Nutrition: Keep the vitamin D coming

By Rosie Schwartz, RD on July 23, 2013
It's back to school time. Gone are the endless hours in the great outdoors. It's also a time when vitamin D levels traditionally drop. And according to accumulating evidence, this vitamin D shortfall may take a toll on our health, right through the life cycle from infancy until old age. But first, here’s a little background on vitamin D, also known as the sunshine vitamin. It’s produced by the body when bare skin is exposed to ultraviolet light of sufficient intensity. For much of the year, from September until June, this type of sunlight is missing in action in Canada. Pair that with the practice of safe sunning, especially little ones who may be slathered from head to toe with sunscreen that blocks vitamin D production, shortages of this nutrient are thought to be widespread in Canada, even in the summer months.

Scientists are now investigating vitamin D and its impact on the rising incidence of various auto-immune diseases, type 1 diabetes – what used to be called juvenile-onset diabetes – and multiple sclerosis. And low vitamin D during childhood and adolescence may boost the odds of developing an auto-immune disorder even years later.

Another area being investigated is that of allergies and immune system functioning. Is it a coincidence that the extraordinary increase in the number of peanut allergies seems to go hand in hand with the same time period that safe sun practices began?

Autumn also marks the time when seasonal illnesses are on the rise and again, vitamin D may play a role. Some researchers have taken to calling some infections low vitamin D season flu rather than just the seasonal flu.

Japanese scientists assessed the effect of vitamin D supplements on the incidence of a particular seasonal flu in school children. During flu season, one group was given 1,200 International Units (IU) of vitamin D per day compared to no treatment in the other group. Not only was there a 50 percent drop in the number of youngsters getting the flu in the vitamin D group, they also had a much lower likelihood of experiencing asthma attacks. Other studies are showing that vitamin D may also lower the incidence of common ear infections.

Do the math

If you’re relying on nutrition labels to help you ensure you’re feeding your kids adequate amounts of vitamin D, think again. The nutrition facts box on food labels may lead you astray when assessing how much vitamin D is in a food.

That’s because the Daily Value (DV) on labels is based on 30-yearold information, when the recommended daily intake was 200 IU. So, while the nutrition information for a cup of milk states it contains 45% DV, in reality, that 100 IUs in a cup of milk are nowhere near almost half a day’s intake.

But a number of glasses of milk can add to daily totals, as can foods like fatty fish such as salmon and mackerel. A three-ounce serving of cooked salmon includes just under 500 IU of vitamin D. It’s likely we’re going to see more fortified foods in the marketplace as well. For example, look for a new type of mushrooms containing vitamin D. When the mushrooms are exposed to ultraviolet light of a certain intensity, they also produce vitamin D. A 100-gram serving – less than one half cup of chopped mushrooms – provides a whopping 280 IU of vitamin D.

But getting to the amounts that experts are recommending – 1,000 IU per day – can be tough with food alone. You might want to do a quick general assessment of your children’s totals from food and then use supplements for the rest.

One popular supplement – cod liver oil – can supply a daily dose in just one tablespoon, but be aware that it’s also high in vitamin A, which in larger amounts can lead to bone thinning. Excess vitamin A is also a concern for pregnant women as it is associated with birth defects.

Vitamin D daily quotas for babies and children

Recommended Daily International units (IU), minimum to Upper Limits

Newborn to six months: 400 to 1,000
Six months to one year: 400 to 1,500
One year to three years: 600 to 2,500
Four years to eight years: 600 to 3,000
Eight and up: 600 to 4,000

If the amounts sound like a lot, consider that 20 to 30 minutes outdoors with bare arms and legs during summer would produce about 10,000 IU on average. Those with darker skin would need longer to produce that amount.

Vitamin D food sources

3 ounces cooked sockeye salmon: 447 IU
3 ounces tuna, canned in water, drained: 154 IU
1 cup vitamin-D fortified milk: 100 IU
1 cup vitamin-D fortified orange juice: 100 IU
1 tbsp vitamin-D fortified margarine: 60 IU
1 large egg: 28 IU
1 cup vitamin D-fortified non-dairy milk or other beverage: 100 IU

Rosie Schwartz is a Toronto-based consulting dietitian in private practice and is author of The Enlightened Eater’s Whole Foods Guide (Viking Canada). Visit for more on healthy eating.

Originally published in ParentsCanada magazine, August 2013.

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