I often blog about topics where I’ve done some research and thought I’d save you the time. On topics such as exercise non-responders (Or, are you a non responder?), intermittent fasting and women’s health (Intermittent fasting and why it might not work), and athletes and pain tolerance (Are athletes masochists?) I’m far from an expert in the field but I’ve read enough to have some conclusions to share.

But on some topics, I’m perplexed. I’ve read a fair bit but I’m still not sure what to think or do about Vitamin D.  Let’s start with the question that many of us in the northern hemisphere worry about, are you getting enough Vitamin D?

Some reports suggest nearly half the world’s population suffers from vitamin D deficiency, which is unsettling news given that a lack of vitamin D has been associated with a host of serious conditions: cancer, heart disease, diabetes, multiple sclerosis, tuberculosis and even depression, not to mention brittle bones and the common cold.

But it’s not clear that supplements help. See the Limits of Vitamin D Supplements.

A large review of studies has found that vitamin D supplements have little or no benefit beyond the low levels required for bone health.

The meta-analysis, published in The Lancet Diabetes & Endocrinology, combined data from 290 observational studies and 172 random trials. All the studies used blood levels of vitamin D to measure outcomes. Dosages varied, but most trials used 800 units or more.

The observational studies generally found an association of lower vitamin D levels with increases in cardiovascular disease, lipid concentrations, glucose levels, weight gain, infectious disease and mood disorders. But random trials showed little or no effect of vitamin D supplements on any of these problems. The authors conclude that low vitamin D levels are almost surely an effect of these diseases, and not a cause.

Current guidelines recommend supplements for anyone with a blood level under 30 nanograms per milliliter, but the lead author, Dr. Philippe Autier, said that only at levels of 10 or less would there be a risk to skeletal health. Less than 10 percent of Americans, he estimates, fall into this category. Dr. Autier is a researcher at the International Prevention Research Institute in Lyon, France.

“Unfortunately, there is probably no benefit to expect from vitamin D supplementation in normally healthy people,” he said.

See also, from Precision Nutrition, Vitamin D supplements: Are yours helping or hurting you?

Almost every expert recommends it. And everyone’s taking it. But what if we’ve been using it wrong? What if our vitamin D supplements aren’t really helping us at all?
If your car’s oil light went on once a week…and every time you checked the oil, it was running low…what would you do?
Shrug? Top up the oil tank (again)? Do your best to forget about it?
Or would you try to figure out the cause? Why that oil light kept coming on? Why your oil was running low?
If you’re smart, you take your car to the mechanic. Where you learn that low oil is just a symptom. There, the mechanic looks for the real problem.
Why, then, don’t we take the same approach with our health? With our supplements?
Why’s that vitamin D low?
Research over the last few years has indicated that a large percent of the world’s population is low in vitamin D. However, the response to this is kinda strange.
Healthcare practitioners typically test a patient’s vitamin D levels and notice that they’re low.
Then s/he prescribes a vitamin D supplement.
The patient comes in again a few months later and vitamin D is still low.
So the doctor increases the supplement.
Interestingly, very few professionals ever ask: Why is this person’s “vitamin D tank” leaking in the first place?

In case you thought indoor tanning in the winter was a reasonable response, think again. The Canadian Cancer Society says, “Using tanning beds may increase vitamin D production, depending on the type of bulbs used (only UVB radiation can stimulate vitamin D production). But tanning beds are not a safe way to get vitamin D. There are safer ways to get vitamin D.”  Read more: http://www.cancer.ca/en/cancer-information/cancer-101/what-is-a-risk-factor/sun-and-uvr-exposure/indoor-tanning/?region=bc#ixzz3Kby7OdJm

The International Skin Cancer Foundation puts in in stronger terms.

No … no… no! A tanning bed will never provide you with the vitamin D that you need, nor is it safer than tanning outdoors. Not understanding the facts can literally mean the difference between life and death. Both ultraviolet A (UVA) and ultraviolet B (UVB) radiation cause cell damage that can lead to skin cancer. When you lie in an indoor tanning bed, you are exposed primarily to UVA, which penetrates deep into the surface of the skin, damaging the cells beneath and prematurely aging your skin. But it is UVB (the sun burning rays) — not UVA — which helps the skin make vitamin D, so you are increasing your risk of skin cancer without receiving any benefit!

As for the claim that tanning beds emit a controlled dose of UV radiation, a “controlled dose” of UV radiation from a tanning bed is a dangerous dose: frequent tanners using high-pressure sunlamps may receive as much as 12 times the annual UVA dose compared to the dose they receive from sun exposure.

It’s estimated that 10 minutes in a tanning bed matches the cancer-causing effects of 10 minutes in the Mediterranean summer sun. This may be one reason that indoor tanners are 74 percent more likely to develop melanoma, the deadliest form of skin cancer, than those who have never tanned indoors, and that people who use tanning beds are 2.5 times more likely to develop squamous cell carcinoma and 1.5 times more likely to develop basal cell carcinoma, the two most common skin cancers. In addition to increasing your risk of skin cancer and accelerating signs of skin aging like wrinkles and brown spots, UV radiation also weakens the immune system — which further increases your risk for skin cancer. While there is no question that vitamin D is essential for strong bones and a healthy immune system, current evidence does not support its role in the prevention of breast cancer, colorectal cancer, heart disease and stroke. Adults should obtain their recommended daily dose of 600 IU (international units) of vitamin D safely, from foods such as oily fish and fortified dairy products and cereals. Another easy way to ensure you are getting enough vitamin D is to take supplements. I strongly advise against exposure to artificial UV radiation (tanning beds), since the health risks — including skin cancer and premature skin aging — are significant and potentially life-threatening.

But should we test everyone for vitamin D deficiency?

There are problems with making vitamin D tests a standard part of preventive medicine, a federal panel said. The U.S. Preventive Services Task Force said Monday there’s not enough evidence of benefits or harms to recommend vitamin D testing for all. And even though some studies have associated low levels of vitamin D with a long list of ills, including a higher risk of fractures, falls, heart disease, colorectal cancer, diabetes, depression, thinking problems and death, scientists who evaluated studies for the USPSTF say there is no direct evidence that universal screening would reduce those risks. “The effect of vitamin D levels on health outcomes is difficult to evaluate,” the recommendation statement says.

So what do I do for now? I get outside in the sun when it appears. Walking my dog helps. And I do take a Vitamin D pill in the lowest sun months. Given the above I’m not sure it’s doing me any good but it’s a low enough dose that it’s not doing me any harm either.

What do you do about Vitamin D in the winter? Why? (And although I’m a professor and this is exam season, I don’t mean that question in an exam like way! I’m curious about what decisions others make when it’s not clear what the facts are.)