Nathan Myhrvold Delivers the Straight Poop on Foodborne Illnesses at Harvard

The No Shit Diet

"Just stop eating shit, and you’ll be way better off," said Nathan Myhrvold at his lecture last night, the penultimate talk in this year’s Science & Cooking series at Harvard University. He called it his "no shit diet," acknowledging that it’s surprisingly hard to follow. Oh, and he was talking about literal shit, as in actual feces. Turns out that it’s the source of the vast majority of foodborne illnesses. You may want to wash your hands right now — and again when you finish reading.

Myhrvold, formerly the Microsoft CTO, is the principal author of the growing Modernist Cuisine series, and he works out of a lab in Bellevue, Washington that combines a kitchen, machine shop, photo studio, and more. There, you might find French fries cooking in an ultrasonic bath...right next to a traditional wood-burning oven.

The first segment of last night’s lecture focused on what Myhrvold described as "microbiology for cooks." Microbes are everywhere, present in our bodies in greater amounts than cells, and many are beneficial. Sauerkraut, kimchi, and yogurt, for example, all rely on the activity of microbes, either bacteria or yeast. In basic terms, "microbes are greedy," he said, and that’s why the magic occurs. When microbes find a food source that suits them, they want it all to themselves and thus "piss in the soup," emitting toxins to keep others away. Sometimes, those toxins yield desirable results. Yogurt, for example, is created thanks to "good" bacteria creating lactic acid in a milk culture.

"Microbes are greedy."

But after that brief introduction, Myhrvold gleefully launched right into a discussion of harmful bacteria, telling the audience that one in six of us, on average, would get a foodborne illness this year. While many foodborne illnesses pass uncomfortably but not fatally, that’s not always the case, and he put the numbers into perspective. In the United States each year, about 1,351 people die of an identified foodborne illness. Equalling the same number in total: 717 will die of ATV or off-road accidents, 382 will die of "inhalation of gastric contents" (otherwise known as choking on vomit), 130 will die by way of deer, 99 by electric transmission lines, and 31 by (this one’s his favorite) being bitten or crushed by reptiles. So, add up a few bizarre situations, and you’ve got the same number of deaths. A few other numbers for contrast: 600 people die falling out of bed each year in the United States, and 30,800 die in car crashes. (It’s way more dangerous to drive to the store or restaurant than to eat food, he noted.)

Foodborne illnesses can be divided into roughly three categories, he continued: worms, bacteria, and viruses. And about 99% cases are thanks to "eating feces," as well as vomit and spit, getting back to his shit-free diet plan. "When things aren’t clean, you get sick." Pathogens don’t actually occur naturally in food, for the most part; there’s nothing inherently bad inside muscles, for example. That contamination has to come from an outside source.

Worm Sex and Seal Shit

First, he discussed parasitic worms, which "like to live in your gut or sometimes your flesh." Most common are Trichinella spiralis and Anisakis simplex. While Trichinella is often spoken about regarding uncooked pork, there actually hasn’t been a case of it in commercial pork in 20 or 30 years, said Myhrvold. But it can be found in bears (so he doesn’t recommend that you take anyone up on an offer of bear sashimi), mountain lions, horses, and seals, to name a few. It’s quite easy to kill with cooking, fortunately.

Don't eat bear sashimi.

Anisakis is very thin and only about an inch long and has a tendency to cause some fun appendicitis-like symptoms in humans. Myhrvold and his team found six of these worms in a single pound of halibut from a certain organic grocery chain that he didn’t quite name outright. In fact, these worms are common in many ocean fish that are found near the shore. He provided a simple overview of their life cycle: They normally like to live in seals’ stomachs, where they have wormy sex. Then, "the seal craps out the eggs." Fish eat them, seals eat fish, and so on. However, there are actually less than 10 reported cases a year in the United States, because freezing kills the worms. (Even when you’re eating sushi, it has typically been flash-frozen first, at least in this country.) There may be more cases, but after a few days or a week of severe stomach pain, the worms die off in a human gut, so some victims may attribute the stomachache to other causes.

Cow Pies and Wild Boars

The other two categories, foodborne viruses and bacteria (the bad kind), can both cause invasive infections; some familiar culprits are Salmonella enterica, Escherichia coli, Norovirus, and even ebola (yes, it’s technically a foodborne illness, likely courtesy of fruit bats eaten as bushmeat.)

When bacteria invade, they grow inside your body, absorbing nutrients and secreting chemicals (that’s what’s usually making you sick.) While E. coli gets a lot of name recognition, it only accounts for about 3% of foodborne illness cases and 0.01% of foodborne illness-related deaths. And it’s important to keep in mind that symptoms can appear as many as 10 days after eating the contaminated food, so it doesn’t necessarily make sense to blame your most recent meal. While raw meat often comes to mind when talking about things like E. coli, most recent outbreaks have actually been linked to vegetables like tomatoes and spinach. As was the theme in most of the lecture, it all comes down to fecal contamination.

