I will warn you right up front that when I say complete, I mean COMPLETE. This sustainable protein guide is longer and more information dense than most KineSophy blog posts. So if you just want the CliffsNotes version, I’ve created two free bonus materials: 1) five companion recipes to the guide that incorporate less familiar ingredients like chlorella, nutritional yeast and chicken livers, and 2) a double-sided, one-page grocery shopping cheat sheet that covers the basic points of the guide. Just enter your email address in the form below to access both of these free resources.
At its core, KineSophy is a blog about physical fitness and philosophy. I like to think of philosophy as having two general components: 1) a study of knowledge (how we acquire it, where we store it and how we access it) and 2) a study of ethics, i.e. how we should act. In November 2015, I wrote about my self-experimentation to find a diet that maximizes my physical and mental health and performance. Based on the results of those experiments, I currently consume upwards of 150 grams of protein (the protein equivalent of twenty-two eggs) every day.
In looking at the philosophy of health, my previous diet experiments would fall under the former, knowledge-based element of philosophy. In this guide, I shift my attention to the latter component and investigate how our food choices affect the organisms and environment around us. For example, many people follow a vegan diet, not (only) because they believe this diet improves their overall health, but because they believe it is morally wrong to kill animals or because they believe the way we raise and hunt the animals we eat places a heavy cost on the Earth’s ecosystem.
In terms of animal welfare, eating meat requires the death of an animal. Furthermore, most modern livestock is fed inexpensive, low-quality food and confined to overcrowded and unsanitary living spaces. Many animals are given antibiotics to keep them alive in unhealthy conditions and are bred or treated to grow to an abnormal size. In short, the aim of mass livestock production is to generate the greatest quantity of food with minimal expense and maximum efficiency. Animal welfare is not a primary consideration.
In terms of environmental impact, additional factors complicate the issue. A 2013 study showed that European Union citizens can reduce their water footprint (the amount of water used to produce a particular product) by cutting meat consumption by half or by transitioning to a completely vegetarian diet.  In California, a non-vegetarian diet requires 2.9 times more water, 2.5 times more energy, 13 times more fertilizer and 1.4 times more pesticides than a vegetarian diet.  A 2006 study demonstrated that an omnivorous diet produces 1500 kilograms (kg) more carbon dioxide (CO2) than a vegetarian diet with the same number of calories. 
But these studies don’t necessarily maintain a constant macronutrient breakdown across the different diets under consideration. If you want to be a vegetarian but are concerned about your protein intake, you may still want to make sure your protein sources aren’t more environmentally deleterious than animal protein. Not all plants are equal when it comes to sustainability. Per calorie, fruits require more energy, use more water and produce more CO2 than vegetables. Both fruits and vegetables require more energy and use more water per calorie than poultry, although poultry produces more greenhouse gasses (see Figure 1, taken from Tom et al. ). In fact, transitioning from the current American diet to the United States Department of Agriculture (USDA)-recommended diet would increase energy use, water consumption and greenhouse gas emissions. 
Clearly, we need to evaluate foods in general and protein sources in particular on a food-by-food basis. With these considerations in mind, I have produced the following overview of ethical protein sources that combines protein content, price, animal welfare and environmental impact into a single comprehensive guide. A few considerations for the guide as a whole:
1. Only foods in which the mass of protein in a quantity of food is greater than the mass of both carbohydrate and fat were evaluated in this article. This criterion eliminates foods often claimed to be high in protein like legumes, quinoa, nuts and even milk (5.2 grams (g) of carbohydrate per 100 milliliters (mL) and 3.7 g of protein per 100 mL). Saying you eat black beans for protein is like saying you buy Playboy for the articles. Protein and prose exist in these entities, but they are not the main attractions.
2. Unless otherwise noted, all nutritional information is based on raw quantities of food using data from www.calorieking.com.
3. Price per 10 g protein is based on an average of prices from my local Whole Foods grocery store and Google Shopping searches, selecting the least expensive, organic (when possible), most animal-friendly and sustainable products from the available options.
4. Data on environmental impact of food production was drawn from four main publications: Heller and Keoleian  for greenhouse gas emissions measured in kg of CO2 per kg of food, Mekonnen and Hoekstra, 2010  for total water footprint of plant crops measured in cubic meters (m3) of water per metric ton (1,000 kg) of food, Mekonnen and Hoekstra, 2012  for total water footprint of animal-derived foods measured in m3 of water per metric ton of food, and Tom et al. for energy use per calorie of food based on the authors’ 0-100 scaled index, where lower values indicate less energy was used to produce the food.  Environmental data was not available (NA) for every food in this guide.
