An inverse relationship between dietary vitamin E and kidney cancer and bladder cancer is seen in observational studies. The risk reduction was 19% when highest and lowest intake groups were compared. The authors concluded that randomized controlled trials (RCTs) are needed. A large study comparing placebo to an all rac-alpha-tocopherol group consuming 400 IU/day reported no difference in bladder cancer cases. An inverse relationship between dietary vitamin E and lung cancer was reported in observational studies. The relative risk reduction was 16% when highest and lowest intake groups were compared. The benefit was progressive as dietary intake increased from 2 mg/day to 16 mg/day. The authors noted that the findings need to be confirmed by prospective studies. One such large trial, which compared 50 mg alpha-tocopherol to placebo in male tobacco smokers, reported no impact on lung cancer. A trial, which tracked people who chose to consume a vitamin E dietary supplement, reported an increased risk of lung cancer for those consuming more than 215 mg/day.