A New Look At Vegetarian Versus Omnivorous Diets

You’ve probably heard people tout the benefits of a vegetarian diet. A recent research review is in agreement with those claims, but it’s important to always take a critical look at study design.

There’s been a lot of dogma over the years about the health benefits of vegetarianism. For decades a vegetarian diet has been associated with better health and longer life. The problems of confounding factors and bias have only recently come to light. People who choose to live as a vegetarian because they believe it’s healthier probably do other things that are healthier too, so it’s not possible to discern what really works by any simple method, especially in human beings who have such long lifespans.

One proposed research method is to select dietary facets that have independently been associated with health and test a diet’s compliance with those facets. For example, if eating a lot of vegetables makes you healthier, then any diet that incorporates a lot of vegetables must be better than one that does not. While this isn’t a direct method of research, it is probably more precise when done right. A study this month in Nutrition Journal used this method. It compared a vegetarian diet to an omnivorous diet using two different eating protocols: the Healthy Eating Index, or HEI, and Mediterranean Diet Score, or MDS.

Getting down to brass tacks, the vegetarian diet scored higher on both protocols. The researchers concluded that vegetarianism yields denser nutrition. If I were a less discerning journalist, I suppose I’d call it a day right there. However, there are some major problems with this conclusion as far as I’m concerned.

First, the two protocols make dubious claims as to how healthy they actually are. The HEI is based on the USDA food pyramid. And while the 2010 version of the HEI that they used here is definitely vastly improved over older models, it’s still grain heavy and not really what many nutritionists would say is the best diet. The MDS heavily penalizes the consumption of any meat that isn’t fish and also gives points for grain consumption. I’m not sure I could support the rating system of either of these protocols.

Second, the scores were not that different anyway. When you look at the values the researchers arrived at based on the scores, some of them might make you scratch your head. For example, the HEI lumps together seafood and plant protein, the former of which has numerous healthy fats, the latter of which has had some link to disease. Of course, the vegetarians had more plant protein so they got more points, but that doesn’t necessarily make them healthier, since they ate no animal-based sea food. The omnivores had more protein, which would be better for athletes, and ate fewer refined grains. On the MDS, the omnivores may have scored lower simply because they ate meat at all.

When looking at studies like this, be wary of how they inform your decisions. If you actually look at the individual data points, it seems that the only real health issues surrounding the omnivorous diet are just a matter of simple adjustment. The omnivores consumed more empty calories, less fruits and vegetables, and more alcohol. None of these really has to do with the diets in question, and the omnivores got more protein, which is a good thing.

In the end, I doubt the veracity of the protocols here. Omnivorous eating done right is probably the healthiest way to eat, and if you are a vegetarian, get more protein and cut back on the refined carbs.


1. Peter Clarys, et. al., “Dietary pattern analysis: a comparison between matched vegetarian and omnivorous subjects,” Nutrition Journal 2013, 12:82

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