Health, with a Grain of Salt

Explaining the science and debunking the myths of nutrition, metabolism, and health.

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Don’t Trust the Headline: No, Vegetarian Diets are Not Bad for the Environment

This week in my new favorite segment, “Don’t Trust the Headline,” many, many articles have been reporting that a new study just concluded that “lettuce is worse than bacon for the environment.” As a health conscientious individual, I’m often thinking about how my lifestyle impacts my health as well as this beautiful planet that houses me. Like many people, I limit my consumption of meat for both my wellbeing and that of The Mother, so I was a little perplexed when I saw headlines like the aforementioned as well as this one from Science Daily:

 

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So, like any good scientist, I decided to find said paper and read it for myself. Before reading, I considered that this paper may have been funded by meat lobbying groups, but it wasn’t. It was funded by the Colcom Foundation and a grant from the Steinbrenner Institute for Environmental Research at Carnegie Mellon. Nothing suspicious there.

The paper was published in Environment, Systems & Decisions and the more I read, the less I liked the media.  The aim of this study was to determine how changing our diets can impact the environment as there has been a call for the dietary guidelines to mesh with environmental sustainability goals. Further, given the obesity epidemic, there is also a recommendation for people to eat fewer calories (amongst other goals). The authors of this study evaluated three possible scenarios:

  1. Reduce caloric intake in order to facilitate weight loss.
  2. Adhere to the Dietary Guidelines for Americans (DGA) without reducing caloric intake.
  3. Adhere to the DGA and reduce caloric intake.

This was a meta-analysis that used various databases to determine how many calories we consume in America and how much it costs in terms of blue water, greenhouse gas emissions, and energy usage in order to produce over 400 types of food. What they reported was a bit surprising: “shifting from the current US diet to dietary Scenario 1 decreases energy use, blue water footprint, and GHG emissions by around 9 %, while shifting to dietary Scenario 2 increases energy use by 43 %, blue water footprint by 16 %, and GHG emissions by 11 %.” Shifting to Scenario 3 “increases energy use by 38 %, blue water footprint by 10 %, and GHG emissions by 6 %.”  *cue jaw drop*

That’s about the extent of which the media covered this topic (that is, they read the abstract), but things just didn’t really seem to add up. Here are some things that I took away from this paper:

  • Calorie to calorie comparisons. This analysis compared production costs of one calorie of a given food to another. This is an issue because when we replace meat with vegetables, we typically aren’t aiming to eat the same number of calories.  Four strips of bacon provides 175 calories, whereas you’d need to eat about 20 cups of shredded lettuce to get the same caloric load. Good luck. A better comparison would be pound-to-pound.
  • Food Waste. This study did something that most don’t and considered calorie consumption, not just intake. Calorie consumption includes intake as well as food waste (both personal and what’s lost at the commercial level).  Current caloric intake was estimated at 2,390 kcals/day/adult American. However, calorie consumption was estimated at a whopping 3,620 kcals/day/adult based on the conservative estimate that 34% of food is wasted at the consumer and commercial/retail levels (estimates range from 34-42%). What this tells me above and beyond anything else is that the greatest food production related effect we can have on our environment, not to mention our wallets, is wasting less food.
  • Fish/seafood and dairy consumption. It’s well described that raising meat has a huge impact on the environment. Pork and beef produce lots of greenhouse gases and require a huge amount of energy and water to grow. The DGA recommends eating less meat than Americans currently do, but the guidelines have recommendations for high dairy and seafood/fish consumption. I disagree with the dairy guideline because dairy isn’t necessary to have a healthy diet, but as this study shows, if we are to meet the dairy guidelines, we have to be eating a lot more dairy (~204 more kcal/day). That means that we need more dairy farms, which are not good for the environment. And then there’s fish/seafood. From a health standpoint, I highly recommend eating fish, but based on the results from this study and others,  it isn’t a very sustainable option. Farmed fish requires a lot of energy, while fishing wild fish/seafood is the second highest driving force in greenhouse gas emissions. Neither option is good so unless we come up with something better, the guidelines for fish intake likely need to be altered if we want our recommendations for human health to sync with those for planetary health.
  • Vegetarian diet wasn’t tested. Many headlines claimed that vegetarian diets are worse for the environment than omnivorous diets, but vegetarian diets weren’t actually tested. Perhaps many writers deduced this from the comparison of lettuce to bacon, but most vegetarians aren’t eating lettuce as their main source of calories.  Grains, beans, and soy are the primary caloric sources for many vegetarians. This analysis showed that production of these foods have some of the smallest influence on the environment so changing consumption patterns doesn’t do much to the environmental impact estimates made in this study. Finally, based on results from prior studies, the researchers concluded that “adopting a vegetarian diet or even reducing meat consumption by 50% is more effective in reducing energy use, the blue water footprint, and GHG emissions through the food supply system than adopting a healthier diet based on regional dietary guidelines.” Thanks for not reading the paper, media.

This paper is by no means the final word in deciding how we should eat in order to strike the best balance between human and environmental health. The data they used was limited in that most of it came from other countries because of the lack of analyses done here in the US. Thus, we need more research using more precise methods of data collection that are directly applicable to the US. However, this paper provides the justification to do just that. What I took from this paper, though, is that we waste too much food in the US, we depend too heavily on food from land that can’t support the agriculture (think: drought-stricken California), and the environmental consequence of transporting food all across the country (or world) is enormous. But what I did not take away from it is that we should eat more meat.

Image by Monstruo Estudio.

agricultureenvironmentmeatnutritionsustainabilityvegetarian

caitlindowphd • December 18, 2015


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