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Can You Make Enough Vitamin D from Sunshine Alone?

Centuries ago, Hippocrates observed that the “sunnier side of the hill” was the healthier place to live. Thus, he routinely prescribed sunbaths as part of his therapy for a wide variety of health ailments.

While sunshine provides many benefits, the one with the greatest impact is likely the production of vitamin D.


A common misconception, even by some health care providers, is that “you probably get enough vitamin D with about 15 minutes of sun exposure to the face, arms, and hands at least twice a week without sunscreen.” But is this true?


In fact, it is very unlikely for most individuals, with today’s modern lifestyle, to get enough vitamin D from their sun exposure alone.  While blood levels below 30ng/ml are considered deficient, most Vitamin D experts recommend a minimum level of 40ng/ml and prefer closer to 60ng/ml.

Vitamin D Levels among Individuals Who Don’t Supplement

Let’s first look at data from: GrassrootsHealth.  Participants who were health conscious, but did not take a vitamin D supplement, never reached the target of 40ng/ml at any point in the year and were only at or above 30ng/ml from July – November.  In other words, they never achieved sufficient levels of Vitamin D at any time and spent the majority of the year being outright DEFICIENT in Vitamin D!


Considering the importance of Vitamin D for the Immune System, strong Bones,  good mood, cancer prevention, muscular strength and coordination and pretty much the health of every tissue and organ in your body, relying on the sun for your Vitamin D doesn’t seem to be a good strategy.  In addition, it pretty much guarantees that you will be outright deficient in the wintertime just when you need it the most for immune support.



An interesting article in the journal: Nature Immunology, March 2010, illustrates the central role of vitamin D in supporting a healthy immune system.  Before you read these quotes, it's important to understand that T-cells are powerful immune cells, critical to mounting a strong immune response against a foreign pathogen such as a virus or bacteria.  Professor Geisler, lead author of the article explains:

“When a T cell is exposed to a foreign pathogen, it extends a signaling device or “antenna” known as a vitamin D receptor, with which it searches for vitamin D.”  “This means that the T Cell must have vitamin D or activation of the cell will cease.  If the T cells cannot find enough vitamin D in the blood, they won’t even begin to mobilize.”

Now that’s incredible!!  You literally, cannot mount a strong, healthy immune response without adequate levels of vitamin D. 

In another study in the Journal of Clinical Endocrinology and Metabolism, seniors with higher levels of vitamin D were able to walk faster, rise from a chair faster and balance better.  Conversely, 90% of the seniors with the lowest physical function had insufficient or deficient levels of vitamin D.

A study from McGill University in Canada, published in the same article, found that insufficient blood levels of vitamin D may be associated with the accumulation of fat in muscle tissue, leading to lower muscle strength.  

Multiple studies have shown that seniors with adequate levels of vitamin D have better learning, memory, mood and cognitive function than their peers with suboptimal levels. Higher Vitamin D levels are associated with better mood.

Recent research from the Archives of internal Medicine shows a frank connection between low levels of vitamin D and increased risk of both nonfatal and fatal heart attacks in men.

Vitamin D2 vs D3 – Which Should You Take

Studies show the Vitamin D3 is the better form to Supplement with.  In fact a recent study in Frontiers in Immunology, showed that the two forms have very different effects on the transcription of various genes important for healthy immune function. In addition, Vitamin D3 appears to have more potency in terms of raising Vitamin D levels in the wintertime.


The question becomes: How much should one take to increase Vitamin D levels to optimal which is at least 40 and preferrable 60+ ng/ml.
The answer is: it varies.  I live in NY, where it is impossible to make vitamin D in the winter due to the sun being lower on the horizon.  I take 10,000 IU’s from November through April.   The rule of thumb is that if you live north of Atlanta, you probably don’t make vitamin D in the winter.  Another good rule is the shadow test: If your shadow is longer than you are, the sun’s rays are not strong enough for you to make vitamin D.   

I lower my intake to 2,000 IU’s per day from May to mid October because during this period the sun’s rays are strong enough to make ample vitamin D. I’m a fitness buff, so I’m outside a lot and get plenty of sun (recall, the skin is responsible for making vitamin D upon exposure to direct sunlight).  If you don’t get out in the sun much during summer, or use sunscreen regularly, you will probably need to maintain higher levels of supplementation even in the summer months.  Note that sunscreen effectively blocks the UV B rays which are what create vitamin D when they come in direct contact with your skin.  So, if you regularly use sunscreen, keep your supplementation levels up closer to 5,000IUs even in the summertime.

Your doctor can check your vitamin D levels with a simple blood test.  The next time he/she orders blood work for you, ask him to check your levels of vitamin D by ordering a 25, hydroxyl vitamin blood test.  The levels should be above 30ngs/ml and
50-80 ng/ml is closer to ideal.  If your doctor won’t check your vitamin D level, you can order a kit from Life Extension Magazine: for only $35-.  If your level is significantly lower than 30ngs/ml you should start with 10,000 IU’s per day if it’s summer time and 15,000 to 20,000 IU’s in the winter time.  Keep that routine up for 2- 3 months and recheck your levels.  Adjust your dosage to stay close to 60 ng/ml.

Eat well, exercise, smile and supplement wisely.  That’s how we’ll age gracefully together.

Neil Levin DC  5/17/22