Increased Life Expectancy With Vitamin D?

Christopher P.F. Marinangeli, PhD, RD
Scientific Regulatory Associate, Dicentra Inc.

Everyone is talking about vitamin D – in the nutrition world anyway. Nutritional scientists, dieticians, and government agencies promote vitamin D as a nutrient that supports bone health; mostly because it increases calcium absorption and the number of “bone building” cells called osteoclasts as well as maintains healthy blood calcium levels. However, recent evidence suggests that vitamin D status can reduce the risk of cardiovascular disease, cancer, respiratory infections, respiratory diseases, tuberculosis and diabetes.

In a new study using available ecological and epidemiological data linking vitamin D status to the aforementioned diseases, Grant (2011) calculated that life expectancy can be extended ~ 2 years by increasing serum vitamin D levels from 54 nmol/L to ≥ 100 nmol/L. In addition, it was estimated that increasing circulating vitamin D levels from 50-70 nmol/L to the 105-112 nmol/L range can decrease the economic burden of disease by ~10 %, which is substantial.

Overall, Grant (2011) presents a compelling argument. After reading the author’s thorough review of the literature, which demonstrates inverse associations between vitamin D status and disease, it becomes apparent that the physiological role for vitamin D is much broader than that of bone health. For example, Grant (2011) explains that almost every cell-type in the human body has a vitamin D receptor. Moreover, vitamin D has been shown to modulate levels of cathelicidin, defensin and various cytokines that help mount immunological responses to infectious agents. However, all of the mechanisms by which vitamin D modulates the biological processes that affect the incidence of certain diseases have not been elucidated. Thus, the available epidemiological evidence that demonstrates inverse relationships between vitamin D and disease warrants further research that is focused on deciphering possible mechanisms for how vitamin D reduces disease risk.

Humans get their vitamin D in two ways. First, endogenous vitamin D can by synthesized within the skin via exposure to sun-derived ultraviolet radiation. However, given the association between sun exposure and the incidence of skin cancer, guidelines that quantify the amount of sun required to attain appropriate levels of vitamin D have not been established. Second, vitamin D is obtained from the diet, from vitamin D rich foods (i.e. fish), vitamin D supplementation, or vitamin D fortified foods (i.e. milk and some fruit juices). It should be noted that in the United States milk producers have the option of fortifying milk with ~38.5 IU vitamin D/ 100 ml milk, whereas in Canada, the fortification of milk with vitamin D is required by law at 35-45 IU vitamin D /l00 ml milk (Ross et al. 2011). Canadian and U.S. guidelines for daily vitamin D intake recommend approximately 600 IU/day vitamin D for individuals under 71 years of age (Ross et al. 2011). Grant (2011) advocates that 2000-7000 IU/day vitamin D are needed to increase circulating levels of vitamin D to ~100 nmol/L. However, the Dietary Reference Intake guidelines indicate that that tolerable upper intake level (UL) for vitamin D is 4000 IU/day for males and females over the age of nine. Conversely, a recent risk assessment indicates that vitamin D exposure is safe at levels >10 000 IU/day and that 10 000 IU/day is an appropriate UL for vitamin D (Hathcock et al. 2007). Thus demonstrating controversy regarding the risk of vitamin D toxicity.

Altogether, Grant (2011) presents a convincing and exciting argument for increasing one’s vitamin D intake and, ultimately, circulating vitamin D levels. Despite literature demonstrating inverse relationships between vitamin D status and disease risk alongside a calculated increase in life expectancy of ~ 2 years when serum vitamin D levels are increased to ≥ 100 nmol/L, caution is still necessary because of divisive opinions regarding vitamin D’s UL and the risk of toxicity. Future research investigating mechanisms by which vitamin D modulates processes that reduce the risk of disease is warranted. Until then, any plans to dramatically increase your daily vitamin D intake should be discussed with your doctor.

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References

Grant WB. An estimate of the global reduction in mortality rates through doubling vitamin D levels. Eur J Clin Nutr. 2011. [Epub ahead of print].
Hathcock JN, Shao AS, Reinhold V. Risk assessment for vitamin D. Am J Clin Nutr. 2007; 85:6-18.
Ross AC, Taylor CL, Yaktine AL, Del HB. and Del Valle HB. Dietary Reference Intakes: Calcium Vitamin D. Institute of Medicine of the National Academies. The National Academies Press. Washington, D.C. 2011.