Normal Vitamin D Level: It Isn't What You Might Think
Many experts recommend a normal vitamin D level of 50 ng/ml (125 nmol/L) as indicated in a 25-hydroxyvitamin D blood test. Most North Americans are significantly below the recommended levels.
Fifteen minutes in the sun is insufficient in northern regions.
The NHANES study of over 15,000 people found that 75% of Americans had vitamin D blood levels below what is necessary to support optimal health.
A study conducted by the University of Calgary found that 97% of Canadians are vitamin D deficient at some point in the year.
Part of the problem lies with the popular belief that 15 minutes in the sun will provide all the vitamin D that we need. But this simple formula overlooks the many challenges faced by people living north of 42 degrees latitude...which includes any region north of Boston, Rome and Beijing.
In these areas there is insufficient radiation available for vitamin D synthesis from November to early March. Ten degrees farther north, this "vitamin D winter" extends to almost half of the year.
Conditions That Lessen Vitamin D From The Sun
In addition to the challenges in northern regions, there are other conditions that prevent sufficient intake from the sun.
- Men and women over the age of 50 have a reduced ability to produce vitamin D through the skin.
- People who remain indoors most of the time receive insufficient sunlight, as the ultraviolet radiation necessary for vitamin D production cannot penetrate glass.
- Dark skinned people need 20 - 30 times more exposure to sunlight than fair-skinned people in order to generate the same amount of vitamin D.
- Even weak sunscreens (SPF=8) block our body's ability to generate vitamin D by up to 95%.
Excessive reliance on sunshine and on the 15-minute rule can be one of the barriers to maintaining the normal vitamin D levels needed for optimal health.
Monitor Your Vitamin D With Blood Tests
The best way to monitor your normal vitamin D level is with regular blood tests. Understanding a little about the recommended range for a normal vitamin D level will help you to discuss the test results with your doctor and design a plan for meeting your personal target.
The results from a 25-hydroxyvitamin D blood test may be reported in two different formats. Canadian labs list 75-200 nmol/L as the optimal range... which translates into 30-80 ng/mL in many American labs. (1 ng/mL = 2.5 nmol/L)
Doctors will report that you have a normal vitamin D level if your test results fall within this range. In fact, many doctors will be delighted if you come near this range because they are so accustomed to seeing significant deficiency in their other patients.
People seeking to maintain a normal vitamin D level of 125nmol/L (50ng/mL) will want to know their exact test results so that they can adjust their sunlight exposure and supplements to achieve their target blood level.
Achieving An Optimal Vitamin D Level
The Vitamin D Council has found that most people begin to store the active form of vitamin D when they reach blood levels of 40 ng/ml (100 nmol/L)... and virtually everyone begins to store vitamin D at 50 ng/ml (125 nmol/L). Below these levels, the body is using up vitamin D as fast as it can make it.
There are 3 ways for adults to maintain a normal vitamin D level of 50 ng/ml (125 nmol/L). We can:
- expose as much of our skin as possible for fifteen minutes, to the midday sun in the late spring, summer and early Fall
- use a sun bed (avoiding sunburn) during the colder months, and
- take 5,000 IU of vitamin D supplements per day for 2–3 months prior to taking a blood test... and then adjust the supplement dosage until blood levels are between 50–80 ng/mL (125–200 nM/L) year-round.
If you're taking supplements, vitamin D is best absorbed when combined with the following elements:
Magnesium is the most important of these co-factors, as there is significant magnesium deficiency in North America... although vitamin K2 levels are also below recommended levels.
A high quality bone building supplement is often the best way to get a blend of the recommended elements and an additional 5,000 IU vitamin D gel tab is often recommended for people who know they are deficient.
Vitamin D Supplements Are Not For Everyone
Recent research has shown that vitamin D deficiency does not always result from insufficient exposure to sunshine but may also be the result of a disease process. Unlike vitamin D gained from sunlight, higher doses of vitamin D through supplements may suppress the immune system and make some illnesses worse.
People suffering from a chronic infection, inflammation or an autoimmune disease are especially encouraged to visit their doctor before increasing their vitamin D dosage through supplements.