You may find the two names -- grape seed oil and grape seed extract -- used interchangeably, but they represent two different products. Grape seed oil is commercially produced for use as a cooking oil. Grape seed extract is an antioxidant-containing supplement. While both products are safe for most people, grape seed extract contains active ingredients that can cause side effects.
Grape Seed Oil
The oil pressed from grape seeds is used to produce a light-flavored cooking oil. With 120 calories in 1 tablespoon of oil, a potential side effect may come from the number of calories you'll consume if your diet includes too much oil. All of the calories come from fats, but on the positive side, these fats are predominantly unsaturated fats, which can help to lower cholesterol. The Institute of Medicine recommends getting 20 percent to 35 percent of your daily calories from fats, with the majority coming from sources that are unsaturated.
Grape Seed Extract
Grape seed extract goes though a different processing method than the one used for grape seed oil. As a result, it retains more of the beneficial water-soluble ingredients. It's a good source of antioxidants called oligomeric proanthocyanidin complexes, or OPCs. Grape seed extract also contains flavonoids, another group of plant-based antioxidants. You can find supplemental grape seed extract in the form of capsules, tablets and liquids. The extract is considered safe, but its active ingredients may cause side effects. Dietary supplements are not regulated by the U.S. Food and Drug Administration for safety or efficacy, so always buy from a reputable manufacturer.
Watch for Side Effects
Do not use grape seed oil or extract If you're allergic to grapes. People who are allergic to cherries and strawberries also have a good chance of being sensitive to grapes, so consult your health care provider if you have any food allergy concerns. The National Center for Complementary and Alternative Medicine reports a variety of side effects associated with grape seed extract. You may experience gastrointestinal problems, such as indigestion and nausea, or possibly a headache or dizziness. Other side effects to watch for include an itchy scalp, hives and high blood pressure.
Taking grape seed extract together with vitamin C supplements may increase your blood pressure if you already have high blood pressure, reports Drugs.com. Grape seed extract interferes with enzymes that help your liver detoxify medications, which can affect the concentration of drugs in your bloodstream and increase their impact on your body. The extract is known to enhance the activity of blood-thinning medications such as warfarin, but it can influence other medications, so check with your doctor before using supplements if you take any type of prescription medications.