Updated: Jul 19
Yes, it's the argument everyone loves to hate. It seems like vegetarian and vegan options are springing up everywhere these days. Meanwhile, meat-based (or omnivorous) diets have gotten a bad rap in recent years for a number of reasons, but are they really so bad? Let's see what the evidence says!
Right off the bat, let me acknowledge that this is a controversial topic that many people on both sides feel very strongly about. Do you love meat? I get it. Don't want to see animals suffer? I get that too. There's no judgment here. Besides, change takes time, especially with a practice as cultural, emotional and habitual as eating. Just try to keep an open mind as we follow the data.
What did our ancestors eat?
One way to approach the question of diet is to look to our ancestors for inspiration. We evolved to eat specific types of foods over thousands of years, so if we can mimic that diet, the logic goes, our bodies will be well-suited to digest it. The so-called 'paleo diet', developed by nutrition scientist Dr. Loren Cordain, is often held up as the ideal representation of this ancient diet. It recommends making meat a significant portion of the diet (although perhaps not as much as you think), as well as fruits, vegetables, nuts, and other unprocessed foods. It does not include grains, dairy, sugar in most forms, and oddly, legumes such as beans (a topic of some controversy, although many scientists agree that the benefits of consuming legumes outweigh any risks they might pose). While the paleo diet makes some positive recommendations in terms of eating more fruits and vegetables and avoiding sugary processed foods, it probably isn't a good representation of what our ancestors actually consumed.
Evidence from modern hunter-gatherer communities makes at least one thing clear - there's no such thing as a 'standard human diet'. Some communities living in cold, harsh environments, like Mongolians and the Inuit, get almost all of their calories from meat. Other societies do nearly the opposite, eating whatever plant and animals products they can find, including honey, berries, seeds, and roots. Amanda Henry, a paleobiologist from the Max Planck institute has found evidence from fossilized human teeth that suggests that humans began eating starchy grains tens of thousands of years before the invention of agriculture. Some populations, like those found in the Mediterranean, consume large quantities of grains and vegetables, filling in the rest of their diet with nuts, meat, seafood, and more than a little olive oil.
Summary - Our ancestors ate whatever was available in their unique ecosystems, whether plant or meat-based.
Which is worse for the environment?
It's no secret that producing food requires a lot of resources. All foods require water and nutrients, as well as space to grow. It also takes enormous amounts of energy to harvest, package, and transport food around the world to bring them to you. Ultimately, all of that energy comes from the sun. Even the fossil fuels we burn to power our tractors and factories can be traced back to ancient plants that kept their hard-earned energy stored away from us for millions of years - energy they absorbed from sunlight. Where food is concerned, however, there's a problem of efficiency known as the 10% rule.
At each biological level, organisms can only obtain about 10% of the energy from the level below them. By the time you reach the highest trophic levels (where we are), the sun's energy is nearly gone. This means there is less overall energy available for animals higher up in the energy pyramid, including herbivores like cows and chickens which we happily consume. As a result, we would be better off eating plants directly, bypassing the middle levels and taking advantage of the improved efficiency. This should result in far less energy being wasted, and as a consequence, should also end up reducing the amount of land area and water needed to feed us.
Our World in Data is a great site for all kinds of graphs and statistics. Their data on the environmental impacts of different foods is exceptionally useful for figuring out what you should and shouldn't eat, but there is a lot of information to sort through. Each food is compared in terms of its carbon emissions, water use, land use, and so on. To simplify things, I created the graph above to compare all of these variables at once. In the interests of transparency, I'll briefly explain how I did it. If you hate math or don't care about the details, feel free to skip a few paragraphs.
I first made a spreadsheet using five different variables obtained from Our World in Data. I used production data both per 1000 calories and per kg of food to better account for the vast energy differences in these products. Then I converted the raw data into ratios for comparison. This provided some useful insights right away. For example, a kilogram of beef produces 231 times as many greenhouse gas emissions as an equal quantity of nuts and requires 157 times as much water as a kilogram of rice. That alone should make you think twice about grilling a steak for dinner, but there's far more to examine here.
