Tag: modern times

Just How Sweaty Can Humans Get?

This summer, I, like so many other Americans, have forgotten what it means to be dry. The heat has grown so punishing, and the humidity so intense, that every movement sends my body into revolt. When I stand, I sweat. When I sit, I sweat. When I slice into a particularly dense head of cabbage, I sweat.

The way things are going, infinite moistness may be something many of us will have to get used to. This past July was the world’s hottest month in recorded history; off the coast of Florida, ocean temperatures hit triple digits, while in Arizona, the asphalt caused third-degree burns. As human-driven climate change continues to remodel the globe, heat waves are hitting harder, longer, and more frequently. The consequences of this crisis will, on a macroscopic scale, upend where and how humans can survive. It will also, in an everyday sense, make our lives very, very sweaty.

For most Americans, that’s probably unwelcome news. Our culture doesn’t exactly love sweat. Heavy perspirers are shunned on subways; BO is a hallmark of pubescent shame. History is splattered with examples of people trying to cloak sweat in perfumes, wash it away by bathing, or soak it up with wads of cotton or rubber crammed into their shirts, dresses, and hats. People without medical reason to do so have opted to paralyze their sweat-triggering nerves with Botox. Even Bruce Lee had the sweat glands in his armpits surgically removed, reportedly to avoid on-screen stains, several months before his death, in 1973.

But our scorn of sweat is entirely undeserved. Perspiration is vital to life. It cools our bodies and hydrates our skin; it manages our microbiome and emits chemical cues. Sweat is also a fundamental part of what makes people people. Without it, we wouldn’t be able to run long distances in high heat; we wouldn’t be able to power our big brains and bodies; we wouldn’t have colonized so much of the Earth. We may even have sweat to thank (or blame) for our skin’s nakedness, says Yana Kamberov, a sweat researcher at the University of Pennsylvania. Her team’s recent data, not yet published, suggest that as human skin evolved to produce more and more sweat glands, fur-making hair follicles disappeared to make room. Sweat is one of the “key milestones” in human evolution, argues Andrew Best, a biological anthropologist at the Massachusetts College of Liberal Arts—on par with big brains, walking upright, and the expression of culture through language and art.

Humans aren’t the only animals that sweat. Many mammals—among them, dogs, cats, and rats—perspire through the footpads on their paws; chimpanzees, macaques, and other primates are covered in sweat glands. Even horses and camels slick their skin in the heat. But only our bodies are studded with this many millions of teeny, tubular sweat glands—about 10 times the number found on other primates’ skin—that funnel water from our blood to pores that can squeeze out upwards of three, four, even five liters of sweat an hour when we need them to.

Our dampness isn’t cost free. Sweat is siphoned from the liquid components of blood—lose too much, and the risks of heat stroke and death shoot way up. Our lack of fur also makes us more vulnerable to bites and burns. That humans sweat anyway, then, Best told me, is a testament to perspiration’s cooling punch—it’s so much more efficient than merely panting or hiding from the heat. “If your objective is to be able to sustain a high metabolic rate in warm conditions, sweating is absolutely the best,” he said.

Read: You’re probably drinking enough water

And yet, in modern times, many of us just can’t seem to accept the realities of sweat. Americans are, for whatever reason, particularly preoccupied with quashing perspiration; in many other countries, “body odor is just normal,” says Angela Lamb, a dermatologist at Mount Sinai’s Icahn School of Medicine. But the bemoaning of BO has cultural roots that long predate the United States. “I’ve read discussions well back into antiquity where there are discussions about people whose armpits stink,” says Cari Casteel, a historian at the University of Buffalo. By the start of the 20th century, Americans had been primed by the recent popularization of germ theory to fear dirtiness—the perfect moment for marketers to “put the fear in women, and then men, that sweat was going to kibosh your plans for romance or a job,” says Sarah Everts, the author of The Joy of Sweat. These days, deodorants command an $8 billion market in the United States.

