Vitamin D3 (the active form of vitamin D) is proving to be one of the most overlooked and important vitamins in health and fitness – and just as an FYI, it is not a true vitamin, but rather a steroid hormone. Regardless, thanks to recent research we are gaining an immense amount of knowledge about this vitamin and how it plays into health and performance.
Vitamin D receptors on cells have been found to serve as an “on/off” switch for various cellular functions relating to the immune system, muscle function, inflammatory responses and mental state1. Without adequate vitamin D, as is the case for the majority of the population, these processes may not be fully switched on. Furthermore, vitamin D plays a pivotal role with calcium and phosphorus absorption and therefore contributes to bone and teeth health.
You may be familiar with the fact that our bodies actually produce vitamin D via direct skin contact with UV-B light from the sun; this sun exposure has been found to produce the majority of vitamin D required by our body. However, we typically will not get enough sun exposure to boost vitamin D levels and our diet will likely not make up for this deficiency (Table 1). Additionally, the following variables reduce our ability to reach optimal vitamin D levels: dark skin colour, life-style habits, body fat percentage, restricted exposure to natural sunlight, and sunscreen use1.
The risks associated with vitamin D deficiency are: impaired immunity, risk of stress fracture, depressed mood, inflammation, musculoskeletal pain and reduced strength/power2,3,4,5,6,7. It is important to note that these symptoms can be especially prevalent in winter months. Also, please be aware of milder symptoms such as fatigue, aches and pain, as they tend to sneak under the radar and/or can be misdiagnosed.
What can you do? Get tested! The 25-Hydroxyvitamin D (25 OH D) blood test can be performed to assess your vitamin D levels. There is a fee for this test, but it is the best way to know your levels conclusively. If you choose not to get the test, speak to your nutritional consultant, naturopath or family doctor about vitamin D.
Most individuals, including myself, require a vitamin D supplement. The Canadian government set the recommended daily allowance for adults at 800IU, with an upper tolerance limit of 4000IU8; however, most health care professionals will suggest higher doses. Seek the advice of a professional and get a better understanding of what dose is right for you (the blood test will be the best indicator). It is also noteworthy to share that vitamin D absorption is enhanced by vitamin K2. Therefore, it is important to incorporate foods that contain vitamin K2 (dairy and meat) or vitamin K1 (peaches, green leafy vegetables; which is supposed to be converted to K2 in the body) and/or look for a supplement that contains a complex of vitamin D3 and K2.
The effects of vitamin D on health are significant and this “super” vitamin is continuing to make a name for itself. That being said, it can be easy to fall into the trap of “more is better” so frequently pushed in our society. Supplement if deficient and be aware that too much, or too little, of anything is bad.
Vitamin D Source
Summer Sunshine minutes
Table 1 – Dietary Sources of Vitamin D
Adapted from Keen (2010)
1. Keen R. The importance of vitamin D in human performance. NSCA’s Perfromance Training Journal. 2010; 9(6): 8-9.
2. Aloia JF, Li-Ng M. Epidemic influenza and vitamin D. Epidemiol Infect. 2007; 135: 1095-96.
3. Cannell JJ, Vieth R, Umhau JC, Holick MF, Grant WB, Madronich S, et. al. Epidemic influenza and vitamin D. Epidemiol Infect. 2006; 134(6): 1129-40.
4. Cox AJ, Gleeson M, Pyne DB, Callister R, Hopkins WG, Fricker PA. Clinical and laboratory evaluation of upper respiratory symptoms in elite athletes. Clin J Sport Med. 2008; 18(5): 438-45.
5. Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes: Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride. Washington, DC: National Academy Press, 1997. Retrieved February 28, 2011 from http://ods.od.nih.gov/factsheets/vitamind/.
6. Lehtonen-Veromaa M, Möttönen T, Leino A, Heinonen OJ, Rautava E, Viikari J. Prospective study on food fortification with vitamin D among adolescent females in Lansdowne, ATG, and Provost, SC. Vitamin D3 enhances mood in healthy subjects during winter. Psychopharmacology. 1998; 135: 319-23.
7. Larson-Meyer, DE and Willis, KS. Vitamin D and athletes. Curr SportsMed Rep. 2010; 9(4): 220-
8. Health Canada. Vitamin D and Calcium: Updated Dietary Reference Intakes. Retrieved February 28, 2011 fromhttp://www.hc-sc.gc.ca/fn-an/nutrition/vitamin/vita-d-eng.php.