Too much vitamin A may increase risk of bone fractures

October 8, 2018, Society for Endocrinology
Retinol or Vitamin A 3D space model (balls model). Credit: YassineMrabet, Wikipedia.

Consuming too much vitamin A may decrease bone thickness, leading to weak and fracture prone bones, according to a study published in the Journal of Endocrinology. The study, undertaken in 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.

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. Some evidence has suggested that people who take vitamin A supplements may be increasing their risk of bone damage. Previous studies in mice have shown that short-term overdosing of vitamin A, at the equivalent of 13-142 times the recommended daily allowance in people, results in decreased bone thickness and an increased fracture risk after just 1-2 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, Dr. Ulf Lerner and colleagues from Sahlgrenska Academy at the University of Gothenburg, report that mice given lower doses of vitamin A, equivalent to 4.5-13 times the RDA in humans, over a longer time period, also showed thinning of their bones after just 8 days, which progressed over the ten week study period.

Dr. Ulf Lerner commented, "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. 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."

Next, Dr. Ulf Lerner 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.

Dr. Ulf Lerner cautions: "Overconsumption of vitamin A may be an increasing problem as many more people now take . Overdose of vitamin A could be increasing the risk of 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 A."

Explore further: Vitamin D supplements won't build bone health in older adults

More information: The study "Clinically relevant doses of vitamin A decrease cortical bone mass in mice" will be published in the Journal of Endocrinology on Tuesday 09 October 2018.

Related Stories

Vitamin D supplements won't build bone health in older adults

October 5, 2018
(HealthDay)—Vitamin D supplements have long been touted as a way to improve bone health and possibly ward off the bone-thinning disease osteoporosis in older adults.

Prenatal vitamin D pills won't boost babies' growth: study

August 9, 2018
(HealthDay)—For pregnant women who are vitamin D-deficient, vitamin supplements won't improve the growth of their fetus or infant, Canadian researchers report.

No need for high-dose vitamin D in infants: study

May 29, 2018
Tripling the dose of vitamin D supplementation for babies does not make their bones any stronger by age two, according to a study in Finland published Tuesday.

Higher doses of vitamin D may boost preemies' bone health

October 19, 2017
(HealthDay)—Higher doses of vitamin D can improve the bone health of premature babies, new research suggests.

Calcium, vitamin D don't seem to reduce fracture risk in seniors

December 27, 2017
(HealthDay)—For community-dwelling older adults, supplementation with calcium, vitamin D, or both does not reduce the incidence of fractures, according to a review published in the Dec. 26 issue of the Journal of the American ...

Duration of lactation associated with bone density

November 5, 2015
Maternal bone density decreases after childbirth, but only among women who lactate for at least four months. The lactation period is unrelated to vitamin D status. A PhD thesis at Sahlgrenska Academy has explored the issue.

Recommended for you

Juul e-cigarettes pose addiction risk for young users, study finds

October 19, 2018
Teens and young adults who use Juul brand e-cigarettes are failing to recognize the product's addictive potential, despite using it more often than their peers who smoke conventional cigarettes, according to a new study by ...

Self-lubricating latex could boost condom use: study

October 17, 2018
A perpetually unctuous, self-lubricating latex developed by a team of scientists in Boston could boost the use of condoms, they reported Wednesday in the journal Royal Society Open Science.

Engineered enzyme eliminates nicotine addiction in preclinical tests

October 17, 2018
Scientists at Scripps Research have successfully tested a potential new smoking-cessation treatment in rodents.

Nutrition has a greater impact on bone strength than exercise

October 17, 2018
One question that scientists and fitness experts alike would love to answer is whether exercise or nutrition has a bigger positive impact on bone strength.

How healthy will we be in 2040?

October 17, 2018
A new scientific study of forecasts and alternative scenarios for life expectancy and major causes of death in 2040 shows all countries are likely to experience at least a slight increase in lifespans. In contrast, one scenario ...

Study finds evidence of intergenerational transmission of trauma among ex-POWs from the Civil War

October 16, 2018
A trio of researchers affiliated with the National Bureau of Economic Research has found evidence that suggests men who were traumatized while POWs during the U.S. Civil War transmitted that trauma to their offspring—many ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

FredJose
not rated yet Oct 17, 2018
The study would be much more palatable if they showed how it translates to human consumption of carrots.
How many carrots would one need to consume to have an intake of 4.5 to 13 times the RDA?
One website give the following quote:
when we are in pristine health, it requires at least six units of carotenes to convert into 1 unit of retinol (source). To put this in perspective, that means one must eat 4 1/2 pounds of carrots to potentially get the amount of useable A as in 3 oz. of beef liver (source).


One carrot contains roughly 20000Re.

So if one's digestive system is fairly OK, it's safe to eat lots of carrots without worrying about an overdose.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.