Is there such a thing as winter blues?
Between October and March in Canada, the sun’s UV rays are not strong enough to produce vitamin D (sunshine vitamin) through our skin. Even with our mild winters and the occasional clear sky day, the latitude in Canada doesn’t allow for the hormone conversion to happen through our skin. There is an estimation that a third of Canadians have vitamin D deficiency, as it’s difficult to get enough in our foods. The best sources are milk, egg yolks and fish. People who follow vegan diets or have milk aversion have more difficulty getting enough (of the mainly animal-based sources of) vitamin D.
As vitamin D is critical for the functioning of many systems in our body for health, without enough of this fat-soluble vitamin, deficiency can result. Unfortunately, a reduced immune system is one of the many health problems that can develop due to a lack of vitamin D. Depression, anxiety and low mood can also result from inadequate amounts of this vitamin. Low levels of vitamin D is linked to development of diabetes, high blood pressure, multiple sclerosis, cardiovascular disease, osteoporosis, cognitive impairment in older individuals, cancer and asthma in children.
The daily recommended intake (DRI) in Canada for vitamin D is 600 IU (international units) for adults and 800 IU for those over 70 years of age. There’s an upper limit of 4000 IU/day that can have negative effects on health and generally occurs in chronic mega dose supplementation.
Since vitamin D is fat-soluble, some people take a bigger amount: 10,000 IU once per week. This can support the body’s stores without going over the upper limit for that time period. Once per week method of supplementation reduces medication burden for those who have to take multiple pills daily.
Moods do improve in spring and summer, and so does our exposure to sunlight with that important natural vitamin D production.
Sandra Gentleman, RD, is a Port Alberni-based registered dietitian. Her Active Living column appears every few weeks in the Alberni Valley News and online at www.albernivalleynews.com.