Who Cares about Vitamin D by muq18838



            By: Bryn Sharkey

Summer Work Program – May to August 2008

        Ste. Rose du Lac, Manitoba

      Supervisor: Dr. David O’Hagan
                                                                 Who Cares About Vitamin D?
                                                                              Bryn Sharkey
It has been known for almost a century that Vitamin D is critical to bone development.

Recent research suggests that vitamin D may have a much larger function in healthy

development and disease prevention. Furthermore, there is increasing concern that

vitamin D deficiency may be far more prevalent than previously anticipated.

Vitamin D is a fat-soluble vitamin that can be acquired through both diet and sunlight. It

is found naturally in very few foods but there are small amounts in cheese, fish (salmon,

tuna, mackerel) and egg yolks. Health Canada has made supplementation mandatory in

milk, margarine and other butter substitutes. Producers supplement voluntarily in some

breakfast cereals, yogurts and orange juices (1,2). Unfortunately, those living above 35

degrees latitude, which lies approximately around Atlanta, Georgia, are unlikely to

acquire enough sunlight at certain times of the year for adequate vitamin D production

(3). This is due to the oblique angle of the sun in fall and winter months as well as during

the early morning and evening hours. Thus it is not surprising that vitamin D deficiency

is a concern, especially for those living at higher latitudes.

A study published in CMAJ in 2002 from the University of Calgary estimated vitamin D

deficiency (serum levels <40nmol/L) in western Canadians to be greater than 34%, while

a recent clinical review published in May 2007 in the Canadian Family Physician found

levels of vitamin D deficiency in Canadians to be as high as 97% in the fall and winter

months (4,5). Because the levels of deficiency vary between different demographics, and

because a universally accepted level for vitamin D deficiency has yet to be established, it

is difficult to determine an exact proportion of the population which may be at risk.

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                                                            Who Cares About Vitamin D?
                                                                         Bryn Sharkey
Vitamin D deficiency can result from inadequate exposure to UVB rays from sunlight,

insufficient dietary intake, impaired absorption or increased requirements which are not

met over time(1). Vitamin D deficient diets are often associated with those who are

vegans or have milk allergies or lactose intolerance. However, several other populations

are also at risk. A 2000-2004 study as part of the NHANES (National Health and

Nutrition Examination Survey) revealed groups specifically at risk to be females, those

who are obese, and those with pigmented skin (1,6). The study found the prevalence of

vitamin D deficiency (serum 25-hydroxyvitamin D <25 ng/mL) among African

Americans to be ten times greater than the deficiency among Caucasians. The survey

however, was not designed to assess whether the deficiency had any impact on health. A

2003 report from Memphis revealed that twenty of the twenty-one cases of rickets

reported that year occurred in children of African-American descent (1). Other groups

reported to be at risk of vitamin D deficiency include exclusively breastfed infants, as

their mothers may be lacking in the vitamin, those with limited sun exposure such as

housebound individuals, those at northern latitudes, those who remain covered by

clothing or head coverings for religious or personal reasons, and those whose occupation

prevents them from sun exposure during the peak hours of the day. The increasing use of

sunscreen may be a significant contributor to Vitamin D deficiency. Older adults are at a

particular risk as both the skin and the kidney have a decreased ability to synthesize the

active form of vitamin D. People with a compromised ability to digest and absorb dietary

fats such as in pancreatic enzyme deficiency, Crohn’s disease, cystic fibrosis, surgical

removal of parts of stomach or intestines, or with some forms of liver disease are also at

risk of deficiency (1,3,).

                                       Page 3 of 10
                                                            Who Cares About Vitamin D?
                                                                         Bryn Sharkey
In the 1920’s, vitamin D deficiency was found to be the cause of rickets and osteomalacia

(1). This finding has significantly reduced the incidence of rickets in the developed

world. Apart from its well-known role in promoting calcium absorption in the gut to

assist in bone mineralization and growth, vitamin D has been proposed to have additional

potential benefits. Other roles of vitamin D include contribution to neuromuscular and

immune function, through the activation of mast cells and the potential to decrease

inflammation (1). Several genes involving proteins that function in cell proliferation and

differentiation are modified in part by vitamin D which prompted recent research

suggesting a role for vitamin D in the prevention of breast, colorectal and prostate

cancers (3).

