High protein diets might have a reputation for helping adults stay lean but in small children it can have the opposite effect: too much protein too soon can lead to childhood obesity.
"The timing is critical. In the first two years of life a high protein intake, especially from animal protein, increases the production of a hormone - insulin-like growth factor - which drives rapid growth and which is strongly associated with overweight and obesity in childhood," says Professor Karen Campbell from the Institute for Physical Activity and Nutrition at Deakin University.
![Kids can have too much of a good thing, protein included.](http://web.archive.org./web/20170609155323im_/https://www.fairfaxstatic.com.au/content/dam/images/g/w/k/2/f/2/image.related.articleLeadwide.620x349.gwk1z3.png/1496756107573.jpg)
Yet her research based on a group of 500 Victorian children suggests that Australian babies and small children are often consuming amounts of protein two to three times more than the recommendation for this age.
Campbell isn't the only one raising the alarm. Over the last decade a number of researchers have voiced concerns about high protein intakes in early childhood, and in May a Dutch study of more than 3500 children presented at the European Congress on Obesity found that a high protein intake in early childhood was associated with a higher BMI due to increased body fat.
"But until now little has been known about how much protein children have been eating, where it comes from, and how it relates to breastfeeding or early introduction of solids. We found that stopping breastfeeding early and earlier introduction of solid foods were both associated with higher protein intakes," Campbell says.
Children's diets haven't always been so protein-rich. A 1950s study of Australian children's diets found that by the age of eight to ten, protein made up around 12 per cent of their kilojoule intake, she says - yet her study found that from the age of one, protein was now contributing 17 per cent of kilojoule intake.
So where's all this extra protein coming from? Dairy products including formula are the major source, says Campbell, stressing that while dairy foods are a good source of calcium for kids, an overload of milk and formula can edge out foods that provide other important nutrients.
"At 18 months of age about one quarter of the children we surveyed were consuming more than 500mls of milk each day, but children of this age need just 400mls of milk to meet their calcium needs. Dairy food is convenient but it's not a good source of iron and too much dairy can displace foods that are important sources of iron such as red meat, poultry, fish, tofu and legumes. It can displace vegetables and fruit too," she says.
With red meat, the emphasis is on lean fresh meat - not processed meat like ham and bacon which aren't good sources of iron and are high in sodium - the Deakin study found that processed meat provided five per cent of protein in the diets of children aged three and five.
Legumes like lentils and beans are other protein foods that provide iron and have the added benefit of fibre to promote a healthy gut, Campbell adds.
But despite all those ads on TV promoting formula for raising healthy toddlers, that's more about smart marketing than nutrition science, she says.
"The advice is that children don't need formula after the age of 12 months and if parents do use formula it's best to look for brands with a lower protein content of 1.3 to 1.5 grams of protein per 100 mls," she says, adding that levels of protein in breast milk tend to be lower than in formula.
As for what's causing many children's diets to become unbalanced, Karen Campbell believes parents are often unsure where to get good information from.
"There's a lot of conflicting information around about children's nutrition. We've found that mothers of young children often get their information from a mix of sources like family, friends and the internet - but the quality of nutrition material online isn't always good."
To help fill the knowledge gap, Deakin University has developed a free online course on early childhood nutrition for parents and health professionals. Called Infant Nutrition: from Breastfeeding to Baby's First Solids, it involves three hours a week for two weeks. It begins on August 7 and you can register here.