Vitamin D is Vitamin of the Year
Thursday, November 12, 2009
Vitamin D may just be considered the “it” vitamin of 2009. This year, it seemed stories on the sunshine vitamin were published daily. Studies on its role in bone health, heart health, immune health, weight management, cancer prevention and other health conditions poured from scientific journals. With the outbreak of H1N1 influenza, the Public Health Agency of Canada plans to test vitamin D levels of people who contract the virus in order to find new ways to fight it; and the U.S. Institutes of Medicine (IOM) announced it will review the recommended daily values of vitamin D intake.
Yes, vitamin D was hot this year, and not just because it comes to us from sun exposure. With all the news reports and studies, it’s no wonder awareness of vitamin D is up among consumers. The International Food Information Council’s (IFIC) Functional Foods/Foods for Health consumer survey, released in August 2009, found 90 percent of Americans recognized vitamin D offers bone-health benefits compared to 81 percent in 2007. For responders who had children, 19 percent said they look for their children’s foods and beverages to be fortified with vitamin D.
Vitamin D comes in two biologically inactive precursors. D3, also known as cholecalciferol, is produced by the skin when it’s exposed to ultraviolet B (UVB) radiation; D2, also known as ergocalciferol, comes from plants exposed to UV light. The liver and kidneys synthesize both forms of vitamin D into 1,25-dihydroxyvitamin D (1,25(OH)2D), to make it active in the body. However, most scientist agree, the body prefers consumption of D3, adding, “D3 is said to be the best form of vitamin D as it is the natural type that also is created whenever skin is exposed to sunlight.”
Humans may not be able to get all of their vitamin D from the sun due to amount of skin that is exposed, the length of exposure, UV wavelength, latitude, season, skin melanin content and age. Therefore, people are more interested in increasing their vitamin D by consuming the nutrient, but most unfortified foods do not provide adequate amounts. The few foods that do contain a significant amount of vitamin D—butter, cream, egg yolks and fatty fish, such as herring, catfish and salmon—are not, and in some cases shouldn’t be, prevalent in today’s diets.
The reality is that the average U.S. diet does not provide the required amount of vitamin D. Therefore, dietary supplements may be useful sources for these nutrients that otherwise might be consumed in less than recommended amounts.
U.S. dietary reference intake (DRI) guidelines established in 1997 by IOM recommend 200 IU/d of vitamin D through age 50, 400 IU/d for people ages 51 to 70 and 600 IU/d for those 71 and older. But many experts now say everyone likely needs more. For instance, in 2008, the American Academy of Pediatrics (AAP) recommended breastfed infants receive supplements of 400 IU/d of vitamin D until they are weaned and consume more than 1,000 mL/d of vitamin D-fortified formula or whole milk.1 All non-breastfed infants ingesting less than 1,000 mL/d of vitamin D-fortified formula or milk should receive a vitamin D supplement of 400 IU/d, they said. AAP also recommends older children and adolescents should take a 400 IU vitamin D supplement daily. In response, a new IOM panel is reviewing the recommendations on vitamin D and calcium and a report is expected in spring 2010.
New products fortified with vitamin D may help the many who are deficient. Recent studies have shown pregnant women who lived at a latitude of 54 to 55 degrees north (about as north as Central Canada) had insufficient levels, even among those who use supplements.2 Mothers-to-be who have lower levels of vitamin D are more likely to give birth via cesarean section.3 And Turkish researchers encouraged pregnant women to supplement their diets with vitamin D in order to reduce the risk of their children contracting acute lower respiratory infections.4
Once the children are out of the womb, they may still not be getting all of their vitamin D needs. In the United States, 61 percent of children aged 1 to 21 years who completed the National Health and Nutrition Examination Survey 2001-2004 had insufficient levels of vitamin D.5 Only 4 percent had taken a 400 IU/d supplement of vitamin D for the past 30 days. That same study found deficiency was associated with elevated parathyroid hormone levels, higher systolic blood pressure, lower serum calcium and high-density lipoprotein (HDL) cholesterol levels.
