Would you intentionally eat something that has been “proven” to increase your risk for cardiovascular disease and death by up to 18%, increasing with every additional half serving? [1] Something that has been found to clog your arteries and cause heart attacks and strokes? Probably not.
Actually, though, you probably do—because it’s an egg.
Eggs have also been proven to be an excellent source of protein with healthful antioxidants like lutein and zeaxanthin, and vitamins and minerals such as Vitamin A, D, choline, and selenium. And they’re low-calorie!
Do you ever wonder why there are such contradictions in nutritional advice, so many flip-flopping headlines? One major reason is the complicated nature of performing nutrition research.
The study that “proved” eating eggs increases risk of death was published in the Journal of the American Medical Association in 2019. It involved 30,000 participants over 13 to more than 30 years and considered many factors, including overall fat consumption, smoking, and lifestyle. Seems like a well-designed study, yes?
But…this study surveyed the participants only once on their diet, at the beginning of the study period. Have you ever followed the same diet for 10 plus years? Is it scientifically justified to draw diet conclusions when the diet is surveyed only once in 10 to 30 years?
The gold standard in biological research is a trial in which participants are randomly assigned to receive either the treatment under investigation (the treatment group) or a placebo or standard treatment (the control group). Further, neither the investigators nor the participants should be aware of who is getting the treatment and who isn’t (double-blind)—something that’s impossible to do with food. Gold-standard studies done over a long period of time are extremely difficult and extremely expensive, yet long-term studies are essential when trying to judge the effects of food.
In reality, most nutrition science is blurred, contains no controls, and does not follow the experimental method, much less being double-blind or even randomized.
Additionally, most nutritional studies are observational, with information gathered from participants over several years as to their diets and health, as well as other aspects of their lives which might affect their health. Such studies have two big problems.
- An observational study can never prove that one thing causes another. Even if you did observe that people who ate more eggs had a higher prevalence of cardiovascular disease, all you know is that people who eat more eggs have more cardiovascular disease. Maybe for some unknown reason, people who are inclined to have cardiovascular disease are also more inclined to eat eggs?
The fact is that it’s impossible to determine what is the true cause in observational studies, because there is no way to pinpoint what exactly is leading to the health outcome. You can find only associations, never causations. And yet, that’s where we get most of the results that are reported in nutrition studies.
- Observational studies generally depend on people self-reporting their food intake, which is notoriously inaccurate (if you’ve ever tried to fill out a daily intake report on MyFitnessPal, you know how difficult it is to self-report your diet. And sometimes we just don’t want to admit to ourselves we’ve eaten a whole bag of potato chips in one sitting, much less confess to a stranger our eating vices).
There are also many factors outside of food that contribute to health outcomes. Studies that attempt to control and account for the differences across peoples’ lives are very difficult to manage. Two such studies dealing with the same foods and similar populations can easily yield quite different results, depending on other aspects of the participants’ lives which are not controlled or even measured.
Where does all that leave you? With this advice:
- Ignore headlines about the dramatic results of the latest nutritional study. They are designed to get you to click. If you want to delve into the research, look for long-term meta-analyses or systematic reviews, which are essentially combinations of many individual studies which hopefully will “average out” the flaws of those studies to yield reliable conclusions. Even those may not be reliable, though, if the studies that are included, or their authors, are funded by pharmaceutical or food manufacturing companies. Another approach is to read books by deeply knowledgeable authors who themselves are familiar with—and cite—hundreds or thousands of studies. Even then you have to watch for writers with axes to grind, which is why you’ll want to read a variety of authors.
- Do not act on results of studies based on mouse biology or other animal studies. A scientist who sees something interesting happen with a mouse might justifiably use that to motivate an investigation into what happens in humans, but it’s never a substitute for such an investigation.
- Remember that confusion about food is profitable. If we were all clear about what to eat, we’d be immune to the next fad diet or fad food (the food industry also has been known to fund their own research, publishing findings that support the consumption of their product).
- Finally, look for independent sources of information that have the goal of educating you about the human body rather than persuading you to adopt a particular diet or food.
This doesn’t mean that all nutrition guidelines are invalid. There are eating patterns and ways of eating that are known to be healthful (hint: unprocessed or lightly processed foods)—and there are eating patterns that are known to be the opposite of healthful (hint: processed and ultra-processed manufactured foods). But always keep in mind that we each have a unique genetic code with unique genetic expressions, a unique microbiome, unique locations, cultures, unique body compositions, unique ways of life and activity levels, unique preferences… And that so much more than diet impacts health.
Unfortunately, and fortunately, what you eat is up to you. Perform your own nutritional study with yourself (researchers would call this a “population of 1”). It won’t be random, it won’t have a treatment and control group, and it won’t be blind, but at least there’s little chance of deceiving yourself about what you eat (hopefully!). And paying closer attention to what you eat may be all that’s needed to improve your health.
Reference
1. https://jamanetwork.com/journals/jama/fullarticle/2728487
