What is Vitamin D?
Vitamin D is a fat-soluble vitamin,
although it’s technically not a vitamin because we don’t need food to make it. It’s
commonly known as the “Sunshine Vitamin”, because UVB rays from the sun convert
a cholesterol in our skin to vitamin D3. Our liver and kidneys are then
involved in transforming this to the active form of vitamin D.
Functions of Vitamin D and Implications for
Athletes
Vitamin D is well known for helping our
bodies absorb calcium and phosphorous which in turn helps to keep our bones
strong. Vitamin D acts like a hormone and is used by almost every tissue and
cell in our body. Vitamin D receptors are found in the heart, liver, kidneys,
brain, muscle, immune cells and more. These are some of the ways adequate
Vitamin D is essential for athletes:
Bone strength and minimizing risk of
fractures. This is very important for athletes, as some studies have shown a
correlation between the number of fractures and vitamin D levels.
Keeping our immune system healthy. When
your sick you can’t train, so having adequate Vitamin D stores, especially in
the winter, is important
Reducing blood pressure
Improving muscle mass and strength
Inflammation – low levels of Vitamin D can
contribute to inflammation in the body.
Risk Factors for Low Vitamin D Levels
Many people have low levels of Vitamin D,
and there are a number of factors:
Where you live – Those living at higher
latitudes and in cold climates because of lack of sun exposure
Where you train – If you often train
indoors, like hockey players, or before the sun rises, you may not get enough
sunlight meaning your body won’t make enough Vitamin D
Your age – As we age, our ability to convert
Vitamin D to the active form decreases
Skin colour – Pale skin makes vitamin D
more quickly than dark skin
Sunscreen use - SPF 15 or higher blocks UVB
rays
Also of note – If you think that you get a
lot of sun while driving in the car, glass actually blocks UVB rays.
How Much Vitamin D is Recommended
- Health Canada’s RDA (Recommended Daily Allowance) is 600IU for children aged 1-70 and 800IU for those over 70. The safe upper limit set by Health Canada is 4000IU. It also recommends everyone over the age of 50 should take a 400IU supplement.
- Osteoporosis Canada recommends healthy adults aged 19-50 to consume 400-1000IU per day, and those over 50 or younger and at risk of osteoporosis to consume 800-2000IU daily. They also recommend Canadian adults to supplement all year.
- The Vitamin D Council recommends 5000IU per day and a safe upper limit of 10 000IU.
- The Institute of Medicine recommends 600IU daily for adults up to 70, and 800IU for adults over 70, with an upper limit of 4000IU
- There are varying recommendations because some researchers believe lower amounts are not enough to achieve the correct level of Vitamin D, while others think that the research does not have enough evidence to support high levels.
You can get too much of a good thing. We cannot
reach toxic levels from sunlight (our body can regulate how much is converted
to Vitamin D if we have enough), but you can from supplements. Most often I
recommend 1000IU because it is very difficult to get enough from your diet (see
below), but the best of way to make sure you have adequate levels is to get
tested by your doctor. Tests measure the level of 25-hydroxy vitamin D in your
blood.
Sources of Vitamin D
Food
It is pretty much impossible to meet all of
your vitamin D needs with food alone, but its still a good idea to include
these Vitamin D rich sources regularly in your diet:
- Salmon, tuna, sardines, mackeral – wild fish contains more vitamin D then farmed fish
- Mushrooms – these contain a very small amount, but more than other vegetables
- Egg yolk
- Vitamin D fortified dairy and non-dairy products
Using Health Canada’s Vitamin D RDA for
adults, to meet your needs you would have to eat:
- A serving of wild salmon per day
- About 15 egg yolks per day
- 2300g of cooked Shitake mushrooms per day, or
- 1.5 L of milk every day
These really aren’t the makings of a well
balanced diet! Vitamin D really is the sunshine vitamin, but thankfully there
are supplements available if the sun is not always an option.
Vitamin D supplements
There are both pills and drops – purchase
them in the form of Vitamin D3. You need fat to absorb it, so eat pills with a
meal that contains some fat. Vitamin D drops are already emulsified in fat so
you can take this at any time.
Sunlight
Expose a large area of your skin, like arms
and legs, for about half the time it takes for your skin to turn pink a few
times a week (could be 15-20 mins depending on skin colour). You can build up
reserves that will last a few weeks. In the winter months when you don’t get
sun, you likely will need to supplement.
Takeaways
If you are at risk of being deficient or
having low levels, in order to maintain your health and performance it would be
a good idea to get your blood levels tested. Your doctor can provide some
direction on how to correct this if you need to bring your levels up. Even with
a very healthy diet, you may not be getting all of the Vitamin D that you need.
For maintaining bone health, immunity and much more, consider supplementing
with Vitamin D but remember that you can consume too much since it is fat
soluble.
Andrea Docherty is a Registered Dietitian,
Sports Nutritionist and owner of Andrea Docherty Nutrition, a professional
nutrition consulting and coaching business in Windsor, Ontario. For more
information or to contact her, visit www.andreadochertyrd.com