"When I eat cow pies, I like salad after."

A major 2006 E. coli outbreak, for example, was tied to a pack of roving wild boars eating infected "cow pies" and then traveling a mile to a spinach farm, breaking in "because they’re powerful and somewhat ingenious," and eating spinach. "When I eat cow pies, I like salad after," said Myhrvold. "Turns out so did the boar." Maybe there was even just "a speck of wild boar poop" on one spinach leaf in the whole field, but when tons of spinach were dunked into a big tank together to be washed, that tiny bit of bacteria was diluted throughout the water, spreading to all the spinach — that’s really all it could have taken. It’s very complicated chains like this, he noted, that explain why foodborne illnesses are so difficult to fight.

As for Salmonella enterica, it accounts for 11% of foodborne cases and 13% of foodborne deaths. The name, in case you were wondering, isn’t related to salmon but rather to Daniel Elmer Salmon, a veterinarian in charge of a research unit in the United States Department of Agriculture. Myhrvold claimed that a guy in the unit named Smith discovered the bacterium, naming it after Salmon. "Is it a nice thing to name a deadly bacteria after your boss?" wondered Myhrvold.

One Bout of Diarrhea and Chesapeake Bay

You can't kill viruses. They're not alive.

Viruses — DNA or RNA enclosed by a protein shell — are very different from bacteria. Most importantly, they can only grow inside a living cell, so how long food has been sitting out doesn’t matter. A single virion is usually enough to cause sickness. "The thing that’s awkward about viruses," Myhrvold said, "is that you can’t kill them because they’re not alive." They have to be inactivated with harsh chemicals (like bleach) or heat. Freezing doesn’t work.

Noroviruses account for half of all food pathogen cases and 5% of deaths. In one large outbreak a few years ago, spread by Chesapeake Bay oysters, faulty toilets were found to be the culprit. None of the oyster boats had toilets with appropriate holding tanks; they all flushed right out into the bay. Myhrvold provided a sickening "ideal equation" starting with a single diarrhea-inflicted person "taking a dump in Chesapeake Bay" via one of these faulty toilets. Starting from 200 grams of diarrhea, Myhrvold showed how that single flush could contaminate the bay 880 times over, practically covering the eastern seaboard. Moral of the story? Get proper toilets on your boats.

Don't Eat Beached Whales

Back to bacteria — not all of it lives inside of you and fits into the "infection" frame. Toxic bacteria die when you eat them, but if they produce enough of a toxin through fermentation beforehand, you’re going to get sick. (In fact, if you feel symptoms right away, it’s most likely due to something from this category.) These bacteria multiply the longer food sits out. Bacillus cereus and Clostridium botulinum are common culprits. The latter, more commonly known as botulism, accounts for less than 1% of food-related deaths. It’s often associated with canning (improperly) and can only grow when oxygen isn’t present, so it must be eliminated before food goes into airtight storage. If you see a bulging can, throw it out. And wash your hands. (Also, don’t eat a dead whale that has washed up on a beach, but that’s a story for another time.)

Mold is generally "perfectly safe."

One interesting note on bacteria: spoilage bacteria and molds, while disgusting, are generally "perfectly safe." We’ve evolved to be repulsed by them not because they’re harmful themselves, Myhrvold explained, but because they often act like a coal miner’s canary. When spoilage is present, it’s a good sign that something bad is also colonizing your food, whether it’s E. coli, a norovirus, or something else you don’t want to eat. Be sure to thank mold for keeping you safe next time you spot it.

The FDA: Politics Over Science

The world of foodborne illnesses is clearly diverse, but the FDA takes a one-size-fits-all approach — which really doesn’t fit all. Factors that influence food safety regulations are, in this order, politics, culture, and science (a distant third), according to Myhrvold. That’s why you may be able to eat raw milk cheese, thanks to successful lobbying, on one side of a state line while it’s illegal on the other side.

Temperature and time are both important when cooking meats safely.

FDA regulations on cooking temperatures are also absurd; for example, beef can be eaten rare, but lamb is regulated totally differently, with no real basis in science. Pork has strict rules as well, even though it’s very easy to kill Trichinella at low heat, and commercial pork is frozen to kill it anyway. "Does it make sense?" asked Myhrvold. "No, but there’s a political element to it." And more importantly: temperature doesn’t matter on its own. Time is also part of the equation, and the two work together to kill bacteria at an exponential rate. If you’re told to heat something to a certain temperature "to be safe," that’s a meaningless statement, because time comes into play too. In general, an increase in 10 degrees Celsius kills 10 times more bacteria in the same amount of time.

