Lately, I’ve been hearing a lot of debate about which type of milk is best for kids to drink. As a nutrition scientist and mom of three, I wanted to take the time to explore the science on the topic.

whole milk vs lowfat

What do Pediatricians Say?

The American Academy of Pediatrics (AAP) recommends that kids switch from whole milk to low-fat/non-fat milk starting at age two. With significantly reduced levels of saturated fat and cholesterol, this switch is intended to help reduce the risk of potential long-term health consequences like high cholesterol, heart disease and excessive weight gain, while still providing the same amount of calcium, vitamin D and other essential nutrients.

This recommendation by the AAP was developed by an expert advisory panel comprised of pediatricians and researchers who reviewed dozens of studies on the topic.

So Why Are Some Families Choosing Whole Milk?

Despite the AAP’s recommendation, many families are now choosing to drink whole-fat milk because they believe it is more natural, less processed and, as a consequence, healthier.

Adding more support to the whole milk advocates is a paper recently published in the Archives of Disease in Childhood and a related opinion piece written by two notable nutritionists. The study of more than 10,000 kids found that children who consumed 2% or whole-fat milk at ages 2 and 4 weighed less and were less likely to be overweight/obese than children who consumed 1% or skim milk at these ages.

This finding directly contradicts the AAP recommendation, which as I just mentioned, recommends low-fat milk to help prevent excessive weight gain. But before you swoop in and grab that cup of low-fat milk from your toddler’s hand, pouring the rest of the carton down the drain let’s take a closer look at the science.

Does this Mean that Drinking Low-fat Milk Makes Kids Gain Weight?

According to the study, kids who consumed 1% or skim milk had higher body mass indexes (BMIs) and were more likely to be overweight or obese than kids who consumed 2% or whole-fat milk even after controlling for other factors, like age, gender, and income, which may also affect weight status. This was true when the kids were 2-years-old and when they 4-years-old.

However, I’m still not convinced that low-fat milk is the culprit. Consider this:

  • Kids who consumed 1% or skim milk started out heavier than the kids who drank 2% or whole milk.
  • Over the course of time, the kids who drank 1% or skim milk group did not gain more (or less) weight than those who drank 2% or whole milk. Both groups simply maintained their average weight trajectory.
  • This study is a cross-sectional analysis, which is basically a snapshot of information taken at a very specific point in time. In this case, it means that the type of milk the kids were drinking and the kids’ weight were measured at the same time, so one cannot say that drinking skim milk led to – or caused – higher weight or obesity.

Could Something Else Lead to Weight Gain?

Another consideration is that there are a lot of important measures- contributors to weight gain – that we don’t have comparisons for in these two groups of kids. For example, the number of total calories the kids are eating each day was not accounted for. It is possible that kids consuming 2% or whole-fat milk took in fewer calories overall, compared to kids who drank 1% or skim milk, and that it was the lower total caloric intake that accounted for lower weight gain, not the type of milk specifically. Furthermore, this study did not measure the actual amount of milk consumed or the amount of physical activity the two groups of kids regularly engaged in.

Why does this matter? Because above all else, change in weight (not health) is a function of the balance between the number of calories you take in (through eating) and the number of calories you expend (through exercise). Thus, it is possible that the links between milk consumption and weight observed in this sample are because kids who drink 2% or whole milk also take in less energy overall or are more active.

Is it Possible that Drinking Whole Milk Makes Kids Feel Fuller and Eat Less?

Each cup (8 fluid ounces) of whole-fat milk contains, on average, 150 calories and 8 grams of fat while 1% milk contains 102 calories and less than 1 gram of fat. If fat and calories are the drivers of satiety – the feeling of fullness that comes after eating – then one might come to the conclusion that whole milk would do a better job “filling you up.” While there is some evidence to support this hypothesis, we do not know the extent to which differences in individual’s diet quality or dietary choice would affect calorie replacement or weight gain.

There is some evidence to support this, with studies among various age groups finding the same or greater rates of weight gain with consumption of reduced-fat compared to whole milk suggesting that people were compensating for the lowered calorie content of low-fat milk. But this is just speculation, and we do not know what people were replacing those calories with or the extent to which individual differences in overall diet quality could have affected food choice or, ultimately, weight gain.

What Have Other Studies Found?

Several lines of research have informed the AAP’s recommendations for reduced-fat milk in children over 2 years old which echo other public health dietary guidelines in emphasizing low intakes of saturated and trans fat, cholesterol, and added sugar and salt. However, data linking milk type to weight gain in young children are mixed: one study found no association, one found higher BMIs among kids drinking 1%/skim milk, and yet another found greater weight gain among those drinking 2%/whole-fat milk. Still, beginning around 2 years of age dairy products become a major source of saturated fat and cholesterol in children’s diets. In light of their association with overweight, a transition to reduced-fat milk (and other dairy products) is advocated for the very young.

What Should You Make of All This?

As with most nutrition advice – especially when it comes to a single food item (like milk) or a single nutrient (like saturated fat) – the key is balance. If your child eats a diet that is already low in saturated fat and is a healthy body weight then giving them whole fat milk is a reasonable choice. And while giving your kids a gallon of low-fat milk each day might not prevent them from gaining extra (unwanted) weight, serving a daily cup of low- fat milk, along with a heavy helping of vegetables, some quality protein, and a lot of good old-fashioned active play just might do wonders for their overall health.

Personally, I did switch from skim to 1% milk for my kids, but given that they eat a nutritious and balanced diet and get plenty of time in active play I won’t be making the switch to whole-fat milk just yet.

My oldest daughter, working on her milk pour.

My oldest daughter, pouring herself a glass of low-fat milk.

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