There has been much publicity about our "low" vitamin D levels and how important it is to test and supplement it. However there is little or no actual evidence that low vitamin D levels are dangerous. In fact, the US Public Health Task Force; whose job is to review the literature, recently (in November) stated:
The USPSTF concludes that the current evidence is insufficient to assess the balance of benefits and harms of screening for vitamin D deficiency in asymptomatic adults.
http://www.uspreventiveservicestaskforce.org/Page/Document/UpdateSummaryFinal/vitamin-d-deficiency-screening
A recent study in JAMA (JAMA Intern Med. Published online January 04, 2016 doi:10.1001/jamainternmed.2015.7148) examined supplementation of low vitamin D levels in older adults (over 70). They were hoping to find that these would have a lower risk of falls and fractures. However, they found that the group supplemented had 2-3 times the number of falls!
Low Vitamin D has been defined as below 20; and very low below 7-10. In children with growing bones, extremely low Vitamin D can lead to rickets; this is still extremely rare. But there is little evidence that slightly low levels are dangerous in adults/
A small supplement of Vitamin D is probably safe; recommendations of up to 1-2 thousand s units per day are reasonable and unlikely to be dangerous. Like many other things, moderation is the safer way to go!
