Taking vitamin D supplements does not appear to reduce the risk of cancer, heart attack, stroke or bone fractures, scientists have said.

Vitamin D is essential for healthy bones, but is present in very few foods. It is also known as the sunshine vitamin because it is made in the body when the ultralviolet rays from sunlight strike the skin. However, Ireland's northerly latitude and lack of winter sunlight means that Irish people often cannot make enough of the vitamin in this way. As a result, some people choose to take supplements.

Previous research has shown that people who are deficient in vitamin D are more likely to experience poor health and premature death. However recent evidence suggests that this is not causal - in other words, the low vitamin D levels are likely a consequence, not a cause of poor health, and taking supplements is not likely to offer any benefit.

Scientists from New Zealand decided to investigate this further. They analysed 40 trials that looked at cause and effect and found that vitamin D supplements do not prevent cancer, heart attack, stroke or fractures of the bone by more than 15%.

In real terms, this means that taking these supplements offers little or no health benefit.

The scientists from the University of Auckland noted that there are several multi-million dollar trials currently underway to assess the health benefits of vitamin D supplements. However, they insisted that those findings are unlikely to show anything different.

Details of this study are published in the journal, The Lancet Diabetes & Endocrinology.