However, the question of environmental sustainability must be weighed against efforts to feed a growing human population. In short, those concerned with this issue must determine the food production methods that feed the most people while putting the least strain on the environment. Because human nutrition is assessed in terms of caloric intake rather than food intake by mass, I have also portrayed the data described above in terms of resource use per calorie of food (in g of CO2 per calorie of food and liters (L) of water per calorie of food) based on nutritional values from www.calorieking.com.
5. For the sake of simplicity, I have arranged this guide according to some common diets (e.g. vegan, vegetarian, pescetarian and omnivore). Generally speaking, large livestock like cattle have a greater environmental impact than do low-maintenance plants like soybeans. However, you will see from the data that there is significant overlap in sustainability between categories, with some surprising results (e.g. fishing results in more per calorie energy use and greenhouse gas emissions than poultry production, and raising vegetables requires more per calorie energy and water use than meat). As this article is not intended to advocate one particular diet over another but merely to inform readers of the relevant ethical considerations of various protein sources, the arrangement of foods by diets should allow readers to find the options that correspond to their food preferences.
Soy products (soybeans/edamame, soy milk, tempeh and tofu) have long been a staple in vegan and vegetarian diets. Americans are now eating more soy than ever before, and the Food and Drug Administration (FDA) promotes soy as reducing the risk of heart disease. Unfortunately, several recent studies have shown that consuming large quantities of the estrogen-mimicking isoflavones in soy products may decrease fertility in women, trigger premature puberty and disrupt fetal and childhood development. Infants fed soy formula ingest six to eleven times more of the isoflavone genistein per body weight than the level known to cause hormonal effects in adults. Animal studies show that genistein alters reproduction and embryonic development, and high doses of the compound lead to abnormal growth of breast cells in male rats. 
A 2001 study concluded the soy isoflavones “genistein and daidzein may stimulate existing breast tumor growth” and “women with current or past breast cancer should be aware of the risks of potential tumor growth when taking soy products.”  Another study found that genistein stimulated the growth of estrogen-depended human breast cancer cells and soy protein diets increased estrogen-dependent tumor growth as soy intake increased. 
Osteopathic physician Dr. Joseph Mercola and the nutrition-focused Weston A. Price Foundation point to phytic acid as another potentially dangerous component of soy,  and Mercola and dietician Emily DeLacey recommend fermented soy products like tempeh and fermented tofu over unfermented products like soy beans, soy milk and unfermented tofu since fermentation supposedly neutralizes the phytic acid in raw soy. , However, Mercola also points to genistein and daidzein as beneficial compounds in fermented soy,  the very same compounds shown to be harmful in a soy-heavy diet. At the very least, the jury is still out on soy, but it would seem wise to avoid relying on soy as a primary source of protein.
Fortunately, the most protein-rich vegan foods do not contain soy. The algae chlorella and spirulina have the most protein per mass of any food on this list. Chlorella can also assist with detoxifying the body of pesticides and heavy metals like lead and mercury. Spirulina is rich in vitamins B, C, D and E and contains all of the essential amino acids, though some in lower quantities than found in animal products.  Nutritional yeast, the third most protein-rich food on the list, is deactivated yeast that is sold as yellow flakes or powder and used to mimic the flavor of butter or cheese in vegan recipes. Nori is the seaweed used to wrap sushi rolls, and while it’s protein-dense, it’s also very light, meaning that you’ll need to eat a lot of it in order to get a significant amount of nutrients.
In terms of animal welfare, the benefits of eggs and dairy in comparison to meat are obvious in that chickens and cows provide far more food while alive than what their meat alone can offer. Hens are most productive in their first two to three years of laying, during which the average hen lays 200 to 300 eggs per year, with more productive layers reaching 600 eggs annually.  The average cow produces 6.5 gallons of milk per day and 350,000 glasses of milk over her lifetime. 
But animal welfare also encompasses how livestock is raised. Many labels exist to describe how farm animals are reared and treated, and these categories can be overlapping and confusing. Here’s a brief glossary for poultry/eggs and mammals/dairy, with the most animal-friendly methods listed first.