An ever enlarging body of research suggests vitamin D may help prevent type 1 and type

2 diabetes, hypertension and multiple sclerosis (1,3,7). Most of these studies however,

were animal or epidemiologically based, and not randomized controlled trials.

When UVB photons from sunlight are absorbed into the skin, 7-dehydrocholesterol is

transformed into previtamin D3, which is then converted to an inactive form of vitamin D

with the aid of heat. The compound then diffuses into the capillary beds and is

transformed by the liver into 25 hydroxycholecalciferol (25(OH)D3), and the kidney into

its active form 1, 25(OH)2 D3 (3). For most individuals, only 5-15 minutes of

unprotected sun exposure to the arm and face during the spring and summer is required to

obtain 100% of the daily dose of vitamin D. However, excessive sun exposure cannot

cause toxicity, due to photodegradation of pre vitamin D3 (1).    Thus vitamin D toxicity

is unlikely and would have to result from a constant overdose of vitamin D supplements

over a long period of time (doses of 50 000 IU(International units)/day for eight weeks

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                                                            Who Cares About Vitamin D?
                                                                         Bryn Sharkey
were not shown to cause toxicity). It has been thought that vitamin D toxicity has the

potential to cause nausea, vomiting, constipation and increased blood calcium levels

which may lead to mental status changes, cardiac rhythm abnormalities and kidney

stones(1). One study has shown no toxicity at 10 000 IU of vitamin D, although this

study was not adequately addressed to assess harm (1).

Despite the growing body of evidence that requirements for Vitamin D are greater than

previously thought, Health Canada has yet to update its current 400 IU (International

Units)/day RDI (recommended daily intake), which was suggested in 1997 solely for the

prevention of rickets (3,8). Now many experts believe 1000 IU/day is necessary to

maintain adequate serum blood levels of vitamin D (>30mg/mL). Recently, the

Osteoporosis Society of Canada recommended all adults should consume at least 800

IU/day (9). The Canadian Cancer Society recommends all adults should consume 1000

IU/day, and breast fed infants should get 400 IU/day, especially during fall and winter

months (October to March) (8). For the elderly, those with dark skin, or those who stay

indoors or who wear clothing to completely cover skin, supplementation is recommended

year round. The Canadian Cancer society recommends a few minutes of unprotected sun

exposure per day, while it has not changed its guidelines for skin cancer prevention.

In response to the recent publicity, Health Canada plans to launch a study in the fall of

2008 to investigate claims that lack of vitamin D could lead to ailments such as cancer,

heart disease, and multiple sclerosis. There is rising pressure from the Canadian Cancer

Society and Canadian Pediatric Society to increase the recommended daily intake of

vitamin D because they believe the evidence warrants RDIs 5-10x higher than the current

recommendation (1,2,10). Developing a new recommended daily intake in North

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                                                            Who Cares About Vitamin D?
                                                                         Bryn Sharkey
America will prove difficult, due to the variation of susceptibility among different

populations, including geographic location, age and skin pigmentation.

To investigate the current awareness of vitamin D in the community of Ste. Rose du Lac,

MB, I surveyed 75 clinic patients on June 24, 25, and 26, 2008. The patient population

included both those with scheduled appointments and walk in visits. Ste. Rose is a

farming-based community, which also services several aboriginal reserves in the

surrounding area. My objectives were to assess awareness about vitamin D

supplementation, both the benefits and suggested doses, assess sun exposure, ask about

sources of health information and assess barriers people face to obtaining adequate

vitamin D. Without measuring the serum vitamin D levels, I hoped to make an estimate

of the potential for vitamin D deficiency based on diet, supplementation and sun


Given the demographic, I expected copious sun exposure in the spring and summer

months, but a potential for vitamin D deficiency in the fall and winter due to our northern

latitude. I also expected a lack of awareness about current vitamin D benefits and

recommendations, due primarily to the discrepancies in recommendations among various

health organizations, and the barriers to publicizing a consistent recommended daily

intake of vitamin D.

