Seven in 10 Americans have insufficient or deficient levels of vitamin D.
Substantial epidemiological evidence suggests health benefits from higher blood levels of vitamin D.
Certainty about this has remained elusive, as the few clinical studies conducted to date have been small, short, and tested relatively low doses … and produced inconsistent results.
However, recent studies that compared people’s vitamin D blood levels to their health outcomes seems to bolster the idea that this hormone-like nutrient is a key ally in preventing death and disease.
The current scientific consensus defines vitamin D insufficiency as a blood level under 75 nm/L (30 ng/mL), and deems vitamin D deficiency as a blood level under 50 nm/L (20 ng/mL). (Kerr GS et al. 2011; Binkley N et al. 2012)
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 rank as the richest source, with a single 3.5 ounce serving surpassing the US RDA of 600 IU by about 15 percent:
Vitamin D per 3.5 ounce serving*
Sockeye Salmon 687 IU
Albacore Tuna 544 IU
Silver Salmon 430 IU
King Salmon 236 IU
Sardines 222 IU
Sablefish 169 IU
Halibut 162 IU
*For our full test results, click here.
During the winter months in northern climates, it can be very hard to get enough from sun exposure.
This makes it essential for those who live in northern latitudes – or who get less than 30 minutes of good sun exposure daily – to do get their vitamin D orally.
These folks can frequently eat fatty fish – the only good food source (see our “Fish fit the vitamin D bill” sidebar) – and/or take vitamin supplements (1,000 to 2,000 IU) daily.
Growing evidence favors vitamin D vs. death and disease
Last April, we reported on a six-year University of Kansas study in people aged 43 to 73, which compared the participants’ vitamin D blood levels to rates of death and disease after six years.
The results linked “deficient” levels of vitamin D – defined as below 30 nanograms per milliliter (ng/ml) – to significantly higher rates of hypertension, coronary artery disease, and diabetes.
And the risk of death was 164 percent higher in people deemed deficient in vitamin D… while participants who reported taking vitamin D pills were 61 percent more likely to have avoided death.
Two years ago, doctors from Baltimore’s Johns Hopkins University School of Medicine came to similar conclusions in a six-year-plus study of 1,006 Italian seniors (Semba RD et al. 2010).
Supporting those findings, a study from Oregon State University (OSU) affirms the health value of having adequate-to-optimal blood levels.
Oregon study affirms vitamin D as a life-saver
A new study from OSU concludes that among older adults – especially those who are frail – low levels of vitamin D can mean a much greater risk of death (Smit E et al. 2012).
Using data collected from 4,731 nationally representative Americans over 60 years of age, OSU researchers led by Ellen Smit, Ph.D., RD, compared the subjects’ vitamin D blood levels and “frailty” status to their health status over a 12 year period.
(Frailty was defined as having three out of five criteria: low body mass index (BMI), slow walking, weakness, exhaustion, and low physical activity.)
The OSU team divided people into four groups, based on their vitamin levels.
They defined “low vitamin D” as having less than 50 nanomoles per liter (20 ng/mL), and “high vitamin D” as having 84 nanomoles per liter (34 ng/mL) or higher.
In general, those who had lower vitamin D levels were more likely to also meet the criteria for frailty.
The OSU team’s analysis showed that the older adults with low vitamin D levels were 30 percent more likely to have died within 12 years, compared to the subjects with higher levels.
Overall, people who were frail had more than double the risk of death than those who were not frail.
Finally, frail adults with low levels of vitamin D tripled their risk of death over people who were not frail and who had higher levels of vitamin D.
Smit made an obvious recommendation: “What this really means is that it is important to assess vitamin D levels in older adults, and especially among people who are frail.” (OSU 2012)
She said that prior studies have separately linked frailty and low vitamin D with a greater risk of death over time, while this is the first study to look at the combined effect.
And she supported the value of sun exposure: “As you age, there is an increased risk of melanoma, but older adults should try and get more activity in the sunshine.” (OSU 2012)
Because of the nature of the survey, the OSU researchers could not tell whether low vitamin D contributed to frailty, or frail people became vitamin D deficient because of health problems.
However, Smit said that their analysis on death rates showed it may not matter which came first.
“If you have both, it may not really matter which came first because you are worse off and at greater risk of dying than other older people who are frail and who don’t have low vitamin D,” she said. “This is an important finding because we already know there is a biological basis for this. Vitamin D impacts muscle function and bones, so it makes sense that it plays a big role in frailty.” (OSU 2012)
OSU’s Linus Pauling Institute recommends adults take 2,000 IU of supplemental vitamin D daily. The current federal guidelines are 600 IU for most adults, and 800 for those older than 70.
“We want the older population to be able to live as independent for as long as possible, and those who are frail have a number of health problems as they age,” Smit said (OSU 2012).
“A balanced diet including good sources of vitamin D like milk and fish, and being physically active outdoors, will go a long way in helping older adults to stay independent and healthy for longer.” (OSU 2012)
Binkley N, Ramamurthy R, Krueger D. Low vitamin D status: definition, prevalence, consequences, and correction. Rheum Dis Clin North Am. 2012 Feb;38(1):45-59.
Kerr GS, Sabahi I, Richards JS, Caplan L, Cannon GW, Reimold A, Thiele GM, Johnson D, Mikuls TR. Prevalence of vitamin D insufficiency/deficiency in rheumatoid arthritis and associations with disease severity and activity. J Rheumatol. 2011 Jan;38(1):53-9. Epub 2010 Oct 15.
Oregon State University (OSU). Lower vitamin D could increase risk of dying, especially for frail, older adults. July 26, 2012. Accessed at http://oregonstate.edu/ua/ncs/archives/2012/jul/lower-vitamin-d-could-increase-risk-dying-especially-frail-older-adults
Semba RD, Houston DK, Bandinelli S, Sun K, Cherubini A, Cappola AR, Guralnik JM, Ferrucci L. Relationship of 25-hydroxyvitamin D with all-cause and cardiovascular disease mortality in older community-dwelling adults. Eur J Clin Nutr. 2010 Feb;64(2):203-9. Epub 2009 Dec 2.
Shardell M, D'Adamo C, Alley DE, Miller RR, Hicks GE, Milaneschi Y, Semba RD, Cherubini A, Bandinelli S, Ferrucci L. Serum 25-hydroxyvitamin D, transitions between frailty states, and mortality in older adults: the Invecchiare in Chianti Study. J Am Geriatr Soc. 2012 Feb;60(2):256-64. doi: 10.1111/j.1532-5415.2011.03830.x. Epub 2012 Jan 27.
Smit E, Crespo CJ, Michael Y, Ramirez-Marrero FA, Brodowicz GR, Bartlett S, Andersen RE. The effect of vitamin D and frailty on mortality among non-institutionalized US older adults. Eur J Clin Nutr. 2012 Jun 13. doi: 10.1038/ejcn.2012.67. [Epub ahead of print]