It’s finally spring in Canada, the sun is out and the question arises just how much sun exposure should we allow ourselves. Sunlight gives us vitamin D, but it can also cause skin cancer. Certainly a growing body of research recommends far higher doses of Vitamin D than we’ve been getting and the most effective source is sunlight. Skin synthesizes vitamin D3 from direct exposure to sunlight, but anxieties over skin cancer keep people covered up and limited dietary sources, mean most don’t get enough of it, especially in Canada where sun exposure is not an option for nearly six months of the year.
Getting enough vitamin D from diet is challenging. Dietary sources for vitamin D include fortified dairy products, soy products, margarine and cereals. It occurs naturally in fatty fish and eggs; for vegans the main sources are mushrooms and yeast.
Why vitamin D
“Vitamin D has always been important for health and disease prevention, but recent attention relates to new research on the effects of higher amounts of vitamin D supplementation,” says Dianne Oickle, public health nutritionist, Leeds, Grenville, and Lanark District Health Unit, Canada.
There is new evidence suggesting vitamin D reduces cancer rates – as much as 50 per cent in some cases. Researchers are also discovering connections between low vitamin D intakes and multiple sclerosis, juvenile diabetes, autism, influenza, osteoporosis and bone fractures among the elderly. To add to the conundrum, no two authorities seem to agree on just how much vitamin D any given person may need.
“I’d estimate that 97 per cent of the Canadian population is vitamin D deficient,” says Dr. Reinhold Veith, a nutritional scientist at University of Toronto, and one of the world’s leading authorities on vitamin D. He explains that one of the functions of vitamin D is to produce a signaling molecule that helps cells communicate effectively with each other.
“Vitamin D is like the paper supply in an office (before email!), too little paper and inter-office memos can’t be circulated, too little vitamin D compromises the quality of communication in the body,” explains Veith. It’s the sort of communication that signals what type of cells are produced or tells cells to die so they don’t replicate uncontrollably as they do in cancer. Vitamin D also boosts blood vessel health and the immune system.
How much is enough
For Canadians the best way to ensure enough vitamin D is through over the counter supplements, which cost pennies a day. Even the Canadian Cancer Society has posted new recommendations.
“Due to our northern latitude, we recommend that Canadian adults consider taking a vitamin D supplement. Talk to your doctor about taking 1,000 international units (IU) a day during fall and winter months,” states the website.
Canada’s Food Guide suggests adults 19-50 consume 200IU of vitamin D per day through diet – two glasses of milk. The only recommendation for vitamin D supplementation in the food guide is 400IU for adults over 50.
“That’s far too low,” says Veith.
Even the Canadian Pediatric Society recommends higher supplements for both babies and new mothers.
Veith recommends a minimum of 2,000IU to 4,000IU per day for all Canadians, more if they are dark skinned – because dark skin needs 10 to 20 times the sun exposure to produce the same amount of vitamin D as fair skin.
Meanwhile, the Dietary Reference Intakes (DRIs), which sets recommendations for nutrient intake in North America, states that supplements should not exceed 2000IU per day. The difficulty with vitamin D is it has a half-life, in other words it remains in the body and an overdose is possible.
“If you consume excess amounts of vitamin D it can be toxic, possibly leading to kidney stones or kidney damage, weak muscles and bones, excessive bleeding, and other problems. An overdose usually comes from supplements, not foods, which is why it is recommended not to exceed 2000IU of vitamin D supplement per day,” concludes Oickle.