I. Sources and recommended intake
- Primary dietary sources are meat, fatty fish, eggs, and fortified milk (in US)
- Also synthesized in humans with exposure to ultraviolet-B radiation (e.g.
- Recommended dietary intake:
- < 12mo: 400 IU/d
- 1-18yo: 600 IU/d
- Adults: 600IU/d (800IU if > 70yo)
- Some at-risk adults might require 1500IU
- Specific compounds grouped under heading of "vitamin D":
- Ergocalciferol ("vitamin D2")-Found in some plants
- Cholecalciferol ("vitamin D3")-The compound synthesized in
humans with UV exposure; SUpplements are derived from oily fish
- For pharmacologic vitamin D preparations, 10 mcg = 400 IU
III. Vitamin D deficiency
- Risk factors
- Low sunlight exposure
- Low dietary intake
- Infants exclusively breast-fed
- Dark skin pigmentation
- Elderly are at particular risk for deficiency because of low sunlight
exposure, decreased synthetic capacity of Vit. D in the skin, and
decreased absorption and activation of the vitamin.
- Serum assays can be variable; 25-hydroxyvitamin D is usually what is measured
- Deficiency often defined as 25-hydroxyvitamin D level <20 ng/mL (50
- There may be adverse effects with elevated levels (> 50 ng/mL)
- Lowers risk of osteoporosis
- May lower risk of falls in elderly
- Treatment in children
- 2,000 IU/d of vitamin D2 or D3, or 50,000 IU Qwk x 6wks
- Can supplement with either D2 or D3 (see above) but D3 supplementation raises serum levels more than D2
- Adequate levels of vitamin D are associated with reduced risk of falls in patients > 65yo and also in hip fractures
for other benefits from vitamin D supplementation (reductions in BP,
coronary events, infections, type 1 DM, multiple sclerosis, and
malignancies) is very limited as of 2012
- Vitamin D + Ca for elderly at risk for deficiency (home-bound,
poor nutritional status, unsunny climate)
- 389 healthy men & women >65yo, residing in
non-institutional settings, randomized to Ca 500mg + vit.
D3 700IU QD vs. placebo; at 3y f/u, tx group had sig.
increases in bone density at femoral neck, spine, and
total body; sig. decreased incidence of a first
nonvertebral fx (6% vs. 13%) (NEJM 337:670, 1997-JW)
- In a trial of 2686 community-dwelling pts 65-85yo randomized to vit.
D 100IU PO Q4mos vs. placebo, over 5y f/u, vit. D group had sig. lower
incidence of fx (RR 0.78) (BMJ 326:469, 2003--JW)
a meta-analysis of 5 RCT's of vitamin D vs. placebo in elderly
populations (mean age 60y), use of vitamin D was ass'd with OR of 0.78
for falls (sig.) (JAMA 291:1999, 2004--abst)
- In a meta-analysis of seven randomized trials of Calcium + Vitamin D
in elderly patients (mean age 79y), vitamin D at dose of 400IU was not
associated with reduced risk of fracture, but 700-800IU/day was
(OR 0.75, NNT = 50) (JAMA 293:2257, 2005--AFP)
- In a randomized study in 625 residents in nursing homes and
assisted-living facilities randomized to vitamin D 1000IU/d vs.
placebo + Ca supplements (600mg elemental ca/day), over 2y f/u, vit.
D. recipients had sig. lower incidence of falls (1.37 vs.
1.86/person/yr_ (J. Am. Geriat. Soc. 53:1881, 2005--JW)
- In a study in 5,292 pts > 70yo with h/o low-trauma fractures
randomized to vitamin D 800IU/d, Ca 1000mg/d, both, or placebo, at
24-62mo f/u, there was no sig. diff. in incidence of fracture, death,
or falls between the two groups (Lancet 365:1599, 2005--JW)
- In a study in 36,282 postmenopausal women randomized to
CaCO3 1g/d + Vit. D 400IU/d vs. placebo, over 7y f/u,
there was no sig. diff. in overall incidence of spine,
hip, or total fractures, though among the subgroup of
women not using supplemental Ca/Vit. D outside the
treatment protocol, RR for hip fx was sig. lower in
supplemented group (HR 0.7); ctive-tx group had sig.
higher incidence of kidney stones (WHI Trial; NEJM 354:669, 2006--JW)
- In a study in 3,314 community-dwelling women >
70yo with one of (prior fx, body weight < 58kg, fair or poor
self-reported health, cigarette use, or maternal h/o gracture)
randomized to calcium 1000 mg/vit. D3 800IU/d vs. printed information
only, over 2 mo, there was no sig. diff. in incidence of self-reported
fx (BMJ 330:1003, 2005--JW)
- In a meta-analysis of 12 randomized trials
of oral vitamin D supplementation in 42,279 pts > 65yo, over at
least 1y f/u, doses of < 400 IU/day was associated with no sig.
diff. in incidence of nonvertebral fx, but doses of > 400 IU/d was
associated with sig. lower incidence of nonvertebral fx (RR
0.80); Ca supplementation was not associated with sig. additional
decrease in nonvertebral fx risk (Arch. Int. Med. 169:551, 2009-AFP)
(Sources include Core Content Review of Family Medicine, 2012)