Babies and young children who are breastfed may not be getting enough vitamin D – especially if they live in northern parts of the world.
That’s the conclusion of Canadian researchers who followed the progress of breastfed children, some of whom were given vitamin D supplements and some not.
The researchers, from St Michael’s hospital in Toronto, found that the longer children breastfed, even if they also ate solid food or were older than one year, the greater their odds of having low levels of vitamin D.
Dr Jonathon Maguire and his coauthors studied how long children were breastfed and their blood vitamin D levels using data from about 2,500 healthy children aged one to five years in Toronto. Mothers reported how long their child had been breastfed and doctors collected blood samples from the children.
Mothers also reported whether their child was taking vitamin D supplements. Half of the children had been breastfed for 10 months or more, and 53% received vitamin D supplements.
As breastfeeding duration increased, blood vitamin D levels decreased for children who did not take supplements. For every month of additional breastfeeding time, the odds of abnormally low vitamin D levels increased by 6%.
The pattern was so consistent that researchers predicted 16% of 2-year-olds breastfeeding but not receiving extra vitamin D would be seriously deficient, and by age 3, that would rise to 29%.
“We’re not saying that breastfeeding 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,” Dr Maguire, told the Reuters news agency.
Commenting on the findings, Andrew Thomas, founder and managing director of pioneering supplement specialist BetterYou, said: “The UK Department of Health highlights children under five years as an at risk group for vitamin D deficiency and recommend that they should be given a daily supplement.”