Some of your readers do not seem to be current with the best information about the effects of vitamin D deficiency on human health. For example, one poster thinks that a 30 ng/ml of blood serum level of vitamin D is sufficient. It isn't. The Vitamin D Council website and all of the research shows that everyone, whether living in the tropics or at higher latitudes, should be between 50 and 80 ng/ml. On my website, leonardogreenfield.com is a research article on Vitamin D and Your Health - it is written in plain English so that the knowledge will be accessible to the general public. Please visit my free website - my photo is there as well.