About OPCs
Class marker for the OPC/condensed-tannin flavonoid family. Evidence is source-specific: grape seed proanthocyanidins have a meta-analysis showing modest blood-pressure reduction, and cranberry proanthocyanidins have UTI-prevention trials — but these belong to the named source extracts (grape_seed_extract, pine_bark_extract, anthocyanins), which are scored separately with their own evidence. An unlabeled 'proanthocyanidins' or 'OPC' amount, or a standardization percentage like '95% Proanthocyanidins', is a marker for the extract's active fraction. Graded low as a generic class term; score the named source where present.
What OPCs supports
- Grape seed proanthocyanidins modestly lower blood pressure in trials (source-specific)
- Cranberry proanthocyanidins studied for urinary tract infection prevention (source-specific)
How much OPCs to take
The RDA prevents deficiency. The effective range is what clinical trials used to actually move the outcome.
Effective
150–300
mg
Nominal range from OPC trials (e.g. ~150 mg/day used in cardiovascular/antioxidant studies; cranberry UTI trials standardize to 36 mg PAC). Doses vary widely by source, so this is an approximate blend-marker range, not a validated therapeutic dose for an unspecified proanthocyanidin.
Clinical evidence
Limited clinical evidence. Class marker; RCT evidence is source-specific (grape seed BP, cranberry UTI), not for a generic OPC dose.
NIH Fact Sheet