The Good, the Bad, and the Heme Iron
The line was about thirty people long, snaking out of the store, spilling onto the sidewalk. At least two hours would go by before the person at the end of the queue could make a purchase. But they all stood patiently, shuffling a few steps ahead every four minutes or so. In their hands, they clutched polyester bags and wicker baskets, which they hoped to fill with meat. And yet, it was likely some of the shoppers would have to go home with nothing. The butcher’s store was a white, tiled expanse of emptiness. Only a few sad sausages dangled on a line of hooks sticking out of the wall. Everybody wanted those sausages.
During my childhood in Poland in the early 1980s, such scenes were common. Just like everyone else, my mother and I would wait for hours for a chance to buy some pork or beef. Meat was rationed back then; it was scarce and voraciously craved. I doubt my mother, or anyone else I knew, would sacrifice so much time to buy a few ounces of beans or a head of cabbage. But for meat, we waited.
The late anthropologist Marvin Harris was so fascinated by this Polish desire for sausages and schnitzels that he used it as a prime example of what he called “meat hunger”—a universal human craving for animal flesh that can’t be satisfied by any other foods, no matter how plentiful. In the 1980s most Poles were far from malnourished. We ate over three thousand calories per person and loaded up on over one hundred grams of protein a day. Still, we would spend drudgingly long hours queuing in butcher shops. Why were we so hooked on meat?
Harris may have been the most famous believer in meat hunger, but he wasn’t the first. Back in the nineteenth century, missionaries and explorers wrote quite extensively about a condition they encountered in Africa and South America: no matter how abundant their food, the locals would complain of being hungry if they didn’t have meat to eat. In 1867 one French American traveler described a “disease” prevalent in Central Africa called gouamba: “An inordinate longing and craving of exhausted nature for meat.” A person touched by gouamba would refuse any vegetarian dishes brought before him and stubbornly beg for meat.
In many languages there actually exists a word for “meat hunger” to show that it’s a different thing from the regular, empty stomach type of hunger. It’s called ekbelu by the Mbuti tribe of Central Africa and eyebasi by the Yuquí of Bolivia. The Mekeo of New Guinea say that “hunger for plant food” comes from the abdomen while “hunger for meat” comes from the throat. In Uganda, locals have been known to exchange plantain that could feed a family for more than half a week for a bony chicken that won’t last them even a day. Anthropologists say that meat hunger is not physiological but rather cultural—a lack of animal flesh in the diet is a sign of scarcity, a symptom of problems with a tribe (or nation). And yet, there may indeed be something about meat’s nutritional value that makes us prize it above such foods as plantain, something that makes meat hunger real. That thing is protein.
Paul Breslin’s fly lab at Monell Chemical Senses Center in Philadelphia smells of honey. It’s a small room, with little more inside than a desk, a computer, and a big, white fridge. In here, Breslin, a professor of nutritional sciences at Rutgers University in New Jersey, studies the feeding behavior of an animal species that is particularly fond of wine, beer, and freshly baked bread. And no, I’m not talking about humans—Breslin studies fruit flies. According to Breslin, fruit flies’ appetites are very similar to that of humans and even more similar to that of chimps—at least taste-wise. “They practically are chimps,” he jokes, as he pulls open the fridge to reveal rows of transparent vials, each buzzing with tiny, orange-hued flies. The vials have a hardened, gooey substance at the bottom—fruit-fly food, Breslin tells me (hence the honey-ish smell). By studying fruit flies and mosquitoes, Breslin seeks to understand what drives their protein hunger and, in turn, what may be causing our own desire for protein. “These flies eat little but fruits, but once they get pregnant, the female’s protein hunger turns on, and she starts looking for yeast—that’s a source of protein for them,” Breslin says. It’s similar with the mosquitoes. Breslin believes that if it wasn’t for the itchy bites (annoying) and diseases such as malaria (deadly), we would smile at any mosquito trying to get our blood. After all, the female mosquito is steered by her protein hunger: she is pregnant and trying to get enough of the nutrient to feed her babies.
