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My expectation going into the conference was to learn the BLACK and WHITE facts to share with clients and colleagues. What I actually learned is that the science of vitamin D is a lot GREYER than I originally thought! The conclusion of the conference was "we don't know."
Seriously.
This topic is important, yet the experts seem unable to come to consensus about when, who, and how much to treat.
In the U.S. Preventive Service Task Force (USPSTF) statement published last month, they wrote that "No consensus exists on the definition of vitamin D deficiency or the optimal level of total serum 25-hydroxyvitamin D [25-(OH)-D] (the major form of vitamin D that circulates in the body). Depending on which cut point is used (usually less than 20 ng/mL or 30 ng/mL) some studies have shown that lower levels of vitamin D are associated with increased risk for fractures, functional limitations, cancer, diabetes, cardiovascular disease, depression and death."
First of all, the definition of deficiency is controversial.
- The U.S. Institute of Medicine (IOM) report from 2010 stated that "almost all individuals get sufficient vitamin D when their blood levels are at or above 20 ng/mL."
- One year later, The Endocrine Society released clinical guidelines, defining vitamin D deficiency as less than 20 ng/mL and insufficiency as 21-29 ng/mL.
- At the conference, I heard Michael Holick say that less than 30 ng/mL is deficient, 40-60 ng/mL is preffered and that up to 100 ng/mL is safe. This is echoed in his book The Vitamin D Solution.
Labwork - depending on the detection method used, the measured value of total serum 25-(OH)-D between laboratories vary by up to 15 ng/mL - which can mean the difference between sufficiency vs. treatment!
Individual requirements - vary according to genetic polymorphisms, usually fall within a bell-shaped Gaussian distribution
Effective dosage - studies may not use a high enough supplemental dose to impact initial vitamin D status.
Initial vitamin D status - most benefit is seen when deficiency is corrected (moving from deficient to sufficient). Without knowing what constitutes "deficient," studies working with populations who already have "sufficient" vitamin D status may not show any experimental impact and vice versa. There is a big difference between making sick people healthy and making healthy people healthier.
Validated Intermediate endpoint - does not exist (yet?) for vitamin D
There have been 247 new studies on Vitamin D in the last five years, but none of them change the recommendations for chronic disease. The strongest evidence in support of vitamin D supplementation is in bone health and fracture prevention, yet many family doctors are prescribing vitamin D for depression. This is partly due to vitamin D coverage in the media, where journalists claim that vitamin D may help with a whole host of diseases.
The USPSTF's Final Recommendation Statement is that "The evidence is insufficient to assess the balance of benefits and harms of screening for vitamin D deficiency in asymptomatic adults." In other words, they do not (yet?) recommend screening the general population for vitamin D deficiency.
In the U.S. Preventive Service Task Force (USPSTF) statement published last month, they wrote that "No consensus exists on the definition of vitamin D deficiency or the optimal level of total serum 25-hydroxyvitamin D [25-(OH)-D] (the major form of vitamin D that circulates in the body). Depending on which cut point is used (usually less than 20 ng/mL or 30 ng/mL) some studies have shown that lower levels of vitamin D are associated with increased risk for fractures, functional limitations, cancer, diabetes, cardiovascular disease, depression and death."
But that won't keep me from encouraging my clients to get their vitamin D levels tested. Especially if they live above the 40th parallel (for reference, Washington, DC is at 38.9° N, Boston 42.3° N, Seattle 47.6° N), have darkly pigmented skin, shield their skin from the sun with sunscreen and/or clothing, spend most of their time indoors, if their diet lacks dairy products and other vitamin D-fortified foods (orange juice, energy drinks, etc), or if they are obese.
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| You can get vitamin D from the sun! Your skin makes it! |
As a dietitian, I can help people manage current disease but I prefer to prevent disease in the first place. In addition to disease prevention, I also support optimum cellular function (i.e. helping you go from "good" to "great!"). That being said, here is my recommendation:
Get tested (insurance willing). If your vitamin D is less than 30 ng/mL (75 nmol/L), you should probably try to increase your level - through food, supplementation, or sun exposure - until your vitamin D falls between 30 ng/dL and 100 ng/dL.
Updated (12/10/2014): if you visit a Theranos Wellness Center, the cost of a vitamin D test is only 20.35. Read more here.
