– EN Fitness & Wellbeing – Consuming too much vitamin A may increase the risk of bone fractures, researchers report. 
Vitamin A, also known as retinol, helps the body’s immune system work properly, benefits vision and aids skin, with good food sources including cheese, eggs, oily fish, milk and yoghurt.
However, academics at the University of Gothenburg in Sweden have now undertaken a study in mice and 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.
“Previous studies in rodents have shown that vitamin A decreases bone thickness but these studies were performed with very high doses of vitamin A, over a short period of time,” said Dr. Ulf Lerner. “In our study we have shown that much lower concentrations of vitamin A, a range more relevant for humans, still decreases rodent bone thickness and strength.”
In addition, previous investigations using mice have shown that short-term overdosing of vitamin A, at the equivalent of 13-142 times the RDA in people, results in decreased bone thickness and an increased fracture risk after just one to two weeks.
Going forward, Dr. Lerner want to conduct a study into whether human-relevant doses of vitamin A affect bone growth induced by exercise, and also analyse the effects of vitamin A supplementation in older mice.
“Overconsumption of vitamin A may be an increasing problem as many more people now take vitamin supplements,” he warned. “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.”
The U.K. National Health Service (NHS) currently recommends that adult men consume 0.7mg of vitamin A each day, while women need 0.6mg a day.
Full study results have been published in the Journal of Endocrinology.