The first Canadian study to investigate vitamin D levels in toddlers has found that more than 80 per cent of the children tested didn't have enough of the sunshine vitamin and nearly a third had such low amounts that doctors classified them as deficient.
The finding, based on blood tests of two-year olds from the Toronto area, suggests that shortfalls in vitamin D may be widespread in young children across the country, potentially placing them at an elevated risk of developing a wide range of diseases later in life, including multiple sclerosis, cancer and juvenile diabetes.
"Vitamin D deficiency is associated with a number of chronic medical conditions," observed Jonathon Maguire, a researcher at Toronto's Hospital for Sick Children and lead author of the study, who called the results "concerning."
Up until now, not much has been known about vitamin D levels in Canadian toddlers. Researchers say that babies generally have high levels because formula is fortified with the nutrient and mothers who breastfeed are strongly advised to give their children supplements of 400 International Units daily up to the age of one.
But the new study was designed to see whether youngsters were able to maintain the decent levels they likely had as babies, as they grew older and moved onto solid foods, which don't have much of the vitamin.
The finding of widespread insufficiency indicates most children aren't getting enough vitamin D either through diet or through sunlight exposure. Dr. Maguire said that developing strategies to prevent deficiencies "would seem to be a prudent thing to do."
The 92 children tested were normal, healthy toddlers who had gone to a pediatric clinic for a routine check-up. Most of the tests were conducted during the fall and winter, when levels of the nutrient reach their seasonal lows in Canadians not taking some in supplements.
The researchers asked parents about the habits of their children and found that those who drank less milk, watched television while snacking or were hefty tended to have the worst vitamin D status.
Dr. Maguire said these risk factors are "probably representative of a population of children who lead a relatively unhealthy life style" without much outdoor exercise or sun exposure.
Milk is linked to vitamin D because the drink is fortified with small amounts of the nutrient at the rate of 100 IU per cup. For children to raise their levels through milk alone would require drinking huge amounts - perhaps as much as a litre a day - something Dr. Maguire doesn't recommend. Some foods, such as oily, cold-water fish, also contain it naturally, but seafood is not a major component of the diet of children.
Most of the vitamin D circulating in people they make themselves from cholesterol in naked skin that is exposed to strong spring or summer ultraviolet light, hence the reason its often dubbed the sunshine vitamin. It isn't possible to make the vitamin this natural way in Canada for most of the fall and winter, leading levels in the body to plunge unless amounts are replenished through diet or supplements.
There has been a flurry of medical interest in vitamin D because of tantalizing hints that it plays a far wider role in promoting good health than just helping ensure proper bone development, for which it is well known. New research has linked deficiencies to many cancers, heart disease, to such autoimmune conditions as MS and diabetes and even influenza.
What many researchers would like to see is children maintaining the same levels of vitamin D that they would get from modest, summer sun exposure, year round. At Canada's high latitude, this is only possible through taking supplements or consuming large amounts of the foods containing the nutrient.
The finding of low levels in most toddlers is "very worrying," said Dr. John Godel, a vitamin D expert at the Canadian Pediatric Society, who said that if children in the Toronto area don't have enough, "you can imagine what it must be like up in the north" where there is less sun exposure. Health Canada says that children older than one should get 200 IU of the vitamin a day, but Dr. Maguire said the American Academy of Pediatrics last year doubled the amount youngsters of all ages should have to 400 IU daily, the dose in a typical multivitamin.
Dr. Godel said the new study indicates the Canadian recommendation "may need to be modified."
The new Canadian research is being presented today in Baltimore, Md., at the annual meeting of the Pediatric Academic Societies, a forum for doctors to present new scientific findings on the health of children.