Vitamin D supplements might not be doing what you think for your cardiovascular health! In fact, claims of change in certain cardiovascular risk factors derived from Vitamin D itself that you produce endogenously are likely overstated.
A study just published in this month’s edition of the American Journal of Clinical Nutrition looked at how correcting Vitamin D deficiency with supplements or UV light (UVB) changed markers we use to assess risk of heart disease.
Manish and pals randomized individuals with Vitamin D levels below 20ng/mL to UVB or oral supplementation groups. The primary endpoint measured was LDL cholesterol. Treatment lasted 8 weeks. At the end of the treatment period the UVB group and oral supplementation group had similar suppression of parathyroid hormone and increases in Vitamin D levels of 14ng/mL and 33ng/mL, respectively. There were no clinically significant differences in lipid profile.
If you look at the baseline characteristics of subjects, their lipid profiles were not too bad! There certainly was room for improvement in my book. Some have beat up on this study for not including subjects with lipid profiles indicating greater risk for heart disease. But you might also argue that if Vitamin D had a significant bearing on cardiovascular risk, these subjects with baseline Vitamin D levels of 13-14ng/mL should have had uglier lipid profiles!
That being said, we know there are other risk factors for heart disease, and this study only looked down one alley. Hypertension or obesity for instance. But we know disordered lipoprotein metabolism is up there.
There certainly are epidemiological studies suggesting that those with lower Vitamin D levels have greater risk of suffering from chronic degenerative disease. But here’s the thing. In those studies, it is those with the diseases that have the lowest Vitamin D levels. Is the low Vitamin D level cause or consequence?
When we try to tease out this detail with more controlled trials, we find that correcting vitamin D deficiency with supplements results in minimal change or none at all. Despite this discordance between the epidemiology and controlled trials, prescribing oral vitamin D is a common practice.
The issue here is that there are many reasons your Vitamin D levels can be low. Further, simply taking a supplement reinforces poor behavior. That behavior being cutting corners on efforts to get good sun exposure, regularly.
Vitamin D and Sunlight
You need that sun exposure!
Many of you know Vitamin D is produced in your skin. Your skin cells secrete a substance called dehydrocholesterol. UVB converts dehydrocholesterol into a Vitamin D precursor. What you may not be aware of is that the precursor is converted into a number of other compounds. And like the earlier part of the story, these conversions require sunlight.
You can see this in the graphic below.
There is little we know about these Vitamin D metabolites, but it’s thought that they have systemic effects.
One of the most interesting things about this study is that oral Vitamin D and UVB treatment had different effects on the immune system.
From Manish and Friends…
“Interferon signaling was consistently upregulated with oral Vitamin D and downregulated with UVB. More generally, several other immune signaling pathways were downregulated in blood after UVB treatment including complement, inflammatory-response, and IL-6 signaling pathways; meanwhile complement signaling and IL-6 signaling were upregulated with oral Vitamin D in the skin.”
“…during exposure to sunlight there are innumerable photochemical and biological processes that occur in the skin. These include, among others, the production and release of nitric oxide, carbon monoxide, and b-endorphin; increased expression of the proopiomelanocortin gene, resulting in an increase in adrenocorticotropin hormone; and enhancement of collagen synthesis and wound healing, to name a few.”
“In addition, it is well documented that solar exposure has a direct influence on the immune system, inducing immune tolerance and enhancing the production of cathelicidin to reduce infection by virulent pathogens.”
Translation. Appropriate sunlight exposure has the potential to:
-Decrease blood pressure
-Decrease likelihood of infection
-Help you heal faster
I’ve actually been told, “I’m taking a Vitamin D supplement. I don’t need sunlight.” This is short sighted. Clearly, taking a supplement is far different from getting your Vitamin D from sun exposure.
What does this all mean?
Low levels of Vitamin D are likely a proxy for a deeper health issue in the context of chronic disease. A big culprit being infection, which you can read more about here.
If you have low levels of Vitamin D and your metabolic profile suggests you are at increased risk for cardiovascular disease, you should not expect a supplement to do much of the leg work for you. You might not expect sunlight alone to do that either.
What is going to decrease your risk factors are the basics. Cleaning up your sleeping habits, eating a nutrient dense diet, appropriate activity levels and destressing. Locking these components down should be supplemented with appropriate sunlight exposure.
Get your sunlight exposure
The authors in this recent publication subjected participants to a phototherapy unit an average of 2 treatments weekly ranging anywhere 45 seconds to 4.5 minutes depending on skin type. This was sufficient to create a 17 ng/mL change in 8 weeks.
While treatment with a phototherapy unit produced a response, it is likely better to opt for actual sun exposure. It wouldn’t surprise me if there was some element missing from tanning units that you would be getting from sun exposure.
It’s a good idea to aim for daily exposure during the middle of the day. Duration depends on season, skin type and how much skin you can expose. Stripping naked for most of us just isn’t practical. I usually find a quiet place during my lunch hour where I can ditch my shirt. If you’re a little shy, you can carry a meshed singlet. Like a basketball jersey. Kobe or Iverson, works.
Pay attention to your skin during your time out in the sun. When your skin starts to look a little flushed, you’ve had enough. Obviously, if you have darker skin this can be a little harder to gauge. You’ll have to experiment and see what works for you.
You should work with your doctor, and regularly monitor your Vitamin D levels. You can use these readings to determine whether or not you are at least getting enough sun exposure to optimize your Vitamin D levels.
All of that being said, if Vitamin D levels remain low in the face of regular exposure to sunlight, you may need to ask other questions. You can read about those questions here.
Ponda, Manish P., et al. “A randomized clinical trial in vitamin D–deficient adults comparing replenishment with oral vitamin D3 with narrow-band UV type B light: effects on cholesterol and the transcriptional profiles of skin and blood.” The American Journal of Clinical Nutrition 105.5 (2017): 1230-1238
Holick, Michael F., and Arash Hossein-Nezhad. “The D-lemma: narrow-band UV type B radiation versus vitamin D supplementation versus sunlight for cardiovascular and immune health.” The American Journal of Clinical Nutrition 105.5 (2017): 1031-1032
Oh, Susan, Rita R. Kalyani, and Adrian S. Dobs. “Modern Nutrition in health and disease.” Wolters Kluwer Health Adis (ESP). 201