Last weekend, my sister mentioned that she had come across an article being shared on Facebook that claimed that children who drink non-cow's milk end up being shorter than those who drink cow's milk. My nephew doesn't drink cow's milk due to allergies, so she was concerned (my family is also vertically challenged to we need all the help we can get). In the next few days I saw the article everywhere. The study being referred to in the media was a study conducted at the University of Toronto that compared the height of kids who drank cow’s milk with those who drank non-cow alternatives such as soy, almond, cashew, rice and goats milk. The result of the survey showed that children who drank cow’s milk were 1.5 cm taller at three years old than those who drank non-cow milk.
But does that mean if you feed your kids cow’s milk alternatives, you could potentially be blamed for their insufferably underdeveloped height?
I don’t think so. Here’s why.
This particular study, cited in various news articles including one in the National Post, was a cross-sectional style study. This means that researchers analyzed data collected from a population at a specific point in time, and the study involved no real “experiment” per se, but was observational in nature instead. With cross-sectional studies, because data on each participant is recorded only once, it is difficult to assume that a risk factor caused an outcome over time. To simplify things, you can’t say one thing “caused” something else when using this study style with any degree of confidence. Also the researchers have no data to indicate how long the children have been consuming cow’s milk or non-cow alternatives, and there will be no follow-up in the future.
5,034 healthy Canadian children aged 2 – 6 years old were a part of this study. Of the 5,034 children involved, 92% consumed cow’s milk, and only 13% consumed non-cow milk. Moreover, the researchers did not ask participants to specify the type of non-cow milk that was consumed by their children. Rather, the investigators categorized non-cow alternatives such as almond milk, soy milk, rice milk, cashew milk, and goat’s milk together, a research approach that is somewhat problematic. Let me explain.
Are all non-cow milk the same?
The simple answer to the above question is no. Unlike cow’s milk, non-cow milk is not standardized in terms of the nutritional content. To say it another way, different non-diary milk sources contain different amount of nutrients, including protein, an oversight that the study did not consider before lumping all non-cow milk together and making spurious conclusions.
Using data from the USDA Food Composition Database, the amount of protein in different milk is shown below:
As shown in the graph, the amount of protein in different milk varies considerably. For example, the protein content of soy milk is 5 times more than that of almond and cashew milk. It is well known that children need adequate protein from their diet to grow and develop healthily. Researchers hypothesize that milk proteins (casein and whey) and insulin-like growth factor (IGF-1) in cow’s milk might contribute to an increase in height. Insulin-like growth factor is important in encouraging growth and development in children. Cow milk protein has also been shown to stimulate the human body to make its own IGF-1, which in turn may increase height. However, protein from other sources such as beef, chicken, and plants (lentils, chickpeas, and beans) can also stimulate increased production of IGF-1. As such, children do not need cow’s milk to produce it on their own.
The researchers claim that all questionnaires and physical measurements were collected by trained researcher assistants; however, such procedure is usually fraught with human errors. Just imagine trying to get a three-year-old to be still long enough to accurately measure their height. I myself have worked at a family medical clinic and can assure you that accurately measuring a toddler is not an easy feat. Measurement error, to at least some degree, is not unlikely.
With regards to how intake data were collected, the only questions asked in the study were as follows: “How many 250-mL cups of cow milk does your child have in a typical day?” and “How many 250-mL cups of non-cow milk (soy, rice, goat, etc.) does your child have in a typical day?”. Several studies have demonstrated that dietary intake is difficult to measure, and any single method cannot assess dietary intake accurately. People generally tend to have difficulty in recalling dietary intake, and numerous studies have shown that self-reported dietary intake is consistently inaccurate. Therefore, the estimates of intake of cow’s milk or non-cow milk are gross estimates vs. accurate and exact amounts.
What about genetics?
Additionally, researchers had incomplete data for parental height, the height of the child’s parents. Thus, they did not take note of the relationship between parental height and the height of the children, and there is no way researchers can determine with certainty that at least some of the height difference observed between kids who drank cow’s milk and kids who did not drink cow milk was due to genetic differences in height.
What about the rest of their diet?
The researchers also acknowledged that they could not account for other dietary factors that might contribute to height because of data limitations. They did not collect information about the general diet of the children; rather, they only asked specific questions about cow’s milk and non-cow milk. Therefore, the overall protein intake of the children studied cannot be comprehensively determined. Many other dietary and non-dietary factors could also account for the difference in height between the two groups.
What to consider if you’re still going to choose non-cow milk
If you choose to feed your child non-cow milk, there are a few things to consider:
- If you choose a lower protein option (e.g., almond or cashew milk), you may want to ensure that your child is getting enough protein from other dietary sources.
- You should avoid or limit flavoured non-cow milk (and cow’s milk) as they can pack a heavy sugar punch. For example, Silk, a popular brand of alternative milk, sells a chocolate soymilk that has 19 g of sugar per one cup. That’s almost four teaspoons. Here is some perspectives: for someone consuming a 2000 calorie diet, the World Health Organization recommends that such person consume no more than 25 g or 5 teaspoons of sugar a day.
Tip: there are 5 g of sugar in a teaspoon
- If you don’t like an alternative milk because your family doesn’t like it for some reasons, you should consider choosing goat milk, which is equivalent in protein and calcium to cow’s milk and is easy to digest.
In conclusion, you are not a bad parent if you are not feeding your child cow’s milk. There are cow’s milk alternatives that are nutritionally comparable, and there are other ways to compensate for lower consumption of protein. PLEASE don’t believe every nutrition headline you read in the media - they are notoriously bad for sensationalizing research. In fact, I haven’t had a glass of cow’s milk since I was 8 years old and I have never broken a bone in my life (nor have I melted).
Do you think there is any consequences if parents decide to start using non-cow milk alternatives instead of cow’s milk? Feel free to drop your comment.
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