Which is Healthier: Whole Milk or Skim Milk?
Let’s take a minute to talk about the differences between whole milk and skim milk and help shed some light on which one may be a healthier choice for you. I’m just going to focus on these two categories and not discuss organic, 1 or 2% milk or any other categories of milk.
The big difference between skim milk and whole milk begins with it’s preparation. Milk production in general is relatively straight forward: it’s harvested from the cows at the dairy farm, transported to a processing facility and goes through pasteurization, homogenization and further processing. Pasteurization involves heating the milk to kill the bacteria and homogenization involves “mixing” the fat evenly throughout the milk so that all the fat doesn’t sit at the top. It is at this point it can also be separated for other products like cream, cheese, yogurt, etc. Since nothing has been removed from the milk, it is considered whole milk and can now be sent off to retail.
Skim milk undergoes the same process until it gets to the processing phase. Here it is allowed to sit in one place where the heavier fats can float to the surface forming a cream. This creates a a more fat dense cream at the top which can be skimmed off, leaving the lighter “skim” milk to be processed. After that, it goes through the same processing as whole milk.
So that’s the background, now let’s look at the nutritional content of the two.
At face value, it seems obvious that skim milk is healthier because it has less calories and less saturated fat. So the first question to ask: Is skim milk healthier?
A 2003 study (AAFP, Schoof et al.) assessed the effects of low fat diets and low calorie diets on sustained weight loss. They concluded “The review suggests that fat-restricted diets are no better than calorie-restricted diets in achieving long-term weight loss in overweight or obese people”. So this study is telling us that low fat is not necessarily better.
A 2012 study (Archive of Diseases in Childhood, DeBoar et al) investigated the relationship between types of milk consumption and body habitus among young children. The study results were very surprising. They found that children who consumed 1% or skim milk were more likely to be overweight or obese than children who consumed whole milk.
Studies have shown that low fat and low calorie foods do not necessarily lead to lower calorie consumption and healthy weights. Researchers don’t really know why this happens, just that people who consume low calorie drinks are not necessarily healthier.
People who drink skim milk, which contains less calories, may increase their calorie intake other places leading to a zero sum calorie intake or perhaps more net calories. These calories may come from other, unhealthier sources. Additionally, in an effort to get children to drink more milk, some milk producers have been adding sugar to sweeten skim milk.
The second question one can ask is: is whole milk bad for us in the first place?
Historically, it was believed all fat was bad and this lead modern society to turn to low fat products, including skim milk. This was a logical conclusion that assumed that all dietary fat intake lead to an increase in body fat. Fortunately, it’s not that simple.
A 2013 study (Scandinavian Journal of Primary Health Care, Holmberg et al.) concluded “A high intake of dairy fat was associated with a lower risk of central obesity and a low dairy fat intake was associated with a higher risk of central obesity” among a population of 1700 40-60 scandinavian men.
Another 2013 study (European Journal of Nutrition, Kratz et al) completed a meta analysis of 16 different studies looking at whole milk consumption and concluded “The observational evidence does not support the hypothesis that dairy fat or high-fat dairy foods contribute to obesity or cardiometabolic risk, and suggests that high-fat dairy consumption within typical dietary patterns is inversely associated with obesity risk.”
These two studies strongly suggest that whole milk consumption does not increase your risk of obesity or cardiometabolic risk factors. In fact, it suggests that whole milk has a protective effect against these diseases.
Why this occurs is not entirely clear. Whole milk is known to contain more fat (obviously), and this means more omega 3 fatty acids. Omega 3 fatty acids are known to be protective against obesity and cardiovascular disease. Additionally, this phenomenon may be regulated in part but cholecystokinin, a hormone that is released in response to the presence of fat and protein in the gut and helps tell us that we are full.
So in summary, I think we can draw two conclusions.
The first is that skim milk is not necessarily a “healthier” or “better” alternative to whole milk. While it does have fewer calories and less fat, both good and bad, this does not always translate to a lower daily caloric intake or a healthier body mass. That said, skim milk is not intrinsically bad for you. You can drink it and get good fats from other sources and still be very healthy.
The second is that whole milk is “unhealthy” or has “too much fat”. The fat in whole milk includes more healthy unsaturated fats, including omega 3 fatty acids. It also appears to have an inverse relationship with the risk of obesity and cardiometabolic risk factors. This counterintuitive evidence is a stark contrast to historical dietary advice that whole milk was bad for you.