Mosquitoes and fruit flies aren’t the only creatures driven by their desire for protein. Stephen Simpson, professor of biological sciences at the University of Sydney, has studied slime molds (jelly-like creatures that resemble toxic spills), cockroaches, rats, monkeys, and humans and discovered that all share a special craving for protein. Simpson told me once that for people the desired ratio of calories from protein in the diet is about 15 percent. Whenever in his experiments Simpson offered volunteers diets too low in protein, they ended up snacking on savory foods, as their bodies told them to meet their “protein target.” Since it’s usually the taste of salt and umami that signals the presence of protein, Simpson listens carefully to what his own body is trying to tell him. If he finds himself craving salty potato chips between meals, he thinks, “Oh, here comes the protein hunger again”—and eats an egg instead.
It appears that our bodies are designed to prioritize protein and actively seek it out—whether you’re a mosquito sucking blood and spreading malaria or a human scavenging the fridge for bacon. From this perspective, the Ugandan family exchanging plantain for a bony chicken makes sense. Plantain is quite energy dense but has very little protein: about one gram per one hundred grams of fruit. To meet daily protein needs, an adult man would have to gorge on thirty pounds of plantain in a single day. Meanwhile, the scrawny chicken has about twenty times more protein per one hundred grams than the plantain and would satisfy the protein hunger much more efficiently.
Yet Simpson’s and Breslin’s research can’t explain such cravings completely. Though they have helped explain why humans may sometimes fall victim to meat hunger, they haven’t shown that we have an innate hunger for meat per se—just that the human body craves protein. It also doesn’t mean we need to cram ourselves with as much protein as our belts will allow—15 percent of calories from protein is actually not that much. The beliefs that so many Westerners hold—that meat equals protein and that our bodies require vast amounts of the nutrient—are nothing more than a myth. Or two myths, to be precise, both of which have roots in science.
In 1824, Justus von Liebig became a professor at the University of Giessen, Germany, at barely twenty-one years old. Von Liebig’s career was not only fast but also quite impressive: for his discoveries of the role of nitrogen in plant nutrition, he is still known as the father of the fertilizer industry. Some of von Liebig’s fame was due to his research, and some of it due to his charm: he was a great self-promoter. And that definitely helped spread his ideas about nutrition and meat.
Von Liebig glorified protein as the only real nutrient and believed that without it our muscles just wouldn’t work. To him, carbohydrates and fat were only needed to react with oxygen in the lungs to produce heat. The fact that his ideas about the role of proteins in human nutrition were purely speculative and not based on experiments didn’t deter him from turning them into a business opportunity. His “Liebig’s Extract of Meat,” an essence made of Uruguayan beef, was widely marketed as a “powerfully-acting panacea” capable of restoring health. According to von Liebig, meat was what people needed to be strong, and since he was a famed scientist, many believed him.
It wasn’t only von Liebig, though, who was behind the protein myth that took hold in nineteenth-century Germany and spilled from there all over the world. It was also his student, Carl von Voit. Although von Voit did conduct quite a few experiments that have helped us understand proteins better, his nutrition advice was based on rather shaky science. He calculated how much protein soldiers, laborers, or prisoners consume each day and from this inferred that the resulting number represented how much their bodies actually need. The problem with his methodology is obvious: it’s a bit like observing children stuffing themselves with cookies and concluding that young humans require tons of sugar to grow. Von Voit advised that hard workers should eat a staggering 150 grams of protein a day and that at least 35 percent of the nutrient should come from meat. The idea that we need plenty of protein swiftly became popular among nineteenth-century elites, most of them devout meat lovers already, and soon even scurvy was blamed on inadequate protein intake.
