The influence of jamaican herb teas and other polyphenol-containing beverages on iron absorption in the rat

Abstract

The content of total polyphenols in a series of Jamaican herb tea infusions ranged from 1.9–39.6 mg/100 ml and was lower than in infusions of black tea, green tea, coffee and cocoa (79.7–136.2 mg/100ml). The polyphenols of black tea and cocoa included a substantial quantity of tannins. All infusions contained substances which bound iron and either enhanced or prevented its passage through a 6000–8000 molecular weight cut-off dialysis membrane. When added to a cereal-milk meal however only black tea, green tea and cocoa reduced dialysable iron whereas the herb teas and coffee had no effect. When administered to rats at an identical polyphenol concentration either alone (4 mg/ml) or with a cereal meal (4 mg/g), absorption of 59-Fe was reduced by 0–45%. Assam tea and the herb teas, pepper elder and basil, were the most inhibitory, followed by coffee and cocoa. One herb tea, sour sop, had no effect. Some, but not all, reference polyphenols tested also reduced iron absorption in the rat. It was concluded that cocoa and some herb teas of high polyphenol content might, like black tea and coffee, also reduce iron absorption in man if consumed with a meal.