Pasture-raised: Chickens are raised on an outdoor pasture and are free to roam
Organic: USDA-certified organic eggs come from uncaged hens with some outdoor access. The birds’ feed is organically raised, and they can’t receive antibiotics.
Free-range: Chickens are uncaged and have some outdoor access, but the type and duration of that access are not specified and may be limited (e.g. to a screened porch).
Cage-free: Chickens are uncaged and able to freely roam a barn or other facility, but usually don’t have outdoor access.
Vegetarian-fed: Chickens receive only vegetarian feed with no animal byproducts. However, since chickens are natural omnivores, this label also means the birds are raised indoors and are unable to eat grubs, worms or other bugs.
All natural: The USDA has no standards for chickens’ living conditions and feed under this label and considers all eggshells natural. 
Organic: Animals must be raised under USDA-certified organic management from the final third of gestation to harvest. Their diets must be 100% organic with no genetically modified feed crops, and at least 30% of daily intake during the growing season must come from forage. Vitamin and mineral supplements are allowed, but antibiotic use and growth-promoting agents are prohibited. Cattle that become ill or injured may receive therapeutic antibiotics, but must then be marketed as conventionally produced beef.
Grass-fed: Animals must be fed grass, legumes and forage and not grain and must have continuous access to pasture during the growing season. Routine vitamin and mineral supplementation may be included in the feeding regimen. Antibiotics, growth-promoting implants and chemicals called ionophores are prohibited. Cattle that become ill or injured may receive therapeutic antibiotics, but must then be marketed as conventionally produced beef.
Natural: Most fresh, conventional cattle and dairy qualify as natural, which only requires that a product is minimally processed and does not contain any artificial ingredients or preservatives. Different natural beef programs have different brand-specific designations, including no antibiotic use, limited antibiotic use, possible ionophore use, no growth-promoting implants, and possible restriction of feed containing mammalian protein or fat.
Conventional: Calves graze alongside their mothers until five to eight months old and are then moved to a feed yard and fed on a high-energy, grain-based diet. Antibiotics may be used therapeutically, and ionophores and growth-promoting implants may be used to enhance feed efficiency and weight gain. 
Generally speaking, more animal-friendly classifications are less efficient and thus more expensive for the producer (and hence, consumer). However, while macronutrient content may be comparable for any particular animal product regardless of production method, evidence shows that more humane methods also have health benefits for human consumers. Eggs from pasture-raised hens have more vitamin E and omega-3 fatty acids and a higher concentration of vitamin A that conventional eggs.  Free-range eggs have more vitamin A, vitamin E, beta-carotene and omega-3s, and less cholesterol and saturated fat than those from confined hens.  Eggs from confined hens also had 7.77 times greater odds of harboring salmonella bacteria than eggs from non-caged hens, according to a 2010 study. 
Compared to grain-fed cows, grass-fed cow milk contains five times as much of an unsaturated fat called conjugated linoleic acid (CLA), which has been shown to aid heart health and weight loss.  Cheese from grass-fed cows has over four times as much CLA as cheese from grain-fed cows.  Organic milk contains 50% more omega-3s  and fewer omega-6 fatty acids  in comparison to non-organic milk (consuming excess omega-6 versus omega-3 has been linked to heart disease, cancer, autoimmune diseases and systemic inflammation). So if your budget can handle it, choose vegetarian proteins from organic/pasture-raised/grass-fed animals for a greater benefit to animal welfare and your own health.
Yes, you read that right. People consume insects in 80% of the world’s nations, with over 1,000 different species on the global menu.  A 2013 United Nations Food and Agricultural Organization report claims that edible insects could stabilize the global food supply amidst rapid population growth and shrinking agricultural land. Though they have about half the protein of traditional livestock, crickets contain the essential amino acids lysine and tryptophan, which are scarcely present in beef and chicken, emit far fewer greenhouse gasses than livestock and demand far less space (and less deforestation) than a typical farm or ranch. 
In theory, insects seem like an ideal source of sustainable protein: abundant, low demand for resources, and minute carbon emissions. The problem, as you’ll see in the table below, is that edible insects like crickets are very expensive, as the entomophagy (insect-eating) industry has struggled to keep up with recently rising demand.
“The market [for ground cricket flour] has easily doubled in size every year since 2010,” says Harmon Johar of the edible insect supplier World Ento (now part of Aspire Food Group). “But while other flours are milled from grains that are cheap to produce and have little to no protein content, cricket powder is extremely high in protein—always the most expensive form of food—as well as essentials like iron and calcium. Cricket production is also currently very labor intensive and is only just becoming automated.” 