Our aversion to sweat doesn’t make much evolutionary sense. Unlike other excretions that elicit near-universal disgust, sweat doesn’t routinely transmit disease or pose other harm. But it does evoke physical labor and emotional stress—neither of which polite society is typically keen to see. And for some, maybe it signifies “losing control of your body in a particular way,” says Tina Lasisi, a biological anthropologist at the University of Michigan. Unlike urine or tears, sweat is the product of a body function that we can’t train ourselves to suppress or delay.

We also hate sweat because we think it smells bad. But it doesn’t, really. Nearly all of the sweat glands on human bodies are of the so-called eccrine variety, and produce slightly salty water with virtually no scent. A few spots, such as the armpits and groin, are freckled with apocrine glands that produce a waxy, fatty substance laced with pheromones—but even that has no inherent odor. The bacteria on our skin eat it, and their waste generates a stench, leaving sweat as the scapegoat. Our species’ approach to perspiration may even make us “less stinky than we could be,” Best told me. The expansion of eccrine glands across the body might not have only made our skin barer; it’s also thought to have evicted a whole legion of BO-producing apocrine glands.

As global temperatures climb, for many people—especially in parts of the world that lack access to air-conditioning—sweat will be an inevitability. “I suspect everyone is going to be quite drippy,” Kamberov told me. Exactly how slick each of us will be, though, is anyone’s guess. Experts have evidence that men sweat more than women, and that perspiration potential declines with age. But by and large, they can’t say with certainty why some people are inherently sweatier than others, and how much of it is inborn. Decades ago, a Japanese researcher hypothesized that perspiration potential might be calibrated in the first two or three years of life: Kids born into tropical climates, his analyses suggested, might activate more of their sweat glands than children in temperate regions. But Best’s recent attempts to replicate those findings have so far come up empty.

Read: The man who did not sweat

Perspiration does seem to be malleable within a lifetime. A couple of weeks into a new, intense exercise regimen, for instance, people will start to sweat more and earlier. Over longer periods of time, the body can also learn to tolerate high temperatures, and sweat less copiously but more efficiently. We sense these changes subtly as the seasons shift, says Laure Rittié, a physiologist at Glaxo-Smith Kline, who has studied sweat. It’s part of the reason a 75-degree day might feel toastier—and perhaps sweatier—in the spring than in the fall.

But we can’t simply sweat our way out of our climatic bind. There’s a ceiling to the temperatures we can tolerate; the body can leach only so much liquid out at once. Sweat’s cooling power also tends to falter in humid conditions, when liquid can’t evaporate as easily off of skin. Nor can researchers predict whether future generations might evolve to perspire much more than we do now. We no longer live under the intense conditions that pressured our ancestors to sprout more sweat glands—changes that also took place over many millions of years. It’s even possible that we’re fast approaching the maximal moistness a primate body can produce. “We don’t have a great idea about the outer limits of that plasticity,” Jason Kamilar, a biological anthropologist at the University of Massachusetts at Amherst, told me.

For now, people who are already on the sweatier side may find themselves better equipped to deal with a warming world, Rittié told me. At long last: Blessed are the moist, for they shall inherit the Earth.

Katherine J. Wu

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August 8, 2023
Someday, You Might Be Able to Eat Your Way Out of a Cold

When it comes to treating disease with food, the quackery stretches back far. Through the centuries, raw garlic has been touted as a home treatment for everything from chlamydia to the common cold; Renaissance remedies for the plague included figs soaked in hyssop oil. During the 1918 flu pandemic, Americans wolfed down onions or chugged “fluid beef” gravy to keep the deadly virus at bay.

Even in modern times, the internet abounds with dubious culinary cure-alls: apple-cider vinegar for gonorrhea; orange juice for malaria; mint, milk, and pineapple for tuberculosis. It all has a way of making real science sound like garbage. Research on nutrition and immunity “has been ruined a bit by all the writing out there on Eat this to cure cancer,” Lydia Lynch, an immunologist and a cancer biologist at Harvard, told me.

