Why is it so hard to figure out what to eat?
Michael Pollan made the argument in his book the Omnivore’s Dilemma that with a vast amount of choice and change in the food industry comes added challenge, disease, and confusion, which has resulted in a kind of “national eating disorder.” Entire books have been written about this topic, but I’m concerned with a specific part of this question. As I begin my graduate program in the field of nutrition, I believe the more prevalent question is:
Why is it so hard to figure out what to eat for health?
Different from what every best selling diet author would have you believe, eating for optimal health is confusing and complicated for most people. There are hundreds of fad diets and books by PhDs, physicians, chefs, and journalists advocating for some specific diet supposedly supported by a mountain of evidence and claiming phenomenal results for your weight, your health, and your well-being. Many of these books present contrasting dietary advice, which just adds to general confusion. As rates of obesity and metabolic diseases continue to climb, we are still confused about how to eat for our health. Here are some of the factors that contribute to this confusion.
1. There’s still much we don’t know
The more we learn in this field, the more we realize how much is still unknown. We know a lot, but aspects of nutrition and metabolism are still somewhat unexplained. For example, although we’ve known about the existence of microorganisms in the human body since the late 1800s, it was only in the past ten years that we’ve begun to understand the role that these microbes play. In fact, it was only recently that we discovered the symbiotic role our natural microbiota (these species of bacteria that colonize our bodies) may play. Recent research even suggests that these gut bacteria have a role in our weight; however, there is still much unknown regarding specific species, ratios, and mechanisms.(1) There are so many factors that contribute to health, and we are still learning.
2. Blame it on the Research… or those interpreting the research.
Have you ever been confused by all the contrasting dietary advice you hear on different podcasts/the news/books/blogs/various documentaries? They all cite what appears to be research to back up their stories, and to many it sounds promising. Then you hear someone else on the radio saying the complete opposite and backing it up with other research studies, and whenever these podcast hosts/ authors/documentarians/bloggers are confronted with opposing research, they fire back with the limitations/drawbacks/conflicts of interest associated with the opposing research. And we wonder why nutrition is confusing…
The vegan crew constantly claims that there is a mountain of evidence that meat and dairy products cause cardiovascular disease and cancer, while the Ketogenic crew claims that a diet high in fat and protein (and often meat) results in weight loss, clearer thought, and reduction in cardio metabolic risk factors. Then there are the grain-free gluten-free people spouting that gluten and grains cause scary chronic inflammation and autoimmune disease, which is opposed by research suggesting that whole grains improve gut microbiota diversity and reduce inflammation. Don’t even get me started on the shit show that is the saturated fat and coconut oil debate. So, why is it that we appear to have mountains of research with contradictory results? Well, one reason is that results are often misinterpreted by experts and non-experts alike leading to utter chaos and rapid fad change in the health and wellness world. Another is the research, specifically, the type of research thats conducted, population studied, quality of research, and statistical analysis.
On Nutrition Research
There are many different ways research is conducted in the field of nutrition. I won’t bore you with the intricate details of how research in this field is conducted, but I will give you a general overview of some of the types of studies being conducted in this field, and the drawbacks associated with each kind of research.
It’s not ethical or practical to lock up a person and force them to eat only lard for months in a controlled environment, but we can do that with mice. Mouse models are used in preliminary research on everything from fecal transplants to developing new cancer drugs. The problem with this type of research is that humans aren’t exactly mice, so the findings don’t always transfer to humans, but this type of research has been important in developing and testing the safety of all kinds of drugs, and has proved monumental in the fields of nutrition and genetics. Note: there’s an interesting Freakonomics Radio episode that discusses this.
Observational Epidemiological Studies
Observational epidemiological studies examine patterns of disease and health in a defined population. These studies allow researchers to draw inferences in large samples when the researcher is unable to control the independent variable due to logistical or ethical concerns. These are used to identify risk factors for disease, influence policy making, and are commonly used in public health. The problem here is that correlation does not equal causation. It is almost impossible to exclude external causal effects, and most of these studies are only able to establish correlation (a connection), which is NOT causation. In fact, you can find a number of hilarious examples of things that are highly correlated statistically but seemingly unrelated such as the divorce rate in Maine and per capita consumption of margarine or people who can’t type preferring thin crust over deep dish pizza. Now, I’m not saying that observational epidemiological studies are of no use, but I am saying that we should be careful not to jump to conclusions when a study has shown solely correlation between variables.
Randomized Controlled Clinical Trials
These are considered the gold-standard of research, the most rigorous type of study scientifically speaking, providing the highest quality results. There are, however, issues researchers face when conducting randomized controlled clinical trials. All clinical trials must pass rigorous examination, and must be deemed both ethical and relatively safe prior to enrolling humans. Also, it can be extremely challenging enrolling a large enough sample size of participants. The last study I worked on was only able to enroll 54 participants over the course of two years for just a ten-week study. Another issue researchers face is levels of adherence. You can ask a participant to eat a certain way, but that doesn’t mean they’ll do it. Finally, if it’s difficult enrolling participants for a short study, try getting a large number of participants and asking them to do something for a longer period of time. There are many other challenges that researchers face when conducting this type of research, but the evidence and conclusions emerging from these types of studies is considered by the research community relatively strong.
So, hopefully you have a better idea why the research can be confusing and difficult to interpret.
3. Everyone is Different
We are all different, not just genetically, but also in terms of environment, exposure, and experience, and the medical field is finally starting to take this into account. We have now progressed into an era of personalized or precision medicine, which seeks to tailor treatment based on an individuals predicted risk or response to disease, but it’s not an exact science. Nutrition also plays a part in this, with recent studies suggesting that a one-size-fits-all approach to dieting may not be effective.(2)(3) With this in mind, it’s important to understand that what makes your friend or family feel or perform optimally may not work for you.
So, how do we make sense of all of this conflicting dietary advice?
My advice for anyone confused is to remain skeptical. The key is to educate yourself, and don’t believe everything you read on a blog or on Instagram. Seek out reputable sources and advice from professionals (such as registered dietitians, physicians, and scientists). Learn the science so that you are able to pick out statements that don’t quite seem right, or ask someone who does know the science to explain it to you. Most importantly, seek out medical professionals who are passionate about evidence-based practice and who are willing to work with you and your needs and preferences.
What works for me is balance, moderation, and enjoying what I eat, but I admit that my methods may not work for others.
(Sacks FM, Bray GA, Carey VJ, et al. Comparison of Weight-Loss Diets with Different Compositions of Fat, Protein, and Carbohydrates. The New England journal of medicine. 2009;360(9):859-873. doi:10.1056/NEJMoa0804748.