The protein myth had decisively taken root. But in coming years, well-designed scientific experiments cast a long shadow of doubt over the German scientists’ claims. By 1944 the US Department of Agriculture (USDA) recommended only seventy grams of protein per day for adult men and sixty grams for women, “regardless of the degree of activity,” and von Liebig’s and von Voit’s prescription for excessive protein began fading away fast. It may have disappeared altogether if it wasn’t for kwashiorkor.
In Ghana kwashiorkor means “evil spirit that infects the first child when the second child is born.” It’s not an evil spirit, of course, but a disease that commonly falls upon an older sibling taken off a mother’s breast so that a newborn can be fed. Once the first child is weaned onto a starchy, nutritiously inadequate diet, he may develop swelling of the legs and the ill-famed bloated belly and become susceptible to infection. Observations in Uganda in the 1950s led many scientists to believe that the disease was caused by too low an intake of protein. Soon the world fell into what some now call a “protein hysteria,” with charities and governments worrying about the “protein gap” between the rich and the poor countries and sending skim milk and fish flour overseas to boost the protein intake of hungry African children. But the truth was, as scientists finally admitted in the 1970s, that kwashiorkor was more about inadequate dietary intake than about protein. If your total dietary intake is too low, your body will burn whatever protein you eat for energy, instead of using it to make your own proteins—like insulin, collagen, or antibodies.
In general, diets that are sufficient in calories will also provide enough proteins. Of course, it is possible to imagine a diet loaded with calories but with barely any protein in it: a cotton candy regime, for example. But if your menus are fairly balanced, you should be fine, even if you are eating vegan. What’s more, the reason why we don’t see many people with kwashiorkor walking the streets of upper Manhattan is that it’s extremely hard to succumb to this condition in the West unless you are truly starving, an AIDS patient, or a drug addict. Detailed studies of diets in developing countries showed that even there the lack of protein itself was rarely a problem; there just wasn’t enough food in general. Once children were given a diet with sufficient calories, the intake of protein in most cases was adequate. It was soon discovered, too, that the protein requirements of children were previously deemed too high. They were calculated based on experiments on rats, but nonprimate animals grow much faster than human babies do and so require more protein. This is reflected in the protein content of rat breast milk, which is much more loaded with the nutrient than human milk is. (Compared to other mammals, human breast milk is very low in protein.) Once that was corrected for, children’s protein requirements were slashed to less than half of what they were in the 1940s. The protein gap practically disappeared, but the protein myth persisted.
If you leaf through today’s consumer magazines, especially those intended for men, or if you browse the nutrition pages of the Internet, you will soon discover that the protein myth is still going strong. “Simply put, our muscles are meat, so we need to eat muscle to gain it,” claims Flex, a bodybuilding magazine. “Muscle is made of protein, so to grow lean mass you need to eat protein. Ample protein,” warns an article in Muscle & Fitness.
So how much protein do we actually need? According to the Centers for Disease Control and Prevention (CDC), the recommended dietary allowance (RDA) for protein is 0.8 gram per kilogram of body weight per day. It’s the same for all adults, both women and men, and covers everyone from couch potatoes to gym bunnies. The RDA (just like the British Reference Nutrient Intake) is so designed that consuming this amount of the nutrient is more than enough for 97 percent of the population. So it will cover the needs not only of a regular adult but also those of people with significantly elevated protein requirements, such as those with cancer, for example, or other serious diseases. The protein requirement of an “average” American, according to the CDC, is just 0.66 gram per kilogram of body weight per day.