In recent years, though, plenty of legit studies have confirmed that our diets really can affect our ability to fight off invaders—down to the fine-scale functioning of individual immune cells. Those studies belong to a new subfield of immunology sometimes referred to as immunometabolism. Researchers are still a long way off from being able to confidently recommend specific foods or dietary supplements for colds, flus, STIs, and other infectious illnesses. But someday, knowledge of how nutrients fuel the fight against disease could influence the way that infections are treated in hospitals, in clinics, and maybe at home—not just with antimicrobials and steroids but with dietary supplements, metabolic drugs, or whole foods.

Although major breakthroughs in immunometabolism are just now arriving, the concepts that underlie them have been around for at least as long as the quackery. People have known for millennia that in the hours after we fall ill, our appetite dwindles; our body feels heavy and sluggish; we lose our thirst drive. In the 1980s, the veterinarian Benjamin Hart argued that those changes were a package deal—just some of many sickness behaviors, as he called them, that are evolutionarily hardwired into all sorts of creatures. The goal, Hart told me recently, is to “help the animal stay in one place and conserve energy”—especially as the body devotes a large proportion of its limited resources to igniting microbe-fighting fevers.

The notion of illness-induced anorexia (not to be confused with the eating disorder anorexia nervosa) might seem, at first, like “a bit of a paradox,” says Zuri Sullivan, an immunologist at Harvard. Fighting pathogenic microbes is energetically costly—which makes eating less a very counterintuitive choice. But researchers have long posited that cutting down on calories could serve a strategic purpose: to deprive certain pathogens of essential nutrients. (Because viruses do not eat to acquire energy, this notion is limited to cell-based organisms such as bacteria, fungi, and parasites.) A team led by Miguel Soares, an immunologist at the Instituto Gulbenkian de Ciência, in Portugal, recently showed that this exact scenario might be playing out with malaria. As the parasites burst out of the red blood cells where they replicate, the resulting spray of heme (an oxygen-transporting molecule) prompts the liver to stop making glucose. The halt seems to deprive the parasites of nutrition, weakening them and tempering the infection’s worst effects.

Read: Why science can be so indecisive about nutrition

Cutting down on sugar can be a dangerous race to the bottom: Animals that forgo food while they’re sick are trying to starve out an invader before they themselves run out of energy. Let the glucose boycott stretch on too long, and the dieter might develop dangerously low blood sugar —a common complication of severe malaria—which can turn deadly if untreated. At the same time, though, a paucity of glucose might have beneficial effects on individual tissues and cells during certain immune fights. For example, low-carbohydrate, high-fat ketogenic diets seem to enhance the protective powers of certain types of immune cells in mice, making it tougher for particular pathogens to infiltrate airway tissue.

Those findings are still far from potential human applications. But Andrew Wang, an immunologist and a rheumatologist at Yale, hopes that this sort of research could someday yield better clinical treatments for sepsis, an often fatal condition in which an infection spreads throughout the body, infiltrating the blood. “It’s still not understood exactly what you’re supposed to feed folks with sepsis,” Wang told me. He and his former mentor at Yale, Ruslan Medzhitov, are now running a clinical trial to see whether shifting the balance of carbohydrates and lipids in their diet speeds recovery for people ill with sepsis. If the team is able to suss out clear patterns, doctors might eventually be able to flip the body’s metabolic switches with carefully timed doses of drugs, giving immune cells a bigger edge against their enemies.

But the rules of these food-illness interactions, to the extent that anyone understands them, are devilishly complex. Sepsis can be caused by a whole slew of different pathogens. And context really, really matters. In 2016, Wang, Medzhitov, and their colleagues discovered that feeding mice glucose during infections created starkly different effects depending on the nature of the pathogen driving disease. When the mice were pumped full of glucose while infected with the bacterium Listeria, all of them died—whereas about half of the rodents that were allowed to give in to their infection-induced anorexia lived. Meanwhile, the same sugary menu increased survival rates for mice with the flu.

