A new study – cannily published while all those mummy bloggers are on holiday – has found children who drink full-cream cow’s milk tend to be skinnier than kids given skimmed and reduced-fat milk.

A systematic review and meta-analysis of 28 studies from seven countries found children who drank whole milk had a 40 per cent lower risk of being overweight or obese.

None of the studies – which involved a total almost 21,000 children between the ages of one and 18 – showed kids who drank reduced-fat milk had a lower risk of being overweight or obese.

These studies were observational, not clinical and the researchers – from St. Michael’s Hospital of Unity Health Toronto – don’t know why full-cream milk might protect against weight gain.

There are many questions. Does the full-cream milk keep kids fuller for longer? What are children eating when they drink a glass of milk? How many of the children, when drinking reduced-fat milk, stir in a spoon of sweet flavouring?

As they stand, the findings challenge international guidelines – including Australian – that recommend children “mostly” consume reduced-fat cow milk and other dairy products instead of whole milk, starting at age two, to reduce the risk of obesity.

“The majority of children in Canada and the United States consume cow’s milk on a daily basis and it is a major contributor of dietary fat for many children,” said Dr Jonathon Maguire, lead author of the review and a paediatrician at St. Michael’s Hospital.

“In our review, children following the current recommendation of switching to reduced-fat milk at age two were not leaner than those consuming whole milk.”

Dr Maguire, who is also a scientist at the MAP Centre for Urban Health Solutions, next hopes to establish the cause and effect of whole milk and lower risk of obesity in a randomised controlled trial.

“All of the studies we examined were observational studies, meaning that we cannot be sure if whole milk caused the lower risk of overweight or obesity. Whole milk may have been related to other factors which lowered the risk of overweight or obesity,” Dr Maguire said.

“A randomised controlled trial would help to establish cause and effect but none were found in the literature.”

In August, a review by the Australian Heart Foundation led to new dietary recommendations regarding dairy (full-cream is fine) and eggs (eat as many as you like).

As The New Daily reported at the time, Heart Foundation chief medical adviser, cardiologist Professor Garry Jennings, advised:

“We have removed our restriction for healthy Australians on eating full-fat milk, cheese and yoghurt. While the evidence was mixed, this type of dairy was found to have a neutral effect, in that it doesn’t increase or decrease your risks for heart disease or stroke.

“Given this, we believe there is not enough evidence to support a restriction on full-fat milk, yoghurt and cheese for a healthy person, as they also provide healthy nutrients like calcium.”

But the new advice applies to healthy people only.

According to nutritionaustralia.org, most Australians don’t include enough dairy in their diet. Most Australian children also need to increase their intake of the dairy food group in order to meet recommendations.