Originally published 24 Jan 2020. Last updated 13 Sept 2020.
1. Cow's Milk for Human Consumption
This week, I received a question from a listener asking if cow's milk was harmful to women.
If you identify as male and are listening to this episode, I promise that I will talk about whether cow’s milk is helpful or potentially harmful to all, regardless of gender.
But, first, I have to share a story with you.
Should Humans Be Drinking Cow's Milk?
Anytime the topic of cow’s milk and its potential health effects comes up, my mind immediately flashes back to a moment in grad school.
One of my professors was completely against anyone drinking milk that came from an animal. In one of my classes, he mentioned human beings are the only species that he knows of that continue to consume milk after infancy. So, after the age of 1, he questioned why we need to consume milk at all.
At the time, I was nodding my head in class thinking, “Yeah! He’s so right! That IS interesting.” But, as I progressed beyond graduate school, I began to think more critically about this statement. For example, there are certain cultures around the world that view animal milk as a gift from the heavens. This is likely because it was a valuable food source for hundreds if not thousands of years and may have been crucial for their survival.
Now that we live in more modern times, what’s the real story behind cow’s milk and its relationship with health? Let’s dive in…
What is Cow's Milk Made Of?
First, we need to think about what cow’s milk is made up of. It’s composed of quite a bit of water, different types of sugars (mostly in the form of lactose), some protein, some fat, and vitamins and minerals. So, it’s pretty nutrient-dense when we think about it — it’s got a little bit of everything: water, carbs (in the form of sugar), proteins, fat, and vitamins and minerals, like calcium. How could this be bad, right?
Well, first of all, some individuals are intolerant of the sugar (lactose) found in cow’s milk. Others may have an allergy to the proteins found in cow’s milk. But, I’m not going to go into detail here about those particular situations. Instead, let’s assume you are able to consume cow’s milk with no immediate health effects. Is it beneficial to do so?
Can You Get Cancer from Drinking Cow's Milk?
When we look at the data, it turns out that consuming cow’s milk regularly may not increase your risk for most diseases. Now, I need to point out that cow’s milk can come in different forms, from the stuff you add to you morning bowl of cereal or cup of coffee, to yogurt, and probiotic drinks.
I’m going to strictly talk about cow’s milk in its most common form — basically, what you pour from a carton into your cereal bowl or coffee mug. When it comes to ovarian cancer risk, scientists closely examined 22 separate studies to see if a relationship between milk and the risk for developing ovarian cancer exists. They found consuming milk and dairy did not increase ovarian cancer risk. Instead, they found that consuming high fat dairy products, like butter, increased cancer risk. This link between a high saturated fat diet and risk for cancer has been found in other studies as well.
There have also been a number of studies looking at whether milk and dairy consumption increase a person’s risk for developing colon cancer. The good news here is that milk consumption was not associated with an increased risk of colon cancer in both men and women. Same goes for Type 2 diabetes. Low-fat dairy was associated with a decreased risk for developing Type 2 diabetes.
Yet another study examined the link between milk and dairy and cardiovascular disease, like heart attack and stroke. The researchers concluded that milk and dairy may protect against cardiovascular disease. Another study looked at whether milk consumption shortened our lifespans. The researchers concluded that consuming milk does not shorten lifespan.
Milk and Disease Studies
So, now you may be wondering, “Uh… it seems pretty clear that milk doesn’t seem to be a problem, so why the controversy?” The reason is because when foods and their respective nutrients are studied, researchers have different ways of looking at them. Said another way, researchers use different study designs or different research methodologies to look at the links between foods and disease risk.
For example, if a researcher today wanted to study this very same topic and ask, “Does consuming milk increase a person’s risk for developing disease?” she or he would have a lot of options. They could set up their study this way: they could ask a bunch of folks that are in the later stages of life whether they have any diseases and then ask them to remember how much milk they consumed when they were younger. They would then perform their analysis and see if milk led to their disease.
Or, they could recruit some younger individuals and follow them into their twilight years, all the while monitoring how much milk they consume. Then, 50 years down the line, they could look at which of them end up with a disease and see if milk may have led to that. Or, they could randomly assign people to experimental groups: where 1 group is asked to consume milk and the other group isn’t allowed any and then we see what happens to their health. And, the list goes on and on.