In this case, the difference doesn’t seem to boil down to what the microbe was eating. Instead, the mice’s diet changed the nature of the immune response they were able to marshal—and how much collateral damage that response was able to inflict on the body, as James Hamblin wrote for The Atlantic at the time. The type of inflammation that mice ignited against Listeria, the team found, could imperil fragile brain cells when the rodents were well fed. But when the mice went off sugar, their starved livers started producing an alternate fuel source called ketone bodies—the same compounds people make when on a ketogenic diet—that helped steel their neurons. Even as the mice fought off their bacterial infections, their brain stayed resilient to the inflammatory burn. The opposite played out when the researchers subbed in influenza, a virus that sparks a different type of inflammation: Glucose pushed brain cells into better shielding themselves against the immune system’s fiery response.

Read: Feed a cold, don’t starve it

There’s not yet one unifying principle to explain these differences. But they are a reminder of an underappreciated aspect of immunity. Surviving disease, after all, isn’t just about purging a pathogen from the body; our tissues also have to guard themselves from shrapnel as immune cells and microbes wage all-out war. It’s now becoming clear, Soares told me, that “metabolic reprogramming is a big component of that protection.” The tactics that thwart a bacterium like Listeria might not also shield us from a virus, a parasite, or a fungus; they may not be ideal during peacetime. Which means our bodies must constantly toggle between metabolic states.

In the same way that the types of infections likely matter, so do the specific types of nutrients: animal fats, plant fats, starches, simple sugars, proteins. Like glucose, fats can be boons in some contexts but detrimental in others, as Lynch has found. In people with obesity or other metabolic conditions, immune cells appear to reconfigure themselves to rely more heavily on fats as they perform their day-to-day functions. They can also be more sluggish when they attack. That’s the case for a class of cells called natural killers: “They still recognize cancer or a virally infected cell and go to it as something that needs to be killed,” Lynch told me. “But they lack the energy to actually kill it.” Timing, too, almost certainly has an effect. The immune defenses that help someone expunge a virus in the first few days of an infection might not be the ones that are ideal later on in the course of disease.

Even starving out bacterial enemies isn’t a surefire strategy. A few years ago, Janelle Ayres, an immunologist at the Salk Institute for Biological Studies, and her colleagues found that when they infected mice with Salmonella and didn’t allow the rodents to eat, the hungry microbes in their guts began to spread outside of the intestines, likely in search of food. The migration ended up killing tons of their tiny mammal hosts. Mice that ate normally, meanwhile, fared far better—though the Salmonella inside of them also had an easier time transmitting to new hosts. The microbes, too, were responding to the metabolic milieu, and trying to adapt. “It would be great if it was as simple as ‘If you have a bacterial infection, reduce glucose,’” Ayres said. “But I think we just don’t know.”

All of this leaves immunometabolism in a somewhat chaotic state. “We don’t have simple recommendations” on how to eat your way to better immunity, Medzhitov told me. And any that eventually emerge will likely have to be tempered by caveats: Factors such as age, sex, infection and vaccination history, underlying medical conditions, and more can all alter people’s immunometabolic needs. After Medzhitov’s 2016 study on glucose and viral infections was published, he recalls being dismayed by a piece from a foreign outlet circulating online claiming that “a scientist from the USA says that during flu, you should eat candy,” he told me with a sigh. “That was bad.”

Read: You can’t “starve” cancer, but you might help treat it with food

But considering how chaotic, individualistic, and messy nutrition is for humans, it shouldn’t be a surprise that the dietary principles governing our individual cells can get pretty complicated too. For now, Medzhitov said, we may be able to follow our instincts. Our bodies, after all, have been navigating this mess for millennia, and have probably picked up some sense of what they need along the way. It may not be a coincidence that during viral infections, “something sweet like honey and tea can really feel good,” Medzhitov said. There may even be some immunological value in downing the sick-day classic, chicken soup: It’s chock-full of fluid and salts, helpful things to ingest when the body’s electrolyte balance has been thrown out of whack by disease.

The science around sickness cravings is far from settled. Still, Sullivan, who trained with Medzhitov, jokes that she now feels better about indulging in Talenti mango sorbet when she’s feeling under the weather with something viral, thanks to her colleagues’ 2016 finds. Maybe the sugar helps her body battle the virus without harming itself; then again, maybe not. For now, she figures it can’t hurt to dig in.

