Getting to know vitamin D

Why we need it and where to get it.

You may know vitamin D by its other name, the “sunshine” vitamin. Known for its role in maintaining bone health and monitoring calcium levels, getting enough vitamin D is particularly important for Canadians in the Northern hemisphere. This article takes a close look at the importance of vitamin D, how much sunshine is needed to keep your vitamin D levels at a healthy level and where it can be found if there’s no sunshine in the forecast.

 

What is vitamin D?

 

Vitamin D is set apart from other nutrients for several reasons, the most important being that it is converted into a hormone called calcitriol once absorbed by the body. Calcitriol is associated with phosphorus and calcium regulation, healthy bone growth and is currently being studied for its effects on the immune system, cellular growth, and the inflammatory system. Vitamin D is a fat-soluble nutrient which means it can only be absorbed if accompanied by adequate fat intake; those who are unable to absorb fat can be prone to vitamin D deficiency.

 

Step into the sunshine: getting enough vitamin D

 

There are two types of vitamin D; vitamin D2 and D3. Both types are important but vitamin D3, the kind that is absorbed through sunlight and via animal-based foods, does the best job of maintaining vitamin D levels throughout the body. Dietitians recommend at least 10-30 minutes of uninterrupted exposure to midday sun which can pose serious logistical problems for at least half of the year in Canada (those who live on the rainy west coast may see even less sunshine than the rest of the country.) Although sunscreen blocks UVB light, there has been no evidence to suggest that it successfully blocks vitamin D absorption. People with very pale skin will absorb vitamin D with greater efficiency than individuals with a higher concentration of melanin so exposure time should be monitored carefully.

 

Supplementing with vitamin D

 

If you’re unsure of or concerned about your vitamin D levels a simple blood test can reveal whether or not you’re getting enough of this nutrient. Unless you live in a warm, sunny climate year-round you may need to take vitamin D supplements during darker times of the year.

 

How much vitamin D do I need?

 

According to reference material from Dietitians of Canada, the RDA for vitamin D is as follows (with these numbers being the upper limit for vitamin D intake):

  • 1000 IU for infants 0-6 months
  • 1500 IU for infants 7-12 months
  • 2500 IU for children 1-3 years
  • 3000 IU for children 4-8 years
  • 4000 IU for children over 9 years of age and adults (including pregnant or lactating women).

 

Food sources of vitamin D

 

With very few exceptions, food sources of vitamin D come from animal products such as egg yolks, pork, beef, offal, fatty fish, and cod or anchovy liver oil. Vitamin D does not naturally occur in milk, orange juice, almond milk, grains, margarine, and soy foods but these foods are almost always fortified with this nutrient. Plant-based and synthetic sources of vitamin D are considered inferior in quality when compared to animal sources, but they still have some nutritional value.