Dietary reference intake (DRI) value for dietary polyphenols: are we heading in the right direction?

Abstract

Dietary Reference Intake (DRI) values exist for vitamins and minerals, and provide a guideline on the optimal dose range to avoid deficiency and prevent toxicity. Polyphenols are widely distributed in plant foods, and have been linked to improved human health through reduced risk of chronic diseases, especially cardiovascular. Although they do not cause classical deficiencies, recently they have been discussed as 'lifespan essentials because they are needed to achieve a full lifespan by reducing the risk of a range of chronic diseases. A recent meta analysis shows promising actions of polyphenols from cocoa, soya and tea on flow mediated dilation, blood pressure and LDL cholesterol. Many epidemiological studies support the action of polyphenols or polyphenol-rich foods on health, but there are still many gaps in our knowledge. More adequately powered, randomised, placebo controlled human studies are needed on polyphenols. There is a large number of structurally different polyphenols which are relevant for health, and obtaining enough information to set a DRI for each of these will not be feasible in the foreseeable future. A new approach is needed, and a new way of thinking, which would apply not only to polyphenols but also to other phytochemicals. Today, a target intake value of polyphenols as 'lifespan essentials' needs to be based on the amount of polyphenols in '5-a-day'. We are heading in the right direction towards a DRI, but bioavailability and dose-effects, including toxic levels, need to be established before DRIs can be considered.