I used the averages of each ratio to create a score for each food item, with the highest scores being the most environmentally damaging. This is what appears on the graph above.
As you can see, the first five foods are all meat or meat-derived products, yet not all meats are created equal. Pork finds itself in the middle at about a third of the impact of beef, and down at the bottom we find chicken and eggs well below chocolate and tomatoes.
What's going on here? Well, a tomato, for example, requires a lot of water, and is often grown in parts of the world where water is already scarce. Nuts such as almonds are even worse, as seen in this study. Interestingly, the same study reveals that spinach is a winner when it comes to high nutrient density and low water needs. So are strawberries.
Love milk? Looking at the graph might give you the sense that milk's impact is relatively low, but you can't forget about the animal it comes from and the other products derived from it. As you can see, cheese and dairy beef are in the 4th and 5th position on the graph, so there's no escaping the impact cows have regardless or which of their food products you enjoy. As a result of this, alternative milks are gaining popularity around the world. Despite being generally inferior in terms of nutrient density, their environmental impacts are drastically reduced when compared with animal milks, a trade-off that many find worthwhile. For example, 1 in 4 adults in the UK now consume alternative milks, and among younger demographics, it's closer to 1 in 3.
As the graphs above make clear, dairy milk has a far greater impact on the environment than any of the plant-based alternative options. So which is the best choice? Well, almond milk uses too much water, and rice milk contributes to significant eutrophication. Oat milk and soy milk have similar profiles, and are probably your best bet, assuming you like the taste of one or both. That said, any of the alternative milks are obviously a better choice than cow milk, although, as previously stated, the nutrient quality is not as robust. With a well-rounded diet, however, this is unlikely to be an issue.
What about coffee and chocolate, two food items that appear to be quite detrimental to the environment? While it is true that both foods, and coffee in particular, have a higher impact than many others, neither are significant parts of your diet (hopefully) and never will be. There are other ethical and economic reasons to avoid these products, but I won't get into that now.
Summary - Meat has a significantly higher impact on the environment than any other food source (poultry and eggs being an exception) considering greenhouse gas emissions, water use, land use, and eutrophication. Beef is by far the worst, including derivative products like cheese and milk. Grains have some of the lowest environmental impacts among food groups.
Which is better for your health?
According to Harvard Medical School, a plant-based diet reduces your risk of cardiovascular disease (CVD), but other studies have failed to confirm this relationship. For example, a meta-analysis of hunter-gatherer societies, who obtain an average of 65% of their calories from meat, did not indicate a link between meat-based diets and increased risks of CVD. The authors did, however, acknowledge that other factors may offset potential risks in the diet, such as low stress and salt intake as well as more exercise. Also, the fact that life expectancy is much lower among such societies cannot be ignored, as CVD is more prevalent with age. Current mortality rates show, for example, that a 30-year-old hunter-gatherer is equivalent to a 72-year-old Japanese person. Diet can't be the only factor contributing to this, of course, but it may very well be one of them.
In general it is best to avoid saturated fats, which contribute to CVD and, because of their chemical structure, tend to be solids at room temperature. Foods high in saturated fats include red meats like beef and pork, dairy products, as well as coconut and palm oils (used in many processed foods). While reducing these fats can be good for your health, it should be noted that saturated fats should be replaced by other healthy macronutrients like the unsaturated fats found in olive oil and fish, not refined carbohydrates.
It has long been recognized that fish are a good source of nutrients such as omega-3 fatty acids and selenium, but the type of fish matters a great deal. Smaller, short-lived species like herring and mackerel are preferable to larger, predatory species such as tuna and swordfish due to bioaccumulation of mercury contamination. The Monterey Bay Aquarium's Seafood Watch is a good resource for North Americans looking to make good seafood choices, although it mainly focuses on environmental concerns rather than human health.
