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Vitamin D: Do Coloradans Get Enough?

Posted by admin on 16 August, 2009

When a friend mentioned taking vitamin D supplements, I scoffed. Everyone knows that a little sun exposure is enough for our bodies produce enough vitamin D, right? Although Colorado isn’t ranked in the top five sunniest states, we still get a lot of sun. Since I am an outdoor-loving Coloradan, I never worried about getting enough vitamin D. However, after a bit of research, I realize that maybe I should worry.

Why is vitamin D important to health?
Vitamin D is necessary for calcium and phosphorus absorption, bone growth and bone strength. It is necessary for preventing osteoporosis and rickets. Additionally, vitamin D deficiencies are correlated to some very serious health problems such as certain cancers, multiple sclerosis, Chrohn’s disease and other autoimmune and infectious diseases.

Dietary sources
One way we can obtain vitamin D is from our diet. Only several foods contain vitamin D. Certain fish products (cod liver oil, salmon, tuna and sardines) provide the most, followed by fortified milk, fortified juices and cereals, eggs, beef liver, and cheese. Dietary vitamin D may also be obtained through supplements as D2 or D3. The D3 form is currently shown to have wider benefits.

Sun exposure
The other method of obtaining vitamin D is through sun exposure. UVB rays penetrate the skin and divide cholesterol-like molecules in the epidermis of the skin into vitamin D. However, spending a few minutes in the sun does not produce adequate amounts of vitamin D for many people. Other factors must met:

* Time of day: exposure must occur between 10 AM – 3 PM
* Length of exposure: anywhere from 3 – 60 minutes if the face, arms and hands are exposed
* Frequency of exposure: two times per week
* Skin tone: lighter skin synthesizes vitamin D faster than dark skin
* Latitude and season: latitudes exceeding 42 degrees do not receive enough UVB light for adequate vitamin D synthesis during the 6 months of winter. Latitudes from 0 – 32 degrees get enough throughout the year. Grand County lies at approximately 40 degrees, so we may get slightly more than 6 months of adequate UVB exposure.
* Obstructions to exposure: sunscreen, cloud cover, pollution
* Elevation above sea level: If you live at higher elevation, the atmosphere is thinner and you receive more UVB rays

How much do we need?
The answers to this question are commonly debated. The US Institute of Medicine of The National Academies recommends the daily “Adequate Intake” (AI) of vitamin D to be between 200 and 600 International Units (200 IU of vitamin D are equal to 2.4 micrograms). However, in 2007, articles challenging this number emerged from the Harvard School of Public Health and American Journal of Clinical Nutrition. Researchers claimed that the number is much too low for optimum health benefits. Those researchers suggested that the figure for daily AI for adults should increase to 1,000 to 2,000 IUs and that some people may need up to 4,000 IUs per day.

The dramatic jump from 200 to 2,000 IUs may raise concerns about the safety of taking so much more vitamin D. The Institute of Medicine maintains that more clinical trials are necessary to determine risks of taking vitamin D supplements above existing recommended levels. High vitamin D levels may result in calcium and phosphate deposition in the kidneys and other soft tissues. Toxic vitamin D overdose from supplements generally occurs after 40,000 IUs are taken daily over a long period of time. Symptoms may include nausea, vomiting, confusion and heart rhythm abnormalities. If you want to know how much vitamin D you should be taking, you may ask your physician to order a blood test for vitamin D.

Sun exposure can generate more vitamin D than is typically required. According to McGill University researchers, in the right conditions, a white adult in a bikini can accumulate as much as 10,000 IUs of vitamin D in 15 – 20 minutes. This is five times more than the Institute of Medicine’s “Upper Limit” (UI) figure. However, a vitamin D overdose from sun exposure is not possible because the vitamin is degraded by UVB rays after a certain point. Although sunlight will not cause toxic levels of vitamin D, it does frequently cause skin cancer. The American Academy of Dermatology states that any unprotected exposure to UV rays increases the risk of skin cancer. Therefore, the AAD unsurprisingly recommends that vitamin D be obtained exclusively from dietary sources.

So, how much sun exposure do Coloradans need?
This is a difficult question to answer since there is so much controversy regarding the right amounts to obtain and the safety of UV exposure. However, to get a rough idea of how much sun exposure I might need to get 1,000 IUs of vitamin D, I used an online calculator created by the Norwegian Institute for Air Research. I entered data indicating that I am fair skinned, live in Denver, and it is summer. The results told me that I only need to expose my face, arms, and hands to the sun for 4 minutes midday, every other day. I found this number pleasantly achievable. However, during the winter, I would need to expose the same amount of skin for 45 minutes. Unfortunately, the chilly temperatures and frequent snowfalls prevent me from basking sleeveless in the sun for 45 minutes during the winter.

I must admit, I rarely take vitamins although I know I should. I try my best to get my vitamins from the foods I eat, and I think I do a fairly good job. However, after learning more about vitamin D, I doubt that I am getting an ideal amount during the winter months when the sun is lower in the sky and I stay bundled up in my scarf, hat and gloves. Since vitamin D deficiency may be linked to such debilitating diseases as MS and cancer, I don’t want to take the risk. Whether it’s a capsule of cod liver oil or a pill of the synthesized stuff, this Colorado gal is going to be supplementing this winter.

Vitamin D Resources:
National Institute of Health
World Health Organization
Harvard University