New insights into the distinct roles of flavanols and procyanidins in the human body have been provided by collaborative research by Mars, Incorporated and the University of California, Davis.
Recently published online in the American Journal of Clinical Nutrition, the findings significantly advance understanding of how these phytonutrients may work in the body to exert cardiovascular benefits. In ways not previously possible, the researchers were able to gain novel insights that further our understanding of the metabolic fate of procyanidins, and highlight the need for more careful discrimination between flavanols and procyanidins when examining the health benefits of foods. Taken together, these findings may enable stronger and clearer associations between health and the intake of specific food components, and a more comprehensive understanding of the cardiovascular health benefits of flavanols and procyanidins.
Flavanols and procyanidins are sub-classes of a group of natural compounds called flavonoids. A growing body of evidence demonstrates that foods rich in flavanols and procyanidins, such as cocoa, can have a positive impact on blood vessel function and cardiovascular health. To understand how the flavanols and procyanidins present in certain foods may exert their cardiovascular effects, it is crucial to assess what happens to these compounds in the body following consumption. Previous studies have demonstrated that flavanols are absorbed, enter the body, and directly mediate improvements in cardiovascular function. In contrast, procyanidins have been shown to be poorly absorbed or not at all and evidence for a direct effect of procyanidins on blood vessel function is therefore limited. Nevertheless, as flavanols are the structural building blocks of procyanidins, it has been proposed that digestive processes in the gut may cause the break-down of procyanidins into flavanols, which may subsequently be absorbed into the body. If correct, this "break-down hypothesis" would mean that procyanidins exert cardiovascular benefits by acting as precursors of flavanols. Answering this question is therefore crucial for a comprehensive understanding of the role of these phytonutrients for human health and nutrition.
As flavanols and procyanidins are commonly found together in foods, such as cocoa, grapes, and apples, up until now it has not been possible to directly assess the individual contribution of procyanidins to the circulating pool of flavanols in the body. Using carefully developed, nutrient-matched cocoa-based drinks, containing flavanols and procyanidins either in combination or individually, the researchers in this study were able to confirm that procyanidins are poorly absorbed. More importantly, the study also demonstrated for the first time that procyanidins do not break-down in the gut to contribute to the flavanols present in circulation. This outcome makes it very unlikely that procyanidins affect blood vessel function, either directly or through a break-down into flavanols. Interestingly, the research also demonstrates that micro-organisms in the digestive system transform both flavanols and procyanidins into another group of compounds called gamma-valerolactones. Further research is needed to investigate if, and to what extent, these compounds formed in the gut contribute to the cardiovascular health benefits observed following the consumption of foods rich in flavanols and procyanidins. In addition, the data of this study do not rule out the possibility that procyanidins may exert biological activities in the digestive system that may be beneficial for human health.
Dr. Schroeter further commented on the implications of these findings, "The differences between the absorption and metabolism of flavanols and procyanidins, as demonstrated by this research, may prompt changes in how scientists design and interpret epidemiological investigations and in vitro studies to more meaningfully reflect what happens in the body. Furthermore, the fact that our results mean that it is unlikely that procyanidins exert direct effects on blood vessel function, may lead researchers to focus specifically on studying the mechanisms by which flavanols - and perhaps even gamma-valerolactones - affect cardiovascular function."
The research has been published in the American Journal of Clinical Nutrition and is available online here: http://www.ajcn.org/content/early/2012/02/28/ajcn.111.028340.abstract. It was part-funded by the European Commission under the FLAVIOLA project and forms part of a wider body of work examining the health benefits of diets rich in flavanols and procyanidins.