In a world full of health “shock-umentaries” and scathing personal health opinions, dietitians and other medical professionals rely on high quality scientific evidence to debunk pseudoscience for the public. But what happens when trusty science can no longer be trusted? As of late, this is happening more often than it should be.
Is Dairy Bad for You?
In a recently published review article in The New England Journal of Medicine, Dr. Walter Willet and his colleagues detail possible negative health outcomes of consuming dairy products. At first glance, this article appears to be like any other scientific review, but upon close examination, the paper contains a lot of overstating of the science, and what we call in research ‘fallacious arguments’ – arguments that are deceptive and appear convincing, but lack scientific rigor. This article is an excellent example of strategically skewed science, often with the goal of pushing the personal agenda of the researchers.
Bias – Why it Matters in Science
Dietitians are scientists. We all have Bachelors of Science, and many of us go on to get our masters or PhDs, or contribute in research. Part of being a good researcher is reflecting on your personal bias, and most importantly, getting another group of scientists, those that would be MOST critical to your arguments, to review and explore your research. It shocks me that a peer reviewed, reputable journal would publish this review – and frankly – I’m looking forward to the published rebuttals that are undoubtedly going to happen.
Being a scientist requires being open to where you have your blinders up – your personal biases and working to filter your work through a lens that is neutral, or even opposing. At Ignite Nutrition, we look at everything through the lens of gut health and pull in our experienced colleagues when we need another opinion – and a lot of times we do! We can’t possibly know everything, and there are times when our biases inevitably get in the way. The difference is flexibility and the ability to take a step back and reflect upon them.
This article lacks a strong peer review, and frankly, pushes a particular view, rather than an article that weighs evidence and draws conclusions based on all the data. Is there some evidence to support their take? Sure. But – what about the mountain of evidence assessing dairy consumption and benefits to health? A good scientific review not only looks at all the evidence but identifies limitations (on both sides). This paper basically ignores it. So, let’s jump into some of those arguments.
The Shaky (At Best) Evidence
For starters, the authors state that there haven’t been any established health benefits of consuming dairy products. Wait, WHAT? So, they’re saying that there’s never been any research to confirm that milk products support our health? I can think of numerous studies and reviews that would say otherwise. In fact, the majority of the paper overlooks the compelling data on dairy, to go on to suggest that not only is dairy unnecessary, it’s harmful.
For example, the authors start the paper by suggesting bone fracture incidence is linked to dairy consumption through correlative data, when in fact there are many strong meta-analyses to confirm that foods high in calcium, protein, and vitamin D (like dairy) appear to be preventative for good bone health. Dr. René Rizzoli provides an excellent meta-analysis of the current literature on calcium, vitamin D, and bone health which can be found here. The compiled research shows that dairy products (due to their specific nutrient content) are related to reduced fracture risk and overall improved bone health.
And yes, as the research suggests, you can also get calcium, vitamin D, and protein from other sources, and THAT’S OK! However, this recommendation becomes a problem when an entire food group is villainized to push a vegan agenda.
When it comes to nutrition research studies, nutrition science is one of the hardest things to research, and research well. In fact, no matter where you look, you will find data seemingly in conflict with other published research. It’s normal and expected – because we cannot control for every variable in someone’s lifestyle. What we want to understand is, over time, which way does the cumulative evidence lean? This particular paper pulls only the studies that support their conclusion and ignores the mountain of evidence to suggest the opposite – a BIG red flag.
Correlation vs. Causation
While the authors acknowledge that the link between dairy consumption and fractures is correlative, they go on to build their argument around this correlation. By stating that countries with high intakes of milk actually tend to have the highest rates of hip fractures as well, they are making the assumptive claim that consuming more dairy actually puts us at higher risk of developing bone fractures.
That’s like me saying that because I’m blonde, I ride the bus to work. While both of these things are true, we can’t assume that they are related. Instead, things like socio-economic status, environmental values, and other lifestyle choices would need to be considered. Similarly, the rocky evidence from the authors on this claim doesn’t consider vitamin D status, genetics, longevity, exercise, environmental factors, or overall diet quality – because a lot more goes into building strong bones than simply calcium.
