Harvard Medical School found that 1 in 10 premature deaths is caused by eating red meat:

It was found that for every serving of red meat – equivalent to 3 ounces (85 grams) – eaten each day there was an 18 per cent increased risk of dying from heart disease and a 10 per cent increased risk of dying from cancer.

The study published in the Archives of Internal Medicine followed more than 100,000 people for around 28 years asking them periodically about their diet and lifestyle.

Red meat often contains high amounts of saturated fat, while bacon and salami contain large amounts of salt. Replacing red meat with poultry, fish or vegetables, whole grains and other healthy foods cut the risk of dying by up to one fifth, the study found.

Small quantities of processed meat such as bacon, sausages or salami can increase the likelihood of dying by a fifth, researchers from Harvard School of Medicine found. Eating steak increases the risk of dying by 12%.

Other studies have also found that eating too much meat causes cancer and other health problems.

But how much of the problem isn’t red meat … but the fact that what we’re eating isn’t what our grandparents wouldn’t even recognize as meat at all?

For all of human history – until the last couple of decades – people ate beef from cows (or buffalo or bison) which grazed on grass. The cows were usually strong and healthy. Their meat was lean, with very little saturated fat, as the critters ate well and got outdoor exercise. Their meat was high in good Omega 3 fats. See this and this, and humans evolved to consume a lot of Omega 3 fatty acids in the wild game and fish which they ate (more).

Today, on the other hand, beef is laden with saturated fat and almost entirely lacking healthy fats like Omega 3s, because the cows are force-fed food which makes them sick. Specifically, instead of their natural menu - grass - they are force-fed corn, which makes them sick. Because their diet makes them ill, they are given massive amounts of antibiotics. Even with the antibiotics, the diet and living conditions would kill them pretty quickly if they aren't slaughtered.

They are also given estrogen to fatten them up. And they are fed parts of other animals, which can give them mad cow disease.

Well-known food writer (and meat-lover) Michael Pollan gave a must-read account of modern beef practices in the New York Times in 2002:

Cows raised on grass simply take longer to reach slaughter weight than cows raised on a richer diet, and the modern meat industry has devoted itself to shortening a beef calf’s allotted time on earth. ”In my grandfather’s day, steers were 4 or 5 years old at slaughter” …. now we get there at 14 to 16 months.” Fast food indeed. What gets a beef calf from 80 to 1,200 pounds in 14 months are enormous quantities of corn, protein supplements — and drugs, including growth hormones.

***

Calves have no need of regular medication while on grass, but as soon as they’re placed in the backgrounding pen, they’re apt to get sick. Why? The stress of weaning is a factor, but the main culprit is the feed. The shift to a ”hot ration” of grain can so disturb the cow’s digestive process — its rumen, in particular — that it can kill the animal if not managed carefully and accompanied by antibiotics.

***

Growing the vast quantities of corn used to feed livestock in this country takes vast quantities of chemical fertilizer, which in turn takes vast quantities of oil — 1.2 gallons for every bushel. So the modern feedlot is really a city floating on a sea of oil.

***

Tanker trucks back up to silo-shaped tanks, into which they pump thousands of gallons of liquefied fat and protein supplement. In a shed attached to the mill sit vats of liquid vitamins and synthetic estrogen; next to these are pallets stacked with 50-pound sacks of Rumensin and tylosin, another antibiotic.

***

Corn is a mainstay of livestock diets because there is no other feed quite as cheap or plentiful: thanks to federal subsidies and ever-growing surpluses, the price of corn ($2.25 a bushel) is 50 cents less than the cost of growing it. The rise of the modern factory farm is a direct result of these surpluses, which soared in the years following World War II, when petrochemical fertilizers came into widespread use. Ever since, the U.S.D.A.’s policy has been to help farmers dispose of surplus corn by passing as much of it as possible through the digestive tracts of food animals, converting it into protein. Compared with grass or hay, corn is a compact and portable foodstuff, making it possible to feed tens of thousands of animals on small plots of land. Without cheap corn, the modern urbanization of livestock would probably never have occurred.

