Vitamin D is an essential nutrient. Vitamin D helps the body to absorb calcium and phosphorous, which are necessary for building and maintaining strong bones and teeth. The body produces vitamin D upon exposure to ultraviolet rays from sunlight.
People with very little vitamin D in the body have decreased blood phosphorous and calcium levels. Low calcium levels make the body obtain calcium from the bones in order to maintain healthy levels. This leads to an increased risk of having thin and brittle bones, which can lead to rickets in children or osteoporosis in adults.
It is very important to get enough vitamin D in order to keep the bones strong and to protect them against possible fractures. Our body also needs vitamin D to help the muscles absorb calcium. If muscles don’t get enough calcium, it results in muscle cramps and weakness.
Measurement of vitamin D in the body
Vitamin D levels are measured by a simple laboratory blood test. The test results provide numbers in nmol/L (nanomoles per litre). These numbers will fall into a range that will provide information on whether you are deficient, somewhat lacking (insufficient), or have sufficient vitamin D levels. Most experts agree that levels of vitamin D above 75 nmol/L are sufficient.
What is the recommended dietary allowance (RDA) per day for vitamin D?
According to Health Canada, the recommended dietary allowance (RDA) per day for vitamin D for different age groups is as follows:
RDA per day
Infants 0-6 months
|400 IU (10 mcg)|
Infants 7-12 months
400 IU (10 mcg)
Children 1-3 years
600 IU (15 mcg)
Children 4-8 years
|600 IU (15 mcg)|
Children and Adults
600 IU (15 mcg)
|Adults > 70 years|
800 IU (20 mcg)
|Pregnancy & Lactation|
600 IU (15 mcg)
What are the best ways to get vitamin D?
1. Spend time in the sun
Sun exposure is the most important source for vitamin D. This is why vitamin D is also called the sunshine vitamin. In Canada, vitamin D from sun exposure can only be synthesized in bare skin during late spring, summer and the early fall months, from around 10 am-2 pm. During these times, the UV index is above 3.
The amount of time to be spent in sunlight to make sufficient vitamin D depends on factors such as clothing coverage, use of sunscreen, skin pigmentation, and age. Usually, normal sun exposure during the right time of the year (5-15 minutes around midday, many times a week, without using sunscreen) is thought to be sufficient to produce enough vitamin D.
During winter, most individuals living in Canada and the northern United States are not able to get enough vitamin D from the sun between the months of March and November. However, individuals should spend even small amounts of time outside whenever the sky is clear and the sun is shining. Planning vacations to warmer areas can also help with vitamin D levels, albeit temporarily. The best way to get vitamin D during winters is to rely on diet and supplements.
2. Eat food high in vitamin D
Vitamin D can be naturally found in foods such as fatty fish (e.g. salmon, tuna, mackerel), fish liver oil, beef/pork liver, egg yolks, some cheeses, and mushrooms. In Canada, certain foods are enriched with vitamin D, such as milk, margarine, infant formula, orange juice, yogurt, soy drinks, and breakfast cereals. However, the quantity of vitamin D present in the food is very small and vitamin D, obtained from diet alone is not sufficient to maintain adequate levels of vitamin D for most of the people.
3. Take vitamin D supplements
Dietary supplements are the major source of vitamin D and are considered the best way to obtain vitamin D, especially during the winter seasons in Canada when sunlight exposure is relatively quite low. Supplements are measured in international units (IU) and are sold commonly in bottles of 400 IU, 500 U, 600 IU or 1000 IU.
Multivitamins also contain vitamin D between 200-600 IU. Some groups of the population are at a greater risk of not getting enough vitamin D as compared to others. These groups of the population include all babies from birth until the age of one year, all children from one to four years of age, and people who do not get enough exposure to sunlight.
If you are deficient in vitamin D, the best treatment is with supplements. Ask your healthcare provider how much vitamin D you need to take, how often, and how long you need to take them.
So what can we do to get enough vitamin D all the year around?
Here are three simple suggestions:
- Get 15 minutes of sun exposure every day in the late spring, summer and early fall
- Eat two servings of fatty fish, every week from November to March
- If you are a vegetarian, drinking vitamin D fortified milk may be helpful from November to March
Read more about the latest research on vitamin D here.
Written by Pratibha Duggal
- Vitamin D and Calcium: Updated Dietary Reference Intakes – Canada.cahttps://www.canada.ca/en/health-canada/services/food-nutrition/healthy-eating/vitamins-minerals/vitamin-calcium-updated-dietary-reference-intakes-nutrition.html#a9
- Getting Enough Calcium and Vitamin D. https://www.healthlinkbc.ca/health-topics/za1487
- Vitamin D Deficiency: MedlinePlus. https://medlineplus.gov/vitaminddeficiency.html
- How to get vitamin D from sunlight. https://www.nhs.uk/live-well/healthy-body/how-to-get-vitamin-d-from-sunlight/#how-do-we-get-vitamin-d
- Vitamin D Fact Sheet. Multiple Sclerosis Society of Canada.