The widespread use of vitamin D supplements in healthy adults for the prevention of osteoporosis is not necessary, according to a new study by one of  the leading medical scientists in New Zealand.

The study, led by Professor Ian Reid from the University of Auckland’s Bone Research Group, found that taking vitamin D supplements does not improve bone mineral density in adults with a normal Vitamin D level.

Professor Reid and colleagues conducted a systematic review and meta-data analysis of the effects of vitamin D supplements on bone mineral density. Data from more than 4,000 healthy adults in 23 randomized trials was analyzed.

Researchers found that taking vitamin D supplements did not improve bone mineral density in the hip, spine, forearm or in the body as a whole.

“Most healthy adults do not need vitamin D supplements,” says Professor Reid. “Our data suggest that the targeting of low-dose vitamin D supplements only to individuals who are likely to be deficient could free up substantial resources that could be better used elsewhere in healthcare.”

“This systematic review provides very little evidence of an overall benefit of vitamin D supplementation on bone density. Continuing widespread use of vitamin D for osteoporosis prevention in community-dwelling adults without specific risk factors for vitamin D deficiency seems inappropriate.”

Analysis of data from the 23 studies did not identify any effects for people who took vitamin D for an average period of two years, apart from a small increase in bone density at the femoral neck that is unlikely to be clinically significant.

Those at risk of vitamin D deficiencies, such as children without access to conventional diet, might need vitamin D supplements to avoid conditions like rickets that affect the growing skeleton and cause bowed legs and knock knees.

“Most healthy adults, especially in New Zealand, who live a normal, active life and get out regularly for activities such as walking, shopping and gardening, get vitamin D from the sun, and do not need vitamin D supplements,” says Professor Reid.

“We do know that maintaining good blood vitamin D levels is important for promoting absorption of calcium from the diet. Very high levels of Vitamin D may have the opposite effect, and take calcium out of the bone and weaken the skeleton. There is a sweet spot in the middle, where not too much and not too little is a good level.”

The results of this study were published in the medical journal The Lancet.