A new study of more than 5,000 children has associated consumption of non-cow's milk with shorter height, raising concerns about the nutritional content of cow's milk alternatives.
Researchers found that children who consume non-cow's milk may be shorter than average for their age, compared with children who drink cow's milk.
Furthermore, the study revealed that the greater children's intake of non-cow's milk, the shorter they are likely to be.
Lead study author Dr. Jonathon Maguire, of St. Michael's Hospital in Canada, and colleagues recently reported their findings in The American Journal of Clinical Nutrition.
According to the National Institutes of Health (NIH), the advice is that cow's milk should not be given to children under the age of 1 year, as it lacks many of the required nutrients. What is more, the protein and fat in cow's milk is hard for babies to digest.
For children over the age of 1 year, however, cow's milk is considered beneficial for the developing brain and bone health, due to its high content of fat, protein, and calcium.
Studies have also associated cow's milk consumption in childhood with increased height. The new study supports this association, after finding that children who drink non-cow's milk are likely to be shorter.
Each cup of non-cow's milk linked to shorter height
Dr. Maguire and team came to their findings by analyzing the data of 5,034 children aged 24 to 72 months who were a part of the Canadian Applied Research Group for Kids cohort.
The researchers looked at each child's daily intake of cow's milk, as well as their daily intake of non-cow's milk, such as soy milk and almond milk.
Cow's milk was consumed on a daily basis by 92 percent of the children, while 13 percent of the children drank non-cow's milk every day.
Compared with children who consumed cow's milk, those who drank non-cow's milk were shorter than average for their age; for every 250-milliliter cup of non-cow's milk consumed daily, children were an average of 0.4 centimeters shorter.
For each cup of cow's milk consumed daily, however, children were an average of 0.2 centimeters taller.
The team identified a height difference of 1.5 centimeters for a 3-year-old who drank three cups of non-cow's milk daily, compared with a 3-year-old who consumed three cups of cow's milk every day.
The researchers also identified shorter-than-average height among children who drank a combination of cow's milk and non-cow's milk, suggesting that cow's milk does not offset the link between non-cow's milk and reduced height.
Nutritional content of non-cow's milk may be to blame
The study was not designed to pinpoint the underlying mechanisms for the link between non-cow's milk intake and shorter height, but the researchers suggest that it might be down to the lower levels of protein in non-cow's milk.
As an example, Dr. Maguire notes that two cups of cow's milk contain around 16 grams of protein, which is 100 percent of the daily protein recommendation for a 3-year-old child. In comparison, two cups of almond milk contain just 4 grams of protein.
"The nutritional content of cow's milk is regulated in the United States and Canada, while the nutritional contents of most non-cow's milks are not," says Dr. Maguire. "The lack of regulation means the nutritional content varies widely from one non-cow's milk product to the next, particularly in the amount of protein and fat."
Given that childhood consumption of non-cow's milk is on the rise - due to allergies and perceived health benefits - the researchers believe that there should be increased focus on the nutritional content of such products.
"If products are being marketed as being equivalent to cow's milk, as a consumer and a parent, I would like to know that they are in fact the same in terms of their effect on children's growth," says Dr. Maguire.