What Is Grape Seed Extract?

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.

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.

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.