What is Vitamin D?

Vitamin D is a group of water-soluble secosteroids produced naturally in the human body by exposure to sunlight, earning it the moniker “the sunshine vitamin”.  The two most-found forms in humans are known as D2 (ergocalciferol) and D3 (cholecalciferol).  In order to be properly absorbed by the human body, vitamin D requires co-factors such as magnesium, zinc, vitamin K2, boron, as well as a small amount of vitamin A.

Although it is possible to fulfill the body’s vitamin D needs by exposure to sunlight and consumption of some vitamin D-rich foods such as fatty fish, beef liver, eggs, and mushrooms, studies have found that vitamin D insufficiency is a widespread problem across all segments of the population.  A recent study conducted by Statistics Canada found that an astonishing two-thirds of the population has vitamin D levels below that recommended for reducing the associated risk of cancer and other chronic illnesses, while one in ten have vitamin D levels so low as to damage bone health.  4% of children had such low levels that they were at risk for rickets, a devastating childhood bone disease.  In the United States, 9%, or 7.6 million, of children had serious vitamin D deficiency, while another 61%, or 50.8 million, had vitamin D insufficiency, as measured by the National Health and Nutrition Examination Survey.

Since a large proportion of the populace is unable to obtain sufficient amounts of Vitamin D from exposure to sunlight and intake from foods alone, many turn to Vitamin D supplements to reach the recommended daily amount of Vitamin D.

Scientific Research on Vitamin D

Vitamin D’s most basic role in helping the body absorb calcium has long been well-documented.  After two hydroxylation reactions in the body, the normally biologically inert Vitamin D is turned into its active form in the human body – calcitriol, or 1,25-dihydroxycholecalciferol.  Calcitriol plays a major part in the absorption of calcium and phosphorus from food, thus increasing the levels of calcium in the bloodstream needed to maintain healthy bone health and prevent hypocalcemic tetany, a symptom of low calcium levels marked by uncontrolled and often painful muscle spasms.

Recent studies have also shown, however, that Vitamin D’s importance may be far greater.  Scientific research has linked Vitamin D deficiency to such chronic and debilitating diseases such as depression, heart disease, and even cancer.

Vitamin D and Mental Illness

An Australian and Danish study released this September found from a sample of 848 individuals (424 subjects with schizophrenia with 424 controls matched for sex and date of birth) that those with lower than normal concentrations of 25-hydroxyvitamin D3 (25-OH D3) in their neonatal blood sample had a significant twofold risk for developing schizophrenia in their later life.  Surprisingly, the study also found that those with highly above normal levels of 25-OH D3 were at an increased risk for developing mental complications down the road.

The study concludes that low levels of vitamin D in infancy and early childhood caused by vitamin D deficiency of the mother can adversely affect the child and lead them to become more prone to severe and debilitating mental illnesses such as schizophrenia.

Vitamin D and Heart Disease

The human body has a large number of vitamin D receptors with a broad tissue distribution, including receptors in the vascular smooth muscle, the endothelium, and cardiomyocytes.  Due to this, it was long suspected that vitamin D levels can impact the cardiovascular system, with recent scientific studies confirming this view.

A 2007 study was conducted as an offshoot of the Framingham Heart Study, a study first started in 1948 to identify the common factors and causes of cardiovascular disease.  Using 1,739 participants from the Framingham Offspring Study pool (children of the original Framingham participants, recruited in 1971) who had not yet shown overt signs of cardiovascular disease (CVD), the study measured their vitamin D levels as well as cardiovascular status over a span of more than five years.  Vitamin D status was ascertained by measuring the levels of 25-dihydroxyvitamin D (25-OH D) against a predetermined threshold level, less than 15 ng/mL and less than 10 ng/mL.  During the length of the study, 120 participants developed their first cardiovascular event.  It was determined that those with 25-OH D levels less than 15 ng/mL had a multivariable-adjusted hazard ratio of 1.62 compared with those who had levels more than 15 ng/mL.  There also existed a graded increase in the risk of CVD for different levels of 25-OH D, with multivariable-adjusted hazard ratios of 1.53 for levels from 10 to 15 ng/mL, and an increased ratio of 1.80 for levels less than 10 ng/mL.  The findings were not impacted by further adjustments for C-reactive protein, physical activity, and vitamin use.  This study proves a link between vitamin D deficiency and risk of CVD but does not include in their findings whether or not correcting vitamin D deficiencies via supplements or lifestyle changes can reduce risk and prevent CVD