We have come to think of ”cornfed” as some kind of old-fashioned virtue; we shouldn’t. Granted, a cornfed cow develops well-marbled flesh, giving it a taste and texture American consumers have learned to like. Yet this meat is demonstrably less healthy to eat, since it contains more saturated fat. A recent study in The European Journal of Clinical Nutrition found that the meat of grass-fed livestock not only had substantially less fat than grain-fed meat but that the type of fats found in grass-fed meat were much healthier. (Grass-fed meat has more omega 3 fatty acids and fewer omega 6, which is believed to promote heart disease; it also contains betacarotine and CLA, another ”good” fat.) A growing body of research suggests that many of the health problems associated with eating beef are really problems with cornfed beef. In the same way ruminants have not evolved to eat grain, humans may not be well adapted to eating grain-fed animals. Yet the U.S.D.A.’s grading system continues to reward marbling — that is, intermuscular fat — and thus the feeding of corn to cows.

The economic logic behind corn is unassailable, and on a factory farm, there is no other kind. Calories are calories, and corn is the cheapest, most convenient source of calories. Of course the identical industrial logic — protein is protein — led to the feeding of rendered cow parts back to cows, a practice the F.D.A. banned in 1997 after scientists realized it was spreading mad-cow disease.

Make that mostly banned. The F.D.A.’s rules against feeding ruminant protein to ruminants make exceptions for ”blood products” (even though they contain protein) and fat. Indeed, my steer has probably dined on beef tallow recycled from the very slaughterhouse he’s heading to in June. ”Fat is fat,” the feedlot manager shrugged when I raised an eyebrow.

F.D.A. rules still permit feedlots to feed nonruminant animal protein to cows. (Feather meal is an accepted cattle feed, as are pig and fish protein and chicken manure.) Some public-health advocates worry that since the bovine meat and bone meal that cows used to eat is now being fed to chickens, pigs and fish, infectious prions could find their way back into cattle when they eat the protein of the animals that have been eating them. To close this biological loophole, the F.D.A. is now considering tightening its feed rules.

***

”When we buy supplement, the supplier says it’s 40 percent protein, but they don’t specify beyond that.” When I called the supplier, it wouldn’t divulge all its ”proprietary ingredients” but promised that animal parts weren’t among them. Protein is pretty much still protein.

Compared with ground-up cow bones, corn seems positively wholesome. Yet it wreaks considerable havoc on bovine digestion. During my day at Poky, I spent an hour or two driving around the yard with Dr. Mel Metzen, the staff veterinarian. Metzen, a 1997 graduate of Kansas State’s vet school, oversees a team of eight cowboys who spend their days riding the yard, spotting sick cows and bringing them in for treatment. A great many of their health problems can be traced to their diet. ”They’re made to eat forage,” Metzen said, ”and we’re making them eat grain.”

Perhaps the most serious thing that can go wrong with a ruminant on corn is feedlot bloat. The rumen is always producing copious amounts of gas, which is normally expelled by belching during rumination. But when the diet contains too much starch and too little roughage, rumination all but stops, and a layer of foamy slime that can trap gas forms in the rumen. The rumen inflates like a balloon, pressing against the animal’s lungs. Unless action is promptly taken to relieve the pressure (usually by forcing a hose down the animal’s esophagus), the cow suffocates.

A corn diet can also give a cow acidosis. Unlike that in our own highly acidic stomachs, the normal pH of a rumen is neutral. Corn makes it unnaturally acidic, however, causing a kind of bovine heartburn, which in some cases can kill the animal but usually just makes it sick. Acidotic animals go off their feed, pant and salivate excessively, paw at their bellies and eat dirt. The condition can lead to diarrhea, ulcers, bloat, liver disease and a general weakening of the immune system that leaves the animal vulnerable to everything from pneumonia to feedlot polio.

