Green conundrum

So much nutrition and health gospel spreads through word of mouth. Often, these truths are simply based on conjecture and “common” knowledge.

Which means that, in fact, they may not actually be true at all.

At the end of the day, it can be tough to distinguish facts from beliefs in this business. That’s why I want to tell you about an interesting article that I came across recently.

It deals with the widely held opinion that plant-based diets are more earth-friendly. And as it turns out, this may not be true after all. At least, not according to the results of a new study from France.

Researchers analyzed the eating habits of more than 2,000 French adults, based on food diaries the subjects kept for seven days.

They identified the most frequently eaten foods and evaluated the carbon footprints of each choice. (That is, the amount of greenhouse gas emitted during production, measured in grams of carbon dioxide per 100 grams of food.)

In generating these values, researchers addressed every move from farm to table, including how the food was cooked. With one exception–they didn’t factor in transportation from the market to a consumer’s home.

If you ask me, this is a pretty important omission. Surely, walking to the Farmer’s Market isn’t the same as driving several miles or more through rush-hour traffic to get to a major supermarket chain. (And that’s after the cross-country trek that most supermarket produce already takes.)

The EPA estimates that driving your average car generates 423 grams worth of carbon dioxide emissions per mile. You do the math.

Anyway, this study found that meat production generated 1,600 grams of greenhouse gas for every 100 grams. That’s way higher than the amount of carbon dioxide that came from fruit, vegetable, or starch production–more than 14 times higher, in fact. And it’s more than double the carbon footprint of fish, pork, poultry, or egg production.

But, when the researchers parsed these emissions calorie for calorie, they found that this seemingly huge gap wasn’t really so wide after all.

In fact, every 100 calories of meat only produces about three times the emissions of the same amount of fruit and veggies. Greens in particular emit as much carbon dioxide per calorie as pork, poultry, or eggs–and even more than starches, sweet and salty snacks, dairy, or fats.

When it came down to practical results–that is, how much of any of these foods people actually ate to get their energy every day–this study revealed a surprising conclusion.

Namely that diets rich in fruit, vegetables, and fish aren’t more earth-friendly than junky diets packed with sugar and salt. And, in fact, high-nutritional quality diets have a significantly larger carbon footprint than their low-quality counterparts… by as much as 22 percent.

Obviously, there are plenty of potential flaws in this research. For one thing, food diaries aren’t particularly reliable. And then there’s the obvious problem with comparing animal products to produce, calorie for calorie.

Still, it’s hard to ignore a finding like this.

I’m always hearing people say that vegetarianism is the most ecologically responsible way to eat. These findings certainly fly in the face of that common claim. And as someone who believes firmly in the health benefits of animal protein, I’m happy to hear it.

But it’s a bittersweet victory for omnivores, because the results of this study shed light on a much larger problem. And that’s the carbon footprint that comes with bringing any form of real food, plant-based or otherwise, to consumers.

And I would hardly call forsaking leafy greens a viable solution to this issue. I think everyone can agree on that.

Ultimately, sustainable eating appears to be a much more confusing topic than we thought. Especially as we look more closely into how our food is produced.

But I do know of one guaranteed way that you can make your meals better for your health and the earth: Buy local whenever you can.

High nutritional quality is not associated with low greenhouse gas emissions in self-selected diets of French adults. Am J Clin Nutr. March 2013, vol. 97 no.3, 569-583.