Vitamin D for Athletes

 

With all the rage about finding the newest supplement for performance and recovery in the endurance world, we may not need to look any farther then a tried and true vitamin that is quickly becoming a major fixture in ergogenic aids for athletes (see SportLegs.com).

Vitamin D is best known for the supporting role it plays to Calcium in the formation and maintenance of strong teeth and bones, however, it is also extremely important in neuromuscular function and reduction of inflammation.

Vitamin D (also known as calcitriol in its active form) is a fat-soluble vitamin that is naturally present in few foods and fortified in even fewer. Luckily, our bodies can synthesize vitamin D with adequate sun exposure. An inactive form of vitamin D lives in our skin as a hormone. When met with sufficient sunlight, this hormone is converted into an active form of vitamin D through a process in the kidneys and liver.

Adequate sun exposure has been defined as:

o      two days per week during peak sun hours (10 a.m. to 3 p.m.)

o      on the arms and legs for 5-30 min

o      depends on time of year, latitude, and skin pigmentation

There is a long list of people at higher risk of vitamin D deficiency- from older adults to obese individuals and several groups in between.  Relative to other populations little is known about vitamin D status among athletes.  However, emerging evidence tells us that vitamin D deficiency has a range of implications that could affect not only an athlete’s ability to train, but also their overall health status, which includes:

o      increased risk of autoimmune diseases

o      greater incidence of nonskeletal chronic diseases (diabetes, multiple sclerosis, various cancers, heart disease)

o      profound effect on immunity, inflammation, and muscle function

So how much vitamin D do you need?  This is still hotly debated among vitamin D researchers and as a result there isn’t a “one size fits all” answer just yet.  Current recommendations (published in 1997) suggest the following daily intake:

–        Up to age 50:  200 International Units (IU) or 5 micrograms (mcg)

–        51-70:  400 IU (10 mcg)

–        71 and up:  600 IU (15 mcg)

The majority of research suggests these recommendations are much too low, with some researchers estimating adults need as high as 1000 IU per day.  Safe supplementation has been documented for up to 2000 IU per day.  Updated recommendations are expected to be published in May 2010.

Below is a short list of food sources of vitamin D.  As you can see, foods that naturally contain vitamin D aren’t all that common in the American diet, and those that are fortified with vitamin D (most notably milk) are not very rich sources.

Food sources of vitamin D:

Food source International Units (IU)
Cod liver oil, 1 tablespoon 1360
Salmon, cooked, 3.5 ounces 360
Mackerel, cooked, 3.5 ounces 345
Tuna fish, canned in oil, 3 ounces 200
Orange juice fortified with vitamin D, 1 cup 142
Milk, 1 cup (includes skim, reduced fat, or whole) 98
Egg, 1 whole (vitamin D is found in the yolk) 20

Source: http://ods.od.nih.gov/factsheets/vitamind.asp

So unless you typically consume a tablespoon of cod liver oil daily, or drink upwards of 48 ounces of milk, or can be sure you’re getting adequate sun exposure-

 

it’s best to rely on supplementation to meet vitamin D needs

When shopping for supplements, you will likely see two forms- D2 (ergocalciferol) and D3 (cholecalciferol).  Because they are metabolized differently in our body, the D3 form is the better choice.

Fore more information on vitamin D, check out the National Institutes of Health Office of Dietary Supplements vitamin D fact sheet.

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