Tuesday, 12 November 2013
The supplement industry is a booming business. You can pretty much find a vitamin combo to cure whatever ails you. Wherever possible I like to recommend good old-fashioned food. Mother Nature knew what she was doing when she combined vitamins, minerals and macronutrients in just the right combination for our bodies to absorb and utilize. But the one exception just might be Vitamin D.
Our bodies can produce Vitamin D when we are exposed to sunlight. But this can only happen when the UV Index is greater than 3 and in the Great White North we don't see many of these days. In fact for 6 months of the year we don't reach UV levels high enough to generate adequate vitamin D production. Researchers think that this is why Vitamin D deficiency in the North is almost epidemic. And when I say 'The North' I mean any place north of the 49th parallel....all of Canada.
According to Statistics Canada on average about 32% of Canadians have insufficient blood concentrations of vitamin D. But during winter months that increases to 40%. And the worst age group is aged 20 to 39 year olds, 59% of whom do not have adequate serum vitamin D levels.
Any sunlight that we are exposed to is reduced by smog, cloud cover, and sunscreen. And darker skinned people don't produce as much vitamin D from sun exposure as light skinned people do. We don't need very much sun to start producing vitamin D (two to three 15 minute sessions per week) but there is concern about having any sun exposure at all. To reduce the incidence of skin cancers most dermatological associations would prefer it if we got our vitamin D from food or supplements.
So how easy is it to obtain vitamin D from food? Not very. Vitamin D is added to some foods such as cereal, dairy products, bread products and margarine. But there is concern that not enough vitamin D is added to these foods to meet daily requirements (1 cup of milk contains about 100 IU of vitamin D). And what if you don't eat these foods?
Whole foods that contain vitamin D include some fish (wild salmon has 447 IU per serving, tuna 154 IU, mackerel 388 IU), fish liver oils (1360 IU per 1 tbsp cod liver oil), cheese, eggs and beef liver (15 IU per serving). Mushrooms also have trace amounts of vitamin D.
Vitamin D is important. In fact it's essential. For a long time it has been recommended for bone health because we know you need D in order to absorb calcium and phosphorous to maintain healthy bones (avoid osteoporosis, osteomalacia, and rickets).
But in recent years research has shown that vitamin D helps the body in many other ways. We know that D helps the immune system fight infections (like cold viruses) and recover from major infections like Tb. It's now believed that it can also help to reduce obesity and maintain a healthy body weight by activating the production of leptin, our "I'm full" hormone, that signals the brain to stop eating. Vitamin D also improves muscle function so it helps us to recover from exercise, provides us with muscle energy for activity, and can reduce chronic muscle pain.
There is now ongoing research demonstrating that vitamin D can reduce the risk of cancers (particularly colorectal and breast), heart attacks, hypertension, rheumatoid arthritis, asthma exacerbations, psoriasis exacerbations, cognitive impairment, depression, and multiple sclerosis (Canada has one of the highest MS rates in the world).
That's quite a list.
If you're thinking about taking a supplement what and how much should you take? There are five forms of vitamin D (D1 to D5) and D2 and D3 are the ones used in supplements. D3 (cholecalciferol) is the recommended form to take because it increases serum levels most effectively.
The amount recommended varies from country to country and by age and season. In Canada people aged 9 to 70 years should take 600 IU per day and those over 70 years should take 800 IU per day. The Canadian Paediatric Society says that infants should have 800 IU per day in winter months. You will find guidelines or websites that recommend higher doses. Beware that the maximum amount per day is 4000 IU. More than this can lead to toxicity. More is not necessarily better.
A simple blood test can tell us if your serum levels of vitamin D are adequate or below recommended levels. If you have any kind of risk factors (e.g. osteoporosis or a malabsorption syndrome like Crohn's disease) this test is covered under the OHIP program. Discuss both vitamin D intake and blood tests with your health care provider.
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Resources & References:
Vitamin D (Health Canada)
Vitamin D Health Benefits (The VitaminD Society - Canada)
Vitamin D & Cancer (Canadian Cancer Society)
Vitamin D blood levels of Canadian (Statistics Canada)
Make vitamin D, Not UV, a priority (Skin Cancer Foundation)
MS rates (MS Society of Canada)
Vitamin D supplementation Recommendations for Canadian mothers and infants. (Canadian Paediatric Society).