WASHINGTON, Oct. 9 (Xinhua) -- Research carried out on mice revealed that consuming too much vitamin A may decrease bone thickness.
The study published in the latest Journal of Endocrinology found that a sustained intake of vitamin A, at levels equivalent to 4.5 to 13 times the human recommended daily allowance (RDA), caused significant weakening of the bones.
The findings suggest that people should be cautious in their diets of over-supplementing vitamin A, 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.
Previous studies in mice have shown that short-term overdosing of vitamin A, at the equivalent of 13 to 142 times the recommended daily allowance in people, results in decreased bone thickness and an increased fracture risk after just one to two weeks.
This study 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.
In this study, Ulf Lerner and colleagues at the University of Gothenburg, reported that mice given lower doses of vitamin A, equivalent to 4.5 to 13 times the RDA in humans, over a longer time period, showed thinning of their bones after just 8 days, which progressed over the ten week study period.
A balanced diet is perfectly sufficient to maintain the body's nutritional needs for vitamin A, according to the authors.