This is not to say that proteins are not important. They are, and you need to eat them. What you don’t need to consume, though, is animal flesh. The second myth is that protein equals meat, and that by going meatless, vegetarians are somehow endangering their bodies and minds. This particular myth goes deep into human history, but in one of its modern incarnations, it can be traced back to a best-selling 1971 book, Diet for a Small Planet by Frances Moore Lappé. The myth starts with a correct assumption that not all proteins are created equal: some are just better for you than others. It’s all down to their amino acid composition. Proteins are built from about twenty common amino acids that can be assembled together like chains of beads. When you eat a protein-rich food, your body breaks the protein down into separate amino acids (think of beads from a broken necklace, scattered on the floor) and then rearranges them into your own, different proteins (a new necklace). Your body can synthesize a few of the amino acids by itself and doesn’t need to get them served on a spoon: these are called nonessential. Other amino acids are essential, and you have to get them with food. Some proteins have all the nine essential amino acids, and for this inherent goodness are called complete proteins. Egg proteins are like that, or the ones found in meat. But most plants lack several of the essential amino acids; so for example, if you eat nothing but beans, you won’t get methionine, and your body functions will soon start to fail. This may sound scary if you are a vegetarian, but the good news is that all essential amino acids are found in plants, spread among different veggies, fruits, and grains. So even though beans lack methionine, you can get this amino acid from grains, making a black bean burrito a perfect protein match. Another classic combination is a peanut butter sandwich. But what if you don’t eat grains and beans at the same time? Here is where Frances Moore Lappé comes in. When her book was originally published in 1971, she wrote that people should combine plant amino acids on their plates to create foods equal in their protein goodness to meat. If vegetarians were careful and charted the essential amino acids to assemble their foods, they would be just fine.
The problem was the charting, of course. You had to be aware of which plant foods are short in which essential amino acids and plan your meals accordingly. It wouldn’t do to polish off a spoonful of peanut butter at 9:00 a.m. and have a slice of bread at noon. You had to eat them together. Vegetarian books started printing charts of complementary proteins that were supposed to help, but mainly just added ammunition to meat eaters’ claims that plant-based diets are a disaster waiting to happen.
We now know that vegetarians don’t need to chart their amino acids any more than omnivores need to chart their vitamins to make sure they get all of them at every meal. A human body is perfectly capable of complementing the proteins by itself. Lappé admitted in the twentieth-anniversary edition of her book: “In combatting the myth that meat is the only way to get high-quality protein, I reinforced another myth . . . Actually, it is much easier than I thought.”
Not only is it unnecessary to chart your amino acids, there are some plant foods that have high-quality protein just like meat. Soy is one example, as are buckwheat, quinoa, and even potatoes. If you went on a potato-only diet (fries for breakfast, purée with chips for lunch, and potato pancakes for dinner), your body would get all the essential amino acids it needs. About three pounds of potatoes a day should do the trick.
If you are a Westerner, you most likely don’t have to worry about eating enough protein—just the opposite. People in developed countries tend to pack in far too much of the nutrient. Americans eat about twice as much as they should. Even professional Olympic athletes generally don’t have to supplement their meals with additional protein. Their protein requirements are at best only a little higher than those of the general population: 1.2 to 1.7 grams per kilogram of body weight per day. Sportspeople burn tons of calories. Scott Jurek, one of the world’s best ultramarathoners (and a vegan), once told me he has to down about six thousand to eight thousand calories each day to make up for all the exercise he does. Because of such elevated food intake, professional athletes can easily meet their protein needs with their regular diets. If you go to the gym a few times a week, by the way, you basically still only have to get 0.8 gram per kilogram of body weight per day, like everyone else. As Breslin told me in his fly lab: “Humans who want to look like Schwarzenegger eat a lot of protein to grow their muscles, but they’ll never look like gorillas, never be as muscular, even though gorillas don’t eat meat.”
