What's the Deal With Vitamin D?

Vitamin D and Strength Training – A Potent Combo to Reduce Dangerous Visceral Fat

 One of the most exciting findings is that vitamin D supplementation combined with resistance training may help decrease your waist-to-hip ratio – a measurement that is far better at determining your risk for type 2 diabetes and heart disease than body mass index (BMI).

The study, published in the journal Clinical Nutrition,¹ included 23 overweight and obese participants, all of whom completed 12 weeks of resistance training. Half of them also received 4,000 IU's of vitamin D, while the other half got a placebo. Interestingly, analysis revealed an inverse association between the change in vitamin D status and the change in waist-to-hip ratio.

According to the authors:

"The results of the current study demonstrated that vitamin D supplementation improved muscular power in healthy overweight and obese individuals within four weeks and that elevated vitamin D status was associated with greater losses in waist circumference, with no additional benefits in lean mass accumulation, muscular strength, or glucose tolerance during participation in a 12-week resistance exercise training program.

The current results support previous findings that indicate a relationship between vitamin D status and waist circumference rather than fat mass. The inverse relationship with waist circumference is particularly important as abdominal fat has been implicated as an important factor in the development of Type 2 diabetes... 

Waist circumference is also an independent risk factor for cardiovascular disease. Therefore, the greater decrease in waist circumference associated with higher vitamin D intake represents a potential reduction in risk for metabolic disease and cardiovascular risk.

 More Evidence Vitamin D May Help Prevent Type 2 Diabetes

Additional support for the theory that vitamin D can be beneficial in the fight against type 2 diabetes was published in June.³Here, the researchers found "a strong additive interaction between abdominal obesity and insufficient 25(OH)D in regard to insulin resistance." They also claim 47 percent of the increased odds of insulin resistance can be explained by the interaction between insufficient vitamin D levels and a high BMI. They concluded that:

"Within a cross-sectional, nationally representative sample, abdominal obesity and insufficient 25(OH)D interact to synergistically influence the risk of insulin resistance."

Yet another study⁴ published in Diabetes Care also suggests vitamin D supplements may help prevent type 2 diabetes mellitus in people with pre-diabetes. While the study is only an observational one and cannot establish causality, the researchers report that the participants who had the highest vitamin D levels were 30 percent less likely to develop diabetes during the three-year evaluation period, compared to those with the lowest levels.

Vitamin D Shows Eye Health Benefits

Next, a study⁵ published in January found that supplementing with vitamin D3 helps rejuvenate aging eyes by reducing inflammation and amyloid beta – a risk factor for age-related macular degeneration, which is the leading cause of blindness. According to the authors:

"Vitamin D3 plays a key role in immune regulation and may protect against the aging process. A focal point for age-related changes is the outer retina of the eye where there is high metabolic demand resulting in a gradual increase in extracellular deposition, inflammation, and cell loss giving rise to visual decline. Here, we demonstrate that vitamin D3 administration for only 6 weeks in aged mice significantly impacts on this aging process... Recently, vitamin D3 has been linked epidemiologically to protection against age-related macular degeneration. Hence, vitamin D3 enrichment is likely to represent a beneficial route for those at risk."

Dietary Vitamin D and Sun Exposure Linked to Reduced Alzheimer's Risk

Speaking of amyloid beta, this component is not just a risk factor for macular degeneration, it's also found in the brains of Alzheimer's patients. No wonder then that scientists have discovered an association between vitamin D status and your risk of developing Alzheimer's disease.⁶ As reported by Dr. William Grant for The Vitamin D Council:⁷

"This cohort included women over the age of 75 years at time of enrollment and was designed to study risk factors for hip fractures over a four-year period. Women who had taken vitamin D supplements in the 18 months prior to enrollment were excluded. Dietary factors and midday sun exposure habits were examined at time of enrollment. The mean dietary vitamin D intake was 334±172 IU/day. The presence of Alzheimer's disease and other dementias was assessed seven years after enrollment.

Those in the highest fifth of vitamin D intake had one-quarter the incidence rate of Alzheimer's disease as the other four fifths... In addition, those in the highest fifth of sun exposure had half the incidence rate of Alzheimer's disease..." "

Reminder: The Best Form of Vitamin D Does Not Come in a Pill...

Again, while this article is focused on research related to vitamin D supplementation, it's important to remember that the IDEAL way to optimize your vitamin D levels is through appropriate sun. While your skin does create vitamin D3 in response to sun light, which is theoretically the same as the D3 you get from an oral supplement, there's cause to believe that the vitamin D created from sun exposure may have additional health benefits.

If Taking a Vitamin D Supplement, Take the Right Form

Keep in mind that if you do opt for a supplement, make sure you're taking vitamin D3 and not the synthetic D2. This is important, as a recent analysis¹⁷ of 50 randomized controlled trials, which included a total of 94,000 participants, showed:

• A six percent relative reduction in mortality among those who used vitamin D3, but
• A two percent relative risk increase among those who used D2

Also, while Europe is doing the responsible thing by increasing the recommended daily allowance for vitamin D, it's important to realize that the most important factor is your serum vitamin D level (the level in your blood), not the dose. The only way to determine whether you're within the therapeutic range is to regularly test your vitamin D levels. If you're like most people, you'll likely need far more than 4,000 IU's a day. According to the most recent research, the ideal adult dose is closer to 8,000 IU's a day in order to achieve serum levels at or above 40 ng/ml.

That said, you really should be taking whatever dosage required to obtain a therapeutic level of vitamin D in your blood.