Oligomeric Proanthocyanidins (OPCs)
What is it? Overview Usage Side Effects and Warnings

What is Oligomeric Proanthocyanidins (OPCs)?

One of the bestselling herbal products of the early 1990s was an extract of the bark of French maritime pine. This substance consists of a family of chemicals known scientifically as oligomeric proanthocyanidin complexes (OPCs) or procyanidolic oligomers (PCOs). Similar (but not identical) substances are also found in grape seed. The research record is complicated by the fact that certain identically named proprietary products have consisted at different times of various proportions of these related substances.

OPCs are marketed for a wide variety of uses. As yet, however, there is no solid evidence that they are effective for any medical condition.

The best-documented use of OPCs is to treat chronic venous insufficiency , a condition closely related to varicose veins. In both of these conditions, blood pools in the legs, causing aching, pain, heaviness, swelling, fatigue, and unsightly visible veins. Fairly good preliminary evidence suggests that OPCs from pine bark or grape seed can relieve the leg pain and swelling of chronic venous insufficiency. 1 2 3 4 However, no studies have evaluated whether regular use of OPCs can make visible varicose veins disappear, or prevent new ones from developing.

Other small, double-blind trials suggest that OPCs may help reduce swelling caused by injuries or surgery . 5 6 Evidence from one small, double-blind trial suggests that OPCs from bilberry and grape seed may reduce the...

Safety Issues

OPCs have been extensively tested for safety and are generally considered to be essentially nontoxic. 7 Side effects are rare, but when they do occur they are limited to occasional allergic reactions and mild digestive distress.

However, one study unexpectedly found that a combination of OPCs and vitamin C might slightly increase blood pressure in people with high blood pressure . 8 Neither treatment alone had this effect. These results may have been a statistical fluke, but nonetheless people with hypertension should use the combination of vitamin C and OPCs only with caution.

Maximum safe dosages for young children, pregnant or nursing women, or those with severe liver or kidney disease have not been established.

OPCs may have some anticoagulant...