The findings, published in the journal Nutrients, also associated intakes with a significant decrease in markers of insulin resistance, while dried forms of cranberry within supplements were found to notably decrease fasting insulin levels.
No associations were reported with TC, HDL-C, low-density lipoprotein cholesterol (LDL-C, triglyceride (TG), fasting blood glucose (FBG), glycated haemoglobin (HbA1c) and fasting insulin.
"This meta-analysis demonstrated that cranberry consumption improves blood TC and HDL-C ratio and HOMA-IR levels," the Chinese researchers wrote. “In summary, cranberry might have potential benefits in regulating lipid and glucose profiles."
Polyphenols and biomarkers of health
Cardiovascular disease (CVD) is a leading cause of mortality across the globe, placing a significant burden on society. It is known that individuals with CVD have changes in insulin sensitivity, glucose tolerance and lipid profiles.
Cranberries are known to be particularly rich in polyphenols, in addition to containing an array of vitamins, minerals and dietary fibres. Previous in vitro and animal studies have previously reported that cranberry polyphenols may benefit glucose and lipid metabolism.
In addition, there has been emerging human trials suggesting cranberry extracts may lower LDL-cholesterol and regulate fasting blood glucose. Yet, further studies have proved inconsistent and have failed to identify a positive effect.
Lipid and glucose regulation
The researchers conducted the literature search using the PubMed, Web of Science and Scopus databases to collate relevant articles using specific search terms and study criteria.
A total of 16 final studies were included in the review. It was observed that cranberry consumption was associated with a significant decrease in TC to HDL-C ratio and homeostasis model of assessment of insulin resistance (HOMA-IR). Yet, no association was found between intakes and TC, HDL-C, LDL-C, TG, FBG, HbA1c, and fasting insulin.
Following subgroup analysis, it was noted that cranberry intakes in dry delivery formats such as capsules, powders and tablets, resulted in significantly decreased fasting insulin levels.
"The possible mechanism involved was that cranberries were rich in polyphenols, especially anthocyanins, phenolic acids, and flavonoids,” the researchers wrote. "Anthocyanins were considered to have the potential ability to prevent hepatocellular lipid accumulation and lipogenesis by reducing sterol-regulated element binding protein 1c (Srebp1c), promoting lipolysis by activating peroxisomes proliferator-activated receptor (PPAR) in hepatocytes, and reducing oxidative stress.”
They suggested that anthocyanins can rapidly degrade glucagon-like peptide (GLP-1) and gastric inhibitory peptide (GIP), promote the function of insulin secretion of islet beta cells, and then improve HOMA-IR.
For further research, they called for investigations into the association due to the limited availability of evidence and the potential influence of between-study heterogeneity.
Source: Nutrients
“The Effects of Cranberry Consumption on Glycemic and Lipid Profiles in Humans: A Systematic Review and Meta-Analysis of Randomized Controlled Trials”
Authors: Xiangrui Li et al.