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What Is Gluten?

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Gluten is one of the most talked about topics in nutrition today—a quick googling yields more than 280 million results—and nearly everyone has an opinion on it. In 2014, talk show host Jimmy Kimmel summed up L.A.'s consensus on the subject: "It's comparable to Satanism." But despite the mother lode of information (and misinformation) available, few people actually know what it is. Mental Floss spoke to a pair of experts about this misunderstood substance. Here's the lowdown.

Gluten is a marriage of two proteins found in wheat, barley, rye, and oats. A marvel of food chemistry, gluten mixed with water transforms into a gluey, stretchy mass. Heat up the mixture, and you get a light, airy framework, making it a valued partner in the kitchen. "Gluten provides structure to baked products," Carla Christian, a registered dietitian and professional chef, tells Mental Floss. "Without gluten, you'll end up with a product that's crumbly and will fall apart because there's nothing holding it together."

Chefs and home cooks rely on gluten to provide the textural and aesthetic qualities in baked goods such as breads, pastries, and cakes. Gluten also plays an important nutritional role, providing a tasty source of plant-based protein in seitan and other meat substitutes, including mock duck, with its strange "plucked" texture.

Its culinary and nutritional qualities notwithstanding, gluten has a darker side. "For some reason, gluten seems to be the trigger in developing celiac disease in those who are genetically susceptible," Runa D. Watkins, an assistant professor and pediatric gastroenterologist at University of Maryland's School of Medicine, tells Mental Floss.

Celiac disease is an autoimmune disorder that affects the small intestine. When a person with celiac disease eats foods containing gluten, their immune system reacts by attacking their small intestine, destroying its ability to digest and absorb nutrients. Celiac disease can cause diarrhea, bloody stools, skin rashes, vitamin and mineral deficiencies, and a host of other unpleasant symptoms.

Although as much as 40 percent of the population carries the gene for celiac disease, fewer than 1 percent—roughly 3 million people in the U.S.—will develop the condition. Why some do, and others don't, is a mystery, says Watkins. The prevailing theory is that some sort of infection is the trigger. One recent study found a virus that can cause celiac disease.

The default setting in the human gut is one of tolerance. It typically receives all visitors (in the form of foods, beverages, or microbes) and allows them to pass without argument. After an infection, however, the gut can become hypervigilant—overly cautious about who comes and goes. In some cases, gluten becomes an unwelcome guest.

Although scientists aren't sure why gluten becomes so offensive, the reasons may lie in the protein's unique makeup.

Proteins are strands of amino acids folded into long, twisty coils. Gluten is rich in two particular amino acids, proline and glutamine, that set it apart from other proteins.

Proline makes gluten "kinky"—helping it form a tight, compact structure that's nearly impenetrable to digestive enzymes, a biological version of a lock-on. Some scientists believe gluten's impervious nature is responsible for triggering an overzealous immune response in susceptible people.

The glutamine in gluten (say that five times, fast) is a target for an enzyme called tissue transglutaminase, or tTG for short. Under certain conditions, tTG goes rogue: It alters glutamine's otherwise benign structure, making it more allergenic and initiating a cascade of immune-related events that ultimately leads to the development of celiac disease. When doctors test for celiac disease, they look for abnormally high amounts of antibodies like tTG in the blood. However, the only definitive way to diagnose the condition is by biopsy of the lining of the small intestine.

The only "cure" for celiac disease is total avoidance of gluten. "If a person has celiac disease, even a little bit of gluten can make them very sick," says Christian.

That can be hard, because gluten is everywhere. It can be found in the usual wheat-containing suspects (breads, pasta, cereals), less obvious candidates (communion wafers), and hidden in strangely odd places (soy sauce, beer, and some cosmetics). The average person consumes between 4 and 20 grams of gluten per day. Most of that comes from wheat-containing bread: One slice contains about 4 grams of gluten. To counter this abundance—and to capitalize on the myth that gluten is bad for everyone—a thriving gluten-free market has emerged. In 2015, one market analysis estimated that the global market for gluten-free foods was worth roughly $4.2 billion; an analysis from May 2017 put it much higher, at nearly $15 billion

With celiac disease affecting only 1 percent of the population, why are so many people buying and eating gluten-free foods? Gluten takes the blame for a litany of other ills, ranging from skin disorders and headache to fibromyalgia and psychiatric problems, often lumped into a condition known as non-celiac gluten sensitivity, or NCGS, for short. The number of people with NCGS may be high—as many as 18 million people in the U.S.—but its occurrence is hard to measure.

"Unfortunately, there's no specific test for [NCGS], so it's basically a diagnosis of trial and error after ruling out celiac disease," says Watkins. Scientists aren't in agreement that NCGS is a legitimate health concern, however, and some suggest its symptoms might be due to something unrelated to gluten.

With all the talk about gluten, it seems gluten sensitivities are becoming more common. "Celiac disease is becoming more prevalent because we're doing a better job of finding it, I think," says Watkins. But the rest of it? Probably just a fad.

