Children who drank whole milk tended to be leaner than those who drank low fat or skim milk, a study by Toronto researchers has found.

The new findings, published in Wednesday's online issue of the American Journal of Clinical Nutrition, suggest a need to take a closer look at those guidelines, said study author Dr. Jonathon Maguire, a pediatrician at St. Michael's Hospital in Toronto.

"If you don't get fat from someplace, then you take energy from somewhere else, and it may be that children who are receiving reduced fat milk seek foods that are higher in caloric density, and maybe that's why they're a bit bigger," Maguire said in an interview.

It really amazes me today in 2016 that we don't know what the right answer is and that we need to find out. - Dr. Jonathon Maguire, pediatrician

The reverse is also possible, as parents of children who are overweight may choose to provide them with low fat milk, he added.

Childhood obesity in North America has tripled in the past 30 years. Children's consumption of whole cow's milk has halved over the same period.

Current guidelines from Health Canada and the American Academy of Pediatrics recommend two servings of low fat milk (one per cent or two per cent) milk for children over the age of two to reduce the risk of childhood obesity.

Maguire expects people to ask doctors and researchers for guidance on what kind of milk to give their children.

"It really amazes me today in 2016 that we don't know what the right answer is and that we need to find out."

The study's authors focused on 2,745 children, with an average age of almost three, who were recruited from primary health-care practices in the city. Heights and weights were measured and blood samples were taken to examine vitamin D levels.

The parents were surveyed on whether their child's diet was mainly skim, 1 per cent, 2 per cent or whole milk.

BMI scores

Children who drank whole (3.25 per cent fat content) milk had a Body Mass Index (BMI) score that was 0.72 units lower than those who drank 1 or 2 per cent milk.

The difference in BMI score is almost the difference in weight between an overweight and obese child, Maguire said.

Among the children in the study:

49 per cent drank whole milk.

35 per cent consumed 2 per cent milk.

12 per cent drank 1 per cent milk.

4 per cent consumed skim milk (0.1 per cent fat).

For the 122 children who consumed more than one type of milk, researchers averaged the milk fat per cent.

The researchers didn't study why consuming higher fat milk was associated with leaner children.

Vitamin D implications

Another aspect of the research focused on milk fat intake and vitamin D levels. The vitamin helps strengthen our bones and may play a role in reducing the risk of chronic diseases later in life.

The researchers found that roughly one cup of whole milk had the same effect on children's vitamin D levels as three cups of 1 per cent milk.

Since both vitamin D status and fat are important for a child's growth and development, the study's authors said the findings could have implications for maintaining health at a population level.

Childhood obesity in North America has tripled in the past 30 years. At the same time, children's consumption of whole cow's milk has halved. (iStock)

But no cause-and-effect relationships can be drawn from the data.

"The choice of milk fat content that parents choose to provide their children is really a personal choice," Maguire said.

'Not the greatest idea'

Dr. Daniel Flanders is a pediatrician in Toronto who wasn't involved in the study. He usually give parents a range of options on buying milk and suggests they choose what's convenient for the family.

"May be it's not the greatest idea to put two-year-olds on skim milk," Flanders said. "We still don't know the answer, but this another step in the direction of making our recommendations more evidence-based."

Canada's Food Guide currently recommends two servings of milk or alternatives each day for children aged two to eight.



Health Canada is currently in the process of reviewing and seeking input to update the food guide. The public consultations end Dec. 8.

Funding of the Target Kids research network was provided by the Canadian Institutes of Health Research and the St. Michael's Hospital Foundation.