Scientists from the Tehran University of Medical Sciences in Iran also report that a daily dose of anthocyanins of more than 300 mg for at least 12 weeks may lead to significant improvements in total and LDL cholesterol.
Writing in the journal Clinical Nutrition, the scientists noted that many other ‘cardio-metabolic’ measures were unaffected by anthocyanin intake.
“To the best of our knowledge, this study is the first meta-analysis that investigated the influence of anthocyanin on several cardio-metabolic factors in adults,” they wrote. “The results in the current study showed a beneficial effect of taking anthocyanin supplements on HOMA-IR in adults, however there were no significant effects of anthocyanin supplementation on anthropometric indices, lipid profile, blood pressure and [fasting blood sugar] and serum insulin.”
In addition to changes in the homeostasis model (HOMA-IR), which is a measure of insulin resistance, the scientists also reported a “marginally significant effect” on HbA1c (glycated hemoglobin), which is a marker of long-term presence of excess glucose in the blood.
The scientists arrived at their conclusions after pooling data from 19 randomized clinical trials (RCTs) that investigated anthocyanin supplementation in doses ranging from 31.45 mg to 1,050 mg per day.
While many of the variables measured showed no significant changes in response to anthocyanins, significant effects were observed for HOMA-IR in adults.
The scientists noted that they would have expected weight loss and by increasing insulin sensitivity with anthocyanin, but changes in weight and BMI were only observed in longer term studies (minimum supplementation period of 12 weeks).
An effect of duration and dose was also observed for cholesterol levels, with improvements recorded for supplementation at a dose exceeding 300 mg per day for more than 12 weeks.
The scientists noted that the average daily intake of anthocyanins in the US, which is usually from fruit, is a measly 12.5 mg, with intakes in Europe ranging from 20 to 65 mg per day for men and 18 to 44 mg per day for women.
“[This meta-analysis] demonstrates some interesting evidences, suggesting that anthocyanin supplementation might be effective on reducing some blood sugar factors such as HOMA-IR in adults,” wrote the researchers.
“Moreover, supplementation for more than 12 weeks had significant effects on weight and HDL-C.
“Due to variation in sample size and population of the included studies, further high-quality and well-designed RCTs are needed, particularly with a homogeneous population,” they concluded.
Source: Clinical Nutrition
Published online ahead of print, doi: 10.1016/j.clnu.2018.06.979
“Effect of anthocyanin supplementation on cardio-metabolic biomarkers: a systematic review and meta-analysis of randomized controlled trials”
Authors: Daneshzad E, et al.