Doubts about lutein

I found it amusing that in the same issue in which one of CMAJ's editors educated Steve Arshinoff about the journal's new conflict of interest policy,1^,2 there is a rambling opinion piece by Sylvia Santosa and Peter Jones on the possible benefits of lutein in the eye.3 I know the journal's policy had not taken effect at the time of submission, but I feel I must respond to the article.

To date, there has been no convincing research to show lutein supplementation to be of any real use in age-related macular degeneration. The evidence that lutein can slow the progression of cataracts is spotty at best, as demonstrated by the articles that are cited in this piece. The first reference is a review article,5 albeit of the data mined from the Beaver Dam Eye Study. Although the scope and size of the Beaver Dam Eye Study are laudable, it was not really a prospective study from which causality could be established. The nutritional information in the study was gathered using questionnaires, which are always subject to recall and compliance biases. The Beaver Dam Eye Study also suffered from „multiple looks”: relationships were investigated for any and all possible population factors. The bottom line is that even though a role for lutein in treating age-related macular degeneration and cataracts was suggested in these two references, the studies don't demonstrate a cause-and-effect relationship. Plausibility is an important criterion for causality but it is not a sufficient one.