Sep 01 2010
Vitamin D: What you need to know
What does vitamin D do for my health?
Vitamin D is often called the ‘sunshine’ vitamin as the skin is able to make the vitamin when exposed to sun. Vitamin D is best known for its role in keeping bones healthy. It is also involved in fighting infections, keeping blood pressure within a healthy range and helping control insulin production. Recent research suggests that vitamin D may also have benefits in preventing some types of cancers, especially colorectal cancer. It may help prevent diabetes and multiple sclerosis as well. As yet, we do not fully understand the role of vitamin D in these three conditions.
What are food sources of vitamin D?
Vitamin D is provided in a limited number of foods, either occurring naturally or added to the product. Only fatty fish such as salmon, mackerel, sardines and tuna naturally contain substantial amounts of vitamin D. Cow’s milk, infant formula, margarine and plant-based beverages (e.g. soy beverages) are fortified with vitamin D, as required by the Canadian government. Vitamin D is now fortified in some ready-to-eat cereals and orange juice, and yogurt made with vitamin D-fortified milk. To determine if a packaged food contains significant amounts of vitamin D, look for food labels that show greater than 20% Daily Value (DV) for vitamin D per serving.
Am I at risk of being deficient in vitamin D?
Some people may be at risk of not getting enough vitamin D because they don’t get enough in their diet or because they have more limited sun exposure which reduces the amount of vitamin D their bodies make.
Those at risk include:
Breastfed infants require 400 IU vitamin D per day from birth. Because breast milk is naturally low in vitamin D and infants are not usually exposed to the sun, a vitamin D supplement of 400 IU is recommended, although for infants living in the far Canadian north in the winter, the recommendation is for a daily supplement of 800 IU. These amounts of vitamin D are available as drops in many grocery stores and pharmacies. Healthy term infants fed infant formula do not require a vitamin D supplement as it is already added to the formula.
Pregnant women should consume vitamin D from food (for example, from at least 3 glasses of milk per day) or supplements (usually 200-400 IU is provided in a supplement) to ensure the baby is born with optimal vitamin D in their body. If a supplement is taken, be sure not to exceed 2000 IU vitamin D per day.
Adults over 50 years may not produce vitamin D in skin as well as when they were younger. HealthCanada recommends that adults (men and women) over 50 years take a supplement of 400 IU/day. People with skin darkly pigmented with melanin are less able to make vitamin D from exposure to sunlight. Since many people with darker skin colour also avoid vitamin D fortified milk due to lactose intolerance, their dietary intake of the vitamin may be low, so extra vitamin D, such as the amount typically found in a general multivitamin-mineral supplement (200-400 IU) would be a good idea.
People with limited sun exposure
If sun exposure is limited due to mostly living or working indoors, wearing clothing such as long robes and head coverings, or living in the more northerly regions of Canada, then it is wise to carefully choose vitamin D rich foods (see above) or to take a vitamin D supplement, such as the amount typically found in a general multivitamin-mineral supplement (200-400 IU).
Some medical conditions such as Crohn's disease, cystic fibrosis, celiac disease, surgical removal of part of the stomach or intestines, and some forms of liver disease, interfere with absorption of vitamin D. Being overweight and obese causes fat to stay stored in fat tissues and not be released into the blood, preventing vitamin D from being available to the body. If you have one of these conditions, check with your doctor to ask if a vitamin D supplement is needed.
Can I take too much vitamin D?
Yes. Too much vitamin D can be harmful. The total daily intake from food and supplements combined should not exceed 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, and children-adults 9-70 years 4000 IU.
The Bottom Line
Most people, except those in the risk groups noted above, can get enough vitamin D if they eat enough vitamin D rich foods (for example, milk, vitamin D fortified foods and some fatty fish) and if they engage in safe sun practices. If you are concerned about your vitamin D status, discuss the issue with a health care professional such as a physician or dietitian.