There is a 7-minute interview with Dr Robert Heaney at http://www.youtube.com/watch?v=IEYkjvUVFVw
giving information on the latest (February 2011) research on optimum vitamin D levels and dosage, which is very different from the current officially set levels.
Dr. Cannell of The Vitamin D Council says it is important to be taking certain co-factors along with vitamin D. More information at http://www.vitamindcouncil.org. The most important co-factor is magnesium and daily requirements for it vary a great deal according to the individual’s metabolism. At http://drcarolyndean.com/natural-health-resource/ there is a 1-hour audio recording (called “Magnesium and Our Health”) of Dr. Carolyn Dean talking with Dr. Lani Simpson about magnesium. A lot of it is about osteoporosis and bone health and it can be downloaded free of charge. Dr. Dean is a specialist in magnesium and she keeps her website updated with recommended magnesium supplement products.