Don’t Believe The Headlines From Every Nutrition Study. Here’s Why — From a Nutritional Sciences PhD
By: Brandon J Eudy
Tags: Eggs, Health, Science, Vegan, Nutrition

Don’t Believe The Headlines From Every Nutrition Study. Here’s Why — From a Nutritional Sciences PhD

Image by Lebid Volodymyr on Shutterstock

I am always scouring the latest articles published in nutrition journals to find interesting new research on diet and health. Sometimes, I find studies like these two below that advertise striking findings, but actually, turn out to be all smoke and mirrors.

Two recent nutrition studies separately suggested that A) vegan diets can be useful for weight loss and B) egg consumption is associated with type 2 diabetes. Although the results of these studies agree with those themes, what these studies DO NOT show is that C) Vegan diets are superior to other diets for weight loss or optimal health and D) Any mechanism or proof that egg consumption causes type 2 diabetes. In other words, the results of these studies were very weak!

Unfortunately, news headlines have taken these studies and presented them in a very misleading manner. The researchers are also somewhat guilty for not indulging the full limitations of their respective studies. Here, I want to discuss what these studies actually show, and provide some of the contexts that would be easily missed if you only took a quick glance at the headlines or study abstracts.

Study 1 — Vegan diets help you lose weight

The first study was a randomized controlled trial in which a vegan diet promoting medical doctor, Neil Barnard, was an author. The authors claimed that following a low-fat vegan diet for 16 weeks resulted in weight loss (approximately 13 pounds) and reductions in liver and muscle fat content in already overweight study participants.

The vegan intervention group was compared to study participants who continued to eat their normal (likely bad) diet. This choice of the control group is the first major problem with this study.

If you compare nearly any diet to a standard American diet and measure weight loss as an outcome, literally any other diet will win!

This is why the authors should have reported weight loss as a function of “cutting out the junk food” rather than consuming a low-fat vegan diet. Replacing junk food with “something else” is the exact mechanism of how this dietary intervention was successful!

I do, however, have to give the authors credit in stating the difficulty in determining whether it was diet or weight loss that drove the reductions in liver and muscle fat. I would wager weight loss drove these effects because weight loss and calorie restriction are understood to be one of the best ways to reduce fat content in organs, especially the liver. Keep in mind, the participants in the low-fat vegan group were also eating fewer calories during this study.

In summary, the authors showed that following a reduced-calorie, low-fat, vegan diet could be a useful weight-loss tool. However, they missed (or didn’t admit to) the major reason these participants lost weight: fewer calories and less junk food. I have a feeling this reflects the personal bias of the authors, which is to be expected and not entirely out of bounds.

We can all fall in love with our hypotheses at times, right Dr. Ancel Keys?

Study 2 — Egg consumption is associated with type 2 diabetes

The second study was epidemiological (showing association, not cause) and demonstrated that egg consumption was associated with type 2 diabetes in a Chinese population.

Here, the authors tracked the diets of over 8000 participants from urban and rural regions across nine Chinese provinces for 18 years and correlated self-reported egg intake to diabetes status. Egg intake was defined as eggs from any type of fowl and also “foods containing eggs”. Diabetes status was defined as fasting blood glucose above 7 mM.

The participants were divided into quartiles of egg consumption with the lowest quartile representing 0–9 grams of egg per day and the highest quartile representing >37.6 grams of egg per day.

This was strange to me since a large egg weighs ~50 grams without the shell and eating one egg per day is NOT what I would consider a high intake.

The study participants also ate high carbohydrate diets with 63% of calories from carbohydrates in the low egg group and 54% of calories from carbohydrates in the high egg group.

This study design is problematic. The authors are trying to determine how eating as little as one egg per day might influence diabetes risk in the context of a high carbohydrate diet. Furthermore, the high egg group contains more overweight and obese participants. It turns out that being overweight is ALSO associated with developing type 2 diabetes and thus, is a confounding factor.

Another problem with how this study has been disseminated is that the authors included “foods which are made with eggs” as egg consumption. Eating a boiled egg is different than eating a muffin containing eggs.

A major problem with epidemiological studies is that they provide little context. For example, imagine you and a large group of friends go to a party and enjoy a delicious cocktail spread. About half of you, including yourself, want to be healthy and avoid ultra-processed foods, so you pick out some boiled eggs, veggies, and maybe a small dessert. You were very hungry and by the end of the night, you have eaten seven boiled eggs! Now let’s look at the other half of your friends, including Archibald. Archibald fills his plate with a few meatballs (warmed from frozen and filled with soybean oil). He has two slices of pecan pie for dessert. He has eaten zero eggs!

In this situation, do you think the “high-egg” or “low-egg” meal would be the healthier choice? Understanding the limitations of epidemiology is that simple. These types of studies should be hypothesis generating, not conclusion generating.

Fortunately, the authors do address this to some extent, suggesting that dietary patterns in different countries (such as the US vs Spain) might place egg consumption in a different context and could be a reason for the discrepancy between previous epidemiological studies.

Finally, I do see why the authors wanted to conduct this study. Back in the 1990s when the study began, eggs were not seen as anything close to healthy food (at least in the US)! When it comes to very-long-term nutritional studies, interventions are not feasible. Epidemiology is sometimes the best data we can get. However, I hope we learn lessons from this study and others about the difficulty of interpreting this type of data.

Nutrition science always requires context

The first randomized controlled feeding trial shows us that replacing junk food in the diet with more “Real Foods” promotes weight loss and reductions in intra-organ fat. This makes perfect sense and it is incorrect to directly attribute these results to following a low-fat vegan diet. However, I have to throw a bone to the authors and agree that a low-fat vegan diet could be one of many “tools” for weight loss in a context similar to that seen in the study.

The second study is even less informative. In a Chinese cohort, eating at least the equivalent of one egg per day was associated with a 65% increase in the prevalence of type 2 diabetes. When correcting for obesity and overweight status, that increase dropped to only 17% and became nearly insignificant. This study gives zero proof OR mechanism indicating that eating a plate of scrambled eggs for breakfast is going to trigger any sort of chronic biochemical cascade resulting in type 2 diabetes.

When it comes to eggs, let’s stick to what we know. Eggs are a rich source of nutrients like choline, vitamin D, and protein. Not to mention, they are delicious and of great importance to many cultures and cuisines around the world. If you enjoy eating eggs,…please continue! I eat eggs for breakfast every morning and will certainly continue to do so.

Brandon J. Eudy, PhD

https://realfoodexplored.com