Cows rarely live on feedlot diets for more than six months, which might be about as much as their digestive systems can tolerate. ”I don’t know how long you could feed this ration before you’d see problems,” Metzen said; another vet said that a sustained feedlot diet would eventually ”blow out their livers” and kill them. As the acids eat away at the rumen wall, bacteria enter the bloodstream and collect in the liver. More than 13 percent of feedlot cattle are found at slaughter to have abscessed livers.

What keeps a feedlot animal healthy — or healthy enough — are antibiotics. Rumensin inhibits gas production in the rumen, helping to prevent bloat; tylosin reduces the incidence of liver infection. Most of the antibiotics sold in America end up in animal feed — a practice that, it is now generally acknowledged, leads directly to the evolution of new antibiotic-resistant ”superbugs.” In the debate over the use of antibiotics in agriculture, a distinction is usually made between clinical and nonclinical uses. Public-health advocates don’t object to treating sick animals with antibiotics; they just don’t want to see the drugs lose their efficacy because factory farms are feeding them to healthy animals to promote growth. But the use of antibiotics in feedlot cattle confounds this distinction. Here the drugs are plainly being used to treat sick animals, yet the animals probably wouldn’t be sick if not for what we feed them.

I asked Metzen what would happen if antibiotics were banned from cattle feed. ”We just couldn’t feed them as hard,” he said. ”Or we’d have a higher death loss.” (Less than 3 percent of cattle die on the feedlot.) The price of beef would rise, he said, since the whole system would have to slow down.

”Hell, if you gave them lots of grass and space,” he concluded dryly, ”I wouldn’t have a job.”

***

I stopped by the shed where recent arrivals receive their hormone implants. The calves are funneled into a chute, herded along by a ranch hand wielding an electric prod, then clutched in a restrainer just long enough for another hand to inject a slow-release pellet of Revlar, a synthetic estrogen, in the back of the ear. [This] is virtually a universal practice in the cattle industry in the United States. (It has been banned in the European Union.)

American regulators permit hormone implants on the grounds that no risk to human health has been proved, even though measurable hormone residues do turn up in the meat we eat. These contribute to the buildup of estrogenic compounds in the environment, which some scientists believe may explain falling sperm counts and premature maturation in girls. Recent studies have also found elevated levels of synthetic growth hormones in feedlot wastes; these persistent chemicals eventually wind up in the waterways downstream of feedlots, where scientists have found fish exhibiting abnormal sex characteristics.

The F.D.A. is opening an inquiry into the problem, but for now, implanting hormones in beef cattle is legal and financially irresistible: an implant costs $1.50 and adds between 40 and 50 pounds to the weight of a steer at slaughter, for a return of at least $25.

***

The unnaturally rich diet of corn that has compromised [the cow's] health is fattening his flesh in a way that in turn may compromise the health of the humans who will eat him. The antibiotics he’s consuming with his corn were at that very moment selecting, in his gut and wherever else in the environment they wind up, for bacteria that could someday infect us and resist the drugs we depend on. We inhabit the same microbial ecosystem as the animals we eat, and whatever happens to it also happens to us.

I thought about the deep pile of manure that [the cows] and I were standing in. We don’t know much about the hormones in it — where they will end up or what they might do once they get there — but we do know something about the bacteria. One particularly lethal bug most probably resided in the manure beneath my feet. Escherichia coli 0157 is a relatively new strain of a common intestinal bacteria (it was first isolated in the 1980′s) that is common in feedlot cattle, more than half of whom carry it in their guts. Ingesting as few as 10 of these microbes can cause a fatal infection.

Most of the microbes that reside in the gut of a cow and find their way into our food get killed off by the acids in our stomachs, since they originally adapted to live in a neutral-pH environment. But the digestive tract of the modern feedlot cow is closer in acidity to our own, and in this new, manmade environment acid-resistant strains of E. coli have developed that can survive our stomach acids — and go on to kill us. By acidifying a cow’s gut with corn, we have broken down one of our food chain’s barriers to infection. Yet this process can be reversed: James Russell, a U.S.D.A. microbiologist, has discovered that switching a cow’s diet from corn to hay in the final days before slaughter reduces the population of E. coli 0157 in its manure by as much as 70 percent. Such a change, however, is considered wildly impractical by the cattle industry.

