There is one vitamin, however, that is difficult to get enough of through food sources alone. Vitamin D!
Vitamin D's Role
Vitamin D is a nutrient that helps the body use calcium and phosphorous to build and maintain strong bones and teeth. Vitamin D is unique in that it can be synthesized by the body after exposure to ultraviolet rays from sunlight. Research suggests that vitamin D may have benefits related to cancer, mental health, and autoimmune diseases but more studies are needed.
Amounts and Recommendations
International Units (IU) as well as micrograms (mcg) are both units of measures for Vitamin D. To convert IU to mcg, divide by 40.
Recommended Vitamin D intakes in Canada:
Children & Adults (9-70 years): 600 IU (15 mcg) daily
Adults > 70 years: 800 IU (20 mcg) daily
For optimal health, some experts recommend 1000 to 2000 IU (25 - 50 mcg) of vitamin D2 or D3 daily
Upper Intake (maximum) for Adults: 4000 IU/day (100mcg/day)*
*from combined food + supplement unless under medical supervision.
There are three common sources: sun, food, and supplements.
1. Sun: our bodies can use the sun's rays to convert inactive vitamin D into its active form when the sun comes in contact with our bare skin. Amazing! But there are some factors to consider:
- Location. If you live close to the equator, 10-15 minutes of whole body exposure to the summer sun may easily meet your daily vitamin D needs. In countries like Canada, 30-90 minutes of exposure to the sun rays from March to October can produce sufficient vitamin D. In the fall and winter months, the sun's rays are inadequate to meet the needs of most.
- Skin exposure to sun. The skin needs to be bare and free of sunscreen for the UV rays to penetrate the skin and produce vitamin D.
- Skin colour. Darker pigmented skin is less efficient at converting vitamin D to the active form; therefore longer exposure to sun is required than for a person with more fair skin.
- Age. Unfortunately, the efficiency of vitamin D conversion decreases with age.
2. Food Sources: the major sources of vitamin D are fortified foods and few foods are a natural source of vitamin D.
Fortified Foods. In Canada, cow's milk and margarine must be fortified with vitamin D. Goat's milk, fortified plant based beverages (e.g., fortified soy beverages), and some calcium-fortified orange juices are permitted to be fortified with vitamin D. Cheese and yogurt can be made with vitamin D-fortified milk, however, the final product does not contain as much vitamin D as fluid milk alone.
Natural Sources. The only natural sources of vitamin D in the Canadian food supply are fatty fish and egg yolks. Fortified foods and natural food sources of vitamin D alone are usually not enough to meet vitamin D needs.
3. Supplements: for most Canadians, the sun's rays are only strong enough for our bodies to make vitamin D between March and October; during the other months supplements are needed. Taking 400IU of vitamin D should be enough (when combined with fortified and natural foods) to meet your vitamin D needs. Most supplements are sold in 1000IU tablets which is safe to consume and does not exceed the Upper Limit of 4000IU.
There are two kinds:
- Vitamin D2 (also known as: ergocalciferol): D2 is made when yeast is exposed to UV light. D2 is a vegan form.
- Vitamin D3 (also known as: cholecalciferol): D3 is made when sheep's wool is exposed to UV light.
*Research comparing the two types of vitamins shows that vitamin D2 tends to be less potent, meaning larger doses may be needed to achieve the same effect.
Multivitamins: can also contain vitamin D which should be considered when calculating your total intake.
Taken with food: studies indicate vitamin D can be taken with or without food, despite being a fat-soluble vitamin.
Side effects: excess supplemental vitamin D can cause calcium to be deposited in the body leading to calcification of the kidney and other soft tissues including the heart, lungs, and blood vessels.
Depending on where you live, you may be able to synthesize vitamin D from sunlight. If not, it is recommended to take a supplement in addition to enjoying foods rich in natural or fortified vitamin D.
- Sun: During the months of March through October (in Canada), 30 - 90 minutes of sun on bare skin can be enough to meet your vitamin D needs (the length of time depends on the month with less time in summer months).
- Food: although natural foods (eg. egg yolks and fatty fish) and fortified foods (eg. milk or almond milk) offer vitamin D, they typically will not meet your vitamin D needs.
- Supplement: During the months of November through February (in Canada), supplement with vitamin D. A minimum of 400 IU (10 mcg) vitamin D3 combined with natural and fortified sources will meet the recommended intake of 600IU.
Want to Learn More?
Read the previous article on evening snacking.
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