Thursday, May 31, 2012

Vitamin D

The Essentials of Vitamin D

Vitamin D is one of the most misunderstood and important nutrients for human health.

What Exactly Does Vitamin D Do in Your Body?
  • Helps to maintain strong bones and teeth
  • Enhances the strength and efficiency of your immune system, which decreases your risk of developing autoimmune conditions like rheumatoid arthritis and lupus
  • Helps your body regulate its blood sugar levels, playing an important role in preventing type II diabetes
  • Helps to prevent high blood pressure
The conventional medical perspective on vitamin D is that you can get all that you need by exposing your arms and legs to sunlight for 10 minutes a day. If only it were that simple!

It's true that a great source of vitamin D is sunlight. Sunlight contains ultraviolet (UV) rays that come in three different lengths: UV-A, UV-B, and UV-C. UV-B rays are the ones that are capable of producing vitamin D in your body by acting on the cholesterol found in your skin.

The reason why conventional advice about getting 10 minutes of exposure to sunlight everyday is woefully simplistic is that the amount of UV-B rays that reach your skin and produce vitamin D depends on a variety of different factors, the main ones being:
  1. Skin Colour
    Lighter skin colour allows deeper penetration by UV-B rays, which decreases the amount of sunlight exposure needed for adequate vitamin D production. Needless to say but I'll say it anyway, the darker your skin, the harder it is for UV-B rays to penetrate it and produce vitamin D, increasing your need for sunlight exposure.
  2. Season
    People living in Canada, Europe, and the lower 48 states of America receive little to no UV-B rays from early autumn to late spring.
  3. Altitude and Latitude
    The higher you live above sea level, the greater exposure you have to UV-B rays. The higher you live above the equator, the less exposure you have to UV-B rays.
  4. Pollution and Clouds
    Both decrease the number of UV-B rays that reach you.
  5. Age
    As people age, natural degenerative changes that occur in skin make it harder for UV-B rays to convert cholesterol to vitamin D. Elderly people typically need to rely more on food sources than sunlight for their vitamin D needs.
So How Much Do You Need?
The current Dietary Reference Intakes by the Institute of Medicine range from 200 to 600 IU per day depending on age, with the U.S. upper limit for vitamin D being 2,000 IU per day. Ultimately, the most responsible recommendation that I can make is to strive to take in no more than 800 IU per day without regular blood testing for vitamin D status. This number takes into account my own clinical experiences as well as the work and recommendations of Krispin Sullivan, C.N., and Reinhold Vieth, M.D., both of whom have a wealth of experience and knowledge regarding the relationship between vitamin D and human health.

Here are some healthy food sources of vitamin D:
Food Sources
Vitamin D (IU)
3 ounces
1 teaspoon
Sardines, canned
3 ounces
1 medium

How to Test Your Vitamin D Status
If you plan on getting more than 800 IU of vitamin D per day, I highly recommend that you have your blood level of vitamin D monitored about once every 6 months. Ask your doctor or laboratory for the 25(OH)D test, also known as the 25-hydroxyvitamin D test. Please note that some labs do a similar test called 1-25(OH)D test, which is not as accurate a marker of your vitamin D status.

If your test shows a level lower than 20 ng/ml (50 nmol/l), you have a higher than average risk for prostate and breast cancer, as well as autoimmune conditions like rheumatoid arthritis and lupus.

If your test shows a level higher than 70 ng/ml (175 nmol/l), you have a high risk of suffering from kidney stones, heart disease, and bone loss. Please know that while having too little vitamin D in your blood is a huge problem, having too much vitamin D in your blood can cause equally dangerous health problems.

I believe that a healthy range for the vast majority of people is between 35-50 ng/ml (87.5-125 nmol/l).


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