Too much vitamin D as unhealthy as too little?

A large study by Danish researchers has concluded that too much vitamin D may be as unhealthy as too little.

The study, based on blood samples from 247,574 Copenhageners,  is published in Journal of Clinical Endocrinology and Metabolism.

As well as being vital to bone health, a huge body of research now shows that vitamin D is also beneficial in combating heart disease, depression and certain types of cancers – benefits confirmed by the University of Copenhagen study. But the research results also show higher mortality in people with “too high” levels of vitamin D in their bloodstream.

Lead researcher, Darshana Durup, said: “We found higher mortality in people with a low level of vitamin D in their blood, but to our surprise, we also found it in people with a high level of vitamin D. We can draw a graph showing that perhaps it is harmful with too little and too much vitamin D.”

The Danish study, the largest of its kind, showed that where blood contains less than 10 nanomol (nmol) of vitamin D per litre of serum, mortality is 2.31 times higher. But if the blood contains more than 140 nmol of vitamin per liter of serum, mortality is higher by a factor of 1.42. Both values are compared to 50 nmol of vitamin per liter of serum, where the scientists see the lowest mortality.