Ronald L. Prior and co-workers in the USA calim that inclusion of cranberry in the diet is effective in modulating some aspects of the metabolic parameters associated with metabolic syndrome. However, a high dose of cranberries does not neccessarily result in a metabolic response.
Metabolic syndrome refers to the clustering of cardiometabolic risk factors, although it was believed initially to be associated with increased risk of cardiovascular disease; metabolic syndrome has a stronger association with type 2 diabetes. A characteristic of type 2 diabetes and metabolic syndrome is insulin resistance, a condition where insulin becomes less effective at reducing glucose levels in the body. 
Recently, cinnamon has been shown to reduce plasma glucose levels in diabetic patients and a class of phenolic phytochemicals called A-type procyanidins are responsible for this. A-type procyanidins are only found in a limited number of foods and other than cinnamon, cranberry has the highest concentration.
The team from the U.S. Department of Agriculture and the University of Arkansas set out to determine if phytochemicals in cranberry were effective in normalising selected metabolic parameters associated with metabolic syndrome in high fructose (HF) fed rats. Rats were fed on low, medium or high levels of cranberry powder (CP). Fasting plasma glucose and triglycerides were higher in HF fed rats than control rats and were reduced by feeding CP; similarly, oral glucose tolerance test responses were improved and similar to control animals when fed low or medium levels of CP. Insulin resistance and β-cell function were reduced by CP with medium levels being most effective, furthermore, kidney weight was higher in the HF fed group but feeding with CP decreased kidney weight to normal levels. More importantly, Prior et al. highlights the importance of dose-response studies and that more is not always better.
Interested in knowing more? Read the full article here:
Effects of dietary consumption of cranberry powder on metabolic parameters in growing rats fed high fructose diets
Ramesh C. Khanal, Theodore J. Rogers, Samuel E. Wilkes, Luke R. Howard and Ronald L. Prior
Food & Funct., 2010, Advance Article
DOI: 10.1039/C0FO00089B , Paper