What’s more, too much protein is not just bad for you, it may possibly kill you. By 1919 Vilhjalmur Stefansson, a Canadian explorer of Icelandic origin, had spent a total of ten winters and twelve summers north of the Arctic Circle. Sometimes for as long as a year and a half, he would live in the frozen expanse of northern Canada on nothing but wild game that he managed to hunt down with his rifle. He survived with no fresh veggies, no bread, no tea, or even a pinch of salt. Although Stefansson believed that humans could live well on meat without vegetables (he actually managed to gain fifteen pounds on one of his trips), he also described the dangers of very lean, very protein-rich meat: “If you are transferred suddenly from a diet normal in fat to one consisting wholly of rabbit you eat bigger and bigger meals for the first few days until . . . you are showing both signs of starvation and of protein poisoning . . . Diarrhoea will start in from a week to 10 days and will not be relieved unless you secure fat. Death will result after several weeks.” This condition, called rabbit starvation, was reported by many travelers in the nineteenth and twentieth centuries. Even though there weren’t any actual experiments done on rabbit starvation in humans (it would be rather hard to find volunteers, I presume), quite a few studies show that it can be dangerous if over 35 percent of the calories a person eats come from protein. If you are a 110-pound woman, for example, just 125 grams of protein a day may be too much for you, an amount that may be exceeded in a single McDonald’s visit (the Mighty Wings, ten pieces, have 60 grams of protein). What happens if you overindulge on animal protein? Your kidneys may stop functioning properly, even fail if you are a diabetic. A high-protein diet may also set you on the way to developing osteoporosis, heart problems, and cancer. Studies show that mice fed a diet with a high protein-to-carbohydrate ratio have a shorter life span, especially if the protein comes from animals. In a more prosaic scenario, you can suffer from constipation. Up until the mid-nineteenth century, it was considered a national affliction among Americans, precisely because of a meat-heavy but veggie-light diet.
So if meat is not necessary in the diet for its protein content, is there something else in it that does make it indispensable or at least much better than plant foods? Some important nutrient that keeps our bodies craving for more? When you read about the adequacy of vegetarian diets, usually a list of vitamins and minerals is provided as the ones to watch out for: iron, vitamin B12, zinc. Could it be that one of these nutrients, if lacking, turns the meat hunger on?
If anything, iron would be the most likely candidate, since not all iron in food is created equal. Some of it is in “heme” form (derived from hemoglobin, the protein that makes blood look red) and can only be found in animal products: meat, eggs, fish. The rest is nonheme iron, again found in meat, eggs, and so on, but also in plants—particularly in beans, spinach, and nuts. If you’ve heard about heme and nonheme iron, you’ve probably also heard that heme iron is much more easily absorbed by the body. You may have heard that for this reason heme iron is better for you. But more and more research shows that heme iron may actually be the bad guy, and that anemia can sometimes have benefits (yes, that’s right).
What’s wrong with heme iron? It may promote cancer and cardiovascular disease. Many of the studies headlined in the media, which connect red meat consumption with these conditions, point to heme iron as the likely culprit. As for anemia, it’s not always due to inadequate consumption of iron. Even though anemia is the top nutritional deficiency in the world—almost half of children and women in developing countries are anemic—sending them steak and bacon would not automatically solve the problem. Studies show that not enough iron in the diet is less of an issue than are genetic disorders, chronic inflammation, and worms. Among Tanzania’s schoolchildren, for example, 73 percent of incidents of severe anemia were brought on by hookworm infections (that’s because the creepy-crawlies cause intestinal bleeding). Besides, anemia itself is not necessarily all bad, either. Evidence is starting to pile up that anemia can sometimes protect us from succumbing to infectious diseases, such as malaria, tuberculosis, or even HIV. Most bacteria and viruses need iron to survive in a human body. If there is a shortage of the nutrient, they can’t multiply as successfully and overwhelm the immune system. It has been suggested that anemia might be an adaptation that allows us to live in places where infections are common. Meat-scarce diets could have actually helped our ancestors survive the unhygienic world of the past.
Today, Western vegetarians are no more likely to have anemia than are omnivores. Even though nonheme iron is less well absorbed by the body, contemporary plant-based diets are more abundant in this nutrient, making up for the difference. And it’s not just spinach and broccoli that can load a vegetarian with iron. Keeping anemia at bay can actually be quite pleasant; one good source of iron is the candy licorice allsort (at eight milligrams of iron per one-hundred-gram serving, it has nearly four times as much iron as a three-ounce sirloin steak). Of course, in the past the story was significantly different. If you lived in a medieval European village circa 1300 and ate little but turnips, your risk of anemia was much higher, and a steak would have helped.