The heart-health benefits of vitamin D don’t stop with the youth. A University of Colorado study found an inverse relationship between vitamin D levels and cardiovascular disease (CVD), as well as all-cause mortality.6 A review in The American Journal of the Medical Sciences states cross-sectional studies found vitamin D deficiency was associated with increased risk of CVD, including hypertension, heart failure and ischemic heart disease.7 And Reuters reported at a September 2009 meeting of the American Heart Association in Chicago, researchers presented a study that found younger white women with vitamin D deficiencies are about three times more likely to have high blood pressure in middle age than those with normal vitamin levels.
Because vitamin D is necessary for calcium absorption into the body, vitamin D is closely associated with bone health. In fact, one Swiss study found among men and women, vitamin D status seems to be the dominant predictor of bone mineral density (BMD) relative to calcium intake.8 In the study, only women with vitamin D concentrations less than 50 nm seem to benefit from a higher calcium intake alone. In a later review of eight randomized controlled trials, those same researchers found supplemental vitamin D in a dose of 700 to 1,000 IU/d reduced the risk of falling among older adults by 19 percent.9 However, doses of supplemental vitamin D of less than 700 IU or serum 25-hydroxyvitamin D concentrations of less than 60 nmol/l did not reduce the risk of falling.
The benefits of vitamin D go well beyond the heart and bones. Keeping vitamin D levels high may also protect against colon cancer,10 cold and flu,11 Alzheimer’s disease,12 multiple sclerosis,13 ovarian cancer14 and weight gain.15
1. Wagner CL, et al. “Prevention of rickets and vitamin D deficiency in infants, children, and adolescents.” Pediatrics. 2008 Nov;122(5):1142-52.
2. Holmes VA, et al. “Vitamin D deficiency and insufficiency in pregnant women: a longitudinal study.” Br J Nutr. 2009 Sep;102(6):876-81.
3. Merewood A, et al. “Association between vitamin D deficiency and primary cesarean section.” J Clin Endocrinol Metab. 2009 Mar;94(3):940-5.
4. Karatekin G, et al. “Association of subclinical vitamin D deficiency in newborns with acute lower respiratory infection and their mothers.” Eur J Clin Nutr. 2009 Apr;63(4):473-7.
5. Kumar J, et al. “Prevalence and Associations of 25-Hydroxyvitamin D Deficiency in US Children: NHANES 2001-2004.” Pediatrics. 2009 Aug 3.
6. Ginde AA, “Prospective Study of Serum 25-Hydroxyvitamin D Level, Cardiovascular Disease Mortality, and All-Cause Mortality in Older U.S. Adults.” J Am Geriatr Soc. 2009 Jun 22.
7. Judd SE, Tangpricha V. “Vitamin D deficiency and risk for cardiovascular disease.” Am J Med Sci. 2009 Jul;338(1):40-4.
8. Bischoff-Ferrari HA , et al. “Dietary calcium and serum 25-hydroxyvitamin D status in relation to BMD among U.S. adults.” J Bone Miner Res. 2009 May;24(5):935-42.
9. H A Bischoff-Ferrari, et al. “Fall prevention with supplemental and active forms of vitamin D: a meta-analysis of randomised controlled trials.” J Bone Miner Res. 2009 Oct 1; 339:b3692
10. Freedman DM, et al. “Sunlight, hormone replacement status and colorectal cancer risk in post-menopausal women.” Int J Cancer. 2009 Sep 30.
11. Ginde AA, Mansbach JM, Camargo CA Jr. “Association between serum 25-hydroxyvitamin D level and upper respiratory tract infection in the Third National Health and Nutrition Examination Survey.” Arch Intern Med. 2009 Feb 23;169(4):384-90.
12. Masoumi, A, et al. “1α,25-dihydroxyvitamin D3 Interacts with Curcuminoids to Stimulate Amyloid-β Clearance by Macrophages of Alzheimer’s Disease Patients.” J Alzheimers Dis. 2009 July; 17(3): 703-717
13. D.Sioka C, et al. “Multiple sclerosis, osteoporosis, and vitamin D.” J Neurol Sci. 2009 Sep 30.
14. Toriola AT, et al. “Serum 25-hydroxyvitamin D and the risk of ovarian cancer.” Eur J Cancer. 2009 Aug 25.
15. The Endocrine Society (2009, June 12). Successful Weight Loss With Dieting Is Linked To Vitamin D Levels. ScienceDaily. Retrieved October 6, 2009, from http://www.sciencedaily.com /releases/2009/06/090611142524.htm