For elderly, whose sceletal strength weakens, can Vitamin D supplements slow down the degeneration of bones?
I have found this source discussing which supplement works best, but it never established if Vitamin D supplements actually help.
According to some studies, adequate vitamin D intake from foods and supplements may prevent bone weakness (osteporosis) in elderly, but according to others it may not.
...vitamin D intake of 10-17.5 μg/day (400-700 IU/day) or more is effective in preventing bone loss in late postmenopausal women and an intake of 17.5-20 μg/day (700-800 IU/day) or more together with a calcium supplement reduces the risk of osteoporotic fractures.
The results of a meta-analysis of 23 randomized controlled trials with more than 4,000 participants (mean age, 59 years) showed little evidence for an effect of vitamin D supplementation on bone mineral density at any of the five skeletal sites examined...
A prospective cohort study that followed more than 72,000 postmenopausal women in the US for 18 years found that those who consumed at least 600 IU/day of vitamin D from diet and supplements had a 37% lower risk of osteoporotic hip fracture than women who consumed less than 140 IU/day of vitamin D (73). However, daily supplementation with 400 IU of vitamin D3, in combination with 1,000 mg calcium, did not significantly reduce risk of hip fracture compared to a placebo in 36,282 postmenopausal women from the Women's Health Initiative trial...
According to Mayo Clinic:
Logically, vitamin D supplements could help to prevent osteoporosis in people with insufficient vitamin D intake or sun exposure, but since this can be corrected by adequate vitamin D intake from foods and by sun exposure, the supplements may not be necessary.
In people without vitamin D deficiency but with other risk factors for osteoporosis, vitamin D supplements would be much less likely effective, as suggested by the above studies.