Aside from bone fracture risk, the authors also look at how dairy consumption links to cardiovascular disease. They state that milk is beneficial to the heart when being used as a substitute for sugary beverages (like pop or juice) and then state that milk isn’t beneficial if it replaces whole fruit, nuts, and legumes in the diet. My question is – Why are they assuming that milk is replacing those other foods? Isn’t there room for both in a balanced diet?
As a dietitian, I think it’s important to reflect on how nutrition is not black and white, but rather, grey. It makes room for cultural preferences, personal preferences, and that a healthy diet is not ‘one size fits all’. This review serves to scare the crap out of people by cherry picking data that lean hard on personal bias, not illicit positive behaviour change.
In fact, we’ve seen many health professionals jump on this review as an opportunity to say no dairy at all, ever, should be consumed. Yep – our own colleagues.
Frankly – if a professional doesn’t explore the roles that autonomy, culture, and preference play in food choice, this is a sign to RUN for the hills.
What About Dairy Intolerances?
While dairy is not the health problem that this article makes it out to be, there are certainly people that have dairy intolerances and simply feel better when avoiding it. Many people are intolerant to lactose (the carbohydrate in dairy) and have a difficult time breaking it down, which can cause digestive upset.
Additionally, some people have cow’s milk allergies to the proteins in milk, which can also lead to digestive issues, hives and skin rash, and even anaphylaxis. But keep in mind, these people are not ALL people.
When talking about milk allergies in this article, Willet and his colleagues point out a study in which 67% of children with a diagnosed intolerance to cow’s milk had reduced symptoms when switched to soy milk. Well, OF COURSE! They were diagnosed with a milk intolerance, so drinking an alternative would surely help. It seems the researchers felt the need to include this study as yet another way to create buy-in to avoiding cow’s milk at all costs.
At the end of the day, you can choose to avoid milk products if you feel better by doing so. As digestive health dietitians, we frequently work with patients who simply feel better when they aren’t drinking milk. We don’t care what you choose as long as you’re choosing it for the right reasons. However, we DO care if the driving factor behind your nutrition choices is fear. You should never have to be scared into a diet.
Additionally, not all dairy is the same! Many people who have lactose intolerance can still tolerate hard cheese, fermented yogurts, and lactose-free dairy products.
The Bottom Line on Dairy
We can’t rely on observational data alone to make health recommendations. We need a combination of varied study designs in order to look at the data as a whole prior to fear mongering people into cutting out an entire category of food. Additionally, we can’t take each individual published paper at face value. There is A LOT to unpack with any scientific research. It is important that we continue to challenge science and revisit our assumptions to remove bias.
Additionally, carefully reading between the lines is SO important. Does the author “breeze over” scientific research that doesn’t support their hypothesis? In research, this is what we call a ‘fishing expedition’. Instead of forming a hypothesis (your research question -ie. Does milk consumption impact risk of cardiovascular disease?) the authors clearly formulate their conclusion (we need to prove milk causes cardiovascular disease) and formulate data and statistics around it. This is sloppy, and dare I say, irresponsible science. This appears to be the case with Willet’s article, as he rushes through studies in which milk is deemed beneficial and spends paragraphs reviewing studies that support his theory of milk being unhealthy for us.
And if you’re still unsure about what all of this “science” means, let me be clear. There is NOT an inherent risk to drinking milk as this article presents. You can enjoy cheese, milk, and yogurt if those are foods that you value in your diet. Alternatively, you can absolutely meet your calcium and vitamin D requirements in other ways.
You can enjoy cheese, milk, and yogurt if those are foods that you value in your diet. Alternatively, you can absolutely meet your calcium and vitamin D requirements in other ways.
As a consumer, YOU get to decide whether you drink milk or not. A review like this should never be enough to justify the blanket recommendation that nobody should be drinking milk ever. And this applies to ANY nutrition research – you get to decide about carbs, meat, vegetarianism, and so on.
*Side note: after this article was written, a new article associating milk drinking with breast cancer came out. Our colleague, Abby Langer covered it SO well here if you want to learn more!