Time for vitamin D?

With the impending arrival of winter, the sunshine is slowly disappearing on us — and it’s for that reason experts recommend people consider taking vitamin D this time of year.

Why vitamin D?

Experts know we need it for healthy bones and muscles — especially for young children and older adults. It’s the vitamin that helps our body absorb and process two key minerals for healthy bones, muscles and teeth: calcium and phosphorous. Experts also believe it could be important for a healthy immune system too — which we’ll need with cold and flu season ahead!

The benefits may not end there: some research suggests that adequate vitamin D intake could be important for preventing certain types of cancer. For instance, the Canadian Cancer Society notes that there is some research suggesting that vitamin D helps reduce the risk of colorectal and breast cancers.

Other studies are currently looking at the benefits of vitamin D for other conditions like autoimmune disorders, type 1 diabetes, depression and heart disease. (Don’t get too excited just yet — Health Canada notes the research is still in its early stages and more investigation needed.)

Why now?

During the spring and summer months, it’s easy to get our daily dose from nature itself. Just a few minutes exposure to sunlight (minus the sunscreen) is enough.

However, fall and winter are another story. Thanks to our northern latitude, the sun’s rays aren’t so strong during these seasons here in Canada. The days are getting shorter, and cold temperatures have us bundling up or spending more time indoors. While that’s good news in terms of lowering our UV exposure, it also means that our bodies don’t produce enough vitamin D of their own.

Many experts argue we need a little extra help this time of year — and some people need more vitamin D than others. For instance, you might not be getting enough vitamin D if:

– You are over age 50. Some research suggests that the body’s ability to produce and use vitamin D decreases as we age.

– You have dark skin. The pigments in the skin can influence vitamin D production.

– You don’t go outside often.

– You wear clothing that covers most of your skin. (And who doesn’t in the winter?)

While not as much of an issue in the winter as in the summer, sunscreen use also affects our bodies’ ability to produce vitamin D. Some sources also indicate that people who have osteoporosis may need more vitamin C and D in addition to calcium.

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How much is enough?

Unfortunately, not everyone agrees on the amount of vitamin D we need. Both Health Canada and the U.S. Food and Nutrition Board (part of the Institute of Medicine) recommend that children and adults from ages 9-70 need 600 IU (international units) per day and adults over the age of 70 need 800 IU to get their Recommended Dietary Allowance (RDA). (You can read their recommendations here and here.) Currently, these sources report that there are no additional health benefits if you exceed the recommended daily allowance (RDA). In other words, consuming 1500 IU may not be more any more helpful than 800 IU.

However, we do get some of that RDA from our diets and sun exposure. Health Canada currently recommends that adults over age 50 take a daily vitamin D supplement of 400 IU (though it doesn’t specify during which seasons). Babies need a little help too — 400 IU until age 1 — but children and adults don’t need supplements if they’re drinking two glasses of milk (or two glasses of a fortified milk alternative) per day, says Health Canada.

For some experts, those guidelines don’t go far enough. For example, the Canadian Cancer Society recommends talking to your doctor about taking 1000 IU of vitamin D per day during the fall and winter. If you fall into one or more of the groups listed above, your doctor might also recommend taking a supplement year round.

Osteoporosis Canada recommends adults take a vitamin D supplement year round. It recommends healthy adults between the ages of 19 and 50 get 400 IU to 1000 IU per day. People over age 50 or who have at risk of osteoporosis should take between 800 IU and 2000 IU.)

To add further confusion, some sources say even 1000 IU still won’t cut it, but scientific evidence can be conflicting or inconclusive when it comes to amounts. Again, more research is needed

So whose advice should you take? As always, talk to your doctor about any supplements you’re thinking of taking. The amount you need depends on a lot of factors, and some research disputes claims that most people are deficient.

What about when to take it? Experts note that vitamin D is more easily absorbed when taken with a food containing fat. Some sources recommend taking the D3 form.

How much is too much?

While you can’t overdose on vitamin D, you can have too much of a good thing. Health Canada and other experts warn that too much vitamin D can lead to high levels of calcium in the body — a condition known as hypercalcemia. You might experience symptoms like nausea, vomiting and weakness — and hypercalcemia can lead to a build up of calcium in tissues and organs such as kidney stones.

Health Canada has therefore set a limit: the “Tolerable Upper Intake Level” (UL) is 4000 IU per day from all sources. Some experts warn not to exceed 2000 IU without medical supervision. Some research suggests that too much vitamin D may make some chronic conditions worse and increase the risk of some cancers — but again, more research needs to be done.

Where to get your D

Sunshine and supplements aren’t the only sources of vitamin D. Some multivitamins and calcium supplements contain vitamin D too. While the vitamin doesn’t often appear in nature, there are some dietary sources, including:

– fatty fish (like Atlantic herring, salmon and tuna)
– egg yolks (or eggs from chickens fed vitamin D-enriched feed)
– milk

You can find a full list on the HealthLinkBC website.

In addition, many foods are enriched with vitamin D, such as fortified cereals, milk, soy milk and rice milk. You can check the nutritional labels to get a rough idea of how much is in the foods you are eating — but beware that labels list the per cent Recommended Daily Intake, not the amount of IU.

What’s the bottom line?

There is a lot of confusing and sometimes conflicting information out there, but experts always advocate talking to your doctor and/or other healthcare providers to find out if — and how much — vitamin D you need. When considering your vitamin D needs, make sure to factor in all sources such as your diet and exposure to sunlight.

ON THE WEB

For more information on vitamin D, here are some good places to start:

Health Canada Vitamin D and Calcium: Updated Dietary Reference Intakes
Canadian Cancer Society: Vitamin D
Office of Dietary Supplements (U.S. National Institutes of Health): Vitamin D
The Vitamin D Society

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