If you’re health-conscious, you know something about Vitamin D.

If you’re health-conscious and you live anywhere that has a real winter, you’ve likely worried about whether you’re getting enough of this vitamin.

For the often kooky world of “health and wellness”, Vitamin D has undergone an enormous amount of research. More than most things you’ve probably heard are beneficial to good health.

There are over 70,000 published papers on this vitamin (three times more papers than vitamin K which is another fat-soluble vitamin).

But what the sum of these papers indicate still isn’t well understood: Talk to 5 “health experts” about Vitamin D and you might get 5 different answers.

In this article, I’d like to give the current scientific consensus on Vitamin D and discuss what it means you should (or shouldn’t) do about your own levels of this vitamin.

What Actually Is Vitamin D?

It is a fat-soluble vitamin which is derived from cholesterol. It would be safe to say that this vitamin is ‘trending’ in the published scientific literature. There is growing interest in its role of in a wide range of chronic diseases such as cancer, heart disease, and autoimmune disorders.

There are also a set of tangible health benefits to Vitamin D supplementation that are well established by serious research.

It’s Proven To Improve Bones

Vitamin D supplementation has been shown to reduce the risk of osteoporosis and fracture in older patients. A meta-analysis of seven randomized clinical trials showed that vitamin D3 supplementation at doses of 700 IU reduced the risk of hip fracture by 26% and nonvertebral fracture by 23% (Bischoff-Ferrari).

The fracture protective effect was not seen at lower doses of the vitamin replacement such as 400 IU.

It’s Proven to Reduce Falls

The deficiencyof vitamin D causes muscle weakness which increases the risk of falls. A meta-analysis of five clinical trials involving 1237 patients showed that vitamin D supplementation at 700 IU per day reduced the risk of falls by 22% (Bischoff-Ferrari).

It’s Proven to Reduce Cancer Risk

Studies show that low levels of 25-hydroxy vitamin D (<20 ng/ml) are associated with an increased risk of cancer of the colon, prostate, and breast. Outcomes in patients with cancer who have low levels of 25-hydroxy vitamin D are also worse (Holick).

It is thought that the vitamin exerts an anti-cancer effect by inducing cell death and cutting off the blood supply to malignant cells.

It’s proven to Reduce Hypertension

People with high blood pressure who were exposed to ultraviolet light (three times per week) were noted to have a 180% increase in vitamin D levels and a reduction in both the systolic and diastolic blood pressure (Krause). It also is beneficial in patients with cardiac failure.

It’s proven to reduce Death

A comprehensive meta-analysis looked at the effect of vitamin D on all-cause mortality (death from all causes). The review looked at 56 trials in 95,286 participants (aged 18 – 107) in high-income countries (Bjelakovic). Trials included in the analysis involved supplementation with either D2 or D3.

The study found that only D3 supplementation reduced mortality. D2 did not significantly affect mortality. In fact, a sub-group analysis showed that this vitamin can actually increase mortality.

The D2 versus D3 Controversy: Are All Sources Equal?

There are two main forms of ‘the big D’ – Vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). The World Health Organization regards the two as equivalent. Emerging science suggests that D2 and D3 supplementation may not be equal (Houghton).

A number of clinical studies in the literature demonstrate that D3 is more efficient than D2 at raising serum 25 hydroxyvitamin D levels (Heaney, Trang, Tripkovic L Wilson LR).

A systematic review of the literature identified seven high quality randomized human clinical trials that compared the effects of D3 and D2 supplementation on 25 hydroxyvitamin D levels (Tripkovic L, Lambert H). Studies included in the meta-analysis were conducted in the USA, Australia, Canada, Denmark, and Italy.

Overall, the meta-analysis showed that D3 was statistically more efficacious at raising serum 25 hydroxyvitamin D levels than D2.

There are a number of possible explanations for the superiority of D3 over D2. Firstly, the half-life of D3 is longer than that of D2 which means that it stays around in the blood longer.

Secondly, D3 is better at binding to the receptors, proteins, and enzymes which are essential in the life-cycle of vitamin D.

Thirdly, D2 seems to activate enzymes that break down both D2 and soured D3 obtained from external sources.

Bottom Line

Undiagnosed vitamin D deficiency is common worldwide (Lips). Vitamin D supplementation has well-established benefits.

But sources are important. Current research suggests D3 supplementation may be more effective than D2 supplementation at actually increase your body’s levels of the vitamin.

For getting more D3, there’s nothing like sunlight. Sensible sunlight exposure can increase fat stores of D3 which can then be released slowly if sunlight is not available. Recommendations are to expose arms and legs for 5 to 30 minutes twice-weekly (Holick).

When the sun isn’t an option, dietary supplements can work to increase vitamin levels. Just remember the main form of supplemental vitamin D in Europe, Japan, Canada is D2 whereas D3 is the key form used in supplements in the USA.

Ensuring adequate D3 intake via sun exposure, regular oily fish, and good quality D3 supplements is essential for our overall health and well-being.


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