Vitamin D for Bone Health

salmon, fish, seafood

What is it?

Vitamin D helps the body use calcium and phosphorus, to build and maintain strong bones and teeth.

Not getting enough Vitamin D can cause calcium and phosphorus levels in the blood to drop, leading to calcium being pulled from our bones to help maintain stable blood levels. This can cause osteomalacia (softening of the bones) or osteoporosis (porous bones) in adults as well as rickets (softening of the bones/deformations of the skeleton) in children. 

On the other hand, too much vitamin D is also a concern as can cause too much calcium to be deposited in the body, which can lead to calcification of the kidney and other soft tissues including the heart, lungs and blood vessels.

Where do we get vitamin D?

We can get vitamin D from three sources:

  1. Sunlight
    • Vitamin D is unique that we can make it ourselves.  It is often referred to as the “sunshine vitamin” because when exposed to the ultraviolet rays of the sun it stimulates the skin to produce vitamin D naturally.  However, there are a number factors that can affect the amount of ultraviolet radiation we receive and therefore vitamin D production such as:
      • Latitude: many Canadians live above 42°North (i.e. Toronto 43°North) where little or no vitamin D can be produced from about November through February/early March and moving further north, for example Edmonton 53°North, the “vitamin D winter” extends from about mid-October to mid-March
      • Season: the sun’s rays are weaker during the fall and winter
      • Time of day: the sun is stronger between 10 AM and 3 PM
      • Cloud cover or smog: for example, complete cloud cover reduces ultraviolet radiation
      • Age: as we age our ability to synthesize vitamin D decreases
      • Skin pigmentation: vitamin D synthesis in darker pigmented skin is reduced and takes a longer time
      • Sunscreen use: can block vitamin D synthesis and heavy clothing that inhibits sun exposure can also block synthesis
  2. Diet
    • Vitamin D is found naturally in only a few foods such as fatty fish like salmon (394 international units (IU) per 75 grams sockeye salmon) and egg yolks (32 IU per yolk). The major sources of vitamin D in the Canadian diet come from fortified foods.  Fluid milk, many plant-based beverages (i.e. soy, almond, rice beverages) and some calcium-fortified orange juices are fortified with vitamin D (100 IU per cup). Cheese and yogurt can be made with vitamin D-fortified milk; however, they do not contain as much vitamin D as fluid milk.
  3. Supplementation
    • A variety of supplements are available on the market in various potencies, commonly ranging between 400 IU – 1000 IU.
    • Vitamin D3 is the preferred supplementary form over vitamin D2, as the D3 form is more efficient in raising vitamin D blood levels.
salmon, fish, seafood

How much do I need?

Health Canada recommends different vitamin D daily intakes based on age and gender. The recommendations are based on maintaining bone health and have been set assuming minimal sun exposure. This is due to concerns about skin cancer from ultraviolet radiation from the sun.

Age GroupRecommended Intake Per Day             Safe Upper Limit
Children 1-3 years600 IU2500 IU
Children 4-8 years600 IU3000 IU
Children 9-18 years600 IU4000 IU
Adults 19-70 years600 IU 4000 IU
Adults > 70 years800 IU4000 IU
Pregnancy & Lactation
600 IU
4000 IU
Source: Institute of Medicine (IOM). Dietary reference intakes for calcium and vitamin D. Washington, DC: The National Academy Press, 2011.

Health Canada also recommends that people over the age of 50 years take a daily vitamin D supplement of 400 IU.

How is vitamin D status measured and how do I know if I am getting enough?

Vitamin D status can be measured in two ways:

  1. Vitamin D dietary intakes
  2. Vitamin D blood levels
    • Since Vitamin D can also be produced when skin is exposed to sunlight, it is the blood level data that gives a true picture of the vitamin D status in the body, reflecting total vitamin D exposure from foods, supplements, and synthesis in the skin from sun exposure.
    • When examining vitamin D blood levels, it is serum concentrations of 25-hydroxyvitamin D that is measured in the blood and different cut points for serum 25-hydroxyvitamin D have been established, relative to bone health.

If you are concerned you are getting too little – or too much vitamin D, speak with your doctor about getting your blood level tested and determine if vitamin D supplementation is right for you.

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