Medical Journals

Vitamin D Deficiency: The Invisible Health Challenge

Vitamin D Deficiency: The Invisible Health Challenge
by Rachel Zambrano – Peaks Coaching Group

It’s been a little while since there has been a medical post on TitaniumGeek. A good friend of mine – Rachel “Ruby” Zambrano – is an excellent triathlete, firefighter, and if I’m completely honest, a bit of a geek as well (as far as I’m concerned that is a compliment)

We’ve had many chats about optimizing an athletes body from both a nutritional but also medical perspective. I’ve always had a leaning towards endocrinology – hormones and the chemicals that make us work, Ruby, has had a burning interest in Vitamin D (which is actually a hormone, not a vitamin D) – but I’ll let her tell her own story about the why’s and wherefores of that.

The actual “Vitamin D” is a misnomer, as the chemical we get from the sun, is cholecalciferol (Vit D 3) is actually a pre-hormone, that gets converted by the body into the active “vitamin” D hormone (1,25 dihydroxyvitamin D)

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But rather than a chemistry lesson, I’m going to stand aside, and allow Ruby to tell you her story.

This post saw the light of day as part of Ruby’s work of Peaks Coaching Group. Being a coach is not just about telling people how many reps to do, but is about looking after the holistic athlete – Mind, Body and Nutrition. As a result Ruby is building a great name for herself in the field, which is why Peaks have snapped her up to work with their athletes and write great pieces like this:

Vitamin D – An Introduction

As an athlete and a multi-sport endurance coach, I’ve learned that there is so much more to sports than just the workout. Nutrition and health are arguably the foundation of the athlete but with perhaps the least focus. Every aspect of the well-tuned athlete comes back to wellness, whether professional or amateur and yet, there’s so much that doesn’t get the attention it deserves. We, as athletes and coaches, joke somewhat truthfully about how we ride because we love to eat, or we run because the road is a good listener, but it’s these motivations that, if they remain an afterthought, threaten to derail the best training of talented athletes.

Vitamin D may seem like a strange topic of conversation for fairly healthy athletes, but a recent conversation with an athlete, in turn, spurred a conversation with my physician.  Once I started digging a little deeper, I realized that vitamin D levels have significant implications for athletes at all fitness levels.

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Vitamin D plays an important role in maintaining good health.  For most of us, it seems something we seldom consider except as just another vitamin/supplement we all find in a dizzying array in our local grocery store or chain pharmacy. It is vitally important that we consider if we have sufficient Vitamin D levels due to the fact that most of us don’t get enough sun on exposed skin throughout the week.

Many adults are vitamin D deficient, and if the data is credible, the numbers top more than a billion people worldwide (1)

My experience with this was limited until that athlete suggested that I get my own Vitamin D levels tested.  What information I initially found was not particularly well organized nor was it very helpful.  On the other hand, knuckling down and combing the research, I realized that the information I was reading was important for other athletes to see, and that they should also have access to a summary of why it is so important.  So… let’s start at the beginning.

The Beginning – Where Vitamin D Comes From:

Vitamin D comes from two sources: it can be synthesized when UVB light from the sun’s rays strikes the skin, or it can be taken in by diet.13 Unfortunately, wearing sunscreen can reduce production of Vitamin D by up to 95% percent 2, and if you’re like me (fair skinned), the sun might as well be kryptonite.  It is estimated that 50-90% of our Vitamin D comes from sunlight (8)

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The Middle – What Vitamin D does for the body:

Vitamin D is required to properly absorb dietary minerals like calcium and phosphorus in order to provide us with effective healthy bone turn over, without it, we can end up with problems – Rickets being a classic from history, with Vitamin D deficient children ending up with bow-legs

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In addition to the obvious bony pathology, evidence-based studies suggest  Vitamin D actually widespread effects on the body.  Thus it is easier to describe Vitamin D by disease and the impact of Vitamin D deficiency on that particular disease, rather than a list of possible changes:


  • Vitamin D allows for better absorption of calcium in the body
  • Insufficient Vitamin D levels stimulate parathyroid hormone synthesis, resulting in the body potentially pulling calcium from the bones, essentially thinning the bones, increasing the risk of fracture


  • Epidemiological data showing serum values show an inverse relationship between incidence of cancer and Vitamin D for prostate, colon, breast, lung and marrow/lymphoma, among others – across several human and animal studies