Dietary fiber, found exclusively in plants, is another important part of the diet apparently lacking in modern populations. According to one study, more than 90% of American adults and children are not meeting their recommended daily intake for fiber. Fiber comes in two forms - soluble and insoluble. Both have benefits for the body, improving fullness while reducing constipation and disease. Consuming generous quantities of whole grains and unprocessed fruits and vegetables is the only way to get enough fiber in your diet.
Summary - Health evidence is mixed regarding the risks of meat-based diets, although with few negative associations and the added benefits of dietary fiber, plant-based diets have the edge. Avoid red meats and saturated fats, as well as refined grains and heavily processed foods. Fish and lean meats are good sources of nutrients and calories, although the origin of such foods should be examined carefully, particularly with seafood.
What about animal welfare?
Even if human health and the health of the environment are not your main concerns, many are attracted to a vegetarian or vegan diet out of a desire to avoid the unnecessary suffering of animals. According to one survey in the UK, 59% of vegetarian and 80% of vegan respondents cited animal welfare and cruelty as reasons for adopting a plant-based diet.
While it is certainly true that most farmers have a great deal of respect for the animals in their care, there is still enormous potential for suffering due to the fast-paced demands of the industry. Improper training, antiquated technology and techniques, negligence, and consumer demand all contribute to cruel practices and systemic problems within the livestock industry. To get an idea of just how bad it can get, check out the 2005 documentary Earthlings, or the 2006 documentary Sharkwater, both fully and freely available online at these links. WARNING: Both documentaries contain graphic footage of animal cruelty and are NOT recommended for children. I regularly show Sharkwater to my high school classes, but I wouldn't show Earthlings to anyone except adults.
After watching either of those documentaries, you may be wondering if you can ever trust that any of the meat you consume was raised ethically, and the honest answer is no, but there are things you can do to ease your mind. Labels such as 'grass-fed', 'organic', 'free range', and others don't tell you anything about how an animal is cared for or killed, so my recommendation would be to make use of your local farms and farmer's markets. Speak with the farmers there and ask them about their methods. Most will be happy to answer your questions, and may even extend an invitation to visit their farms to evaluate their conditions for yourself. If that doesn't do it for you, you've only got one choice left if you want to continue to enjoy meat. You'll have to produce it yourself. It's not as daunting as you think, although there may be regulations to consider depending on where you live. Keeping a couple of chickens for eggs and meat is doable even in the middle of the city, but no roosters, for obvious reasons!
Summary - If you are serious about animal welfare, the only guaranteed solution is to avoid eating animals and animal products altogether. The next best thing is to raise and slaughter animals yourself, but this may not be possible or desirable for everyone. Instead, find local farmers you can buy from directly and inquire about their methods. This will give you peace of mind when buying meat products while helping to support local businesses.
Which is cheaper?
A 2015 nutrition study found that, based on data from France, fruits and vegetables cost an average of 2.27 Euros per 100 calories, the highest among food groups, followed by meats, eggs and fish at 1.61 Euros. At the other end of the scale, starches (grains) cost just 0.19 Euros per 100 calories. The same pattern has been confirmed in Spain, Greece, the United States, and Sweden. In Japan, fish and vegetables were the most expensive (they are pretty particular about their fish here, after all).
The France study also suggests that some fruits, vegetables, canned/frozen seafood, eggs, milk, and yoghurt provide good nutritional value for their costs. Butter, cheese, meat, sugary snacks, and condiments provide comparatively poor nutritional value for their costs. As mentioned above, these trends are likely to be similar elsewhere.
On a related topic, This meta-analysis of 27 studies across 10 countries showed that healthy foods cost on average $1.54 more per 2000 calories than unhealthy foods. Meat and proteins showed the highest differences, costing $4.70 more per 2000 calories than unhealthy options. Unfortunately their standards for what makes a food healthy or unhealthy are not readily apparent. Still, it's no surprise that higher-quality meats and proteins cost significantly more. Just go to your local market and see what a dozen organic, free range eggs costs!
Summary - Both fruits/vegetables and meats have the potential to cost a lot, depending on the quality of foods purchased and their origins. There are smart and cost-effective choices to be made in both categories, but in general, grains are the cheapest (choose whole grains where possible to get the maximum nutrient density). If cost is an issue, avoid expensive imported foods since you're paying a premium for transportation, not quality.
