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Jan 11, 20185 min read

How Our Food Choices Affect the Environment Jeanne Rosner, MD

Updated: Nov 14, 2019

An overview Human survival is dependent on consuming food. What we choose to eat, however, can have an enormous impact on our environment. Twenty-thirty percent of manmade greenhouse gases are related to the food we eat. Our food choices also dramatically affect both our water resources and water pollution.

Of the three macronutrients in our diet: carbohydrates, fats and proteins, protein has the greatest impact on the health of our environment. Protein comes from both animal and non-animal sources. Omnivore protein sources include animals; vegetarians can get some of their protein from items produced by animals (such as butter, eggs and milk); and vegans will not consume any animal sources, nor their products. They get their protein from vegetables, beans, grains, legumes, seeds and nuts.

The modern food chain Greenhouse gas emissions occur every step of the way in our modern, industrial food chain: 

Production –> Processing –> Distribution –> Consumption –> Waste

Three gases are central to this process:

  • carbon dioxide (CO2)

  • methane (CH4)

  • nitrous oxide (N2O)

Each of these gases traps heat in the atmosphere to a differing degree. N2O does it with 300x more efficiency than CO2 does. CH4 traps heat nearly 25x more than CO2. The different gases are also emitted into the atmosphere in varying amounts, with CO2 contributing 76% of emissions, CH4 14% and N2O 8%.

Let’s look at the different protein sources and see how they impact CO2 emissions. This chart differentiates between pre-production CO2 impact and post-production CO2 impact.


Emissions Impossible, Environmental Working Group

The striking conclusion that one can draw from this chart is that animal sources of protein contribute significantly more to CO2 gas emissions than do non-animal sources. The sad consequence is that we are overloading the natural carbon cycle and emitting more greenhouse gases into the atmosphere than it can process, resulting in increasing temperatures. Even the smallest change in temperature wreaks havoc on the earth’s climate.

Deforestation, reliance on synthetic fertilizers and pesticides, enteric fermentation and manure production, transportation of feed, fertilizer and animals, and food wastage all contribute to greenhouse gas emissions. Let’s take a closer look. 

Huge swaths of land are being cleared of trees (our current storage depots for carbon) to plant monocrops of corn and soy as feed for the cows in concentrated animal farming operations (CAFOs). Without a reservoir of trees for carbon sequestration, the carbon is converted to carbon dioxide gas, which is subsequently released into the atmosphere.

Conventional modern farming relies on synthetic fertilizers and pesticides to do the work of nourishing soil and ridding it of pests, rather than relying on compost and cover crops to naturally perform these actions. These synthetic products contain nitrogen, which ultimately contributes to the emission of more greenhouse gases (N2O) into the atmosphere. They also create runoff—the gases enter our waterways, leading to the pollution of our oceans (see below about water impact).

A massive number of cows are raised in CAFOs. Their food source is grain, rather than grass, which is their preferred natural food source. Cattle have a unique digestive system that includes four stomachs, or rumens. In these rumens, enteric fermentation occurs, which results in an inordinate amount of burping. That belching emits large quantities of methane into the atmosphere as a greenhouse gas. Cow manure also emits methane and nitrous oxide. Anyone who has driven down Highway 5 in California knows all about CAFOs and the cows’ excessive belching and manure production. The horrible stench of methane can be detected miles away from these massive cattle complexes. 

Water Agriculture accounts for 70% of all our planet’s water usage. In the graphic below, you can see that animal sources of protein use a tremendous amount of water. Raising meat requires 20x more water than growing grains. The water is used to grow the animal’s feed as well as to hydrate the animal during its life cycle. 


Synthetic pesticides and fertilizers are often used to produce the animals’ grain food sources, making matters worse. The nitrogen and phosphorus from these synthetic products become agricultural runoff, which ends up in our water sources—typically oceans, but also lakes and rivers. The runoff has created large areas of oxygen-depleted water. These dead (or hypoxic) zones are unable to support marine life. Notable dead zones in the US are in the Gulf of Mexico and along the coasts of Oregon and Virginia. Fortunately, dead zones are reversible if their causes are reduced or eliminated.

What can you do? What can we do to mitigate the environmental damage we do through our food production?

  • Eat locally sourced food.

  • Eat seasonally.

  • Eat less processed food.

  • Waste less food (food waste accounts for 40% of food lost, and 25% of our precious water is used to produce this food).

  • If you garden, do it organically. Don't use synthetic pesticides or fertilizers, do not till, use compost to help keep carbon in the soil. (Read more about organic farming here.) 

  • Eat more climate-friendly proteins (beans, nuts, seeds, grains and vegetables).

  • Move meat to the side of the plate instead of serving it as the main entrée.

  • If you eat meat, choose organic, grass-fed and grass-finished meat.

Remember, we have a choice about what we eat. Let’s be mindful of the impact our food choices have on the environment.


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Jeanne Rosner, MD

Jeanne Rosner is a board-certified anesthesiologist who practiced pediatric anesthesia at Stanford Medical Center for nearly 20 years. In 2011, she began teaching nutrition classes in her son’s 5th-grade science class. It was an “aha” moment for her. She realized that learning and teaching about nutrition, health and wellness in her community washer destiny. 

Since retiring from anesthesia, Jeanne has been a nutrition educator in the San Francisco Bay Area. She teaches middle school children the importance of eating food closest to the source, making good food choices and eating in a balanced and moderate way.  Jeanne started SOUL (seasonal, organic, unprocessed, local) Food Salon in 2014. SOUL Food Salon’s mission is to educate and empower people to be healthier. She holds small gatherings (salons) at which experts in the health and wellness community share their knowledge on how to lead a healthier life.


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