Over the last few weeks, here in Western Pennsylvania, the weather has been rather typical January weather, with plenty of snow and miserable cloud covered days. However, today, and over the last few days, it has been a complete 360 as far as the weather goes. With the feeling of spring and the sun shining gloriously, it has been a true delight for everyone! For myself, it has meant being able to run outside, opposed to trudging on the infamous winter “dreadmill,” which got me thinking about my absolute favorite vitamin!
Do you know what vitamin I am talking about? If you did not catch the clue above, this vitamin is somehow associated with the sun….
I hope you said VITAMIN D! If you didn’t know this or you don’t know much about vitamin D, I am very, very excited to introduce you to the amazing world of vitamin D!
Some of you may be asking: “Why is vitamin D often referred to as the ‘sunshine vitamin?’”
Believe it or not, simply exposing your skin to the sun’s UVB rays can form vitamin D! This may sound simple, however the process, of course, is much more complex… Your skin absorbs the sun’s UVB rays this causes 7-dehydrocholestrol (found in your epidermis and dermis) to convert into previtamin D3 (1). From here the previtamin D3 is further converted into vitamin D3 due to the heat from the rays (1). This all occurs in your skin! However, vitamin D3 or cholecalciferol is NOT the Active form of vitamin D responsible for crucial roles in the body (2). Vitamin D3 has to go through further steps or metabolism to become the active form of vitamin D! It has to go through the liver and then the kidneys before it’s converted to the active form of vitamin D: calcitriol (1). Vitamin D consumed in the diet, either as ergocalciferol/vitamin D2 or as cholecalciferol/ vitamin D3, is broken down and absorbed with fat (vitamin D is a FAT soluble vitamin) (2). From here the dietary vitamin D MUST also travel to the liver and then the kidneys for the active form, calcitriol, to become available for important roles in the body (2).
What does vitamin D do? Why is it important?
In a nutshell, vitamin D’s (the active form: calcitriol) main role is to help manage levels of calcium in your blood and also helps your body absorb calcium and phosphorus (2). This is how vitamin D plays a role in bone health! If a child were to become deficient in vitamin D, it could affect and impair their bone growth and could potentially lead to rickets (weak, soft bones) (2). If an adult were to become deficient in vitamin D, it could also affect their bone health and potentially lead to osteoporosis (2).
Interestingly, there has been recent research that has shown that vitamin D (calcitriol) may be able to prevent other chronic diseases such as, high blood pressure, heart disease, diabetes, breast, prostate, and colon caners, fibromyalgia, multiple sclerosis and rheumatoid arthritis (3). Dr. Michael Holick summarized, “Investigators have recognized that living at higher latitudes and thus being prone to vitamin D deficiency increases the risk of dying of many common cancers, of developing several autoimmune disorders including type 1 diabetes and multiple sclerosis, and developing hypertension and cardiovascular heart disease” (pp. 392) (1).
I personally believe this is great reason for getting excited about vitamin D! However, I do believe more research needs to be done.
If you are interested in what diseases vitamin D research has been conducted on check out the National Library of Medicine and the National Institutes of Health’s Medline Plus website about Vitamin D. They have given ‘grades’ to research of vitamin D on various diseases. http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-vitamind.html
I also highly recommend that you listen to the CBC radio’s Quirks & Quarks program titled “The Vitamin D Miracle Cure.” There are also great links there about vitamin D.
According to many health professionals and texts the recommended exposure is 10-15 minutes everyday (2, 3, 4). However, wearing sunscreen will prevent the skin from making vitamin D (1, 3). Without wearing sunscreen for 15 minutes, exposing your face and hands should be adequate if you have light colored skin. If you have dark colored skin the recommendation for sun exposure is doubled at 30 minutes, due to skin melanin content (4). There are other factors that can limit production of vitamin D via the sun such as, the season (ex. Winter months), time of day, and latitude (ex. northern hemisphere, north of 42 degrees) (1). Interestingly, researchers and health professionals are finding that even those living in southern states may be deficient in vitamin D. For example, Jacobs et al. (2008) concluded, “Despite residing in a region with high chronic sun exposure, adults in southern Arizona are commonly deficient in vitamin D, particularly blacks and Hispanics (abstract). Another group at risk is elderly adults. As we age we have a decreased ability to make vitamin D when exposed to the sun’s UVB rays (1).
Natural Sources (2,3):
How much vitamin D do I need?
The following are the Dietary Reference Intake (DRI) for vitamin D, which include the Adequate Intake (AI) and the Tolerable Upper Intake Level (UL). (These do not account for vitamin D made by exposure to sunlight, only dietary sources.)
Age (years) | AI (micrograms/day) (IU/day) | UL (microgramsg/day) (IU/day) | |
Men & Women | 19-50 | 5 (200 IU) | 25 (1000 IU) |
Men & Women | 51-70 | 10 (400 IU) | 50 (2000 IU) |
Men & Women | > 70 | 15 (600 IU) | 50 (2000 IU) |
Pregnant & Lactation | < 18 19-50 | 5 (200 IU) | 5o (2000 IU) |
(1, 2)
About 2 cups of milk (fortified with vitamin D) per day would provide you with 5 micrograms or 200 IU (2).