Some studies do find, though, that even modern plant eaters may have lower iron stores than omnivores do. That’s like having less food stacked in a pantry: you’re still fine (no anemia) but more likely to run short in the near future. But low iron stores are not necessarily a bad thing. First, if someone has low iron stores, his or her body will be more efficient at absorbing the nutrient from meals. Second, low iron reserves may be why premenopausal women have lower risk of cardiovascular disease than do Western men.
What about zinc, then? Is that the nutrient that keeps us hooked on meat? After all, zinc from plant foods is not as well absorbed as the one from meat. But, once again, the answer is no. Study after study shows that vegetarians do not have any zinc deficiencies, no matter what meat producers would like us to believe.
However, there is one nutrient that modern, Western humans tend to only get from animal foods: vitamin B12. There simply are no plant sources of this compound. Kelp, tempeh, and miso, which are all often proposed as great sources for getting B12, contain only inactive analogs of the vitamin and won’t keep deficiencies at bay. The only places to get B12 are meat, eggs, and dairy products. And if you don’t get it, your nerves won’t work as they should, and you won’t be able to make healthy blood cells.
If you wonder how our hominin ancestors survived the Paleolithic without any milk, eggs, or meat in their diet (as was, after all, common) and didn’t die off like flies from B12 deficiencies, the answer is simple: dirt. Vitamin B12 in meat doesn’t come from the animal itself; it comes from microbes. It’s produced exclusively by soil bacteria living among the roots of plants and ends up in meat when an animal eats dirty grass, leaves, fruits, and so on. That is why in developing countries B12 deficiencies are not as prevalent: people there don’t wash and spray their veggies as vigorously as Westerners do. Yet it doesn’t mean that every American vegan should dash to the nearest ditch and gobble up soil three times a day. A supplement will do just fine, or consuming enough B12-fortified foods, such as cereals and soy milk. For vegetarians their regular intake of eggs and dairy is normally enough to keep their bodies well supplied with B12.
It seems, then, that it’s not vitamin B12 that keeps our bodies dependent on meat, just as it’s not protein, heme iron, or zinc. But what if there is some compound in meat that we haven’t discovered yet, some nutrient that, say, in 2030 scientists will finally pin down, and all vegetarians will have to bow their heads in embarrassment and admit: the omnivores were right all along; our bodies do need meat.
Even now some more obscure compounds are being proposed as the ones behind meat’s nutritional superpowers. One study presented at a 2013 congress in Turkey (which was, by the way, sponsored by the meat industry) suggested carnosine and anserine, antioxidative peptides that are only found in meat, as substances that may boost our health. But the fact is, that no matter how many “new” compounds are put in the limelight, it’s highly unlikely that we will ever find anything in meat that makes it necessary for our bodies, or even much healthier than nutrients present in plant foods. Why? Because of all the longitudinal studies that have already been conducted comparing the overall health of vegetarians and meat eaters.
During World War I, an unusual natural “experiment” happened in Denmark. By January 1917, a naval Allied blockade of the country (which was then occupied by Germany) resulted in severe shortages of grain and fertilizer. As the months passed, the threat of hunger loomed larger and larger. Mikkel Hindhede, one of Denmark’s top nutritional scientists, whom some called the “joy-killing missionary,” proposed a drastic move: slaughter most of the country’s pigs and divert the scarce grains directly for human consumption. His advice was promptly followed. Overnight, practically all of Denmark went vegetarian. They subsisted on little but rye bread, barley porridge, potatoes, green veggies, milk, and some butter. Not only did Danes escape hunger, but within a year, the death rate from disease fell by 34 percent. Later, that period from October 1917 to October 1918 was dubbed the “Year of Health.” Of course, the benefits may have been due to other factors, too: the Danes drank much less beer as well, for example. But if meat was truly so indispensable, most likely more people would have died during the blockade, not less.
