Grape seed extract

What is grape seed extract?

Grape seed extract is made from the seeds of wine grapes (Vitis vinifera), usually a by-product of winemaking. It is a concentrated source of proanthocyanidins, a family of polyphenols with antioxidant activity. According to NCCIH, it is promoted for lowering cholesterol and blood pressure, and it also appears in topical products for wound healing and in research on tooth decay.

What the research says

Compared with many botanicals in blood sugar formulas, grape seed extract has a reasonable number of controlled human trials, mostly for cardiovascular markers. NCCIH reports that a 2020 review of 11 studies (536 participants) found grape seed extract may lower LDL cholesterol and triglycerides, and a 2022 review of 19 studies (1,080 participants) found a reduction in diastolic blood pressure but not systolic pressure. NCCIH cautions that these conclusions are not definitive because the studies were small and the products varied.

For blood sugar specifically, a 2020 meta-analysis of 50 randomized controlled trials found a statistically significant but small decrease in fasting plasma glucose (about 2 mg/dL on average), along with lower total cholesterol, LDL cholesterol, triglycerides and C-reactive protein. Grape seed extract did not change HbA1c, the measure of longer-term blood sugar. In practical terms, any glucose effect seems modest, and the stronger case for grape seed extract is cardiovascular.

How it’s used in supplements

Standalone grape seed supplements typically provide 100 to 300 mg of an extract standardized for proanthocyanidins. In multi-ingredient blood sugar blends, the amount is often undisclosed and may be far lower, which limits any expected effect.

NCCIH describes grape seed extract as generally well tolerated when taken by mouth. Little is known about its safety during pregnancy or breastfeeding. NCCIH advises anyone taking medicines to talk with a health care provider before using grape seed extract, because some herbs and medicines interact in harmful ways. That is especially sensible for people on blood thinners or blood pressure drugs, since grape seed extract is studied for cardiovascular effects.

For someone whose main concern is blood sugar, grape seed extract is a supporting ingredient rather than a lead. The meta-analysis results suggest that any change in fasting glucose is likely to be smaller than day-to-day variation in a home glucose reading. Its more plausible contribution is to cardiovascular markers, which matter because people with rising blood sugar often also have rising blood pressure and cholesterol. Those markers are best tracked with your doctor through regular checkups rather than inferred from how you feel.