Katherine J. Wu

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February 2, 2023
The Next Presidential Election Is Happening Right Now in the States

Kristen McDonald Rivet let out a big, slightly rueful laugh. “I was underestimating the level of national attention this race was going to get,” she told me. “In the extreme, I was underestimating it.”

A city commissioner in Bay City, Michigan, McDonald Rivet decided earlier this year to run as a Democrat for the State Senate. She knew the race would be competitive in a closely divided district. But she had little inkling that the seat she was seeking would come to be regarded by Democratic operatives as one of the most crucial in the country.

Thousands of people run for state legislatures every two years, and many of the campaigns are important but sleepy affairs that hinge on debates over tax rates, school funding, and the condition of roads and bridges. Not this year, however, and not in Michigan. With Republican election deniers running up and down the ballot in key battlegrounds, many Democrats believe that the fight for power in state capitals this fall could ultimately determine the outcome of the presidential election in 2024.

Read: How the Democrats rallied

Democrats have carried Michigan in seven of the past eight presidential elections, but they have not held the majority in its State Senate for nearly 40 years. This year, however, they need to pick up just three seats to dislodge Republicans from the majority, and a new legislative map drawn by an independent redistricting commission has given Democrats an opportunity even in a year in which the overall political environment is likely to be challenging for the party.

If Michigan is famously shaped like a mitten, the Thirty-Fifth District sits between its thumb and forefinger, encompassing the tri-cities of Saginaw, Bay City, and Midland near the shores of Lake Huron. The area voted narrowly for Joe Biden in 2020, but Mariah Hill, the caucus director for the Michigan Senate Democrats, told me she considers it the party’s “majority-making seat.”

McDonald Rivet won her election as a commissioner in Bay City with about 350 votes; this year, in her first run for a partisan office, she told me she had raised about $425,000, which is a considerable sum for a state legislative candidate. National groups such as EMILY’s List, the States Project, and EveryDistrict are directing money and resources to her campaign.

Progressives have been intensifying their focus on state legislative power over the past decade. In the 2010 GOP wave, Republicans caught Democrats flat-footed, swept them from majorities across the country in 2010, and then locked in their advantage for years to come through gerrymandering in many states. Democrats reclaimed seven state legislative chambers in 2018, but their momentum slowed in 2020, when they failed to pick up a single chamber. They also lost the majorities they had gained in New Hampshire.

Read: The Democrats whose 2020 goal is grander than the presidency

In an earlier era of U.S. history, battles for control of state legislatures took on national importance as proxy fights for power in Washington. Before the ratification of the Seventeenth Amendment in 1913, state legislatures—not voters—appointed U.S. senators. In modern times, however, state legislatures are frequently overlooked relative to their influence on policies that most directly affect voters’ lives. Donors shell out hundreds of millions of dollars to sway presidential and congressional elections. But while gridlock often consumes Capitol Hill, state capitals are hives of legislative activity by comparison.

The urgency behind the Democratic push to win back legislative chambers escalated in the run-up to 2020, when the party knew that the majorities elected that year would be tasked with drawing legislative and congressional maps after the decennial census. But it might be even greater now. The Supreme Court’s overturning of Roe v. Wade in June allowed states to severely restrict or altogether ban abortion, instantly raising the stakes of legislative races across the country.

Another potential Supreme Court decision has spiked Democratic fears to a new level. The justices in the term that begins this month will hear arguments in Moore v. Harper, an election-law case that legal experts say could dramatically reshape how ballots are cast and counted across the country. Republican litigants want the high court to affirm what’s known as the independent-state-legislature theory, which posits that the Constitution gives near-universal power over the running of federal elections to state legislatures. A ruling adopting that argument—and four conservative justices have signaled that they are open to such an interpretation—would allow partisan legislative majorities to ignore or overrule state courts and election officials, potentially granting legal legitimacy to efforts by Donald Trump’s allies to overturn the will of voters in 2024.

