How we rate
“Strong” = several concordant meta-analyses or systematic reviews. “Moderate” = one synthesis, or several controlled trials. “Limited” = early trials only. The rating is about the quality of the studies, not about how useful the supplement is.
Grape seed extract
Grape seed extract slightly lowers blood pressure and LDL in small trials. EFSA considers the evidence insufficient for a claim, and combined with vitamin C, it increased pressure.
Benefits
- Blood pressure: across 16 trials (810 people), −6.1 mmHg systolic pressure and −2.8 mmHg diastolic pressure on average, more pronounced in younger people, obese individuals, or those with metabolic syndrome.
- Pre-hypertension: 300 mg per day for 6 weeks lowered systolic pressure by 5.6% and diastolic pressure by 4.7% in middle-aged adults.
- LDL and triglycerides: across 11 trials (536 people), −0.17 mmol/l of LDL and −0.11 mmol/l of triglycerides on average.
- Blood sugar and inflammation: across 50 trials, it slightly lowers fasting blood sugar and C-reactive protein, without changing glycated hemoglobin or weight.
- Oxidation: across 19 studies, it lowers malondialdehyde and oxidized LDL, two markers of fat oxidation.
- Vessels: 2 g per day for 4 weeks improved brachial artery dilation by 1.1 points in 36 vascular-at-risk individuals.
- During exercise: a single 300 mg dose lowered mean blood pressure during cycling in 9 pre-hypertensive men (123 versus 126 mmHg at 60% of VO2max).
- Insulin: 300 mg twice a day for 8 weeks lowered insulin and insulin resistance in 40 female volleyball players.
Precautions
Vitamin C: in 69 treated hypertensive subjects, the combination with 500 mg of vitamin C per day increased systolic pressure by 4.8 mmHg compared to placebo. Iron: at 2,500 mg per day, blood iron dropped in two of the 29 volunteers, remaining within normal values, then rebounded upon cessation. Post-ingestion: in 10 at-risk adults, 7 days of extract lowered resting pressure, but temporarily increased it 90 minutes after ingestion. Limitations: EFSA (2021) considers the evidence insufficient for a claim on maintaining normal blood pressure: out of two trials presented, one found nothing at 300 mg per day. In 70 pre-hypertensive or stage 1 hypertensive adults, 300 mg per day for 8 weeks did not significantly lower pressure (−3.0 mmHg systolic). An older meta-analysis of 9 trials found no effect on diastolic pressure, lipids, or C-reactive protein. Muscle: after eccentric exercise, 300 mg per day changed neither strength nor muscle soreness in 16 students.
Recommended dosage
300 mg per day in most trials, ranging from 100 mg to 2 g; up to 2,500 mg per day well tolerated for 4 weeks.
How to take it
- Dose: 300 mg per day, taken once or in two 150 mg doses, in most blood pressure trials.
- Duration: 4 to 16 weeks in the trials; blood pressure returned to baseline 4 weeks after cessation.
- Less can be enough: it was at doses below 300 mg per day, and for less than 10 weeks, that total cholesterol and HDL decreased.
- With a diet: in 40 overweight adults on a diet, 300 mg per day for 12 weeks led to slightly more weight and waist circumference loss than a placebo.
- Not with vitamin C: combined with 500 mg of vitamin C, 1,000 mg of grape seed polyphenols per day increased the blood pressure of hypertensive individuals.
- For whom: trials mainly involve pre-hypertensive, overweight, diabetic adults, or those with metabolic syndrome.
Did you know?
In nine pre-hypertensive men, two hours after a single 300 mg dose, brachial artery dilation reached 18.9%, compared to 12.4% with a placebo.
What the studies say
This meta-analysis synthesized 19 studies to evaluate the effects of grape seed extract (GSE) supplementation on oxidative stress and inflammation. GSE led to a significant decrease in malondialdehyde (a marker of lipid oxidation) and C-reactive protein (a marker of inflammation). It also showed a marginally significant increase in total antioxidant capacity. These results suggest that GSE can modulate the body's redox system, primarily by inhibiting lipid oxidation, with neutral or slightly beneficial effects on inflammatory responses.
Foshati S, Rouhani MH, Amani R. — International journal of clinical practice (2021) — View the source study
For information only: not a substitute for medical advice. Dietary supplements are not a replacement for a varied, balanced diet. Learn more