Each study design has its own strengths and weaknesses.
So how do we make sense of all of this when there are so many different ways this topic could be studied?
The Harvard School of Public Health summed it up well, and I quote, “… when it comes to the health impact of dairy, the existing science is about as clear as a glass of milk.”
Is Low-Fat Dairy Good for You?
So, what should we do? A nutrition research scientist at the aforementioned Harvard School of Public Health was quoted as saying, “Dairy isn't necessary in the diet for optimal health, but for many people, it is the easiest way to get the calcium, vitamin D, and protein they need to keep their heart, muscles, and bones healthy and functioning properly.”
So, here’s the recommendation: consuming 1-2 servings of dairy to your diet each day is likely going to be beneficial for you. 1 serving would be 1 cup of milk (1 cup is about the size of your fist).
If you’re adding ½ cup to your coffee, that would be half a serving. 6 oz. of yogurt would also count as 1 serving. When we think about servings of cheese, it gets a bit more complicated since cheese comes in so many forms. 1 stick of string cheese, which is about 1 oz., would be considered 1 serving. If we’re talking shredded cheese, about 1/3 of a cup would be 1 serving.
And researchers at the Harvard School of Public Health still believe that low-fat dairy is a better option than full-fat options like whole milk.
2. How Common Are Milk Allergies?
Don't you think food allergies seem to be much more common nowadays? Once, we thought of food allergies as really only affecting kids, and is something most eventually grow out of, but now it seems much more widespread.
There are agencies that track how common food allergies are and which are most common. Over the last 20 years or so, the data does in fact reveal a spike in the number of food allergies and intolerances. Many factors are being blamed for this supposed spike. Many are pointing the finger at pesticides, others the widespread use of genetically modified foods (which I will just abbreviate GMOs from here on out).
What’s particularly concerning about GMOs is that when foods are genetically modified, the protein content of the foods are being adjusted – they’re increasing some, while decreasing others.
That seems harmless, right?
Food Allergies and Proteins
Well, when someone has a food allergy, it’s the protein in the food that the body responds to and causes the allergic response. If we mess with the proteins in our foods, could we be changing how the body responds to those foods? Possibly. I am not saying that GMOs are to blame for the spike in food allergies. But this is a very interesting area of future study.
We also need to keep something else in mind when we consider these data. Are we seeing a spike in food allergies and intolerances because people are actually experiencing these more often, or is it because we are getting better at identifying and reporting this information? Allergy testing, while not perfect, has continued to improve over time and maybe this is why we’re seeing an increase in the number of reported cases.
Food Allergies vs. Intolerances
I mentioned food allergies and intolerances above. I want to clarify the difference: a food allergy involves an immune response. This means that the body’s main defense against harmful pathogens (the immune system) starts to wake up when exposed to certain foods.
And it’s not like it just wakes up and goes back to sleep – it wakes up with a roar like it has something to prove. It overreacts and starts to cause symptoms that can range from a stuffy or runny nose, to gas and bloating, to eczema and rashes, all the way to the most serious: anaphylactic shock. How the body will respond depends on the person and how angry their immune system is.
A food intolerance, on the other hand, can still involve uncomfortable symptoms but the immune system basically stays asleep. The body’s response is usually less intense and there’s virtually no risk of someone experiencing anaphylactic shock.
Percentage of Population with a Milk Allergy
It has been estimated that 0.2-0.4% of the U.S. population has a milk allergy. This means roughly 645,000 up to 1.3 million people in the U.S. have a milk allergy. Again, the accuracy of these numbers depends on whether people actually go see an allergist to get tested, whether the allergist reports it to larger agencies, etc. so don’t put too much stock in these numbers. However, typically milk allergies are not all that common in adults–but lactose intolerance tends to be reported more often.
This is because as we get older, our bodies produce less of a very specific enzyme that helps us digest lactose. This happens to all of us as we age, which is why many older adults experience some form of lactose intolerance.
If you have a diagnosed milk allergy, you need to be very careful about staying away from foods that contain any milk products. Because, again, your immune system gets really angry when it encounters milk.
If you have been diagnosed with any food allergy, please speak to your doctor about how best to avoid those foods and how to manage your body’s response to it, if you accidentally consume it.