From endothelial function to blood pressure, this review maps where bioactive compounds in blueberries and grapes hold promise and where clinical evidence is still lacking.
Study: Polyphenols and cardiovascular health: Emerging associations with blueberries, grapes, and red-fleshed table grapes. Image credit: Den Debono / Shutterstock
Recent reviews published in magazines nutrients investigated the evidence regarding the effects of blueberries, grapes, and their bioactive compounds on cardiovascular risk markers.
Cardiovascular disease (CVD) is one of the most prevalent non-communicable diseases and a leading cause of death in Europe. The paper reports that more than 60 million years of life are potentially lost to CVD in Europe. Diet is increasingly recognized as a modifiable risk factor for CVD, and dietary bioactive compounds are gaining attention for their potential role in cardiovascular prevention and risk management. Several fruits, including grapes, have been studied for their potential cardioprotective effects.
Berries and grapes contain a wide range of polyphenolic bioactive compounds, including resveratrol, flavonoids, and anthocyanins, which have potential anti-inflammatory, antioxidant, and cardioprotective biological effects. Experimental evidence indicates that grape polyphenols may influence processes related to CVD by reducing platelet aggregation and low-density lipoprotein (LDL) oxidation, suppressing inflammation, and improving endothelial function.
Evidence also suggests that the gut microbiota metabolizes polyphenols, particularly anthocyanins, to produce bioactive metabolites that influence cardiovascular function. Resveratrol, which is abundant in the skin of black grapes, has been reported to regulate cardiac remodeling, exert antioxidant and anti-inflammatory effects, and promote mitochondrial biogenesis. It may also reduce oxidative stress in cardiac tissue by modulating oxidation-induced proteins.
research and discovery
In this study, researchers reviewed the evidence regarding the effects of blueberries, grapes, and their bioactive compounds on cardiovascular health. First, we conducted a comprehensive systematic literature search in PubMed to identify randomized controlled trials (RCTs), systematic reviews, and meta-analyses published from January 2015 to April 2026. A secondary search of ScienceDirect and Semantic Scholar searched for additional literature containing mechanistic evidence.
Studies were eligible for inclusion if they included interventions involving grapes, blueberries, or red-fleshed table grapes, focused on important bioactive compounds found in grapes or blueberries, and included measurements of cardiovascular outcomes such as endothelial function, platelet aggregation, LDL oxidation, inflammatory biomarkers, and blood pressure (BP). Studies that focused solely on in vitro or animal models were excluded from the clinical synthesis unless relevant mechanistic evidence was provided. Studies containing multiple interventions or mixed polyphenol supplements were excluded.
Validated assessment tools such as the Jadad scale and the Measurement Tool for Assessing Systematic Reviews 2 (AMSTAR-2) were used to assess study quality. A total of 37 publications (including 20 RCTs and 17 systematic reviews and meta-analyses) were included. Two systematic reviews and meta-analyses were of high quality. One study reported that taking grape polyphenols at doses greater than 500 mg per day for at least 12 weeks significantly reduced levels of C-reactive protein, and another study found that 84% of human studies evaluated reported improvements in vascular function or blood pressure, including significant reductions in systolic blood pressure.
Additionally, two other systematic reviews and a moderate-quality meta-analysis reported cardiovascular benefits. One researcher found that flavan-3-ol foods such as tea, apples, cocoa, and grape-derived products slightly lower blood pressure and improve endothelial function. Other studies reported that consumption of whole grape products was associated with significant reductions in systolic blood pressure. The remaining systematic reviews and meta-analyses were of low or very low quality.
RCT evidence was generally based on small, short-term studies, and interventions focused primarily on polyphenols and resveratrol. Seventeen RCTs were of moderate or high quality, while three were of low quality. A more stringent methodological design was associated with more consistent lipid and vascular effects. Nine RCTs focused on grape pomace, whole grapes, red grape cell powder, or grape seed extract and generally reported favorable effects on cardiovascular risk markers.
Moderate and high quality RCTs reported improvements in lipid peroxidation, lipid profile, flow-mediated dilation, diastolic blood pressure, and paraoxonase activity. These lipid changes were often accompanied by reductions in markers of endothelial dysfunction and oxidative stress, especially in populations with metabolic risk and hypercholesterolemia. For example, a low-quality RCT found that consuming 500 g of whole red grapes daily for 8 weeks was associated with reductions in total and LDL cholesterol in adults with hypercholesterolemia.
RCTs of resveratrol and blueberries reported primarily endothelial and vascular benefits, including improved nitric oxide production, flow-mediated dilation, and reductions in blood pressure and inflammatory markers, but limited effects on lipid endpoints. A high-quality RCT of 115 elderly men with metabolic syndrome showed that after six months of daily blueberry consumption, arterial stiffness and endothelial function were significantly improved. The observed changes gave the researchers an effect size that they thought would predict a likely reduction in CVD risk of 12% to 15%. However, no cardiovascular events were measured in this trial.
This review also discusses the compositional analysis of newly developed red-fleshed table grape hybrids, which generally contain more phenolic compounds and anthocyanins than their standard comparison grapes. Nevertheless, there were no human RCTs that tested newly developed red-fleshed table grape varieties, and their potential benefits were inferred from compositional data and evidence involving other grapes, fruits, and bioactive compounds. Comparisons between grape varieties should be interpreted with caution due to differences in analytical methods, extraction protocols, reporting units, and seasonal conditions.
conclusion
Taken together, current evidence suggests that polyphenols from berries and grapes may produce modest, moderately consistent improvements in cardiovascular risk markers, particularly endothelial function. However, this review did not establish whether these changes protect against heart attack, stroke, or cardiovascular death. Increasing awareness of the potential effects of consuming dark-fleshed grapes and blueberries may help inform complementary strategies to promote cardiovascular health.
Many interventions included concentrated extracts, powders, supplements, or red wine rather than whole fresh fruit, limiting direct translation into a habitual diet. Alcohol content and concomitant drug use may also influence some findings. The authors also acknowledged that AMSTAR-2 and Jadad are evaluation guides rather than definitive measures of research quality. Nevertheless, large-scale and long-term RCTs using whole fresh grapes and blueberries at habitual dietary intake are needed, and clinically meaningful cardiovascular endpoints should be prioritized over the use of short-term surrogate markers.
Funding and conflicts of interest
The first author disclosed that Bloom Fresh International Limited provided funding for the time spent conducting the research and drafting the manuscript. The company grows and sells the red-fleshed table grapes we discussed in our review. This disclosure appears to contradict another statement in the paper that the research received no external funding.
Reference magazines:
- Derbyshire, GA, Abellan Aleman, JA, Aslam, NC (2026). Polyphenols and cardiovascular health: Emerging associations with blueberries, grapes, and red table grapes. Nutrients, 18(12), 1968. Doi: 10.3390/nu18121968, https://www.mdpi.com/2072-6643/18/12/1968
