WEDNESDAY, June 7, 2017 (HealthDay News) -- Young children who drink soy, almond or other milk "alternatives" may be a bit shorter than kids who drink cow's milk, a new study suggests.
Researchers found that among more than 5,000 Canadian children, a 3-year-old who drank three cups of non-cow's milk each day was, typically, a half inch shorter than a child who drank the same amount of cow's milk.
The study -- which was funded by the Canadian government and St. Michael's Hospital Foundation -- doesn't prove that parents' milk choices were the culprit.
For one, there could have been differences in the children's overall diets, too, said lead researcher Dr. Jonathon Maguire.
But, he said, the nutritional content in different milk substitutes vary widely. And it's "reasonable to hypothesize" that some shortchange children on protein, fat and other nutrients, said Maguire, a pediatrician at St. Michael's Hospital in Toronto.
A pediatric nutrition specialist who wasn't involved in the study agreed.
"With the exception of soy milk, other (non-dairy) products contain almost no protein," said Erin Corrigan, a registered dietitian at Nicklaus Children's Hospital, in Miami.
When it comes to fat, she said, coconut milk has a relatively higher amount. But many cow's milk alternatives contain little fat -- which may be fine for an adult, but not for a toddler, Corrigan said.
Plus, she added, the calcium from milk alternatives is generally not as well-absorbed as the calcium in cow's milk.
No one argued that young children must have cow's milk.
But, Maguire said, parents who choose alternative products should be "savvy" about reading nutrition labels. And they should be sure their child's overall diet has adequate protein, fat and other nutrients, he said.
The study findings are based on more than 5,000 children between the ages of 2 and 6. In all, 13 percent drank non-cow's milk every day, while 92 percent drank cow's milk daily.
Overall, Maguire's team found, there was a correlation between the type of milk kids drank and their height at age 3: For each daily cup of non-cow's milk, children were 0.4 centimeters -- or 0.15 inches -- shorter than the norm for their age, on average.
On the other hand, for each daily cup of cow's milk, kids were 0.2 centimeters (0.08 inches) taller than the norm.
The study did not ask about the specific type of cow's milk alternative, or about overall diet. Those are two important gaps in the research, according to Corrigan.
"We don't know why kids were drinking non-cow's milk," she said. "We don't know whether the family was vegetarian or vegan, for instance."
In at least some cases, a child's overall diet might have been lacking, according to Corrigan.
It's possible for vegetarian diets to be healthy for young children, she said -- though vegan diets (which exclude all animal products, including eggs and dairy) are trickier.
"It depends on the child and their acceptance of the diet," Corrigan said. "There's a difference between a child who's only eating bagels and pasta, and a child who's eating a variety of foods like quinoa, legumes, tempeh and avocados."
But does it matter if a 3-year-old is a bit shorter than his or her peers?
According to Maguire, height is an indicator of overall "nutritional status" and development. He acknowledged, though, that it is only one measure of development.
It's also possible, Maguire added, that kids who drink milk alternatives "catch up" in height later in childhood.
But, he said, the bottom line is that parents should not assume the alternative products are "healthier" than cow's milk -- no matter what the advertising claims.
Corrigan made another point: Non-dairy milks come in sugar-sweetened varieties, with flavors such as chocolate and vanilla that appeal to young children. She cautioned parents to avoid any products with added sugar.
In general, Corrigan said, if parents want their children to a follow a more-restricted diet -- vegan or otherwise -- it's a good idea to talk to a pediatric nutrition specialist if possible.
The study was published June 7 in the American Journal of Clinical Nutrition.
The Academy of Nutrition and Dietetics has advice on dairy alternatives for kids.