A more recent 2010 study does examine if increasing vitamin D intake can reduce the risk of cardiovascular disease.  Utilizing data from all studies published in English from 1966 to July 2009 that deal with vitamin D intake, calcium supplementation, and cardiovascular events, the study was able to extract the conclusion that moderate to high doses of vitamin D supplements may reduce risk of CVD, while calcium supplements seemed to have little effect on cardiovascular status.  Despite the positive findings, the study has severe limitations in that only research data in English are considered, creating a relatively small sample size.  The lack of specific trials to test vitamin D intake and cardiovascular outcome also preclude this study from establishing a truly irrefutable and conclusive end.  However, it is still interesting to note the distinct possibility that increasing vitamin D levels may indeed a lower cardiovascular risk.

Vitamin D and Cancer

 Following a 2007 double-blind, population-based, randomized placebo-controlled study that examined 1,179 postmenopausal women over a four year period, it was found that improving vitamin D and calcium status significantly lowered the risk of cancer development by 60 to 77 percent in the study group, while the results from the placebo group and the group that only received calcium showed no large reduction in cancer risk.  Following this study, the Canadian Cancer Society had upped its recommended vitamin D intake amount to 1000 IU per day, in light of the possible anti-cancer properties of vitamin D.

However, vitamin D is most definitely not a panacea or miracle cancer cure.  A 2008 study with 749 prostate cancer patients and another 781 matched control subjects found that increasing the season-standardized serum levels of 25-OH D did not reduce the overall risk for prostate cancer.  In fact, the study found that vitamin D levels above that of lowest quintile were actually associated with increased risk of a more aggressive form of prostate cancer.

Despite the controversial findings around vitamin D and cancer prevention, a $20-million new study involving 20,000 people launched in 2009 to study the effects of vitamin D and fish oil on cancer risk, cardiovascular disease, and strokes.  This study will take five years, and may prove to be the definitive study on the benefits of vitamin D.

Possible Detrimental Effects of Vitamin D Overdose

A recent study involving vitamin D supplement use found that there are no immediate adverse effects from the intake of vitamin D levels far above that recommended by the Institute of Medicine (IOM currently).  While examining the benefits of vitamin D for fall and fracture risk (optimal levels were discovered to be at 30-44 ng/mL, equivalent to approximately 1000 IU of vitamin D supplements per day), the study also discovered that vitamin D intake up to 10,000 IU per day caused no risk for elevated blood calcium.

The current Dietary Reference Intakes (DRI) for vitamin D as developed by the Food and Nutrition Board of the Institute of Medicine recommends a maximum of 600 IU of supplement intake per day, and only then for the elderly older than 71 years of age.  For those under the age of 50, the recommended daily supplement level is only 200 IU.  However, pursuant to new studies that highlight the myriad benefits of vitamin D and lack of strong evidence as to the toxicity of vitamin D at high levels, the Institute of Medicine is altering their recommended daily intake levels.  The new DRI is expected to be released on November 30, 2010.

Conclusion

Interest in vitamin D and its effects remain high, fuelled by new research results and widespread media attention.  No matter the possible life-saving benefits, it is at least very clear that vitamin D deficiency can lead to a whole host of problems, and should try to be remedied either through increased sun exposure or intake of vitamin D supplements.  In light of this and increased public awareness of the importance of vitamin D, sales of vitamin D supplements are expected to continue its upward trend in the near foreseeable future.

This article was written by Tracy Gu, of Nutralab Canada.  Nutralab Canada offers a complete one-stop-shop for all your contract manufacturing and private label needs, including contract manufacturing for dietary supplements.  Contact us today at 1-866-446-6766 toll-free or 905-752-1823 local, or visit our website www.nutralab.ca for more information.

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