Grape seed extract
Grape seed extract contains chemicals known as polyphenols, (including the subclass of proanthocyanidins), which are recognized to be effective polyphenol antioxidants.

# Effects
Human case reports and results from some laboratory and animal studies appear to show that grape seed extract may help to prevent and treat heart diseases such as high blood pressure and high cholesterol. By limiting oxidation, antioxidants in gr ape seed extract may help prevent changes, including damage to blood vessels, that may contribute to the development of heart disease. Substances in grape seed extract may also block the effects of enzymes that process fats, including cholesterol, from the diet. Consequently, less fat may be absorbed and more may be eliminated from the body. Other research shows that grape seed extract may help to prevent or control damage to body cells that is caused by drugs, pollution, tobacco, and other toxins. While all of these studies appear promising, much more research including long-term studies in humans is needed to confirm initial findings.
Proanthocyanidins are also believed to block the deterioration of blood vessels, therefore, grape seed extract may improve conditions involving veins and arteries. It has been used to prevent, delay, and treat a condition known as chronic venous insufficiency, which occurs when valves in the veins that carry blood back to the heart are weak or damaged. The blood that collects in the veins of the legs can lead to varicose veins, spider veins, or sores on the legs. Results that are more serious may include blood clots in the legs or sores that do not heal and may become infected. This blood vessel strengthening effect of grape seed extract may also help to prevent and treat hemorrhoids.
Since proanthocyanidins in grape seed extract strengthen the walls of all blood vessels, they may also help to keep damaged, stretched, or stiff blood vessels from leaking. In one area of research, grape seed extract may be effective for slowing retinopathy, the gradual break down of the retinas in the eyes, usually due to blood vessel damage. Individuals with arteriosclerosis (a build up of fatty deposits in the arteries), diabetes, or other conditions that increase the likelihood for damage to the small blood vessels in the eyes are more likely to have serious vision problems as a result of that damage. Grape seed extract may also reduce eye stress caused by bright lights. In studies of laboratory animals, it has shown some possible effectiveness in preventing cataract formation, but further study is needed to determine whether this effect may pertain to humans.
One of the polyphenols contained in grape seed extract is called resveratrol. In laboratory and animal studies, resveratrol from grape seeds has appeared to interfere with cancer cell growth and division, as well as causing some cancer cells to disintegrate faster than they would ordinarily. In addition, it may also block enzymes that prolong the survival of several cancer cell types, including skin cancer, prostate cancer, and breast cancer. As a result, tumors may either stop growing or actually shrink because higher than usual numbers of cancer cells die. Therefore, resveratrol may have direct anticancer activity. It may also increase the effectiveness and/or lower the side effects of drugs currently used for cancer chemotherapy. One possible result is that taking resveratrol during chemotherapy may allow lower doses of cancer drugs to be effective, thereby limiting the potential for debilitating side effects. A similar effect was seen in laboratory studies of grape seed extract against HIV, the virus that causes AIDS. Although the exact ways that grape seed extract may fight HIV and other viruses are not known, it is thought that grape seed extract interferes with viral multiplication, possibly by preventing viral attachment to host cells. How high doses of resveratrol and other chemicals in grape seed extract may affect normal human cells is not yet known.
Grape seed extract may also have topical uses. In preliminary research, grape seed extract appears to be moderately effective for preventing tooth decay. It is believed to delay or stop the breakdown of sugars in the mouth and also to inhibit the growth of certain oral bacteria that may play a role in forming dental cavities. In other studies, injuries to the skin of laboratory animals may have healed better when grape seed extract was applied. Through several possible effects that include promoting the regrowth of connective tissues, grape seed extract is believed to encourage faster, stronger healing with less scarring.
Oil pressed from grape seeds is used as a dietary supplement. It contains a relatively high percentage of linoleic acid, which belongs to a group of nutrients known as essential fatty acids (EFAs). The body needs EFAs to regulate activities that include heart function, insulin utilization, and mood balance. However, the body cannot produce EFAs, so they must be obtained from foods or dietary supplements. EFAs are thought to block the production of chemicals that promote the formation of deposits in the blood vessels. Consequently, blood pressure and blood cholesterol levels may be lowered and the risk of heart disease may decrease. Additional studies are needed to confirm the effects of both linoleic acid and grape seed oil for lowering the risk of heart disease.

# Precautions
Not enough is known about how grape seed extract might affect a developing fetus or an infant to recommend its use during pregnancy or while breast-feeding.

# Side effects
In clinical studies, taking grape seed extract has been associated with mild side effects such as:
- Abdominal pain
- Cough
- Headache
- Nausea
- Sore throat
As with any dietary oil, taking large amounts of grape seed oil may lead to soft stools or oily leakage from the gastrointestinal tract.

# Interactions
Grape seed extract may possibly increase the time blood needs to clot. When it is taken with antiplatelet or anticoagulant drugs (including clopidogrel, Ticlid, heparin, warfarin, and aspirin) the effect of the drug may be increased, resulting in uncontrolled bleeding. Some of the most common herbal products that might inhibit blood clotting are Danshen, Devil's Claw, Eleuthero, Garlic, Ginger (in high amounts), Gingko, Horse Chestnut, Panax, Ginseng, Papain, Red Clover, and Saw Palmetto.
In one small study, individuals taking both vitamin C and grape seed extract experienced increased blood pressure. While the increases were not dramatic, individuals with high blood pressure may want to check blood pressure more often if both grape seed extract and vitamin C are taken together. If blood pressure rises, either vitamin C or grape seed extract or both may need to be stopped.

# Dosage and Administration
In August 2004, the American Heart Association (AHA) published a scientific advisory warning that little evidence was found for the effectiveness of antioxidant vitamin supplements to prevent cardiovascular disease. While acknowledging the benefits of antioxidants, the scientists who prepared the AHA recommendation advise getting natural antioxidants from foods rather than from supplements. Additionally, some evidence from animal studies suggests that very high doses of antioxidants such as those in grape seed extract may actually increase damage from oxidation. Therefore, doses of supplemental antioxidants should be no higher than recommended by the manufacturer of the product.
Oral grape seed extract is available as capsules or tablets usually containing 50 mg or 100 mg, and can also be purchased as a liquid to add drops to water and/or other drinks. While recommended doses are different for specific uses, a common recommendation for maintaining general health is 50 mg to 200 mg per day. Some manufacturers suggest that doses should be higher for older individuals and some animal studies have found few side effects from extremely high doses. Because the effects of high doses on humans have not been documented, however, dosing should be limited to no more that recommended on the package of the product being taken.