Many studies show that vegetarians have lower mortality rates than omnivores and are less likely to succumb to cancer or heart disease. The vegetarian Seventh-day Adventists in California, for example, live on average 9.5 (men) and 6.1 (women) years longer than other Californians. “Nutrition experts have known for decades that plant-based diets provide more than enough protein. In our studies, we consistently find that, as people switch from an animal-based diet to a plant-based diet, their diet becomes richer in vitamins, fiber, and other important nutrients. There is never a need to add animal products,” says Neal Barnard, professor of medicine at George Washington University, who has conducted numerous studies on plant-based nutrition.
Of course, anyone can have a horrible diet, and that applies to both plant eaters and meat eaters. A person surviving on nothing but fried bacon and pepperoni pizza would soon end up with vitamin C and K deficiencies, for example. A fruitarian diet can be dangerous, just like a macrobiotic diet, or those proposed by Robert Atkins and Pierre Dukan (the British Dietetic Association says they are not “nutritionally balanced”).
But just because there is nothing in animal flesh to keep us nutritionally hooked and we, in the twenty-first-century West, don’t need it to be healthy doesn’t mean, however, that this has always been the case. It’s not even true today: in some places on the planet, such as the Arctic, the only food available may be meat. Consider such a metaphor: If you are hiking in the desert with little water available, then drinking out of a dirty creek swarming with bacteria is a good idea, and you should do it in spite of the health risks (dying of dehydration is not very healthy). But if you are hiking with a whole backpack of Evian, then filling your cup in the creek is not only unnecessary but a rather bad idea. Eating meat is like drinking that creek water: it may be absolutely vital at times but not necessarily the best choice if you have great plant foods around.
The premodern diet for the vast majority of the world’s population was poor. There were very few vegetables to choose from, few grains to cook, and, in the North, no vegetable fat to provide calories. There was often not enough protein to satisfy hunger. People needed meat because they couldn’t have a rich diet otherwise. That’s where our stereotype of a sickish, bone-thin vegetarian may come from: most of those who were vegetarian in centuries past didn’t eat meat (or anything else) because they were too poor and so were often hungry and weak. This heritage of “you need meat to survive” may have gotten engraved in our culture as a powerful myth that lives on and keeps us craving animal flesh.
There is another theory, though, that may help explain why human beings desire meat rather than beans, tofu, or spirulina. According to this theory, it’s all due to our so-called selfish genes. Evolution doesn’t necessarily favor those who live the longest; it favors those who can reproduce the most. Studies show that the more animal protein people consume, the sooner they become fertile and the more kids they can have. Girls on meat-rich diets get their first periods earlier than their vegetarian counterparts. If the difference is as big as three or four years, as some studies suggest, it means meat eaters can have a few more kids each. The fact that these prolific parents may die earlier of cancer or heart disease doesn’t matter to the selfish genes.
Besides making us fertile earlier, it’s highly unlikely that meat keeps us nutritionally hooked. There is nothing vital in beef or pork that plants can’t provide. We don’t love eating meat because we have to do so to stay healthy. Yes, meat can satisfy our protein hunger quite well, but so can a peanut butter sandwich. Yes, meat is a great source of iron but so is licorice. There is nothing in meat that the Polish nation can only get from sausages and schnitzels, nothing to justify (from the nutritional perspective) the long waits we endured in the butcher stores of the ’80s.
Yet for the many tribes of Africa or South America, meat hunger may be very real. If there is no other protein around, meat can help people reach their protein targets. The fact that in the past we so often did need meat for its nutrients because there was little else to eat, and that animal protein is good for our reproduction-happy selfish genes, may have left us with taste buds sensitive to the particular mixture of compounds found in animal flesh. Westerners may not need meat anymore to live healthily, but our tongues and noses obviously didn’t get the memo. They still make us crave meat’s perfect brew of flavors—of umami, of fat, of the products of the Maillard reaction—keeping us hooked, even if eating meat may be against our best interests.