Mechanism of Action
Grape seed OPCs have two primary mechanisms relevant to the formulas they appear in. First, they support collagen cross-linking and capillary wall integrity by binding to collagen and elastin fibres, stabilising the walls of the fine blood vessels that supply joint cartilage and the retina. Second, they are potent free radical scavengers with antioxidant activity substantially higher than Vitamins C and E in in vitro assays. In joint tissue, this antioxidant activity reduces oxidative damage to chondrocytes and the extracellular cartilage matrix. In ocular tissue, it supports the microvasculature of the retina and reduces oxidative stress in the lens.
Evidence Summary
Human clinical trials have demonstrated benefit for chronic venous insufficiency, capillary fragility and conditions associated with microvascular damage. A systematic review by Schoonees et al (2012, Cochrane Database) found grape seed extract improved symptoms of chronic venous insufficiency. Veterinary-specific trials are limited. Its use across Petz Park joint and eye formulas is as a supporting antioxidant component at doses appropriate to the species: significantly higher doses in dog formulas (Eye Support 75mg, Hip and Joint 5mg) and proportionally lower doses in cat formulas (Eye Support 17mg, Hip and Joint 1.5mg).
In Petz Park Products
Hip and Joint for Dogs: Grape Seed Extract 5mg per scoop. Hip and Joint for Cats: Grape Seed Extract 1.5mg per scoop. Eye Support for Dogs: Grape Seed Extract 75mg per scoop. Eye Support for Cats: Grape Seed Extract 17mg per scoop.
Safety and Considerations
Grape seed extract standardised for OPCs is safe for dogs and cats at supplemental doses. It is distinct from grapes and raisins, which are toxic to dogs through a separate unidentified mechanism. Always use a supplement product that specifies OPC standardisation. Do not give dogs or cats whole grapes, raisins or grape juice.