That news comes from a research review published in the Archives of Internal Medicine.
The review shows that bone fractures not involving the spine were 20% less likely and hip fractures were 18% less likely among seniors taking more than 400 international units (IU) per day of vitamin D.
"I like what I see in this paper," says J. Edward Puzas, PhD, the Donald and Mary Clark Professor of Orthopaedics at the University of Rochester School of Medicine and Dentistry.
Puzas, who didn't work on the research review, says he isn't surprised to see that vitamin D supplements helped bones, even after age 65.
"Your bone health is important your entire life," Puzas says.
About Vitamin D
The body makes vitamin D when exposed to sufficient sunlight. But aging makes that process harder. People living in northern latitudes are also at a disadvantage when it comes to making vitamin D; so are people with dark skin.
Vitamin D helps the body absorb calcium, and bone cells have vitamin D receptors, Puzas says.
Those bone cells "do respond to vitamin D by stimulating their activity and generally increasing overall bone health," says Puzas, adding that "bone density is higher [and] fractures are lower in patients with adequate amounts of vitamin D."
According to current standards set by the Institute of Medicine (IOM), adequate daily intake of vitamin D is 200 IU per day for children up to age 13, 200 IU per day for men and women aged 14-50, 400 IU per day for men and women aged 51-70, and 600 IU per day for men and women aged 71 and older.
But many experts say those levels are too low.
In October 2008, the American Academy of Pediatrics doubled its recommended daily intake of vitamin D for children and teens to 400 IU per day. And the IOM has formed a committee to review adequate intake levels of vitamin D.
Vitamin D and Bone Fractures
The new research review is based on 12 trials of vitamin D, with or without calcium, to help prevent fractures of bones other than the spine (nonvertebral bones) and eight trials that focused only on hip fractures.
More than 42,000 patients took part in the nonvertebral bone fracture trials, and nearly 41,000 took part in the hip fracture trials.
The patients were at least 65 years old (average age: 78). They took vitamin D pills -- with or without calcium supplements -- or a placebo daily for at least a year. The patients didn't know if they were taking vitamin D or the placebo.
The reviewers pooled data from the trials and concluded that patients who took 482 to 770 IU per day of vitamin D cut their nonvertebral bone fracture risk by 20% and their hip fracture risk by 18%.
Those effects weren't tied to taking calcium supplements.
The review doesn't pinpoint exactly how much vitamin D it's best to take per day; patients took up to 770 IU daily.
"I personally supplement my diet with... about 1,400 [IU] a day, which is probably a target that most people should be at -- somewhere between 1,000 and 2,000 units per day," Puzas says.
The tolerable upper limit for vitamin D is 2,000 IU per day, according to the IOM's current standards. The IOM's review of vitamin D intake is expected next year.