Recommended dosage of grape seed extract supplement

The dosage of grape seed extract has not been strictly established. It is always recommended in a conservative way, even though it is safe at higher than recommended dosage.

For adults: a total OPC quantity of 90-150 mg is usually recommended for normal health maintenance. A higher dosage of 150-300 mg is recommended for people of certain medical conditions. For example: High blood pressure: 150-300 mg; Chronic venous insufficiency: 150 - 300 mg; Edema: 200 - 400 mg.

Side effects of grape seed extract may vary from product to product

Imagine that you take raw grape seeds, you likely get sick soon with headache, itchy scalp, dizziness, and/or nausea, etc. Raw grape seeds don’t help you with health benefits, because there are too much impurities that are harmful.

The true value of grape seed extract is its content of OPC (oligomeric proanthocyandins). The purity of OPC is the key for the quality of a grape seed extract product. Impurities are the major causes of side effects.

There are much more risks if you take cheap capsules or tablets of 300-500 mg each day. In the long term, a grape seed extract of low quality may cause problems to your health, because a low quality grape seed extract contains high polymers of proanthocyanidins. The high polymers are not absorbed by human body because their molecular sizes are too large to cross the cellular wall. The high polymers grab the metal ions (mineral nutrients) tightly, and act as metal chelators to prevent mineral absorption by human body.

OPC molecules, ranging from dimmer to tetramer as described by French Professor Masquelier (the inventor of OPC or pycnogenol), are the best for human body to absorb as the effective antioxidants. There has been no significant documentation of the side effects for a grape seed extract with high purity OPC. It is presumed that grape seed extract is safe in general.

In a 12-month study, the safety is established for dietary intake of grape seed extract in a dose of 100 mg per kg per day in rodents. See: Ray S, Bagchi D, Lim PM, et al.. "Acute and long-term safety evaluation of a novel IH636 grape seed proanthocyanidin extract". Res Commun Mol Pathol Pharmacol. 2001; 109 (3–4): 165–97.

At higher doses (> 300 mg a single dose), rare and minor side effects that have been reported most often include headache, a dry itchy scalp, dizziness and nausea. Due to the astringent taste of grape seed extract, large dose may give mild gastrointestinal problems such as an upset stomach or nausea. Reducing the dosage size or dividing the single dose to multiple doses by taking throughout the day has shown to be a good way to eliminate the problem.

Do not take grape seed extract if you're allergic to grapes. Consult your doctor or pharmacist for any concerns and questions. Get advice from your professional medical careprovider before using any dietary supplement if you have any sickness or if you take prescription drugs.

Drug interactions

There is no direct knowledge on possible interactions of grape seed extract with prescription drugs, as the interactions have not been investigated significantly. But there are a plenty of speculations based on some indirect knowledge, which should be taken for consideration as a general precaution.

One general caution is, due to the possible action of proanthocyanidins in grape seed extract on limiting platelet adhesion, grape seed extract may behave like a blood-thinner, increasing clotting time. Grape seed extract may possibly interact with Anticoagulants (blood thinners), even though some other experts argue that grape seed extract is not blood thinners and does not compete with them. In any case and as a precaution, if you take blood thinning medications or have bleeding disorders, ask your doctor before taking grape seed extract.

Grape seed extract and other related OPC extracts have not been tested in organ transplant patients. This kind of clinical trial is too expensive, and it is very hard to enroll enough patients. Grape seed extract is not recommended to any organ transplant patients as a conservative policy, because the safety has not been firmly established for these patients of extensive care. Some experts believe that grape seed extract may interact with anti-rejection medication, even though there is no firm evidence for that.

Grape seed extract may interact with other prescription drugs. If you take any medicines regularly, talk to your doctor before you take grape seed extract. Grape seed extract may interact with drugs like hypoglycemic agents, certain heart medicines, drugs for cancer treatments, and others.

Grape seed polyphenols may interact with some minerals

Take a grape seed extract supplement separately, at least 2-3 hours apart if you also take a mineral supplement such as calcium or multi-minerals.

For precaution, people of anemia should not take grape seed extract supplement, even though no clinical evidence showing that grape seed extract can interfere with iron absorption.

Grape seed extract for children and pregnant or breastfeeding women?

Children may take grape seed extracts if advised by health care professionals. Whole grapes or grape juices contain the same OPCs at very low concentration, and is safe for children.

Pregnant or breastfeeding women should not take grape seed extract supplements without consulting a medical care professional. It should be noted some expert argues the following:

“No contra-indications are known to Pregnant or breastfeeding women. The first person that Dr. Masquelier recommended to take his extract was the pregnant wife of his dean at the university in Bordeaux. She had severe swelling in her legs and was greatly helped by them. Both the fetus and mother need antioxidant protection during pregnancy and OPC's are ideal.”

† The contents in this website have not been evaluated by the US Food & Drug Administration. Vitaflavan® grape seed extract and FrenchGlory® OPC antioxidants are nutritional supplements, not intended to diagnose, treat, care for or prevent any diseases.

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Grape Seed Extract Is Safe without Significant Side Effects