For now, insect farming remains a fledgling industry. As with any nascent market, expect prices to drop as demand increases and supply becomes more efficient. With more people intrigued by new sources of sustainable protein than ever before, we hopefully won’t have to wait too long for reasonably priced, edible insects.
Seafood production and fishing cover the extremes of energy, water and emissions costs. Harvest requires next to no water, but energy is required for feed production for farmed seafood and fishing vessels for wild, and the machinery used to catch, raise, harvest and transport seafood results in significant greenhouse gas emissions. Exact water footprint figures for seafood could not be found, but per calorie water costs are lower for seafood than for any other food group (see Figure 1 above). In contrast, energy use for seafood is the second highest of any food group, behind only fruits and fruit juices. 
For shellfish and fish, I have listed only the most protein-packed and environmentally-friendly sources in all regions of the United States. I have also indicated the most sustainable option for each food, either farmed (F) or wild (W), based on recommendations from the Monterey Bay Aquarium Seafood Watch (www.seafoodwatch.org). Additional sustainable seafood recommendations for your specific region can be found at www.seafoodwatch.org/seafood-recommendations/consumer-guides.
Ecological problems caused by the fishing industry include overfishing (catching fish faster than they can reproduce), bycatch (accidental capture of unwanted species), damage to ocean habitats from fishing gear, and high energy consumption and CO2 emissions. Fishing methods like massive longlines and gillnets catch more seafood than is sold to market. In the worst cases, for every pound of shrimp caught, up to six pounds of other species are discarded, including fish, turtles and seabirds. Gill nets, purse seines and longlines often capture species other than the intended catch, including sharks, sea turtles, dolphins and seabirds. Gear that is pulled across the seafloor (e.g. trawls and dredges) can destroy ocean habitats. In contrast, harpooning, jigging and pole or troll fishing involve catching one fish at a time and releasing unwanted bycatch. Traps and pots also reduce bycatch and do less seafloor damage than trawls or dredges. ,
Aquaculture, or farming of seafood, offers an alternative method of seafood production that can have less environmental impact than fishing. Yet aquaculture is not a perfect solution. Farmed salmon require over a pound of wild fish for every pound of weight they gain; tuna require fifteen pounds for every pound gained. Farms that operate as ranches remove fish from the wild and raise them in confinement. This practice has a similar environmental impact to fishing, and because the captured fish are often juveniles, ranching can hinder the ability of a wild fish population to regrow its numbers. Waste, uneaten food pellets and the diseases that abound in crowded and open aquaculture pens and cages may pollute the farms and spread to the wild, and many types of aquaculture require chemical treatments for a successful harvest.
Furthermore, seafood farms are often established through the destruction of natural habitats and are sometimes abandoned when waste becomes too great. Recirculating systems can prevent fish from escaping and treat wastewater, but they are expensive and require electricity or another power source. Tilapia, catfish, cobia and Arctic char are examples of seafood raised in more sustainable onshore systems throughout the United States, systems with filtered water that reduce the likelihood of disease and pollution. Shellfish farming can also be sustainable since shellfish are filter feeders and don’t require additional feed that would affect wild fish populations. ,
However, there may be a balance between sustainability and consumer health when it comes to seafood. Tests show that farmed salmon contain five to ten times as much polychlorinated biphenyl pollutants when compared to wild salmon, likely due to pollutants in their feed.  A study on levels of healthy omega-3 fatty acids and carcinogens from contaminants in farmed and wild salmon found that the ratio of omega-3s to carcinogens was significantly greater for wild Pacific salmon than for farmed salmon. However, while wild salmon is generally safer when eaten in moderation, a few subgroups of farmed salmon showed omega-3 to carcinogen ratios similar to wild salmon.  In the case of salmon, wild is both more sustainable and healthier than farmed, but it is not clear whether these findings translate to other farmed fish species. Literature on non-salmon seafood is more scarce, perhaps owing to the popularity of salmon and its prevalence in both wild and farmed harvests.