By the new standards set by the Canadian Cancer Society (1000IU/day), 93% of study

patients did not obtain adequate vitamin D intake year round (based on diet, sun exposure

and supplementation). According to the current Food and Drug Regulations (FDR)

guidelines (400IU/day), 73% were not obtaining adequate levels. As expected, the

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                                                             Who Cares About Vitamin D?
                                                                          Bryn Sharkey
estimated levels of deficiency varied widely with the seasons, with only 4% of people

being deficient in the spring and summer months.

Eighty-five per cent of study participants were unaware of any benefits of vitamin D, and

only 10% knew about benefits to bones. Sixty per cent stated that their primary source of

health information was from a health professional.

Thirty-five per cent expressed that no barriers prevented them from supplementing with

vitamin D, and 36% stated that it was a lack of awareness of the benefits, which

prevented them from supplementing their diets.

I have concluded from this study, that the potential for Vitamin D deficiency during the

fall and winter months is significant in this population, and these results could be

reasonably extrapolated to other northern communities. Moreover, the main barrier to

lack of this vitamin is a simple lack of awareness rather than lack of opportunity.

As primary prevention may be the most effective method to improve the health of the

population, health professionals should consider taking every opportunity to educate their

patients on nutritional status. As new research confirms further benefits of vitamin D and

allows us to reach a more definitive conclusion on the appropriate amount required for

good health, doctors and other health professionals will be more confident in informing

the public about supplementation.

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                                                        Who Cares About Vitamin D?
                                                                     Bryn Sharkey
Vitamin D Survey


1) Do you take any nutritional supplements? Yes/No (Circle one)
If yes….
a) Vit A ___ Vit B___ Vit C ___ Vit D ____ Vit E ____ Multivitamin ___ Calcium

If vitamin D supplement taken... Question 2+3
2)) what dose? 10mcg/400UI____ 25mcg/1000IU ____ unknown_____ other ____
3) Do you take it seasonally? Winter____ spring ___ summer _____ fall____

If vit D supplements NOT taken… Question 4
4) How do you get your vitamin D?
milk (amount in cups) ________ sun exposure _____other ____
5) Are you aware of the health benefits of vit D?
Support bone growth ____ immune function ____ reduce inflammation ____
cancer prevention___ other _____ none____
6) From what source do you get most information about health?
TV ____ Newspaper ____ Magazines ____ Internet _____ word of mouth _____
Health Professional _____ Other _____
7) If not taking vitamin D why not?
Cost ____ not aware of benefits ____ sufficient amount in diet____ other ___ none____
8) How many minutes of unprotected sun exposure do you get per day during the spring
and summer?
None____ 5 min ____10min____15min_____20 min____25 min____
>/=30 min_____
- Age:       Sex: M/F (Circle one)

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                                                           Who Cares About Vitamin D?
                                                                        Bryn Sharkey

1. Dietary Supplement Fact Sheet: Vitamin D. National Institute of Health: Office of

Dietary Supplements; c2008 [2008 May 16;cited 2008 June 15]. Available from:


2. Food and Drug Regulations. Health Canada. 2004 June. Division 8; B.08.003.

Available at: http://www.hc-sc.gc.ca/fn-an/alt_formats/hpfb-dgpsa/pdf/legislation/e_f-


3. Holick MF, Chen TC, Lu Z, Sauter E, et al. Vitamin D and Skin Physiology: A D-

Lightful Story. J Bone and Mineral Res. 2007;22:V28-33.

4. Rucker D, Allan JA, Fick GH, Hanley DA et al. Vitamin D insufficiency in a

population of healthy western Canadians. CMAJ. 2002 June 11; 166(12).

5. Schwalfenberg G. Not enough vitamin D. Canadian Family Physician. 2007 May


6. Prentice A. Vitamin D deficiency: a global perspective. Nutr Rev. In press.

7. U.S Department of Agriculture. Nutrient Data Laboratory. Search the USDA National

Nutrient Database for standard reference. Available at


8. www.cancer.ca [homepage on the internet]. Vitamin D. Canadian Cancer Society.

2008 June 8. [cited 2008 June 20] Available at:


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                                                         Who Cares About Vitamin D?
                                                                      Bryn Sharkey
9. Vitamin D: A key factor in Calcium absorption. Osteoporosis Society of Canada.

2007. Available at:



10. Mittlestaedt M. Canada orders vitamin D study. The Globe and Mail. 2008 May 10.

Available at:



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