Efficacy of Bilberry and Grape Seed Extract Supplement Interventions to Improve Glucose and Cholesterol Metabolism and Blood Pressure in Different Populations—A Systematic Review of the Literature

• Published in: Nutrients Vol. 13; no. 5; p. 1692
• Main Authors: Grohmann, Teresa, Litts, Caroline, Horgan, Graham, Zhang, Xuguang, Hoggard, Nigel, Russell, Wendy, de Roos, Baukje
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 17.05.2021; MDPI
• Subjects: Adult; Age; Aged; Bias; bilberries; black currants; Blood Glucose - drug effects; Blood pressure; Blood Pressure - drug effects; Cholesterol; Cholesterol - blood; cholesterol metabolism; Cholesterol, LDL - blood; Dextrose; Diabetes; diastolic blood pressure; Dietary Supplements; Female; Flavonoids; Fruits; Glucose; Glucose metabolism; Glycated Hemoglobin - drug effects; glycohemoglobin; Glycosylated hemoglobin; grape seed extract; Grape Seed Extract - pharmacology; grape seeds; Health aspects; health status; Humans; Hypercholesterolemia; Hypertension; Intervention; Linolenic Acids - pharmacology; Low density lipoprotein; low density lipoprotein cholesterol; Low density lipoproteins; Male; Metabolic syndrome; Metabolites; Microbiota; Middle Aged; nationalities and ethnic groups; noninsulin-dependent diabetes mellitus; Physiological aspects; Plant Extracts - pharmacology; Plant Oils - pharmacology; Population; Review; Systematic review; Trans fatty acids; Type 2 diabetes; Vaccinium myrtillus; United Kingdom; China; bilberry; blood pressure; glucose; grape seed; human intervention studies; cholesterol; extracts
• ISSN: 2072-6643; 2072-6643
• DOI: 10.3390/nu13051692

Intervention with fruit extracts may lower glucose and lipid levels, as well as blood pressure. We reviewed the efficacy of bilberry and grape seed extracts to affect these outcomes across populations with varying health status, age and ethnicity, across intervention doses and durations, in 24 intervention studies with bilberry and blackcurrant (n = 4) and grape seed extract (n = 20). Bilberry and blackcurrant extract lowered average levels of glycated hemoglobin (HbA1c), at least in Chinese subjects, especially in those who were older, who were diagnosed with Type 2 Diabetes Mellitus (T2DM) and who were participating in longer-term studies. We also found good evidence that across studies and in subjects with hypercholesterolemia, T2DM or metabolic syndrome, intervention with bilberry and blackcurrant extract, and to some extent grape seed extract, significantly lowered total and low density lipoprotein (LDL) cholesterol levels after four weeks. Intervention with grape seed extract may reduce systolic and diastolic blood pressure in subjects with hypertension or metabolic syndrome. Differential responsiveness in cholesterol and blood pressure outcomes between stratified populations could not be explained by age, dose or study duration. In conclusion, bilberry and blackcurrant extract appears effective in lowering HbA1c and total and LDL cholesterol, whereas grape seed extract may lower total and LDL cholesterol, and blood pressure, in specific population groups.