Vitamin D and calcium supplements do not help reduce the risk of osteoporosis and could result in harm, a new study has found.
Two Auckland clinical researchers said there was no scientific evidence to support the use of the two supplements to reduce fracture risk.
They both called on advocacy organisations and academics to abandon industry ties that promote its use.
In the paper, published in the British Medical Journal, associate professors Andrew Grey and Mark Bolland, showed that by the end of 2010, 32 of 38 clinical trials of calcium and vitamin D had reported no health benefit.
Dr Grey said the supplements could instead cause harm, including heart attacks, hospitalisation for abdominal pain, constipation and kidney stones.
"When you weigh up the small benefit in some trials against the harm, there's no net benefit to patients," he said.
Despite this, Dr Grey said some organisation's practising guidelines continued to recommend the use of these supplements for osteoporosis.
"It didn't take too much searching to find that those organisations are quite heavily sponsored by a number of commercial entities who have a vested interest in the sale of dairy foods, calcium supplements and vitamin D supplements."
Dr Grey said the supplement industry is worth billions of dollars, with global annual sales of calcium worth about $6 billion and vitamin D about $1 billion in US alone.
He called for commercial ties to medical societies and advocacy organisations be examined and severed.
But Dr Grey said the prescription of calcium supplements had already dropped in New Zealand by two-thirds in the last three to four years. Although vitamin D was still recommended.
Osteoporosis is when bones become weak and are more likely to break. It is most common in people aged 50 years and over, but young people can suffer from it as well.
According the Ministry of Health website, ways to help reduce the risk of osteoporosis include a healthy body weight and not smoking.