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Posted in: Articles by ProSource, Supplement Articles, Vitamins and Minerals
By Chad Kerksick, PhD | Jun 20, 2013

Links to Strength, Bone Mass, and Immune
Function Underscore Vitamin D's Importance

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We're all guilty of it in one way or another. Whether you're a researcher, an athlete or both, we all like to consider ourselves well-informed. We can tell you every last detail of how that buffered creatine works, or why one pre-workout formula might be superior to another. On our way to working our tails off to get stronger and build bigger muscles, we read the literature and we stay up to date on the latest developments in the field of sports performance and nutrition.

And yet we sometimes lose sight of the most important basics in our diet. And those oversights are the ones that come back to bite us in the end. For instance, what would you say, if I were to suggest there's a very good chance you're deficient in a basic vitamin? A vitamin that has been linked to support of strength, bone mass, and immune function? Impossible, you say?  Impossible because you pay attention to every last detail in your diet?  

Well, let's talk about vitamin D.  That's right, one of the four fat-soluble vitamins. It's just assumed that because our milk, cereals and bread are fortified with vitamin D that poor or deficient levels are only for less fortunate people or people who live in a Third World country.  A number of studies, however, conducted in various parts of the world report that vitamin D levels in our blood are routinely lower than commonly accepted thresholds.  Equally surprising, these levels have been reported in young and old people as well as in several different groups of athletes (Willis 2008).

How Do We Get Vitamin D?
The best way to get vitamin D is via exposing our skin to sunlight.  Easy enough, right?  Actually, it depends on where you live and the time of the year.  Winter-time in the Midwest and Northeast often offer prolonged periods of poor exposure to the sun and studies have shown that vitamin D levels do indeed change with the seasons.  Also, of course, warnings about skin cancer have sent enormous numbers of people scurrying for the shade at every opportunity. These facts of life suggest that additional dietary Vitamin D may be necessary. Several dietary sources offer vitamin D, including fatty fish, mushrooms, egg yolks and various fortified foods (Willis 2008). Finally, supplementation with vitamin D is an option which will discussed in more detail later.

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Am I Really Low in Vitamin D?
Many people don't know their vitamin D levels, but it is something you can ask your doctor to check.  Recommended levels are 75 -- 80 nmol/L (Willis 2008) and several studies in the general public and a few studies in athletes have indicated that vitamin D levels are indeed low.  For starters, one study of 165 young adults between the ages of 18 -- 29 years in Boston, MA found that 36% were deficient (below 50 nmol/L) at the end of the winter (Tangpricha 2002).  A second example in a group of young athletes reported that 68% had a level below 37.5 nmol/L and 13% were below 10 nmol/L (Lehtonen-Veromaa 1999).  Another study of 85 competitive German athletes reported that 37% had levels below 25 nmol/L (Bannert 1991), which was also supported in a study performed in running athletes in Louisiana (Willis 2007).  While aggressive dietary habits can improve your intake of vitamin D, several scientists have recommended vitamin D supplementation.

How Much to Supplement?
No clear answer exists at this point, but one study in competitive athletes reported that supplementing for three months with 400 IU of vitamin D per day, the same amount commonly put into a multi-vitamin/multi-mineral supplement, had no impact over increasing vitamin D levels in the athlete's blood (Lehtonen-Veromaa 1999).  On the other end of the spectrum, published studies have reported that taking 10,000 IU per day for up to 5 months did not cause toxicity and appear to be safe (Willis 2008), but this by no means should be interpreted as a recommended dose.  A number of studies were summarized by a review on vitamin D and reported recommended supplementation levels of 800 – 5,000 IU/day with the most commonly recommended range being 1,000 – 2,000 IU/day (Willis 2008).

How Will Vitamin D Impact My Performance?
For starters, optimal levels of vitamin D are critically important for optimal health and strength of your bones.  Studies in a number of different populations have shown that people with low blood levels of vitamin D have a greater risk for bone fractures.  More importantly, however, might be the fact that studies also indicate the risk for stress fractures (something many athletes must be concerned about) is linked to the amount of vitamin D in your blood (Willis 2008).  In addition to bone health, a few studies have indicated that optimal levels of vitamin D can help to control the inflammation which occurs after every stressful workout and also work towards strengthening your immune system.  You can't train intensely if you are sick, and you can't get geared up for the next workout if you can't recover.

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Vitamin D also has the potential to impact your athletic performance.  For starters, research completed by Russian and German scientists indicated that improved athletic performance occurred after repeated exposure to artificial ultraviolet radiation (the same exposure you get from being in the sunlight).  Much of this work remains a big mystery and secret, however, but other studies also point to improved strength, particularly in older populations.  For example, a number of studies have reported that poor vitamin D status is associated with reductions in strength and poor physical function (Willis 2008).  In other words, people who had the lowest levels of vitamin D also had the lowest strength levels and the poorest indicators of physical function.  While much more research is needed, particularly in studies with healthy athletes, previous research has also shown that women stroke survivors who supplemented with vitamin D at a dose of 1,000 IU/day for two years saw increases in both the number and the size of Type II muscle fibers (Sato 2005).

Consider a Superior-Quality Vitamin D Supplement
In conclusion, it only makes sense to make sure your Vitamin D levels are where they should be. In addition to the food sources listed above, a good, solid Vitamin D supplement like ProSource brand Vitamin D-3 contains 5000 IU of this fat soluble vitamin from superior sources. If you're not already taking a top-quality multi-vitamin/mineral supplement, you're really shortchanging yourself nutrition-wise.  ProSource's Super MegaMax is an excellent example of a multi designed specifically for the nutrient demands of active athletes. Likewise, ProSource's Vital Men's is another specialized complex targeted to men's active lifestyles. Both contain Vitamin D in suitable amounts.

Years of research surrounding vitamin D indicate first that it is an extremely important nutrient for the health of your bones and to support a healthy immune system and control the inflammation which occurs as a result of your workouts.  Only recently, however, has the importance of vitamin D towards your muscle been considered.  Research tells us that optimal levels of vitamin D can have an impact on both the health of your muscle and how your muscle performs.  More specifically, available research findings indicate that: 1) vitamin D levels in many people are not at appropriate levels and 2) when vitamin D is low, performance changes related to strength and muscle function are decreased.  Increasing your vitamin D can occur by getting out in the sun more frequently, eating foods high in vitamin and supplementing your diet with a vitamin D supplement.  Your muscles will thank you for it.

Have you ever gone to the doctor for a blood test and been surprised by the results? Tell us in the comment section below!

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Disclaimer: The articles featured herein are for informational purposes only and should not be construed as medical advice. Specific medical advice should only be obtained from a licensed health care professional. No liability is assumed by ProSource for any information herein.

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