While the potential heart health benefits of flavonoid-rich diets have been reported previously, there was uncertainty about which constituents in flavonoid-rich foods may be behind the benefits, according to the British and Japanese researchers behind the new study.
Findings published in the Journal of Agricultural and Food Chemistry indicate that oligomeric procyanidins (OPC) had “by far the most potent effects” on the function of the endothelium (the cells lining blood vessels).
The research also builds the science and understanding surrounding the consumption of cranberry juice.
“Cranberry consumption is mostly studied in relation to the beneficial effects of A-type procyanidins on urinary tract health,” explained the researchers. “However, when the anti-atherosclerotic actions of OPC are also considered, the daily consumption of cranberry juice is likely to have multiple health benefits.”
The study’s results were welcomed by Bert Schwitters, President of INC, a supplier of oligomeric proanthocyanidins (OPCs). “The study of Richard Corder et al, although performed in vitro, confirms numerous clinical studies performed in the field of vascular health with the products developed by Dr. Jack Masquelier,” Schwitters told NutraIngredients.
Schwitters added that work with one of company’s products (Masquelier’s Original OPCs) was underway at the University of Maastricht to examine the effects of OPCs on endothelial biomarkers in humans.
“The Maastricht study, which was performed on apparently healthy subjects, may provide answers to the question whether dietary consumption of this well characterized OPCs product produces the positive effects observed by the Corder group,” said Schwitters.
Led by Professor Roger Corder at the Queen Mary University of London, the researchers tested the effects of flavonoids on endothelial function. The in vitro tests focussed on measuring of synthesis of the vasoconstrictors endothelin-1 (ET-1).
Extracts of cranberry and cranberry juice (Ocean Spray Cranberries) compared to apple, cocoa (Barry Callebaut), red wine, and green tea showed that OPC content determined the extent of inhibition of ET-1 synthesis, they said.
Procyanidin-rich extracts of cranberry juice were also found to produce changes in the morphology of endothelial cells that were independent of the compounds’ antioxidant activity.
Still work to do
“In agreement with previous studies on cultured endothelial cells or isolated vessels, compared to flavonoid monomers, OPC have by far the most potent effects on endothelial function,” wrote the researchers.
“Whether this is also true following dietary consumption of products containing OPC requires a more detailed examination of the relationship between bioavailability and functional effects,” they added.
Effective doses, actual intakes
Most studies have shown a benefit of OPCs with doses in the range of 100 to 300 milligrams a day, with the company recommending doses of 100 to 200 mg per day.
According to data from the US Department of Agriculture, a healthy diet should provide an adequate intake of OPCs, but studies have suggested that intake of an average diet is only about 25 mg per day.
Source: Journal of Agricultural and Food Chemistry
Published online ahead of print, doi:10.1021/jf9031876
"Regulation of Vascular Endothelial Function by Procyanidin-Rich Foods and Beverages"
Authors: P.W. Caton, M.R. Pothecary, D.M. Lees, N.Q. Khan, E.G. Wood, T. Shoji, T. Kanda, G. Rull, R. Corder