Sunlight vs. Vitamin D

[Reposted from my blog entry on Emergent Fool]

You may have heard there is an epidemic of low vitamin D levels in the U.S.  An estimated 60% of Americans are at a level that has been correlated with increased risk of nearly all chronic diseases, including cancer, heart disease, diabetes, autoimmune diseases, and depression.  My personal belief is that the epidemiology is horribly flawed.  But perhaps not in the way you might think….

As most people know by now, we humans photosynthesize vitamin D in our skin when it is exposed to direct sunlight.  How fast depends on our ethnicity and amount of exposure.  Since I’m light skinned and get a lot of sun in my normal life, it came as a huge surprise when some routine bloodwork I had done about 9 months ago indicated I was “dangerously low.”

My doctor immediately prescribed large doses of vitamin D supplement, but I was convinced that the result was spurious.  Perhaps it was due to an abnormal period of low sun exposure.  After all, I’d been traveling quite a bit and thus not outside much.  Plus, maybe the jet lag was disrupting my metabolism in some way that impacted vitamin D levels?

I vowed to get my 20 minutes of sunscreen-free, noontime exposure per day.  (Morning and late afternoon sun is useless for vitamin D production, and sunscreen blocks the UVB rays which initiate it).  In addition I intended to eat more oily fish (like sardines) as they contain vitamin D.   Though most experts agree it’s almost impossible to get what we need from food alone, I know that such foods are good for me in other ways.   My plan was to get checked in three months and I was confident that I could raise my vitamin D levels back into health range without supplements.

After three months my test came back… unchanged!  This was very alarming.  The medically acceptable range is between 30 and 74, but I was coming in at 15.  These numbers refer to the freely available levels of 25-hydroxy D in your bloodstream.

A brief aside about vitamin D: it’s not really one substance.  There are many different biomolecules that are involved in a complex cycle that initiates when the sunlight hits your skin.  It’s just a few of the many byproducts of this cycle that we call “vitamin D”.  25-hydroxy D is the one we typically measure, but to focus on this one substance seems unwise given how complex the cycle is.  Personally, I’ve come to think of vitamin D not as a noun but as a verb, as in the “vitamin D process” (with kudos to Danny Hillis for coining this metaphor with the verb “cancering”).

Before I resigned to taking the supplements, I did some googling and stumbled across this video which alerted me to a possibly key factor I was ignorant about: soap.  Turns out that if you wash with soap within 48 hours of sun exposure, you are not getting the full benefit.  That’s because you are washing off the D3 that the sun photosynthesizes when it hits your skin.  And it takes 48 hours to fully absorb into your bloodstream, where it is a critical element in the vitamin D process.  So I switched to the recommended “soap only where the sun don’t shine” strategy.  Three weeks later I got a home testing kit and my count almost doubled to 28.  A month after that, I was within range at 34.

Now, it should be noted that these 25-hydroxy tests (whether performed at home or by your doctor) are notoriously poor indicators of pathology.  Even still, I was advised that with a count of 15 it was very unlikely that I was maximally healthy, even though I hadn’t shown any symptoms yet.  Had my low D state continued, the prognosis is that it was a matter of time before symptoms started appearing.  There is another test which measures functional vitamin D efficiency at the cellular level, and which is supposedly a better indicator.  But that I didn’t know about this test until I consulted with Dr. Myles Spar who is an MD with an integrative/holistic practice.  On that test I scored “above 50th percentile” in vitamin D health.  This was around the time of my second home test, where I scored barely within range at 34.  Thus, according to the more accurate test, I am currently fine, but according to the test that is universally used, I am still in danger and almost all MDs would recommend supplements for me.

For the most part, I’m against supplements, but when presented with possibly serious consequences, it’s seductively easy to justify popping the pills “just in case” they help.  After all, the epidemiology shows very strong correlation between absence of the chemical and presence of disease.  There are two problems with this logic, though.  Almost all bioactive substances become toxic at some dosage.  In the case of vitamin D supplements, they can become toxic even at normally prescribed dosages.

But ignoring the toxicity, there is a bigger problem: taking vitamin D supplements has NOT been shown to reduce mortality.  While supplements reduce melanoma incidence, so does sun exposure.  According to the data, the sunlight effect is so powerful that even sunburns may reduce your chances of dying of skin cancer.  Also, vitamin D supplements don’t appear to prevent autoimmune disease, whereas sunlight does.  Finally, obesity is doubly-linked with depression, which is correlated with lack of sunlight.

What does all this mean?

Here is a partial list of lessons I’ve learned about how complex systems theory applies to me as an individual:

• It’s appropriate to use blood level indicators to diagnose potential disorders, but it’s rarely beneficial — and quite often harmful — to treat such indicators directly with drugs.  I would rather understand the etiology and treat the pathology, not the symptoms.
• For every manufactured drug there are natural remedies which have been used for thousands of years without the high level of toxicity.  Many of these are at least as good as the drugs even when focusing narrowly on changing blood level indicators.
• I don’t want to take any substance chronically, whether it’s manufactured or natural.  The only exception would be if an organ stopped functioning properly and its biochemical output could not be manufactured naturally, e.g. if my thyroid was damaged beyond repair.
• Most of my body’s systems are homeostatic, meaning when they are pushed “out of whack” temporarily by outside influences, they move back to their previous state once the influence is taken away.
• In homeostatic systems there emerge one or more “set points” (aka chaotic attractors).  If pushed far enough away from one set point, the body naturally gravitates to a different one.
• The result being that it is often harder to achieve systemic changes than it is to maintain them.  This may be why it is harder for an obese person to lose weight than to maintain a healthy weight.
• A valid use of drug therapy is for acute conditions, to bring the body back into a healthy homeostatic set point (or stabilize the body while other interventions do so).

Combining these lessons with my own experience and the epidemiology, the vitamin D story is not so mystifying (to me at least):

• Why did my vitamin D levels drop suddenly and not bounce back once I resumed my normal lifestyle?
• Why did my vitamin D level double in a short period of time without taking supplements?
• Is there really an epidemic of low vitamin D?
• To what extent is this related to sunshine?
• How does the epidemiology relate to changes in lifestyle trends?

I’ll leave you with a final thought, and I’d be curious what you think.  Could there be an epidemiological tipping point?  One that either already happened, or that may be seen in the future?  How would we look for such an effect in the data?   How would we tell if it’s a true effect, or just something that we sought to discover and then used faulty statistical reasoning to “prove”?