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A Brief Look at the Importance of Ensuring Adequate Vitamin D Status
Posted by Dr. Ben Kim on Oct 29, 2009
I've been working to put together a comprehensive look at why ensuring that you're getting enough vitamin D is one of the most important ways you can prevent disease and increase your lifespan.
My full report should be ready in a few days, but until then, here's a look at a few essential details on vitamin D and some of what it does in your body:
Decreases your risk of all types of cancer
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
Lowers risk of developing Rickets (in childhood)
Helps to prevent high blood pressure
Since the 1980s and until just a few years ago, the conventional medical perspective on vitamin D was that you could get all that you need by exposing your arms and legs to sunlight for 10 minutes a day.
It's true that an excellent 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:
Skin Color: Lighter skin color allows deeper penetration by UV-B rays, which decreases the amount of sunlight exposure needed for adequate vitamin D production. So, 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.
Season: People living above 35 degrees latitude north or below 35 degrees latitude south receive little to no UV-B rays from early autumn to late spring.
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.
Pollution and Clouds: Both decrease the number of UV-B rays that reach you.
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. These numbers are woefully out of date, as they don't take into account a great deal of research on vitamin D and its effect on human health that's been published over the last several years.
Ultimately, the most responsible recommendation that I can make is to take a 1000 IU supplement every day - this applies to children and adults alike, even those who are already getting some vitamin D from an appropriate amount of cod liver oil. This number takes into account my own clinical experiences as well as the work and recommendations of Dr. Michael Holick of the Boston University Medical Center.
The only group of people that I can't recommend 1000 IUs for on a daily basis are those who live between 35 degrees south and 35 degrees north latitude and who get at least 15 minutes of sun exposure on their skin a few times a week. But even some of these people might need supplementation.
Most people should also strive to eat some foods that are naturally rich in vitamin D, such as:
|Food Sources||Serving||Vitamin D (IU)|
|Wild salmon, canned||3 ounces||530|
|Cod liver oil||1 teaspoon||400|
|Sardines, canned||3 ounces||231|
|Organic egg yolk||1 medium||25|
How to Test Your Vitamin D Status
If you plan on getting more than 1000 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 30 ng/ml (75 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 50-60 ng/ml (125-150 nmol/l).
If you're looking for a whole food supplement with a generous amount of vitamin D-3, the one that I use and recommend can be found here:
For a comprehensive look at this topic, including guidelines on how to get the right amount of sun for your skin type, please view:
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