Tea and caffeine has an adverse effect on iron absorption
It's worth bearing in mind that a typical cup of tea contains approximately half the caffeine of a typical cup of instant coffee. Preliminary research has shown that when the level of caffeine in tea and coffee is identical, alertness across the day may be more consistent in the tea drinkers. Scientists now believe that L-theanine in combination with caffeine may well be responsible for the positive effect of tea on alertness. No adverse effects of tea drinking on hydration or iron status have been found at normal levels of consumption.