Vitamin D, that is ;) I stole this catchy slogan from a successful run in Whitehorse a couple years ago. It was a great way to get people's attention on an important concern in northern latitudes. Vitamin D deficiency!
You probably know that Vitamin D is important for bone health. But did you know it keeps your immune system strong? It also plays a role in cell growth and muscle function.
How Much Do We Need?
Our body can make its own vitamin D with the help of sunlight. However, not everyone gets ample sunlight year round. Age, skin tone and sunscreen use also affect our ability to form vitamin D. The recommended intake from food assumes minimal sun exposure. It covers your bases even if you live in the more northern parts of the country.
Those aged 9-70 years old need 600IU daily from diet. Adults should not exceed 4000 IU per day from food and supplements. Vitamin D is fat-soluble, so excess amounts are stored in your fat tissue. You don’t just excrete the excess through urine! Luckily overdose is very rare.
Symptoms of deficiency can be bone pain or muscle weakness. But most people don't feel any symptoms, and doctors don't routinely test for it.
How Can We Get Enough Vitamin D From Food?
Vitamin D is not naturally found in many foods. Foods are often fortified to help us get enough. Here are some examples of sources:
How To Find It On The Label
If a food contains Vitamin D it will usually be listed near the bottom of the nutrition panel. The label will tell you the percentage of your daily value per serving (%DV). For example, if one serving contains 45%DV, that is 45% of the total amount you require for that day.
As Vitamin D is rare in our food supply, many people use supplements to meet their needs. Health Canada recommends everyone over age 50 takes 400IU daily as a supplement. You can find them in two forms, D2 or D3.
Vitamin D3 is the same molecule our body makes with sunlight. D3 supplements are usually animal derived and not vegan friendly (though vegan options do now exist). D2 is made by plants and has a slightly different structure. It may not be absorbed as well.
Vitamin D Can't Work Alone
Other important vitamins for bone health are calcium, magnesium, Vitamin K and phosphorus. They only work together! Most of us get enough phosphorus, but calcium is something you may want to supplement if you aren't big on dairy.
Evidence for Vitamin D and...
Osteoporosis & Fractures
On its own, vitamin D does not prevent fractures. But when combined with calcium it may be effective in senior women, notably those in assisted care homes. Many experts don't think the risks of calcium supplements (heart disease, kidney stones, digestive issues) are worth the benefit, which is modest at best. Reviews here and here.
Research has shown those with adequate vitamin D levels are less likely to develop colon cancer than those who are deficient. They also have better outcomes if diagnosed. Quality of evidence isn't high enough to prove a causal link, but there is a significant association being investigated.
Babies born in winter months are more likely to develop autism. Since this discovery, studies have looked into the vitamin D status of expectant moms & children with autism, and treatment of children with high dose vitamin D. There are not yet enough high quality studies to make official recommendations.
Right now there are large, well-designed studies looking into high dose vitamin D supplements to prevent and treat type 2 diabetes. It may work by increasing our body's ability to use its own insulin. We will have to wait and see!
The only case where vitamin D has aided weight loss was in women who were deficient before they started supplements. And that was in one small study. Taking large doses of it won't help you shed pounds.
Vitamin D may not cure everything under the sun, but it's definitely important. There's virtually no risk to taking it and it's pretty affordable. I personally take it as often as I remember. I recommend you do too, especially if you're over 50, vegan, trying for a baby, or you don't get much sun exposure.