The combination of vitamin C and grape-seed polyphenols increases blood pressure: a randomized, double-blind, placebo-controlled trial, Journal of Hypertension 2005 Feb;23(2):427-34.
Background: There is growing evidence that oxidative stress contributes to the pathogenesis of hypertension and endothelial dysfunction. Thus, dietary antioxidants may beneficially influence blood pressure (BP) and endothelial function by reducing oxidative stress.
Objective: To determine if vitamin C and polyphenols, alone or in combination, can lower BP, improve endothelial function and reduce oxidative stress in hypertensive individuals.
Results: A significant interaction between grape-seed and vitamin C treatments for effects on BP was observed. Vitamin C alone reduced systolic BP versus placebo (-1.8 +/- 0.8 mmHg, P = 0.03), while polyphenols did not (-1.3 +/- 0.8 mmHg, P = 0.12). However, treatment with the combination of vitamin C and polyphenols increased systolic BP (4.8 +/- 0.9 mmHg versus placebo; 6.6 +/- 0.8 mmHg versus vitamin C; 6.1 +/- 0.9 mmHg versus polyphenols mmHg, each P < 0.0001) and diastolic BP (2.7 +/- 0.6 mmHg, P < 0.0001 versus placebo; 1.5 +/- 0.6 mmHg, P = 0.016 versus vitamin C; 3.2 +/- 0.7 mmHg, P < 0.0001 versus polyphenols). Endothelium-dependent and -independent vasodilation, and markers of oxidative damage were not significantly altered.
Conclusion: Although the mechanism remains to be elucidated, these results suggest caution for hypertensive subjects taking supplements containing combinations of vitamin C and polyphenols.
4 comments ↓
You start with Grape Seed and switch to Polyphenols.
Can I assume that Polyphenols are the same?
Other tests showed that Grape Seed, 200 MG daily, lowered blood pressure. So you are saying that the combination of the two, C and Grape Seed raises the Systolic?
Yes, that is what this research found.
As Vitamin C and grapeseed extract taken together raise BP, is it ok to take a vitamin C supplement in the morning, and the grapeseed later in the day? Will this still raise BP?
Hi Vikki, I don’t know personally if there is a safe time where you can mix the two. Perhaps the best advice on this might come from your doctor.
regards,
davidp.
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