With much recent research, many health professionals are recommending people consume much higher amounts of vitamin D than the recommended amounts (1). The position of the American Dietetic Association, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and Athletic Performance (2009) also acknowledge this point, “A growing number of experts advocate that the RDA for vitamin D is not adequate.”
Dr. Michael Holick, a renowned researcher in the field of vitamin D recommends and states the following, “Sensible exposure to sunlight during the spring, summer, and fall can satisfy most of our vitamin D requirement. In the absence of sun exposure, 1000 IU/day of vitamin D is effective in maintaining 25(OH)D levels in what is considered to be a healthy range” (pp. 393) (1).
As with other vitamins and minerals there is a thing called “too much” or toxicity! That is why there is the tolerable upper intake level for people to follow. I realize the UL is 1000 to 2000 IU for most individuals, yet many researchers and health professionals are recommending people consume the UL of 1000 IUs! Dr. Michael Holick writes, “Although the safe upper limit (UL) for vitamin D intake for children and adults was recommended to be 2000 IU/day by the Food and Nutrition Board, mounting evidence indicates that levels greater than 10,000 IU/day of vitamin D are more likely to cause vitamin D intoxication” (pp. 392) (1).
I highly recommend if you are interested in more information and research regarding vitamin D that you check out Dr. Holick’s website:
Dr. Holick is also a very informative and entertaining speaker, so I recommend that you check out a presentation by him:
Vitamin D and Prevention of Chronic Diseases- Presentation by Dr. Michael Holick
What are some sources of vitamin D besides sun exposure?
Unfortunately, there are not a whole lot of foods rich in vitamin D, but thanks to fortification we do have some good sources of vitamin D (2).
Fortified Sources (be sure to read the food label) (2,3):
Milk
Cereals
Some margarine
Fortified yogurts
Fortified orange juice
Fortified soymilk
Natural Sources (2,3):Fish oils
Salmon (especially canned with bones)
Sardines
Herring
Egg Yolks
Liver
If you want to know how much vitamin D (along with other nutrients, vitamins, and minerals) is in your favorite foods check out the following link:
Simply enter the name of the food in the search box and a list will appear. Choose the food that best match your food and hit submit at the bottom. Then enter the amount you eat or ate and hit submit. The nutrition information will appear for your food.
Am I at risk for being deficient in vitamin D? And what about athletes?
There are certain individuals who may be at a greater risk of being deficient in vitamin D, but before I continue on, if you are concerned about your vitamin D status and are interested in supplementing your diet with vitamin D, you should consult your primary physician first or a Registered Dietitian (RD)! The following are individuals and athletes, who may be at risk of being deficient of vitamin D:
- Indoor athletes- athletes who train indoors throughout the year, such as gymnasts and figure skaters are at risk, especially if they do not consume foods rich in vitamin D (3, 5).
- Allergies/Lactose Intolerant individuals- if someone is allergic to foods rich in vitamin D or those who are lactose intolerant to dairy foods rich in vitamin D (3).
- Geographic location- Individuals who live at northern latitudes (1, 5).
- Diet- individuals consuming fewer calories or restricting calories (3, 4).
- Vegans- who does not consume any animal products may be deficient in vitamin D as well as other important vitamins and minerals (3).
- Older Adults- remember above I mentioned how it becomes harder for older adults to be able to synthesize vitamin D from the sun. Also, older adults often consume fewer calories (3).
Obviously good bone health is imperative for athletes to be able to perform at their sport! Along with all of the new and exciting research about vitamin D and various chronic diseases, I hope you are now as excited as I am about vitamin D! Be sure to get some sun and foods rich in vitamin D daily! Hopefully this gives you some good reason to get outside and be active!
Disclaimer: I am not a licensed medical practitioner. The content expressed are my views, opinions and thoughts. I make concerted effort to use and reference scientific and evidence-based information and research. Before changing your diet or exercise regime you should speak to your primary physician. If you are interested in taking vitamin or mineral supplements you should consult your primary physician. The information expressed is for your pleasure and interest, it is not intended to diagnose, treat, prevent, or cure any disease.
REFERENCES:
- Holick, M.F. (2006). Vitamin D. In Shils, M.E., Shike, M., Ross, A.C., Caballero, B., & Cousins, R.J (Eds.), Modern nutrition in health and disease (10th ed.) (pp. 376-395). Baltimore, MD: Lippincott Williams & Wilkins.
- Hedrick Fink, H., Burgoon, L. A., & Mikesky, A. E. (2009). Practical applications in sports nutrition (2nd ed.). Sudbury, MA: Jones and Bartlett Publishers.
- Clark, N. (2008). Nancy clark’s sports nutrition guidebook (4th ed.). Champaign, IL: Human Kinetics.
- Dunford, M (Ed.). (2006). Sports nutrition a practice manual for professionals (4th ed.). Chicago, IL: American Dietetic Association.
- Position of the American dietetic association, dietitians of Canada, and the American college of sports medicine. (2009). Nutrition and athletic performance. Journal of the American Dietetic Association, 109(3), 509-527.
Links for more information:
Vitamin D
Vitamin Needs of Athletes
UW research finds athlete vitamin D levels wobbly; general public probably worse
Phys Ed: Can Vitamin D Improve Your Athletic Performance?
Vitamin D and Prevention of Chronic Diseases- Presentation by Dr. Michael Holick
http://www.youtube.com/watch?v=Cq1t9WqOD-0 
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