Grape seed extract (GSE) is packed with polyphenols and other antioxidants. Many GSE products are available, but their quality and safety can greatly vary. Learn about the dosage range used in clinical trials, reported side effects, and what users say about different GSE supplements.
Grape Seed Extract Side Effects & Safety
Grape seed extract is a concentrated source of antioxidant polyphenols from grape seeds [1, 2, 3].
Supplement manufacturers usually source grape seeds from winemakers, and they extract proanthocyanidins and other healthy components.
For other grape seed products and their uses, check out the FAQ section below.
Reported Side Effects
Grape seed extract was safe in clinical trials, mostly causing side effects at rates similar to placebo. The following side effects have been reported [4, 5, 6]:
- Abdominal pain
- Sore throat
- Dry mouth
- Worsening of high cholesterol levels
- Scalp and skin irritation
- Hair thinning
- Allergic reactions
People who are allergic to grapes shouldn’t use grape seed extract.
Animal safety studies suggested that grape seed extract was safe in long-term lab settings, but proper human safety data are lacking [7, 8, 9].
Effects on the Absorption of Nutrients
Grape seeds and other foods rich in polyphenols may hinder iron absorption. To avoid iron deficiency, don’t take grape seed extract supplements with iron-rich foods (meat, legumes, greens). If you do, you can combine it with vitamin C to improve iron absorption [10, 11].
Pesticides and yeast toxins have been identified in grape skin, juice, and wine made from grapes in some regions of the world. For example, pesticides were found in most grape juice products produced and sold in Canada. On the other hand, juice and red wine from sold in Brazil contained the yeast toxin called Ochratoxin A [12, 13].
These toxins have not been reported to occur in grape seed extract.
Children and Pregnant Women
Children and pregnant and breastfeeding women should avoid grape seed extract because we still lack evidence of its safety in these sensitive groups.
Supplement-drug interactions can be dangerous and, in rare cases, even life-threatening. Always consult your doctor before supplementing and let him know about all drugs and supplements you are using or considering.
Although quite safe on its own, grape seed extract may inhibit some liver enzymes (CYP3A4 and CYP1A2) and thus impact the metabolism of certain drugs, such as [14, 15]:
- Anti-seizure drugs
- Antidepressants (SSRIs)
- Antifungal drugs (azoles)
Grape seed extract prevents blood clotting and may thus interfere with blood thinners such as warfarin (Coumadin) .
Grape Seed Extract Dosage & Supplements
The below-outlined doses used in clinical trials may not apply to you personally. If your doctor suggests using a grape seed extract supplement, work with them to find the optimal dosage according to your health condition and other factors.
Dosage In Clinical Trials
The following grape seed extract doses used by mouth showed potential benefits in clinical trials:
- Antioxidant support: 600 mg daily for 5 days 
- Blood pressure and heart disease prevention: 300-2000 mg for 4+ weeks [4, 17, 18]
- Mental health and cognition: 250 mg daily for 12 weeks 
- Kidney disease: 2000 mg daily for 6 months 
- Skin appearance: 200 mg daily for 6 months 
For grape seed extract skin application, the following formulations were used:
- Anti-aging: 2% GSE cream, 2x daily for 2 months 
- Wound healing: 2% GSE cream, 2x daily for 3 weeks 
Despite the promising clinical and preclinical research, grape seed extract supplements have not been approved by the FDA for medical use. In general, regulatory bodies aren’t assuring the quality, safety, and efficacy of supplements. Speak with your doctor before supplementing.
Grape seed extract supplements usually contain pills with 120-400 mg of the extract. Bulk powders and liquid grape seed extracts are also available. Some products are standardized to 95% proanthocyanidins.
Cosmetics such as face and eye creams can contain grape seed extract, though grape seed oil is a more common ingredient in skincare.
Grape Seed Extract User Reviews
The opinions expressed in this section are solely from the users who may or may not have a medical background. Their reviews do not represent the opinions of SelfHacked. SelfHacked does not endorse any specific product, service, or treatment.
Do not consider user experiences as medical advice. Never delay or disregard seeking professional medical advice from your doctor or another qualified healthcare provider because of something you have read on SelfHacked.
Grape seed extract supplements are very popular; people take them for high blood pressure, varicose veins, swelling, etc. Most user reviews of grape seed extract are positive, though some of them experienced only mild benefits.
Older men report positive results for prostate health and libido while women often use it in skincare. Side effects are not common, and they include mild headache, nausea, and skin irritation.
Here’s what Joe, biohacker and SelfDecode CEO, has to say about grape seed extract:
“I like grape seed extract! It does initially have an immune-stimulating effect, which isn’t great for my overactive Th1-dominant immune system, but it’s good for Th2-dominant people.
So I don’t take it daily, but I think taking a supplement with proanthocyanidins is important, especially for people who don’t get enough antioxidants through their diet.”
Grape Seed Extract FAQ
Does It Contain Resveratrol?
Resveratrol is another antioxidant from grapes with a broad spectrum of potential health benefits. However, grape seed extract is not a good source of resveratrol since most of resveratrol comes from grape skin .
Extract vs. Oil vs. Flour
Grape seed extract is a concentrated source of antioxidant proanthocyanidins and has the most potent health effects.
Grape seed oil contains healthy fats, fat-soluble vitamins, and a fraction of antioxidants from the seeds. It shares some health benefits with the extract, but its main uses are in cooking (nutrition) and skincare.
Grape seed flour is a byproduct of oil extraction from the seeds. It contains antioxidants, minerals, fiber, and other nutrients, which makes it a healthy addition to baked goods.
Is Grape Seed Extract Good for Dogs?
Supplementation with polyphenols from grapes may prevent blood clotting and age-related cognitive decline in dogs [23, 24].
In test tubes, grape seed extract protected the dogs’ eye cells against oxidative stress. It may thus prevent visual impairment in aged dogs [25, 26].
CAUTION: While grape seed extract is safe for dogs, whole grapes and raisins may trigger life-threatening kidney failure [27, 28].
Grapeseed extract is a relatively safe supplement for antioxidant protection and general wellbeing.
The daily dosage ranges from 300 to 2000 mg, depending on the intended health effect.
Children and pregnant women should avoid grape seed extract, while others should consult their doctor before supplementing.