Infection and Immune Response

  • Studies have indicated that the body is better able to fight off infection when Vitamin D levels are optimal


  • One Finnish study indicated the prophylactic effect of Vitamin D supplementation during the first year of life against diabetes later in life
  • Studies indicate Type I and II diabetes are associated with low Vitamin D levels

Hypertension/Cardiovascular Disease

  • Vitamin D levels and hypertension are strongly associated
  • Myocardial infarction risk varied inversely with Vitamin D levels (3)

Other sources indicate fat-soluble vitamins (Vitamin A, D, E)  are related to hair and nail strength. Vitamin D is also an important part of the discussion when it comes to mental health, but seasonal depression is the most obvious effect of insufficient Vitamin D levels (9). Studies in the last decade indicate that there is a positive relationship between pregnancy health and Vitamin D levels, suggesting most women would benefit from supplements during this time

Now that we’ve covered the medical part, let’s get down to why it’s important to you and me as athletes.

More Middle – What Vitamin D Does for ATHLETES

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Muscle mass, strength, and function all share a direct relationship to Vitamin D levels.12  Studies indicate that in trained athletes muscle fiber size varies proportionally with Vitamin D levels. In 1985, a Vitamin D receptor was identified within muscle fibers, ultimately being identified within other tissues, including smooth muscle, heart muscle, liver, lung, colon, gonads, and skin. This means that these tissues the end organs – ie the target location – for Vitamin D’s activities within the body, and as you can see, that is most of the body .5  The referenced study goes on to describe how Vitamin D has a multi-factored role in muscle strength and contraction.  In one study, among preoperative patients with sports injuries, more than 50% of the patients were diagnosed with Vitamin D deficiency, while one-third of those patients were Vitamin D insufficient.

To summarize the previous paragraph, athletes with low Vitamin D levels tended to have smaller, weaker muscles, and higher risk for injury.

In addition to muscles, we need to talk health and nutrition.  Athletes tend to be at higher risk of infection during the peak of their training.  A portion of us may spend seasons dealing with gut issues, only to have to spend another season figuring it out again when things change.  Low Vitamin D levels are linked to inflammation in the gut and irritable bowel syndrome, although cause and effect are difficult to determine.6  When cold and flu season rolls around, Vitamin D deficient athletes also tend to catch more than their fair share of whatever is going around at the time, even though they may be eating correctly and getting adequate exercise. Ultimately, athletes with low Vitamin D levels face more gut issues and more colds/infections than athletes with optimal levels.

Low Vitamin D – The Symptoms

Vitamin D levels are classified as normal, insufficient, deficient or severely deficient. The exact point at which one’s blood levels correspond with a specific range is still being debated as the science develops, but for the most part, they are as follows:

  • Insufficient = 20-30 ng/mL
  • Deficient = 10-20 ng/mL
  • Severely Deficient = <10 ng/mL

It should be noted here that at least one study indicated minimum ideal levels for athletes be 50 ng/mL.

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The symptoms of Vitamin D deficiency are wide and varied.  They focus primarily around:

  • Fatigue
  • Muscle weakness/painFrequent illness
  • Frequent illness
  • Weight gain
  • Bone softening or fractures
  • Depression and mood changes/irritability
  • General unexplained weakness
  • Features associated with inflammatory bowel syndrome
    • Bloating
    • Nausea
    • Vomiting
    • Abdominal Pain
    • Exercise-related diarrhoea

Anecdotal reports also suggest that symptoms may include similar symptoms to menopause like hot flashes and night sweats – but without studies proving the correlation – esp as Vitamin D does not influence menopausal symptoms. (11)

In discussing this article with others, are also different standards in different countries on what Vitamin D levels are acceptable for athletes, which in turn reinforces the need for further, focused research.

Next Steps

When was the last time you saw your physician?  The best thing to do is to go back and see him/her and get a good, thorough physical.  To be honest with you, it’s a great idea to have a physical every year anyway – set that baseline.  Your doctor may look at you with an “eyebrow raised” when you ask for a full blood panel including electrolytes and vitamins, but when you explain why, they may, in fact, support your request.