Kale Regret

After a rousing discussion of poop and worms, Myhrvold decided to wrap up by tackling some common food fads. "I may need bodyguards by the end," he said, noting that people feel very strongly about food, almost in a religious capacity.

"It’s very rare that you can find a food that doesn’t have health claims associated with it," he said," but, as his slide pointed out: "Claims are inconsistent, hard to apply, and ever-changing."

He presented the story of fiber as a typical life cycle of a dietary medical system. In 1938, a man named Denis Burkitt graduated from the Edinburgh Royal College of Surgeons and became an army doctor in Africa, identifying a type of lymphoma in 1957. Through the 1950s, he guessed (although never actually measured) that he saw a lot less colon cancer in Africa than there was in Europe, and he attributed it to two reasons (again, guessing): (1) Africans ate more fiber than Europeans, which, he guessed, beneficially pushed fecal matter through the colon faster, and (2) Africans "squatted to shit" (Myhrvold’s words). "Fortunately only one of his two ideas caught on" in Europe. In the 1970s, he started getting a lot of press for his ideas on the benefits of fiber, and Kellogg and other companies started adding fiber-related health claims to their packaging. The FDA did not object. The high-fiber train chugged along with companies adding fiber to their food, usually in the appetizing form of sawdust or straw. In 1993, Burkitt died. In 1999, a number of studies conclusively disproved his theory, showing that there is no health benefit to fiber with regards to colon cancer, heart disease, or anything.

"The idea that fecal matter is bad for your colon is like saying light is bad for your eyes."

"The idea that fecal matter is bad for your colon is like saying light is bad for your eyes," said Myhrvold. "Colons are made to process fecal matter." It takes a long time — decades — to study things like cancer rates, but by now, even though at least six studies clearly show that Burkitt was wrong, various associations still repeat things about the "benefits" of fiber. "If you’re constipated, fiber’s not a bad thing," Myhrvold conceded, but it went from something that people just liked to eat to something they were told they ought to eat, and then they must eat, and then "you’re unhealthy if you don’t eat it." All with no basis in science.

Myhrvold also noted that no real benefits have been found in eating whole grains or even fresh fruits and vegetables in terms of heart health, colon health, and beyond. "It’s depressing. You may be having kale regret right now."

Next, MSG. The tide has been turning a bit in recent years, but there’s still a "very large xenophobic bias" and "bigotry" about it, Myhrvold said. News flash: most MSG isn’t even found in Asian restaurants; it’s found in some favorite American fast food destinations, from KFC to Burger King to Denny’s. It also occurs naturally in foods like parmesan cheese (making up about 1% by weight). "That’s part of why parmesan cheese tastes good." In double-blind studies, no one has actually been found to be sensitive to MSG.

Bread Is Balloons

Myhrvold wrapped up the lecture with the always-popular-these-days topic of gluten, an important topic for him since he and the team are now working on a Modernist Cuisine book about bread. "Bread is basically a set of balloons," he said. Gluten, which forms from two proteins, gliadin and glutenin, found in wheat and some other grains, is the "rubber" holding those "balloons" together. About 0.75% to 1% of people in the United States have celiac disease, "and they truly shouldn’t eat gluten." But what about people who self-diagnose with gluten "sensitivity"? What about books like the Wheat Belly series, which demonizes grains? And the Paleo diet?

A double-blind study once seemed to find evidence of gluten causing gastrointestinal symptoms in non-celiac subjects...until one of the same researchers went on to study it further and later found no effect of gluten on self-reported non-celiac gluten-sensitive test subjects. The researcher, Peter Gibson, and his team separated out different components of wheat for the latter study and found that some components did have an effect on people, but not the gluten. Studies like this suggest that FODMAPs — fermentable, oligo-, di-, mono-saccharides and polyols, or sugars that the human gut doesn’t absorb — might actually be culprits, and the reduction of FODMAP sources from the diet (including, yes, wheat) may help people with Irritable Bowel Syndrome and certain other gastrointestinal problems. While it’s too soon to tell, said Myhrvold, this might be "the next great treatment"...or the next fad.

"Everyone farts."

By the way, if you don’t eat foods that contain FODMAPs, you fart less, he noted. But "everyone farts. You shouldn’t be ashamed of it. It’s not a medical problem. It’s really OK."

The Harvard Science & Cooking lecture series wraps up its season next Monday, December 1, with Joan Roca of El Celler de Can Roca speaking about "Roots, Innovation, and Creation." The event is free and open to the public; seats are first come, first served. More details can be found on the Harvard website.