Vitamin A may increase risk of bone fractures say researchers

Vitamin A is an essential vitamin that is important for numerous biological processes including growth, vision, immunity and organ function.  Our bodies are unable to make vitamin A but a healthy diet including meat, dairy products and vegetables should be sufficient to maintain the body’s nutritional needs.

A study on mice found that sustained intake of vitamin A, at levels equivalent to 4.5-13 times the human recommended daily allowance (RDA), caused significant weakening of the bones, and suggests that people should be cautious of over-supplementing vitamin A in their diets.

The study by Australian and Swedish researchers, published in the Journal of Endocrinology, is the first to examine the effects of lower vitamin A doses that are more equivalent to those consumed by people taking supplements, over longer time-periods.

Dr Ulf Lerner and colleagues from Sahlgrenska Academy at the University of Gothenburg, reported that the subject mice showed thinning of their bones after just eight days, which progressed over the ten week study period.

Dr Lerner next intends to investigate if human-relevant doses of vitamin A affect bone growth induced by exercise, which was not addressed in this study.

Additionally, his team will study the effects of vitamin A supplementation in older mice, where growth of the skeleton has ceased, as is seen in the elderly.

“Overconsumption of vitamin A may be an increasing problem as many more people now take vitamin supplements, said Dr Lerner. “Overdose of vitamin A could be increasing the risk of bone weakening disorders in humans but more studies are needed to investigate this. In the majority of cases, a balanced diet is perfectly sufficient to maintain the body’s nutritional needs for vitamin A.”