What do clinical studies really show about blood pressure, blood vessels, menopause and oxidative stress?
Grape seed extract is obtained from the seeds of the grape (Vitis vinifera). The focus here is on oligomeric proanthocyanidins (OPC) or proanthocyanidins, i.e. polyphenolic plant substances that are being investigated primarily for their antioxidant properties and their possible effects on blood vessels, blood pressure and inflammation markers.
It is important to note that the clinical study situation is interesting, but not uniform. There are several randomized, placebo-controlled human studies, but some of them differ significantly in terms of dosage, study duration, population and endpoints. Some show clear benefits, others only partial or no significant effects
“We only use Grap’Inside™ grape seed extract in organic quality and use grape seeds that are an upcycled product of French wine production.”
We highlight the results of each study here.
STUDY 1
Terauchi M. et al. (2014). Effects of grape seed proanthocyanidin extract on menopausal symptoms, body composition, and cardiovascular parameters in middle-aged women: a randomized, double-blind, placebo-controlled pilot study. Menopause; 21(9):990-996.
How was the study conducted?
This was a randomized, double-blind, placebo-controlled pilot study involving 96 women aged 40 to 60 years who had at least one menopausal symptom.
In the study, lower and higher doses of grape seed proanthocyanidins were compared with placebo over 8 weeks.
What effects were investigated?
The main areas examined were:
- Physical menopause symptoms
- Hot flashes
- Sleep
- Anxiety/mental state
- Blood pressure
- Body composition, including muscle mass
What was found?
- In the higher-dose group, the physical symptom score, the hot flush score and the sleep score improved after 8 weeks.
- In both verum groups, anxiety levels and systolic and diastolic blood pressure also decreased.
- Muscle mass also increased.
- The authors concluded that grape seed proanthocyanidins can improve physical and psychological menopausal symptoms.
STUDY 2
Odai T. et al. (2019). Effects of Grape Seed Proanthocyanidin Extract on Vascular Endothelial Function in Participants with Prehypertension: A Randomized, Double-Blind, Placebo-Controlled Study.
Nutrients; 11(12):2844.
How was the study conducted?
- This human study was randomized, double-blind and placebo-controlled.
- Thirty adults with prehypertension between the ages of 40 and 64 took part.
- The participants received either 200 mg/day, 400 mg/day GSPE or placebo for 12 weeks.
What effects were investigated?
The focus was on:
- systolic and diastolic blood pressure
- Endothelial function, measured via flow-mediated dilation (FMD)
- other cardiovascular parameters such as pulse wave velocity and vascular stiffness
What was found?
In the high-dose group, mean systolic blood pressure fell significantly by 13 mmHg after 12 weeks. However, FMD did not change. In an additional analysis of the non-smokers, several parameters of vascular stiffness also improved.
The results suggest that grape seed extract could be particularly relevant for blood pressure and possibly arterial stiffness. However, the fact that FMD did not change also shows that not every vascular endpoint benefits automatically.
STUDY 3
Kar P. et al. (2009). Effects of grape seed extract in type 2 diabetic subjects at high cardiovascular risk: a double blind randomized placebo controlled trial examining metabolic markers, vascular tone, inflammation, oxidative stress and insulin sensitivity.
Diabet Med; 26(5):526-531.
How was the study conducted?
This was a double-blind, randomized, placebo-controlled study involving 32 people with type 2 diabetes and high cardiovascular risk. Markers were measured at baseline and after the intervention with GSE or placebo.
What effects were investigated?
Among other things, the researchers looked at:
- Inflammation markers such as hsCRP
- Markers of oxidative stress
- Fructosamine as a marker of short-term blood glucose control
- Lipid profile
- Endothelial function
- Insulin resistance via HOMA-IR
What was found?
After grape seed extract, but not after placebo, there were significant improvements in fructosamine, hsCRP and a marker of antioxidant status. Total cholesterol also decreased slightly.
In contrast, there were no significant changes in endothelial function, HOMA-IR or the overall antioxidant status parameter TAOS.
This study is interesting because it shows that grape seed extract may act on inflammation, glycemia and individual oxidative stress markers rather than on all vascular or metabolic parameters simultaneously.
STUDY 4
Sano A. et al. (2013). Proanthocyanidin-rich grape seed extract reduces leg swelling in healthy women during prolonged sitting.
J Sci Food Agric; 93(3):457-462.
How was the study conducted?
