A Sustainable Diet Must Consider Physical and Ecological Health

In a culture that is increasingly saturated with vegan “life-style influencers,” it is hard to ignore the assumption that a sustainable diet is one that is plant-based, and one whose products use as few natural resources as possible in order to lessen the global impact of climate change. However, a sustainable diet in such strict terms ignores a more comprehensive consideration of human physical health. An answer for what such a diet looks like might be better understood in relation to a continuum with the following extremes: a fully plant-based diet compared to a diet rich in animal products.

The American Journal of Clinical Nutrition defines sustainable diets as “those diets with low environmental impacts which contribute to food and nutrition security and to healthy life for present and future generations. Sustainable diets are … nutritionally adequate, safe and healthy; while optimizing natural and human resources.” It is important to note that some diets are more sustainable than others, but one’s diet must include deliberate considerations of both physical and ecological health to sustain both human life and the earth simultaneously.

The EAT–Lancet Commission expresses in their extensive report on healthy diets within sustainable food systems that “plant-based foods cause fewer adverse environmental effects per unit weight, per serving, per unit of energy, or per protein weight than does animal source foods across various environmental indicators,” while also cautioning that studies have shown that a total vegan diet – that is to say, one that is completely without consumption of any food or product containing animal products – has links to higher risks of type 2 diabetes and coronary heart disease, specifically plant-based diets that include less healthy plant food such as “refined grains and sugar-sweetened beverages.” With this information, it then becomes important to delve deeper into the carbon and water footprints for various foods  – with special attention to meat products in comparison to plant food – to more appropriately determine a diet that is effective in terms of health for both humans and the earth.

Considering the aforementioned definition of a sustainable diet from The American Journal of Clinical Nutrition, which indicates “low environmental impacts”, one must look at what natural resources are used (and/or wasted) in plant-based agriculture versus animal agriculture to understand why moving away from meat and animal products is important. This becomes more obvious when comparing specific effects from carbon dioxide, and overall greenhouse gas emissions.

The Meat Eater’s Guide to Climate Change directly compares the carbon footprint – which includes both production emissions as well as post-production emissions such as transportation – of meat and animal products, with various plant-based foods. According to their findings, it is clear that overall production of emissions from meat and associated animal products far outweigh those of plant-based foods. The values range anywhere from 3-35 kg of CO2 emitted – depending on the meat or animal product compared to the various plant foods researched, shown in the following chart. The meat and other animal products mentioned here are those that would otherwise replace the necessary nutrients for a physically healthy diet. It is also important to look at the water footprint of many of the same animal and plant foods to determine an effective sustainable diet that considers humans and the earth.

For added clarity, according to the U.S EPA Annual Inventory of U.S. Greenhouse Gas Emissions and Sinks, the United States’ agriculture practices make up for 9.5% of total greenhouse gas emission, of which raising livestock accounts for 41%.


While the data show that crop cultivation makes up half of the CO2 emissions – 10 percent more than livestock – up to 70 percent of all grain produced is fed to the livestock raised in the United States. Producing a kilogram of beef emits 26 kilograms of carbon dioxide, and the average person ate 98 kg of red meat and poultry in 2017. So, if Americans decrease their consumption of such foods, it would decrease overall greenhouse emissions.

The Natural Resources Defense Council has found that beef is about “34 times more climate pollution-intensive as beans and lentils, pound for pound”; if beef were entirely cut out of the American diet, it would reduce greenhouse gas emissions between 46 and 74 percent of the reductions needed to reach the goal made in 2009 at the Copenhagen Summit by former President Barack Obama of 17 percent reductions by 2020. This would still be the case, even if other animal products were kept in diets such as chicken, pork, eggs, and cheese.

A healthy diet that is mindful of physical and ecological health instead is one that focuses on whole grains, fruits, vegetables, nuts, and legumes, with minimal amounts of animal products to add much-needed nutrients and proteins. The EAT–Lancet Commission offers what that diet might look like on a daily basis. They define such a diet as consisting of: Nuts: 50 g (1 -3/4 ounces) per day; legumes (pulses, lentils, beans): 75 g (2-1/2 oz) per day; fish: 28 g (less than an ounce) per day; eggs: about 1 egg per week; meat: 14 g (1/2 an ounce per day; chicken: 29 g (1 ounce) per day; carbohydrate: whole grain bread and rice, 232 g carbohydrate per day and 50 g / day of starchy vegetables like potatoes and yam; dairy: 250 g (8 oz. glass of milk), vegetables: 300 g (10.5 ounces) of non-starchy vegetables and 200 g (almost 1/2 a pound) of fruit per day.

While plant foods have less greenhouse gas emissions, and overall need less water to produce than animal meat and products, one does not need to completely eliminate animal products from one’s diet.

-Posted by Brooke

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