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Ladies, see if your doctor will include bone density test, especially if you tickle the bottom of that “healthy body fat percentage” during racing season.  Both men and women should consider a heart scan at least once now and again when their doctor recommends it.  Our kids are doing a ‘heart health for sports’ physical – Why aren’t we, as adults, expecting the same thing from ourselves? The heart health goes back to “muscles are affected by Vitamin D levels, the heart is a muscle.”


Not all deficiencies will require formal treatment, many people can get sufficient vitamin D from their diet. The best foods to eat in order to incorporate more Vitamin D in your diet naturally are egg yolk, fatty fish, fortified dairy products and beef liver.

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Of course, you can also increase Vitamin D levels outside of diet with sun exposure, but for some people that is not possible. If you are one of the lucky people with access to the sun, the recommendation is 15-20 minutes with 40% of the skin exposed. (8)

If your doctor does recommend treatment, they will also recommend what dosage and the method of supplementation.  Due to Vitamin D’s interactions with multiple body systems and its relationship with electrolyte balance, it would be ill-advised to self-medicate at high levels without consulting your physician.

End – Staying Healthy

If Vitamin D levels are low, and supplementation is required, it may take days to weeks to notice a difference.  Since deficiencies don’t occur overnight, supplementing, regardless of the method won’t alleviate the symptoms of the deficiency overnight, thus patience is required. Most of the studies referenced saw a noticeable improvement in subjects by 12 weeks.

Ultimately, the goal is to remain healthy.  Many of us started this journey to take better control of our health. We need to make sure that we are taking care of ourselves while we are racing, training, and in our daily lives.


There are a few people who helped with this article that I need to thank. Amber was the inspiration for the article and the result was an incredible learning opportunity. My husband Gabe – he listened while I poured over the material and worked through all the “if this, then that” pathways that led to the realization that as coaches and athletes this was something we needed to be aware of.  To my partner in coaching, Chris Myers, M.S., CISSN (Ph.D. Candidate, Exercise Physiology, Florida State University) – His education and experience gave him the ability to vet the article for me before sending it out for public consumption, given how impactful the material has the potential to be.  Thank You all!

Who I am – Rachel Zambrano

A fire department Lieutenant and a paramedic with 20+ years of experience, so much of the health and wellness aspects of coaching cross paths with the fire service. I’m a mom, a wife, a firefighter, a women’s’ sports advocate, and a lover of snarky t-shirts!

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1 Naeem, Z. (2010, January). Vitamin D Deficiency- An Ignored Epidemic. Retrieved March 01, 2017,
2 Nair, R., & Maseeh, A. (2012). Vitamin D: The “sunshine” vitamin. Retrieved March 01, 2017,
3 Heaney, R. P. (2008, September 01). Vitamin D in Health and Disease. Retrieved March 01, 2017,
4 Seshadri D, De D. Nails in nutritional deficiencies. Indian J Dermatol Venereol Leprol [serial online] 2012 [cited 2017 Mar 1];78:237-41.
5 Hamilton, B. (2011, December). Vitamin D and Athletic Performance: The Potential Role of Muscle. Retrieved March 01, 2017,
6 Ardesia, M., Ferlazzo, G., & Fries, W. (2015). Vitamin D and Inflammatory Bowel Disease. Retrieved March 01, 2017, 
7 Calton, E. K., Keane, K. N., Newsholme, P., & Soares, M. J. (n.d.). The Impact of Vitamin D Levels on Inflammatory Status: A Systematic Review of Immune Cell Studies. Retrieved March 01, 2017, 
8 Naeem, Z. (2010, January). Vitamin D Deficiency- An Ignored Epidemic. Retrieved March 01, 2017,
9 Vitamin D vs broad spectrum phototherapy in the treatment of seasonal affective disorder. (n.d.). Retrieved March 01, 2017,
10 10 Vitamin D Deficiency Symptoms You Can Identify Yourself. (2017, February 08). Retrieved March 01, 2017, 
12 The effects of vitamin D deficiency in athletes. (n.d.). Retrieved March 01, 2017, 
13 Vitamin D and human skeletal muscle. (n.d.). Retrieved March 01, 2017, 
14 Bodnar, L. M., Catov, J. M., Simhan, H. N., Holick, M. F., Powers, R. W., & Roberts, J. M. (2007, September 01). Maternal Vitamin D Deficiency Increases the Risk of Preeclampsia. Retrieved March 01, 2017, 
15 Athletic performance and vitamin D. (n.d.). Retrieved March 01, 2017