In short, if you care about the sustainability and healthfulness of your seafood, you need to ask the purveyor. Find out if your seafood is wild or farmed and where it’s caught or raised. If it’s wild, know if it was pole- or harpoon-caught or if a net or longline was used. If it’s farmed, know if your shellfish was grown in a sustainable bag-and-rack culture or your fish was raised in a recirculating system instead of unsustainable and pollution-heavy methods like ranches or open net pens and cages. The Monterey Bay Aquarium Seafood Watch is a good guide and is available as an Apple iOS and Google Play app. And the Marine Stewardship Council (MSC)’s blue fish and checkmark logo offers the largest and most globally recognized sustainability label for wild-caught seafood. 
The environmental costs for livestock production presented in this guide do not account for the type of tissue consumed from a particular animal. In terms of carbon emissions, water footprint and energy use, chicken is chicken, beef is beef. Yet a good portion of the animals we consume for food goes to waste, especially in the United States, where almost 20% of edible meat winds up in landfills.  In other words, if it takes 26.0 kg of CO2 and 15.4 m3 of water (converted from 15,415 m3 per metric ton) to produce one kilogram of beef, 5.2 kg of CO2 and 3.1 m3 of water are wasted, to say nothing of the energy used. We can mitigate that waste by consuming all the edible tissues of livestock animals, including blood, bone marrow, brain, ear, eye, face, gizzard, heart, intestine, kidney, liver, sweetbreads (thymus gland) and tongue.
Plus, organ meats are good for you. Animal liver is nature’s most concentrated source of the retinol form of vitamin A, a different form of vitamin A than the carotene found in plants,  and one serving of chicken or cow liver provides 75% of a woman’s and over 100% of a man’s daily iron requirement. Animal heart contains the complete range of B-vitamins, and a serving of kidney fulfills the recommended daily intake of the antioxidant selenium.  Organ meats are also rich in vitamins B, D, E and K, copper, zinc, chromium and other minerals, omega-3s and purines (the precursors to DNA and RNA). 
The table below contains the most protein-dense and easily accessible organ meats, but you can make big strides to improve environmental well-being, animal welfare and your own health by seeking out a variety of organ meats.
I have already explained the various labels for raising poultry and mammals and how these farming practices impact the nutrient content of eggs and dairy. In terms of greenhouse gas emissions, livestock has the greatest environmental impact of any food source, totaling 14.5% of human-related emissions (greater than that of transportation). , However, shifting livestock to pasture-based, grass-fed systems can reduce the environmental load. The one billion metric tons of grain used to feed animals every year could feed 3.5 billion humans. 70% of grain grown in developed countries is used to feed livestock, which consume at least one-third of the world’s cereal grain. Yet ruminants like cattle can eat hay, silage and other high-fiber crop grasses that humans cannot consume, and can graze in areas like mountainsides and wet grasslands that are not used for human agriculture. 
Pasture-based farming can also reduce fossil fuel expense by allowing animals to feed themselves and spread their own manure as fertilizer, instead of using machinery to haul in feed and remove waste. A single cow may produce up to seventy kilograms of manure each day, the equivalent of 128 kilograms of synthetic nitrogen fertilizer derived from fossil fuels and enough fertilizer to supply one hectare of wheat for a year. Furthermore, in addition to the general discomfort of confinement, keeping animals at high densities in close quarters encourages the spread of infectious diseases. 
Aside from the environmental and animal welfare benefits, pasture-raised and grass-fed livestock systems produce healthier products for consumers. Beyond the health benefits for eggs and dairy described above, three decades of research shows that grass-fed beef has significantly more CLA and omega-3 fatty acids per weight than conventional beef.  Perhaps in recognition of the “you are what you eat” mantra, standard poultry feed is supplemented with small amounts of vitamin E. However, there is ten times as much vitamin E in the grass consumed by pasture-raised chickens, a bounty which is passed on to the consumer.  Grass-fed beef has four times as much vitamin E as grain-fed beef and also has more vitamin A.  Pasture-raised pigs have 300% more vitamin E and 74% more selenium in their milk compared to pigs raised in confinement, as well as higher vitamin and mineral levels in their meat.  Pasture-raised pigs are also less likely to foster antibiotic-resistant bacteria, even when the pigs are not given antibiotics. 
That being said, mammals require far more land than do poultry, who still require more land than wild-caught fish or insects. If you do elect to eat meat, choose organic, pasture-raised and/or grass-fed sources for the most sustainable and healthiest animal proteins.
10. Konkel, Lindsey. “Could Eating Too Much Soy Be Bad for You?” Scientific American. 3 Nov. 2009. Online. 29 July 2016. http://www.scientificamerican.com/article/soybean-fertility-hormone-isoflavones-genistein.