The systematic review and meta-analysis, which was published in The American Journal of Clinical Nutrition and led by St Michael's Hospital of Unity Health Toronto, found a 40% reduction in obesity and overweight rates in children who consumed full fat dairy milk.
The researchers analysed 28 studies from across seven countries focused on the relationship between drinking cow’s milk and the 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 years old - showed that kids who drank reduced-fat milk had a lower risk of being overweight or obese. Eighteen of the 28 studies suggested children who drank whole milk were less likely to be overweight or obese.
The report’s authors challenge well-established international dietary guidelines that recommend children consume reduced-fat cow’s milk from the age of two to cut the risk of obesity.
In the UK, the NHS advises: "The fat in milk provides calories for young children, and also contains essential vitamins. But for older children and adults, it's a good idea to go for lower fat milks because having too much fat in your diet can result in you becoming overweight. If you're trying to cut down on fat, try swapping to 1% fat or skimmed milk, as these still contain the important nutritional benefits of milk, but are lower in fat."
Dr. Jonathon Maguire, lead author of the review and a paediatrician at St. Michael's Hospital, noted that cow’s milk is a ‘major contributor of dietary fat’ for ‘many children’ who consume it on a daily basis.
"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.”
Obesity in young children is a growing global problem. According to the World Health Organization, the number of overweight and obese 0- to 5-year-olds has soared from 32 million in 1990 to 41 million in 2016.
Previous studies have also called into question dietary advice to limit consumption of whole fat dairy products. Last year, for instance, a paper was published in The Lancet which concluded dairy consumption was associated with lower risk of mortality and major cardiovascular disease events in a diverse multinational cohort.
The international collaboration of researchers asked over 135,000 people in 21 countries to complete a food diary at the beginning of the study, and followed their health for an average of 9.1 years.
Over the trail period, 3.5% of people in the group with the highest dairy intake (more than two servings per day) developed major cardiovascular disease compared to 4.9% of people consuming no dairy. The high intake group also had a lower rate of stroke (1.2% vs 2.9%) and death (3.4% vs 5.6%) than the no dairy group. However, the research found lower rates of heart and circulatory disease regardless of whether people were consuming full-fat or low-fat dairy.
'Whole milk compared with reduced-fat milk and childhood overweight: a systematic review and meta-analysis'
The American Journal of Clinical Nutrition
Authors: Shelley M Vanderhout, Mary Aglipay, Nazi Torabi, Peter Jüni, Bruno R da Costa, Catherine S Birken, Deborah L O'Connor, Kevin E Thorpe, Jonathon L Maguire