What are the benefits of grape seed extract?

Answer:

Grape seed extract is a source of oligomeric proanthocyanidin complexes (OPCs), which are antioxidant compounds. OPCs are also found in pine bark extracts, such as Pycnogenol.

Health effects of grape seed extract

Venous Insufficiency

Several small studies suggest that grape see extract can help reduce symptoms of venous insufficiency (causing leg swelling), as well as swelling after surgery (such as arm swelling after breast cancer surgery), but larger studies are needed to confirm these benefits (Martinez-Zapata, Cochrane Database Syst Rev 2016; Baruch, Ann Chir Plast Esthet 1984).

Blood Pressure

A small, placebo-controlled study in men and women with prehypertension found that a fruit drink containing 150 mg of grape seed extract (MegaNatural BP, Polyphenolics) consumed twice daily for six weeks reduced systolic and diastolic blood pressures by, 5.6% and 4.7%, respectively (Park, Br J Nutr 2015). Subjects with higher initial blood pressures experienced nearly double the reduction.

A study among 10 overweight/obese men (average age 22) who did not have hypertension or pre-hypertension found that 600 mg of grape seed extract (containing 87.4% total oligomers) taken once daily for seven days slightly decreased systolic blood pressure at rest and after moderate exercise (cycling) by about 6 mmHg and 4 mmHg, respectively. These decreases were statistically significant compared to placebo. However, after more intense exercise, grape seed extract did not decrease systolic blood pressure, nor did it decrease diastolic blood pressure, arterial pressure or heart rate compared to placebo (Dillon, Eur J Sport Sci 2021).

Cognitive function

Grape seed extract contains polyphenol compounds that have been speculated to have cognitive benefits. However, clinical studies have generally not shown a benefit of grape seed extract for cognition. A study among healthy young adults (average age 21) showed that taking 400 mg of grape seed polyphenol extract (MegaNatural-AZ by Polyphenolics Inc.) daily for 12 weeks did not improve most measures of cognition compared to placebo (Bell, Nutr Neurosci 2022). Be aware that this study and some websites incorrectly cite a study of powdered grape juice (Cognigrape) as using grape seed extract; that study showed very small cognitive benefit (1 point on a 24-point scale) in older healthy adults (Calapai, Front Pharmacol 2017). A 6-month study among older adults (average age 70) with mild cognitive impairment showed that taking grape seed polyphenol extract containing 320 mg of procyanidins daily did not significantly improve cognitive function compared to placebo, although both groups showed improvement compared to baseline (Li, Heliyon 2023).

Dry mouth (topical)

A small study in Iran among 78 people (average age 50) scheduled to receive head and neck radiotherapy showed that rinsing with 5 mL of a mouthwash containing 2% grape seed extract three times daily starting on the first day of radiotherapy and continuing for 2 weeks reduced the number of people who experienced dry mouth by a slight, but statistically significant amount, compared to placebo mouthwash (66.7% vs. 71.8%). Using the mouthwash also reduced the percentage of people who experienced grade 2 mucositis (i.e., local redness and ulcers and the inability to swallow solid food) compared to placebo (7.7% vs 48.7%) (Eslami, Int J Cancer Manage 2022).

Safety

Grape seed extract may cause minor side effects but has generally been found to be safe, although it may have anticoagulant properties at high doses (Bijak, Nutrients 2019). As noted below, some grape seed extracts have been reported to be adulterated with peanut skin, a concern for people with peanut allergy.

Be aware that grape seed extract can inhibit iron absorption and has been shown to decrease iron and ferritin levels in children with excess iron levels when taken in addition to iron-chelating medication, compared to medication alone (Ma, J Food Sci 2011; Mottaghi, Complement Ther Clin Pract 2023). Although there do not appear to be any published reports of grape seed extract supplementation causing iron deficiency, people with low blood levels of iron, iron deficiency anemia, or who are at risk of anemia, should consult with their physician before taking grape seed extract.

Quality and Testing

The current method of testing for OPCs is inexact and amounts can be falsely inflated by other ingredients and it has been reported that less expensive ingredients, such as extracts of peanut skin, have been substituted for grape seed extract (Villani, Food Chem 2014). ConsumerLab.com intends to test grape seed extract supplements when more reliable testing methods become available.