Ultimately, the best diet for you is the one that you can afford, contains the nutrients you need, is responsible for the organisms and environments on this planet, and crucially, is the one you enjoy cooking and eating. I bet you were hoping for a clearer answer than that, but it's the reality with most complex choices.
The report states:
"...the planetary health diet... does not imply that the global population should eat exactly the same food, nor does it prescribe an exact diet. Instead, the planetary health diet outlines empirical food groups and ranges of food intakes, which combined in a diet, would optimize human health. Local interpretation and adaptation of the universally-applicable planetary health diet is necessary and should reflect the culture, geography and demography of the population and individuals."
This flexible plan is roughly the diet my family follows, but just in case you are having trouble figuring out how this would look in your shopping cart, I'll help you out. The EAT report recommends that people eat no more than 14g per day of beef, lamb, or pork. That's about the weight of a CD. How on Earth are you supposed to buy, cook and serve that to your family?! That's where some simple math comes in handy. A family of four can consume 392g of beef per week. That works out to be about one 1/4 pound burger patty each. That's not much for a family that eats steak and potatoes every night, but it's what our planet can support, according to the research.
To save you from getting out your calculator every time you go shopping, here are the approximate monthly amounts a single person should consume, according to the Planetary Health Diet. Obviously there's lot of room for modification here. This is just to give you an idea of what you might buy to meet these recommendations.
Macronutrient intake per person per month
Approximate monthly amount to buy
5kg bag of rice, corn, or flour + 3x 500g boxes of cereal
10-11 medium potatoes
1 head of lettuce + 1 cabbage + 8 tomatoes + 8 onions + 4 carrots + 2 broccoli + 2 garlic + 4 bell pepper + 1 pack mushrooms + 1 celery + 6 corn cobs + bag of frozen peas
1 pineapple + 6 bananas + 4 apples + 3 avocadoes + 4 grapefruits + 8 kiwis + 4 lemons + 1 pack of strawberries
2.5kg of cheese + 12 yoghurt cups + 1 large jug of milk (~4L)
Beef, lamb or pork
4 hamburger patties or 1 14oz steak or 4 lamb chops
16 chicken wings or 3 chicken breasts
8 eggs (or roughly 1 dozen eggs every other month)
1 whole snapper or 6 cans of salmon or 4-5 fish fillets
5 cans of beans or 2kg bag of dried beans
3x 500g bag/tin of almonds, walnuts, cashews, etc.
~1.3L of olive oil
3 sticks of butter or ~380mL of coconut oil
~1kg bag of sugar (about 2 pounds)
The full report is chock full of excellent information and very easy to understand, so I would definitely recommended taking a look for yourself.
My family and I have a few additional rules to help make things easier for ourselves. For example, we don't count foods we order at restaurants (which is maybe once a week). We also don't limit ourselves on special occasions (Thanksgiving) or when visiting with friends and relatives (birthdays, etc.). The rest of the time we try to make healthy, low-impact choices, and eat meat only once or twice a week (always chicken or fish).
Summary - For most people, a balanced diet including a wide variety of food items is most appropriate. I encourage you to research more on your own and start by making small changes. Cutting back on or replacing the types of meat you eat is a wise choice, but for many people, it still makes sense to keep some in your diet for a variety of reasons. So-called 'meatless Mondays' are a good place to start if you're a big fan of the grilled goodness, but be sure that you don't just load up on meat for the rest of the week to compensate. Beef should almost certainly be avoided, although the occasional burger isn't going to trigger the apocalypse. Similarly, milk can be replaced with a low-impact, plant-based alternative, assuming you can find one you like.
Thanks for reading this evaluation of meat and plant-based diets. Obviously this is a huge topic that I've only scratched the surface of, so please continue to educate yourself and update your lifestyle choices as new evidence becomes available. Good luck out there, and happy eating!
Pin this article to save it for later: