syndrome. (Metabolic syndrome is a group of conditions, such as high blood sugar, that can contribute to heart disease, type 2 diabetes, and stroke.) The authors suggested a large-scale clinical trial is warranted.

A 2021 systematic review concluded that GSE may improve blood pressure in people with hypertension (high blood pressure) or metabolic syndrome. Further large clinical trials are warranted to clarify the expected outcomes of GSE and appropriate dosing.

Diabetes

There is some evidence suggesting GSE can be beneficial for people with diabetes. A 2020 review of 15 small studies found that GSE lowered fasting blood sugar, but it did not affect hemoglobin A1c (HbA1c)—a more accurate, longer-term measure of blood sugar levels.

More studies are needed. Always consult a healthcare provider for medical advice regarding the treatment or prevention of a health condition.

What Are the Side Effects of Grape Seed Extract?

Grape seed extract is generally well tolerated when taken by mouth. However, it may occasionally cause side effects such as:

Headache
Dry or itchy scalp
Dizziness
Nausea
Indigestion
Diarrhea
Sore throat
Cough
Rash

Precautions

There is a lack of safety data on people who are pregnant or breastfeeding. Therefore, GSE is not recommended for these groups.

You should also avoid supplements containing GSE if you:

Are allergic to grapes
Have a bleeding disorder or are taking blood thinners, such as Jantoven (warfarin) or aspirin
Are about to undergo surgery

Be aware that some GSE products may contain peanut skin extract. For this reason, you should be diligent about researching which supplements to use if you have a peanut allergy.

If you have high blood pressure, do not combine high doses of grape seed extract with vitamin C. The combination might worsen blood pressure.

Dosage: How Much Grape Seed Extract Should I Take?

Due to the lack of supporting research, it’s too soon to recommend a specific dose of GSE for any health purpose. Different doses of the extract have been used in research.

For example, doses ranging from 100 milligrams to 400 milligrams daily for six to 12 weeks have been researched. However, your recommended dose may vary based on gender, age, weight, and medical history.

If you are considering using GSE, talk with a healthcare provider first. Self-treating a condition and avoiding or delaying standard care may have serious consequences.

What Happens If I Take Too Much Grape Seed Extract?

There is not enough data to know what could happen should you take too much GSE. As a general rule of thumb, always follow the instructions on the product label or given by your healthcare provider on how much to take.

Interactions

Grape seed extract may have a blood-thinning effect. Therefore, adding it to your daily regimen, along with prescribed blood thinners, could increase your risk of bleeding and bruising.

Examples of blood thinning medications include:

Warfarin
Aspirin
Plavix (clopidogrel)

This is not a complete list of drugs that can interact with GSE. Ask your healthcare provider or pharmacist for more detailed information on medication interactions.

How to Store Grape Seed Extract

Always follow the manufacturer’s instructions for proper storage. Keep all medications and supplements out of reach of children and pets to prevent accidental consumption.

Frequently Asked Questions

Will eating grapes give me the same benefits as grape seed extract?

Grapes can be a healthy snack, but the concentration of the antioxidant OPC will be much higher in the extract than when you consume a single serving of grapes.

Is GSE recommended for people with cancer?

No. There is not enough evidence to support supplementing GSE if you have cancer. Preliminary studies of GSE have provided mixed results for its use in cancer, and no studies have shown that it prevents cancer. The preliminary studies have suggested it may have a role as adjunctive (add-on) therapy for people undergoing chemotherapy, but further research is needed before recommending it for this use.

Are GSE supplements good for liver health?

There is not enough evidence to determine whether or not GSE is good for your liver. GSE may have a role in improving liver enzymes. A systematic review found that GSE significantly improved liver enzymes compared with placebo; however, the authors questioned if the improvement was enough to be clinically important.

I heard GSE could help reduce leg swelling or edema. Is this true?

There isn’t enough evidence to support this statement. Some small studies have suggested that phlebotonics (including GSE) may help reduce leg swelling associated with venous insufficiency. However, larger clinical trials are needed to confirm these findings before recommending the use of GSE. Additionally, only one of the 53 studies looked into GSE.

Sources of Grape Seed Extract & What to Look For

Grape seed extract is available in capsules and tablets and as a liquid. The antioxidant compound oligomeric proanthocyanidin (OPC) is found in grape skin extracts and grape seeds.

Before buying this or any supplement, the National Institutes of Health recommends looking for a Supplement Facts label on the product. This label will tell you the amount of active ingredient contained in each serving and information about other added ingredients.

Note that in the United States and some other countries, dietary supplements are largely unregulated, and supplements are not tested for safety. As a result, the content of some products may differ from what is specified on the product label. If you choose to use this supplement, look for a product with a seal of approval from a third-party organization that provides quality testing, such as USP, ConsumerLab, and NSF International.

Summary

Grape seed extract is a natural substance usually sourced from grape seeds that can be found in supplement form. It is marketed for use in several health conditions. However, research is lacking to support its use.

Most of the research suggests a possible role in supporting heart health. It may also help reduce high cholesterol, inflammatory markers, and blood pressure. Still, larger studies are needed to confirm these claims.

If you have concerns about heart health, talk to your healthcare provider first to determine your risk factors. A heart health plan should include eating a heart-healthy diet, practicing behavior modification, getting physical activity, maintaining a healthy weight, and sometimes taking prescription medications, if indicated. GSE is not a “magic pill,” and taking it alone is not the answer to eliminating risk factors for heart disease.

16 Sources

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

Pasini F, Chinnici F, Verardo V. Recovery of oligomeric proanthocyanidins and other phenolic compounds with established bioactivity from grape seed by-products. Molecules. 2019;24(4): 677.
National Center for Complementary and Integrative Health, National Institutes of Health. Grape seed extract.
Martinez-Zapata MJ, Vernooij RW, Uriona Tuma SM, et al. Phlebotonics for venous insufficiency. Cochrane Database Syst Rev. 2016;4(4):CD003229. doi:10.1002/14651858.CD003229.pub3
Liu M, Yun P, Hu Y, Yang J, Khadka RB, Peng X. Effects of grape seed proanthocyanidin extract on obesity. Obes Facts. 2020;13(2):279-291. doi:10.1159/000502235
Asbaghi O, Nazarian B, Reiner Ž, et al. The effects of grape seed extract on glycemic control, serum lipoproteins, inflammation, and body weight: A systematic review and meta-analysis of randomized controlled trials. Phytother Res. 2020;34(2):239-253. doi:10.1002/ptr.6518
Anjom-Shoae J, Milajerdi A, Larijani B, Esmaillzadeh A. Effects of grape seed extract on dyslipidaemia: a systematic review and dose–response meta-analysis of randomised controlled trials. Br J Nutr. 2020;124(2):121-134. doi:10.1017/S0007114520000902
Woerdeman J, van Poelgeest E, Ket JCF, Eringa EC, Serné EH, Smulders YM. Do grape polyphenols improve metabolic syndrome components? A systematic review. Eur J Clin Nutr. 2017;71(12):1381-1392. doi:10.1038/ejcn.2016.227
Yousefi R, Parandoosh M, Khorsandi H, et al. Grape seed extract supplementation along with a restricted-calorie diet improves cardiovascular risk factors in obese or overweight adult individuals: A randomized, placebo-controlled trial. Phytother Res. 2021;35(2):987-995. doi:10.1002/ptr.6859
Parandoosh M, Yousefi R, Khorsandi H, Nikpayam O, Saidpour A, Babaei H. The effects of grape seed extract (vitis vinifera) supplement on inflammatory markers, neuropeptide Y, anthropometric measures, and appetite in obese or overweight individuals: A randomized clinical trial. Phytother Res. 2020;34(2):379-387. doi:10.1002/ptr.6529
Feringa HH, Laskey DA, Dickson JE, Coleman CI. The effect of grape seed extract on cardiovascular risk markers: a meta-analysis of randomized controlled trials. J Am Diet Assoc. 2011;111(8):1173-1181. doi:10.1016/j.jada.2011.05.015
Zhang H, Liu S, Li L, et al. The impact of grape seed extract treatment on blood pressure changes: A meta-analysis of 16 randomized controlled trials. Medicine(Baltimore). 2016;95(33):e4247. doi:10.1097/MD.0000000000004247
Grohmann T, Litts C, Horgan G, et al. Efficacy of bilberry and grape seed extract supplement interventions to improve glucose and cholesterol metabolism and blood pressure in different populations-a systematic review of the literature. Nutrients. 2021;13(5):1692. doi:10.3390/nu13051692
Berry AC, Nakshabendi R, Abidali H, et al. Adverse effects of grape seed extract supplement: a clinical case and long-term follow-up. J Diet Suppl. 2016;13(2):232-235. doi:10.3109/19390211.2015.1008617
Villani TS, Reichert W, Ferruzzi MG, et al. Chemical investigation of commercial grape seed derived products to assess quality and detect adulteration. Food Chem. 2015;170:271-280. doi:10.1016/j.foodchem.2014.08.084
Zamani M, Ashtary-Larky D, Hafizi N, et al. The effect of grape products on liver enzymes: A systematic review and meta-analysis of randomized controlled trials. Phytother Res. 2022;36(12):4491-4503. doi:10.1002/ptr.7653
National Institutes of Health Office of Dietary Supplements. Dietary supplements: What you need to know.

Additional Reading

Grape Seed. Penn State Hershey. Milton S. Hershey Medical Center. Health Information Library
Grape. Natural Medicines Database. Professional Monograph. 2/6/2019
Grape Seed. Memorial Sloan Kettering Cancer Center. About Herbs, Botanicals, and Other Products. March 30, 2018
Kar P, Laight D, Rooprai HK, Shaw KM, Cummings M. “Effects of Grape Seed Extract in Type 2 Diabetic Subjects at High Cardiovascular Risk: a Double Blind Randomized Placebo Controlled Trial Examining Metabolic Markers, Vascular Tone, Inflammation, Oxidative Stress and Insulin Sensitivity.” Diabet Med. 2009 26(5):526-31.
National Center for Complementary and Alternative Medicine. “Grape Seed Extract [NCCAM Herbs at a Glance]” NCCAM Publication No. D370. Created March 2007. Updated May 2008.
Sivaprakasapillai B, Edirisinghe I, Randolph J, Steinberg F, Kappagoda T. “Effect of Grape Seed Extract on Blood Pressure in Subjects With the Metabolic Syndrome.” Metabolism. 2009 58(12):1743-6.
Wang YJ, Thomas P, Zhong JH, Bi FF, Kosaraju S, Pollard A, Fenech M, Zhou XF. “Consumption of Grape Seed Extract Prevents Amyloid-Beta Deposition and Attenuates Inflammation in Brain of an Alzheimer’s Disease Mouse.” Neurotox Res. 2009 15(1):3-14.

What are the benefits of grape seed extract?

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Was this helpful?

Grape seed extract is an industrial derivative of grape seeds. It is rich in antioxidants and oligomeric proanthocyanidin complexes and has been linked to a wide range of possible health benefits.

These include the treatment of conditions such as high cholesterol, atherosclerosis, macular degeneration, poor circulation, and nerve damage.

Many of these health claims are still not completely backed by high-quality studies, but some evidence supports its use.

Grape seed extract is available as a dietary supplement in a liquid form, tablets, or capsules. Supplements commonly contain between 50 and 100 milligrams (mg) of the extract.

This article provides details on the benefits of grape seed extract as well as side effects and precautions associated with its use.

Fast facts on grape seed extract

Here are some key points about grape seed extract. More detail and supporting information is in the main article.

Some evidence shows that grape seed extract might aid wound healing.
Grape seed extract should be avoided during pregnancy.
Some researchers believe that the proanthocyanidins it contains hold a range of benefits.

Was this helpful?

Share on Pinterest Grape seed extract may have a range of health benefits.

Studies on animal models have revealed that grape seed extract can be effective in treating heart disease.

Some experts think that grape seed extract could even have anticancer and cancer chemopreventive potential.

Over recent years, there has been a great deal of research pointing to possible therapeutic properties of grape seed extract. Listed below are some of the key findings.

Healing wounds

Grape seed extract has the potential to increase the speed that wounds heal. A study, published in the journal Free Radical Biology and Medicine, applied proanthocyanidin extract onto wounds on the backs of mice. They found that the mice treated with this solution had quicker healing times.

According to the researchers they “provided firm evidence to support that topical application of GSPE [Grape seed proanthocyanidin extract] represents a feasible and productive approach to support dermal wound healing.”

Although it is not clear how this protection occurs, GSPE was found to increase production of vascular endothelial growth factor, a compound important in the wound healing process.

Improving bone strength

Including grape seed extract in your diet with calcium has a “ beneficial effect on bone formation and bone strength for the treatment of bone debility caused by a low level of calcium.”

This is according to a study published in the Journal of Musculoskeletal & Neuronal Interactions that investigated the effects of calcium and proanthocyanidins on the bone structure of mice which had been fed a low-calcium diet.

**Anti-Candida activity**

A study conducted in Italy examined grape seed extract’s ability to attack Candida, a yeast-like parasitic fungus that can, sometimes, cause thrush. Grape seed oil contains flavan-3-ols. The researchers concluded:

“The results pointed out a significant inhibition of Candida albicans load 5 days after challenge. These findings indicate that grape seed extracts with high content of polymeric flavan-3-ols can be used in mucosal infection such as vaginal candidiasis.”

Preventing skin cancer

Grape seeds contain proanthocyanidins which might prevent the development of cancer. A study, published in the journal Molecular Nutrition & Food Research, found that grape seeds have properties that can reduce the severity of skin cancer .

Using hairless mice, the research team tested the ability of grape seed proanthocyanidins to slow the formation of skin tumor development.

The researchers concluded that grape seed extracts “could be useful in the attenuation of the adverse UV-induced health effects in human skin.”

It is thought that the protective nature of proanthocyanidins comes via a number of routes including a reduction in oxidative stress and immunosuppression by altering cytokine activity. Further research is needed to firm up the findings.

Cardiovascular benefits

The antioxidants in grape seed extract can potentially protect the blood vessels from becoming damaged, which may prevent high blood pressure.

According to one study, published in the journal Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis, “grape seed proanthocyanidin extract (GSPE) provides superior antioxidant efficacy as compared to Vitamins C, E, and β-carotene.”

The National Center for Complementary and Integrative Health (NCCIH) note that it may help reduce systolic blood pressure and heart rate, but they point out that it will not help decrease lipid levels, for example, cholesterol, in the blood.

Preventing cognitive decline

Grape seed extract is very high in proanthocyanidins which some believe could prevent cognitive decline.

One study identified “a critical role for grape seed proanthocyanidin extract (GSPE) as a neuroprotectant in the hippocampus and in preventing cognitive loss with aging.”

The NCCIH is supporting studies on the effect of grape seed extract on Alzheimer’s disease.

Other possible benefits

Other possible benefits associated with grape seed extract include:

Share on Pinterest Grape seed extract contains proanthocyanidins

treating tooth decay
protecting against pathogens
improving night vision
Alzheimer’s disease
treating diabetic retinopathy and improving blood sugar control
relieving symptoms of chronic venous insufficiency
anti-aging properties (protecting collagen and elastin)
reducingedema
relieving symptoms of chronic venous insufficiency
reducing iron levels in people with hemochromatosis
reducing inflammation

Estrogen plays a substantial role in breast cancer. Some animal studies inferred that grape seed extract might work to alter estrogen levels.

However, a study in 2014 showed that four daily doses of grape seed extract “did not significantly decrease estrogen or increase androgen precursors.”

Preventing hair loss by consuming grape seed extract has been theorized. Some nutritionists believe that proanthocyanidins inhibit dihydrotestosterone (DHT), one of the hormones thought to be involved in hair loss but, evidence for its effectiveness is scant.

Common side effects include:

headache
sore throat
dizziness
itchy scalp
stomach ache
nausea

It is important to talk to your doctor before taking grape seed extract as it can affect the way that certain medications are broken down in the liver.

Grape seed extract might also act as an anticoagulant, or blood-thinner. It could increase the risk of bleeding if taken with other blood-thinners such as warfarin (Coumadin), clopidogrel (Plavix), or aspirin.

The NCCIH describes grape seed extract as “generally well tolerated when taken in moderate amounts.”

It is available for purchase online, but you should check with a doctor first to make sure it is safe for you to use.

Is is really useful?

The effect of grape seed extract has been investigated for the following:

reducing body weight
lowering lipid levels in the blood
improving insulin sensitivity
drop in diastolic blood pressure

However, the results have shown that it either made no difference or the effect was not significant enough to support its use for these purposes.

Some note that while the procyadins can be powerful in lab experiments, grape seed extract appears to have poor bioavailability, which means the body may not absorb it efficiently enough to make it worth using.

In addition, pregnant women should completely avoid taking grape seed extract supplements.

It may be that grape seed extract can offer multiple health benefits, but more research is needed to confirm this.

Last medically reviewed on February 22, 2018

Nutrition / Diet
Complementary Medicine / Alternative Medicine

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Grape Seed Extract Side Effects