So much comes back to corn, this cheap feed that turns out in so many ways to be not cheap at all. While I stood in [the] pen, a dump truck pulled up alongside the feed bunk and released a golden stream of feed. The animals stepped up to the bunk for their lunch. The $1.60 a day I’m paying for three giant meals is a bargain only by the narrowest of calculations. It doesn’t take into account, for example, the cost to the public health of antibiotic resistance or food poisoning by E. coli or all the environmental costs associated with industrial corn.

For if you follow the corn from this bunk back to the fields where it grows, you will find an 80-million-acre monoculture that consumes more chemical herbicide and fertilizer than any other crop. Keep going and you can trace the nitrogen runoff from that crop all the way down the Mississippi into the Gulf of Mexico, where it has created (if that is the right word) a 12,000-square-mile ”dead zone.”

But you can go farther still, and follow the fertilizer needed to grow that corn all the way to the oil fields of the Persian Gulf. [The cow] started life as part of a food chain that derived all its energy from the sun; now that corn constitutes such an important link in his food chain, he is the product of an industrial system powered by fossil fuel. (And in turn, defended by the military — another uncounted cost of ”cheap” food.) I asked David Pimentel, a Cornell ecologist who specializes in agriculture and energy, if it might be possible to calculate precisely how much oil it will take to grow my steer to slaughter weight…. roughly 284 gallons of oil. We have succeeded in industrializing the beef calf, transforming what was once a solar-powered ruminant into the very last thing we need: another fossil-fuel machine.

***

Much of what happens next — the de-hiding of the animal, the tying off of its rectum before evisceration — is designed to keep the animal’s feces from coming into contact with its meat. This is by no means easy to do, not when the animals enter the kill floor smeared with manure and 390 of them are eviscerated every hour. (Partly for this reason, European plants operate at much slower line speeds.) But since that manure is apt to contain lethal pathogens like E. coli 0157, and since the process of grinding together hamburger from hundreds of different carcasses can easily spread those pathogens across millions of burgers, packing plants now spend millions on ”food safety” — which is to say, on the problem of manure in meat.

***

It’s accepted that the animals will enter the kill floor caked with feedlot manure that has been rendered lethal by the feedlot diet. Rather than try to alter that diet or keep the animals from living in their waste or slow the line speed — all changes regarded as impractical — the industry focuses on disinfecting the manure that will inevitably find its way into the meat. This is the purpose of irradiation (which the industry prefers to call ”cold pasteurization”). It is also the reason that carcasses pass through a hot steam cabinet and get sprayed with an antimicrobial solution before being hung in the cooler at the National Beef plant.

***

I discovered that grass-fed meat is more expensive than supermarket beef. Whatever else you can say about industrial beef, it is remarkably cheap, and any argument for changing the system runs smack into the industry’s populist arguments. Put the animals back on grass, it is said, and prices will soar; it takes too long to raise beef on grass, and there’s not enough grass to raise them on, since the Western range lands aren’t big enough to sustain America’s 100 million head of cattle. And besides, Americans have learned to love cornfed beef. Feedlot meat is also more consistent in both taste and supply and can be harvested 12 months a year. (Grass-fed cattle tend to be harvested in the fall, since they stop gaining weight over the winter, when the grasses go dormant.)

All of this is true. The economic logic behind the feedlot system is hard to refute. And yet so is the ecological logic behind a ruminant grazing on grass. Think what would happen if we restored a portion of the Corn Belt to the tall grass prairie it once was and grazed cattle on it. No more petrochemical fertilizer, no more herbicide, no more nitrogen runoff. Yes, beef would probably be more expensive than it is now, but would that necessarily be a bad thing? Eating beef every day might not be such a smart idea anyway — for our health, for the environment. And how cheap, really, is cheap feedlot beef? Not cheap at all, when you add in the invisible costs: of antibiotic resistance, environmental degradation, heart disease, E. coli poisoning, corn subsidies, imported oil and so on. All these are costs that grass-fed beef does not incur.