Although concerns have been expressed about consumption of iron, existing research and dietary knowledge indicate that tea is not likely to cause health risk, in individuals consuming a typically Western diet.
Dietary iron exists in two forms, heme iron (derived from animal) and non-heme iron (found in plants). The body better absorbs heme iron than non-heme iron. Between 15-35 % of heme iron is absorbed, while 2-20% is absorbed of non-heme iron. Non-heme iron is generally modified by other dietary components.
Certain components in grain, fruit and vegetables as well as polyphenols in tea reduce the availability of iron to the body. However, studies have shown that tea only decreases iron absorption when it is consumed simultaneously with food containing non-heme iron. Tea drinking between meals has no effect on iron absorption.
Moreover the ability of tea polyphenols to decrease iron absorption is reduced by the presence of other dietary constituents particular ascorbic acid (known to increase absorption of non-heme iron) and milk.