By Michelle Roberts
BBC News health reporter
Falls and fractures could be a thing of the past if everyone aged 65 and older were to take extra vitamin D, experts believe.
Hip fractures related to falls cost the NHS about £1.7 billion each year
It would be a quick and easy way to cut morbidity and save NHS money, they say.
Mounting evidence suggests the vitamin not only makes bones stronger, but also has a positive affect on the muscles.
Studies have shown elderly people who take vitamin D supplements are more stable on their legs and less likely to fall and hurt themselves.
But other studies have had disappointing results.
Falls are a major cause of disability and the leading cause of death due to injury in people aged 75 and older in the UK.
Hip fractures related to falls cost the NHS about £1.7bn in England alone and kill up to 14,000 people with osteoporosis in the UK each year.
Dr Heike Bischoff-Ferrari from Harvard University looked at the available trial data on vitamin D and falls spanning more than 30 years and involving more than 10,000 people.
From this, she estimates that taking daily vitamin D supplements would reduce an elderly person's risk of falling by at least a fifth.
"If you realise that 30% of all people 65 years of age report at least one fall per year, that's a lot of falls.
"If you are 80, that rises to 50%. And if you are in a nursing home the rate is even higher," she said.
"We know that 90% of all [hip] fractures are caused by a fall and of course falling itself causes other injuries and problems."
She said many elderly people who have fallen are afraid that they will fall again and can become housebound, for example.
"Many experts in the field are recommending that people older than 65 should take 800 units (20 micrograms) of vitamin D per day as a life insurance against falls and fractures," she said.
The Food Standards Agency has recently reviewed the use of vitamins and minerals.
Its expert group concluded that most active people with a healthy diet should not need to take extra vitamin D.
But they said older people should consider taking extra vitamin D, 10 micrograms per day (or 400 units), if:
- They rarely get outdoors or are housebound
- They always cover up all of their skin when outside
- They don't eat meat or oily fish
The National Institute for Clinical Excellence says although there is evidence that vitamin D supplementation might reduce the risk of falls among elderly people, it is not certain whether this would reduce the number of fractures seen each year.
Also, it says the best dose and route of administration is not known.
Trevor Reid of the National Osteoporosis Society said: "There is good evidence that a daily calcium and vitamin D supplement may be of use for osteoporosis for older sufferers over the age of 75.
"There is research going on into yearly vitamin D injections which may also be beneficial."
The Arthritis Research Campaign is funding a trial to find out if taking Vitamin D can stop or slow knee osteoarthritis and reduce pain.
A spokeswoman said: "People over the age of 60 find might it helpful to take a supplement containing 10-20 micrograms of Vitamin D a day to guard against developing osteoporosis.
"A diet which does not include enough calcium or Vitamin D can make osteoporosis more likely.
"Vitamin D, which is needed for the body to absorb calcium, is produced by the body when sunlight falls on the skin, and can be obtained from the diet (especially from oily fish) or vitamin supplements."
Dr Frazer Anderson and colleagues at Southampton University estimated that daily calcium (1g) and vitamin D (20 micrograms), either alone or in combination, would mean one fewer person each year per 100 would sustain a fracture.
However, their Medical Research Council-funded research, involving 4,200 people aged 70 and older who had already had at least one fracture linked to osteoporosis, has had disappointing results.
He did not think this should include everyone aged 65 and older. "That would be very expensive," he said.
Instead, he recommended it be given to older people who are housebound, those in nursing homes who are still mobile and everybody in residential care.
"These tend to be the groups with the most to gain because they may not get enough vitamin D from their diet or sunlight."
He said it was absolutely clear that vitamin D has a beneficial effect on bones and muscle function.