The sun’s UVB rays trigger the production of vitamin D in our body. But do our day-to-day outdoor activities supply us with the recommended dose of this “sunshine” vitamin?
During the summer, it takes about 20 minutes of exposure to the sun for the body to produce 8,000 to 10,000 international units (IU) of vitamin D. “But if you always stay out of the sun between 11 a.m. and 3 p.m. or if you go outside with sunscreen all the time, it’s difficult to get the proper amount of vitamin D, even in the summer,” says Pierre S. Haddad, full professor with the Department of Pharmacology at Université de Montréal.
Wintertime only complicates matters further. “Starting in early fall, we should be taking supplements, since the sun can’t supply the UVB rays our bodies need to synthesize vitamin D,” explains Jean-Yves Dionne, a pharmacist and expert in natural health products and complementary medicine.
Vitamin D intake recommended by Health Canada
According to Health Canada, the recommended daily intake (RDI) of vitamin D for Canadians between the ages of 1 and 49 is 600 IU. People over 50 need 400 IU, as do nursing babies, since breast milk is low in this particular vitamin. To reach this goal, Health Canada suggests two glasses (500 ml) of milk daily or an enriched soy beverage, both of which are good sources of vitamin D.
Could these recommendations be falling on deaf ears? According to a Canadian study published in May 2011 in the American Journal of Clinical Nutrition, 25 percent of Canadians have blood levels below the RDI of 50 nanomoles per litre. Canadians fare even worse during the winter, with over 30 percent being below the recommended threshold.
Certain experts believe that the dose set by Health Canada is seriously inadequate. Many are calling for clinical studies using elevated doses of vitamin D to explore its full health benefits and disease-preventing potential.
Views from other health organizations
Osteoporosis Canada recommends a daily dose of 400 to 1,000 IU for people under 50 and 800 to 2,000 for those over 50 [http://www.osteoporosis.ca/index.php/ci_id/5536/la_id/1.htm]. As for the Canadian Cancer Society [http://www.cancer.ca/Quebec.aspx?sc_lang=en], it urges Canadians to speak with their doctors about the option of taking 1,000 daily IU, especially during the winter months.
Turn on the lights, please!
We need the sunlight to synthesize vitamin D, but we also need it to keep us smiling! Once winter hits, the lack of sunshine can seriously affect our mood and even lead to seasonal affective disorder (SAD).
Depressed thoughts, irritability, increased appetite, chronic fatigue and loss of libido can result from lack of sunshine. In Canada, 18 percent of the population experiences the winter blues, while another 3 percent develops SAD. Fortunately, there is a proven medical treatment: light therapy. Light therapy involves daily exposure to an artificial source of light that mimics the sun. It works well for 50 to 80 percent of SAD sufferers, a success rate similar to treatment with antidepressants.
To learn more:
“La vitamine D et les suppléments” Protégez-Vous, December 2011. (In French only).