Read: The case that could blow up American election law

With the next presidential election in mind, Democrats have prioritized gubernatorial elections in the closely fought states, including Michigan, Arizona, Pennsylvania, Wisconsin, and Georgia, where Trump tried to jawbone legislators and other high-ranking officials into overturning his defeat in 2020. They’ve also steered donations to long-neglected secretary-of-state races in some of those same battlegrounds. But the looming Supreme Court ruling in Moore v. Harper has, for some Democrats, turned the fight for state legislative control into the most pivotal of all. “A single state legislative race in Michigan or Arizona could well prove more important to our future than any congressional or U.S. Senate race in America,” Daniel Squadron, a co-founder of the States Project, told me.

Squadron’s group is spending $60 million to back Democrats in state legislative races in just five states, in what it is calling the largest investment by a single outside organization ever for those campaigns. The effort is in part designed to counter what has historically been a significant GOP advantage, led by the Republican State Leadership Committee and major conservative donors, such as the Koch family.

Precisely how realistic the States Project’s goals are, and where Democrats should be spending most heavily, is a source of some debate within the party. In Arizona, a swing of just more than 1,000 votes in the State House and 2,000 votes in the State Senate would have flipped those chambers to Democrats in 2020, and the party needs to pick up only one or two seats this year to win majorities. But Arizona’s maps became more favorable to Republicans in redistricting, and the Democratic Legislative Campaign Committee—the party’s official state legislative arm—views winning majorities there as a relative long shot, especially during a difficult midterm year in which Democrats typically lose seats. The DLCC is instead more focused on protecting Democratic incumbents in Arizona and defending the party’s narrow advantages in states like Colorado and Nevada. Jessica Post, the committee’s president, acknowledges that there is a “philosophical difference” between the DLCC and some of the outside progressive groups.

“We think that the playing field is wider than simply flipping three battleground states,” Post told me. “We think that we have to protect Democratic majorities across the country.” The States Project is also investing in a few states where Democrats narrowly control the legislature, including Maine and Nevada. But Squadron defended the decision to play offense elsewhere, noting that swaying state legislative races costs “a fraction” of what it does to influence statewide and national elections. “It’s necessary,” he said. “The stakes are high enough that whether the odds are low, medium, or high, we have to take this on.”

There is widespread agreement, including among Republicans, that the Michigan State Senate is in play, and that the race in the Thirty-Fifth District could be decisive. “There’s no question things are tight right now,” Gustavo Portela, the deputy chief of staff for the Michigan Republican Party, told me. GOP candidates are focusing their campaigns heavily on inflation, he said, though he noted that the new maps tilt toward Democrats and that Republicans currently lag them in fundraising.

Campaigns and outside groups are running TV ads in some districts, but the candidate who wins a state legislative race tends to be the one who knocks on the most doors. McDonald Rivet is facing a Republican state representative, Annette Glenn, who supported Trump and called for a “forensic audit” of the 2020 election in Michigan, which Joe Biden won by more than 150,000 votes. (Her campaign did not respond to requests for comment.)

With an army of about 100 volunteers, McDonald Rivet told me her team has already knocked on more than 30,000 doors. Many of the people who answer cite worries about kitchen-table economic issues, or schools, or health care, or abortion—the topics you’d expect voters to bring up. But a surprising number, McDonald Rivet said, express unprompted concern about the future of American democracy, about whether election results will be respected. “I often hear people say, ‘I never thought I would question the health of democracy,’” she said. “‘These are things I have taken for granted my entire life.’”

Protecting democracy is just one of the many issues McDonald Rivet highlights when she talks with voters, either at their homes or during the small meet-and-greet events she holds in the district. But she, too, is worried. Michigan Republicans have nominated election deniers for both governor and secretary of state. McDonald Rivet told me that some Republican candidates for the state legislature have stated publicly that the only electoral outcome they would accept in 2024 is a Trump victory.

Read: The election denier who could run Michigan’s elections

When I asked Portela whether a Republican legislative majority would honor the result of the popular vote for president, he twice dodged the question. “That’s nothing but fear-mongering from Democrats who are desperate,” he replied. “That’s not what’s at stake right now.” Perhaps he’s right. But to Democrats, it’s the evasiveness, the refusal to affirm a fundamental tenet of American elections, that suggests they are right to worry.

Russell Berman

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October 3, 2022