The study was conducted as a double-blind, placebo-controlled crossover study. Both a single dose and a 14-day intake of grape seed extract versus placebo were investigated in healthy women who then maintained a seated position for 6 hours.
What effects were investigated?
The focus was on:
- Increase in leg volume
- extracellular fluid
- Water retention in the legs during prolonged sitting
What was found?
Leg swelling, extracellular fluid and water retention in the leg were significantly suppressed in the grape seed extract groups. The authors concluded that grape seed extract may contribute to the reduction of leg swelling during prolonged sitting.
This is particularly exciting for topics such as heavy legs, prolonged sitting, traveling or venous stress. However, the study concerns a very specific situation and a healthy population.
STUDY 5
Park E. et al. (2016). Effects of grape seed extract beverage on blood pressure and metabolic indices in individuals with pre-hypertension: a randomized, double-blinded, placebo-controlled study.
Br J Nutr.
How was the study conducted?
This study was randomized, double-blind and placebo-controlled and investigated a grape seed extract-containing drink in people with prehypertension.
What was found?
The focus was on:
- Blood pressure
- metabolic markers
- Safety and tolerability of the drink containing grape seed extract
What was found?
Grape seed extract was found to be safe and improved blood pressure in people with prehypertension.
STUDY 6
Ghanbari P. et al. (2024). The effects of grape seed extract supplementation on cardiovascular risk factors, liver enzymes and hepatic steatosis in patients with non-alcoholic fatty liver disease: a randomized, double-blind, placebo-controlled study.
PubMed entry 2024.
How was the study conducted?
This more recent study was double-blind, randomized and placebo-controlled. 50 patients with NAFLD were divided into two groups and received 520 mg/day of grape seed extract or placebo for 2 months.
What effects were investigated?
The following were examined:
- glycemic parameters
- Lipid profile
- Blood pressure
- Liver values
- hepatic steatosis
- Oxidative stress markers and quality of life
What was found?
improvements in oxidative stress and in several aspects of quality of life. At the same time, the authors emphasize that further studies are needed to confirm the results.
This study expands the picture to include an area in which oxidative stress and metabolic stress play a major role. However, the evidence here is still relatively new for reliable conclusions.
STUDY 7
Terauchi, Masakazu et al. (2014) Effects of grape seed proanthocyanidin extract on menopausal symptoms, body composition, and cardiovascular parameters in middle-aged women: a randomized, double-blind, placebo-controlled pilot study.
Menopause (New York, N.Y.) vol. 21,9
How was the study conducted?
This was a randomized, double-blind, placebo-controlled pilot study involving a total of 96 women aged 40 to 60 who reported at least one menopausal symptom. The study compared daily doses of 100 mg GSPE, 200 mg GSPE, and a placebo over an 8-week period.
What effects were investigated?
The study examined menopausal symptoms as well as physical and psychological parameters. These included, in particular, physical menopausal symptoms, hot flashes, sleep quality, anxiety levels, blood pressure, and body composition, including muscle mass.
What was found?
After 8 weeks, the higher-dose GSPE group showed significant improvements in physical symptom scores, hot flash scores, and sleep scores. In both placebo groups, anxiety levels as well as systolic and diastolic blood pressure also decreased. In addition, muscle mass increased in both GSPE groups. The authors concluded that grape seed proanthocyanidin extract can alleviate physical and psychological menopausal symptoms.
What do the studies show overall?
When the human clinical studies are taken together, an interesting overall picture emerges. Grape seed extract was primarily investigated with regard to the following areas:
Blood pressure and vascular load
Several studies show positive effects on blood pressure, especially in people with prehypertension.
Oxidative stress and inflammatory markers
Some studies indicate improvements in inflammation levels and oxidative stress, especially in metabolically stressed populations.
Heavy legs and prolonged sitting
The crossover study in healthy women indicates that grape seed extract can reduce water retention and swelling during prolonged sitting.
Menopausal symptoms
The pilot study in menopausal women indicates benefits for physical complaints, sleep, blood pressure and psychological well-being.
Conclusion
Grape seed extract with OPC has been much better studied than many people assume. In particular, the areas of blood pressure, vascular stress, oxidative stress, inflammation markers and, in some cases, menopausal symptoms are the focus of clinical human studies.
At the same time, the evidence is promising, but not conclusive. Some of the studies are small, the extracts used are not always directly comparable and the target groups studied are very different. The data therefore suggests interesting scientific potential.
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