Vitamin D is a fat-soluble vitamin that is stored in the liver and fatty tissues. It is a precursor to a steroid hormone and plays a role in bone growth and maintenance, cardiovascular disease, estrogen excess, brain cell growth and the inflammatory immune response. Its major role is the metabolism and maintenance of calcium. Low vitamin D status is linked to a number of conditions including cancer, muscle weakness and diabetes. Low levels of vitamin D in children can cause rickets, while in adults it can lead to osteoporosis.
According to Stats Canada, 32 per cent of Canadians have concentrations of vitamin D below the recommended cut-off and are potentially at risk of inadequacy relative to bone health. Another 10 percent of Canadians were deficient in vitamin D and at risk of deficiency relative to bone health.
Very few foods naturally contain vitamin D, so the best source is sun exposure in moderation. Of course, in our neck of the woods that can be difficult for a good portion of the year and the further north you live, the less likely you are to meet your vitamin D needs. In winter months you should expect very little vitamin D from natural sunlight, which is why supplementation is recommended (of course going down south is great too, but a bit expensive!). Sunscreen also interferes with the production of vitamin D. Additionally, the darker your skin, the less efficiently you produce vitamin D. I am very fair – and I do not use sunscreen in the summer. I just seek out the shade when I feel that I have had enough.
Major food sources of vitamin D are oily fish, eggs and liver. Cod liver oil appears to be the best source, with 1,360 IU per tablespoon (if you can stand it).
Fortified foods and supplements mostly contain vitamin D2 (ergocalciferol) which is created by irradiating molds and yeast. Vitamin D3 (cholecalciferol) is created by irradiating animal oils and cholesterol and is the closest to what sunlight produces in humans. It should also be noted that no clinical trials have shown D2 to be effective at preventing bone fractures, while every trial of D3 does.
Signs Of Vitamin D Deficiency
The common symptoms are vague, such as fatigue or general aches and pains. Some people may get frequent infections, however many people never show any symptoms so it is important to have blood levels tested regularly. There are many chronic diseases fueled by vitamin D deficiency including Alzheimer’s disease, asthma, cancer, dementia, depression, heart disease, infertility, rheumatoid arthritis, schizophrenia and tuberculosis.
The upper limit for Vitamin D is currently set at 4,000 IU per day but this is met with controversy. Some doctors and specialists openly recommend 5,000 IU for adults. In clinical situations, many individuals have needed to excel the upper limit in order to promote optimal health. While I have never been below the conventional blood ranges of vitamin D, my functional medical practitioner likes to see my blood levels much higher that what is considered adequate in the conventional realm. For me, supplementation produces great results. When I supplement with vitamin D3 (about 5,000 IU drops daily) my blood levels of vitamin D rise considerably.