The issue focused on low dose vitamin D deficiency (such as based on studies where participants get 50 IU per day for 8 weeks). Dr. Neil Stanley recently explained his thoughts on low dose vitamin D deficiency and low vitamin D serum levels in his blog post "Low vitamin D serum levels are normal – now just keep taking vitamin D!" This article provides some background information for why low vitamin D serum levels are normal and why taking vitamin D supplements may help lower vitamin D serum levels. It also mentions some studies where vitamin D