Polyphenols and Cardiovascular Diseases: Is there a Role for ther Antioxidant Porperties?

The potential health effects of antioxidants have attracted much interest and enthusiasm of consumers and food industry. Recently, we performed a Google search with the search term “antioxidant foods” and found more than 12 million hits! Among others, the internet gives lists of the “top 10 of antioxidant foods”, and heavily advertises “super antioxidant foods” etc. In this context, the large family of polyphenols, antioxidants ubiquitous in plant foods, has been studied extensively. Many authors have linked the antioxidant activity of polyphenols to the beneficial effects of vegetables and fruit. A still growing number of epidemiological studies showed that the intake of polyphenol-rich foods (tea, red wine, cacao, onions, and apples) was inversely associated with CVD [1]. These associations have also been demonstrated for individual polyphenols (mainly flavonols and flavan-3-ols) [2–4]. In addition, well conducted clinical trials with polyphenol-rich foods showed beneficial effects on intermediate markers of CVD [5, 6]. These studies might suggest that a relation exists between the antioxidant activity of polyphenols and their health effects. However, what’s the evidence for such a relation? The Total Antioxidant Capacity (TAC) of foods and plasma or serum has been commonly measured. These methods try to measure the total amount of antioxidants in these samples. Furthermore, products of lipid peroxidation, e.g. F2 isoprostanen, hydroperoxides and oxidised LDL have been frequently measured [7]. However, a causal relation between these biomarkers of antioxidant activity and CVD has not been established. Thus the physiological relevance of a potential change in this biomarkers is unclear [7]. So, there seems to be no beneficial direct antioxidant effect of polyphenols. The reasons for this lack of effect will be discussed. References: 1 Arts IC, Hollman PC: Polyphenols and disease risk in epidemiologic studies. Am J Clin Nutr 2005;81:317S–325S. 2 Hertog MGL, Feskens EJ M, Hollman PCH, Katan MB, Kromhout D: Dietary antioxidant flavonoids and risk of coronary heart disease: the Zutphen Elderly Study. Lancet 1993;342:1007–1011. 3 Arts IC, Hollman PC, Feskens EJ, Bueno de Mesquita HB, Kromhout D: Catechin intake might explain the inverse relation between tea consumption and ischemic heart disease: the Zutphen Elderly Study. Am J Clin Nutr 2001;74:227–232. 4 Hollman PC, Geelen A, Kromhout D: Dietary Flavonol Intake May Lower Stroke Risk in Men and Women. J Nutr 2010;140:600–604. 5 Hooper L, Kay C, Abdelhamid A, Kroon PA, Cohn JS, Rimm EB, Cassidy A: Effects of chocolate, cocoa, and flavan-3-ols on cardiovascular health: a systematic review and meta-analysis of randomized trials. Am J Clin Nutr 2012;95:740–751. 6 Ried K, Sullivan TR, Fakler P, Frank OR, Stocks NP: Effect of cocoa on blood pressure. Cochrane DB Syst Rev 2012:1–81.