A new study in Canada reveals that Children who breast-feed, especially those living far from the equator, may have low levels of vitamin D, Fox News reports.

Breast milk does not provide enough vitamin D, particularly for people in northern parts of the world.

"We're not saying that breast-feeding is not a really great source of nutrition, but up here in the northern parts of the world not much vitamin D passes through breast milk," said study coauthor Dr. Jonathon Maguire, a pediatrician and researcher at St. Michael's Hospital in Toronto.

The Canadian Paediatric Society recommends that breast-fed children should take supplements containing 400 International Units of vitamin D every day for the first year of life.

The World Health Organization recommends that mothers should exclusive breast-feed their children through the first six months of life. It also recommends that mothers should continue to breastfeed their children in addition to solid foods for the first and second years.

For the current study, Maguire and his coauthors used data from around 2,500 healthy children aged 1 to 5 years in Toronto and studied how long children were breast-fed and their blood vitamin D levels.

The study found that with the increase in the duration of breast-feeding duration increased, the blood vitamin D levels of the children who did not take supplements decreased.

The study also found that for every one month of additional breast-feeding time, the odds of abnormally low vitamin D levels increased by 6 percent.

The study was published in the American Journal of Public Health, online February 18.

"Probably most North American pregnant women get vitamin D supplements during pregnancy, even if this is not a very substantial amount," Martin Hewison of The University of Birmingham in the U.K. told Reuters Health by email.

"Vitamin D-deficiency is so very common during pregnancy and lactation but is still generally ignored unless the child develops rickets," said Hewison, who was not part of the new study.