Comparison of the Bioavailability of Polyphenols From Milk and Dark Chocolate

Dark chocolate is one of the richest sources of polyphenols, for example, a standard 40g portion of dark chocolate contains 400-800 mg of polyphenols, compared to red wine (170 mg /100ml) or an apple (200 mg/piece). Cocoa polyphenols, most notably the catechins, can exist in both lipid and water-based environments (amphipathic), meaning they can spare both lipophillic and hydrophilic vitamins. There have been a number of human trials conducted using chocolate or cocoa and measuring various endpoints. Most have been conducted with dark chocolate. An article in Nature found that the bioavailability of epicatechin from milk chocolate was substantially reduced compared to dark, and even dark taken with a glass of milk (Serafini et al 2003). The hypothesis was that the milk proteins bind to polyphenols, making them unavailable. Subsequent studies have not been able to reproduce this, but none have been conducted using solid chocolate as the first study, all have been done using a drink matrix, which may completely alter the binding interactions of the polyphenols and protein. Previous bioavailability trials with dark chocolate have shown a 12 fold increase in plasma epicatechin 2 hours after consumption of 80g of chocolate containing 557 mg total polyphenols (137 mg epicatechin) (Rein et al 2000) with a concurrent increase in plasma total antioxidant capacity and a decrease in TBARS. Another study showed an increase in epicatechin 2 hours after administering 25g of chocolate chips containing 220 mg flavanols and procyanidins, with a concurrent increase in prostacyclin/leukotriene ratio and reduction in platelet-related hemostasis (Holt et al 2002).

This study is designed as a blinded, three arm crossover trial. The primary outcome measure is to compare plasma polyphenol levels after consumption of 3 chocolates (2 milk, 1 dark) while the secondary outcome measures are to characterise the time course of polyphenols in the blood and to investigate individual variation in Tmax and Cmax for use in future studies. All volunteers will try all chocolate types with a similar taste & appearance (though milk and dark are likely to still be distinguishable for the volunteer, not the investigator). Subjects will undergo medical screening, anthropometry, physical activity and dietary assessments before randomisation for the order of consumption. Bloods are to be taken as a time course for the next 24 hours, as is urine.