Evidence reviews deem the US recommended daily allowance insufficient to reduce the risk of falling among older people
by Craig Weatherby
Falls that break hip or pelvis bones often lead to a serious downward health spiral... and the results of clinical trials indicate that vitamin D pills can reduce the risk of falling among older people.
Vitamin D is a critical factor in bone health
—see “Vitamin D Called More Critical than High-Dose Calcium”
—but it is clearly better to prevent falls than to hope that stronger bones will withstand the shock.
|Fish fit the vitamin D bill; Sockeye salmon stand out|
In addition to getting vitamin D from supplements, certain fish rank among the very few substantial food sources of vitamin D, far outranking milk and other D-fortified foods.
Among fish, wild Sockeye Salmon may be the richest source of all, with a single 3.5 ounce serving surpassing the US RDA of 400 IU by about 70 percent:
Vitamin D per 3.5 ounce serving*
Sockeye Salmon—687 IU
Albacore Tuna—544 IU
Silver Salmon—430 IU
King Salmon—236 IU
*For our full test results, click here.
Now, a new analysis of the best clinical evidence finds that the US recommended daily allowance (RDA) for vitamin D intake by adults aged 51 to 70 (400 IU) is only about half the dose needed to reduce the risk of falls among older people (Bischoff-Ferrari HA et al. BMJ 2009).
The current RDAs for vitamin D are 400 IU for adults aged 51 to 70 and 600 IU for people over 70. And the RDA for all persons younger than 51 is a scant 200 IU.
Better yet, another recent evidence review by some of the same scientists indicates that the risk of falling drops as vitamin D blood levels rise.
This means that the the much higher, proven-safe doses advocated by most researchers (2,000 IU to 4,000 IU per day) could cut fall risks even further.
Let's take a closer look at the findings, and what's known about healthy intakes and blood levels of vitamin D.
Studies finds higher vitamin D doses prevent falls and fractures
Earlier this month, a team led by leading researchers from Harvard, USDA, and Switzerland published their review of the eight best clinical trials on vitamin D, falls, and fractures.
Eight double-blind, randomized controlled trials involving 2,426 older people were analyzed. The test doses used in these trials ranged from 200 to 1,000 IU per day.
Their analysis found that daily supplemental doses of vitamin D between 700 and 1,000 International Units (IU) reduced the risk of falling by 19 percent, while doses below 700 IU per day showed no benefits.
And blood levels of vitamin D above 60 nmol/L (nanomoles per liter) were associated with a 23 percent reduction in falls, while vitamin D levels under 60 nmol/L were not associated with any decrease in falls.
Four years ago, a similar evidence review co-authored by some of the same scientists produced similar findings with regard to the risk of fractures among the elderly, most of which result from falls:
“Oral vitamin D supplementation between 700 to 800 IU per day appears to reduce the risk of hip and any non-vertebral fractures in ambulatory or institutionalized elderly persons. An oral vitamin D dose of 400 IU per day is not sufficient for fracture prevention” (Bischoff-Ferrari HA et al. 2005).
And a study published earlier this year by some of the same Harvard, USDA, and Swiss researchers found that the risk of falls and fractures dropped as the daily dose of vitamin D rose (Bischoff-Ferrari HA et al. Arch Intern Med 2009).
How much do we need?
Most researchers involved in vitamin D studies recommend minimum blood levels ranging from 90 to 120 nmol/L. (Vitamin D levels can also be expressed as nanograms per liter—abbreviated as ng/mL—and 36 to 48 ng/mL is comparable to 90 to 120 nmol/L.)
However, leading vitamin D researcher Ronald Vieth, M.D., notes that normal human blood levels of vitamin D extend above 200 nmol/L or 80 ng/mL (Vieth R 2004).
Dr. Vieth also points out that vitamin D blood levels above 120 nmol/L pose no risk and may confer additional benefits, up to the upper reaches of the normal human range (i.e., 200 nmol/L).
Though the official safe upper intake limit is only 2,000 IU per day, vitamin D intake is proven safe at 10,000 IU per day … a daily level that’s 25 times the current RDA for adults 51 to 70 (400 IU) and 16 times the current RDA for adults over 70 (600 IU).
Most experts recommend taking at least 1,000 IU via food and supplements, and prefer an intake of 2,000 IU to 4,000 IU per day... unless most of your skin is exposed to 20 to 30 minutes of strong sunlight per day.
Darker skinned people, whose greater amount of skin pigment blocks the UV rays that make vitamin D, need more sun exposure... or extra vitamin D supplements and fatty seafood, which is the best food source by far.
While our bodies make vitamin D when skin is exposed to sunshine, the winter sun in northern countries is so weak that the body makes almost no vitamin D at all.
Fortunately, dietary supplements can boost people’s vitamin D blood levels, as can a combination of supplements and fatty seafood.
Milk fortified with vitamin D—often and mistakenly cited as a good source—contains a paltry 100 IU per 8 oz glass, which is far too little to do much good.
Why would vitamin D help prevent falls?
The authors of the new evidence analysis noted that muscle weakness is both an important risk factor for falls and a proven, prominent symptom of vitamin D deficiency (Bordelon P et al. 2009).
As they wrote, vitamin D deficiency “…could plausibly mediate fracture risk through increasing susceptibility to falls” (Bischoff-Ferrari HA et al. BMJ 2009).
Vitamin D stimulates synthesis of protein, the building material for muscle (Hamilton B 2009).
And as USDA researchers wrote this year, “Vitamin D supplementation has been shown to improve tests of muscle performance, reduce falls, and possibly impact on muscle fiber composition and morphology in vitamin D deficient older adults” (Ceglia L 2009).
In fact, when people take supplemental vitamin D this muscle-supportive effect appears even before the better-known, highly positive impacts of vitamin D on bone strength.
And the muscle benefits of vitamin were documented in young girls earlier this year… see “Vitamin D Seen to Strengthen Girls.”
- Bischoff-Ferrari HA, Dawson-Hughes B, Staehelin HB, Orav JE, Stuck AE, Theiler R, Wong JB, Egli A, Kiel DP, Henschkowski J. Fall prevention with supplemental and active forms of vitamin D: a meta-analysis of randomised controlled trials. BMJ. 2009 Oct 1;339:b3692. doi: 10.1136/bmj.b3692.
- Bischoff-Ferrari HA, Willett WC, Wong JB, Giovannucci E, Dietrich T, Dawson-Hughes B. Fracture prevention with vitamin D supplementation: a meta-analysis of randomized controlled trials. JAMA. 2005 May 11;293(18):2257-64. Review.
- Bischoff-Ferrari HA, Willett WC, Wong JB, Stuck AE, Staehelin HB, Orav EJ, Thoma A, Kiel DP, Henschkowski J. Prevention of nonvertebral fractures with oral vitamin D and dose dependency: a meta-analysis of randomized controlled trials. Arch Intern Med. 2009 Mar 23;169(6):551-61. Review.
- Bordelon P, Ghetu MV, Langan RC. Recognition and management of vitamin D deficiency. Am Fam Physician. 2009 Oct 15;80(8):841-6.
- Ceglia L. Vitamin D and its role in skeletal muscle. Curr Opin Clin Nutr Metab Care. 2009 Nov;12(6):628-33.
- Hamilton B. Vitamin D and Human Skeletal Muscle. Scand J Med Sci Sports. 2009 Oct 5. [Epub ahead of print]