Blackberries (Rubus fruticosus) have been studied for their potential effects on cardiovascular health, including hypertension (high blood pressure). The scientific evidence supporting the use of blackberry for hypertension is limited, with most studies conducted in vitro (test tube) or in animal models, and only a few small-scale human trials.

Blackberries are rich in polyphenols, especially anthocyanins, which possess antioxidant and anti-inflammatory properties. Some animal studies suggest that blackberry extracts may help lower blood pressure by improving endothelial function (the health of blood vessel linings), reducing oxidative stress, and modulating nitric oxide production, which helps relax blood vessels. A few small human studies have shown that diets high in berries, including blackberries, may have modest beneficial effects on blood pressure, but these studies often use mixed berries rather than blackberries alone, making it difficult to attribute effects specifically to this fruit.

Overall, while there is a scientific rationale and some preliminary evidence for the potential benefit of blackberry consumption in supporting healthy blood pressure, robust clinical trials on blackberry-specific interventions for hypertension are lacking. Thus, the current evidence base is weak (rating 2 out of 5), and blackberries should be viewed as part of an overall healthy diet rather than a primary treatment for hypertension.