Editor's note: This post has been updated. 

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How Are Vaccines Made?
Quality checks on the Salk polio vaccine at Glaxo's virus research laboratory in Buckinghamshire, UK, in January 1956.
Quality checks on the Salk polio vaccine at Glaxo's virus research laboratory in Buckinghamshire, UK, in January 1956.
Photo by Fox Photos/Getty Images

Vaccines have long been hailed as one of our greatest public health achievements. They can be made to protect us from infections with either viral or bacterial microbes. Measles and smallpox, for example, are viruses; Streptococcus pneumoniae is a bacterium that causes a range of diseases, including pneumonia, ear and sinus infections, and meningitis. Hundreds of millions of illnesses and deaths have been prevented due to vaccines that eradicated smallpox and significantly reduced polio and measles infections. However, some misunderstanding remains regarding how vaccines are made, and why some scary-sounding ingredients [PDF] are included in the manufacturing process.

The production of our vaccines has greatly evolved since the early days, when vaccination was potentially dangerous. Inoculating an individual with ground-up smallpox scabs usually led to a mild infection (called "variolation"), and protected them from acquiring the disease the "regular" way (via the air). But there was always a chance the infection could still be severe. When Edward Jenner introduced the first true vaccination with cowpox, protection from smallpox became safer, but there were still issues: The cowpox material could be contaminated with other germs, and sometimes was transmitted from one vaccinated person to another, leading to the inadvertent spread of blood-borne pathogens. We’ve come far in the last 200 years.

There are different kinds of vaccines, and each requires different processes to move from the laboratory to your physician's office. The key to all of them is production of one or more antigens—the portion of the microbe that triggers a host immune response.

LIVE ATTENUATED VACCINES AND DEAD, "INACTIVATED" VACCINES

There are several methods to produce antigens. One common technique is to grow a virus in what's called a cell culture. Typically grown in large vats called bioreactors, living cells are inoculated with a virus and placed in a liquid growth medium that contains nutrients—proteins, amino acids, carbohydrates, essential minerals—that help the virus grow in the cells, producing thousands of copies of itself in each infected cell. At this stage the virus is also getting its own dose of protective medicine: antibiotics like neomycin or polymyxin B, which prevent bacterial and fungal contamination that could kill the cells serving as hosts for the virus.

Once a virus completes its life cycle in the host cell, the viruses are purified by separating them from the host cells and growth media, which are discarded. This is often done using several different types of filters; the viruses are small and can pass through holes in the filter that trap larger host cells and cell debris.

This is how "live attenuated vaccines" are created. These vaccines contain viruses that have been modified so that they are no longer harmful to humans. Some of them are grown for many generations in cells that aren't human, such as chicken cells, so that they have mutated to no longer cause harm to humans. Others, like the influenza nasal mist, were grown at low temperatures until they lost the ability to replicate in the warmer temperatures of the lungs. Many of these vaccines you were probably given as a child: measles, mumps, rubella ("German measles"), and chickenpox.

Live attenuated vaccines replicate briefly in the body, triggering a strong—and long-lasting—response from your immune system. Because your immune system kicks into high gear at what it perceives to be a major threat, you need fewer doses of the vaccine for protection against these diseases. And unlike the harmful form of the virus, it is extremely unlikely (because they only replicate at low levels) that these vaccines will cause the host to develop the actual disease, or to spread it to other contacts. One exception is the live polio vaccine, which could spread to others and, extremely rarely, caused polio disease (approximately one case of polio from 3 million doses of the virus). For this reason, the live polio virus was discontinued in the United States in 2000.

Scientists use the same growth technique for what are known as "killed" or "inactivated" vaccines, but they add an extra step: viral death. Inactivated viruses are killed, typically via heat treatment or use of a chemical such as formaldehyde, which modifies the virus's proteins and nucleic acids and renders the virus unable to replicate. Inactivated vaccines include Hepatitis A, the injected polio virus, and the flu shot.

A dead virus can't replicate in your body, obviously. This means that the immune response to inactivated vaccines isn't as robust as it is with live attenuated vaccines; replication by the live viruses alerts many different types of your immune cells of a potential invader, while killed vaccines primarily alert only one part of your immune system (your B cells, which produce antibodies). That's why you need more doses to achieve and maintain immunity.

While live attenuated vaccines were the primary way to make vaccines until the 1960s, concerns about potential safety issues, and the difficulty of making them, mean that few are attempting to develop new live attenuated vaccines today.

COMBINATION, BACTERIAL, AND GENETICALLY ENGINEERED VACCINES

Other vaccines aren't made of whole organisms at all, but rather bits and pieces of a microbe. The combination vaccine that protects against diphtheria, pertussis, and tetanus—all at once—is one example. This vaccine is called the DTaP for children, and Tdap for adults. It contains toxins (the proteins that cause disease) from diphtheria, pertussis, and tetanus bacteria that have been inactivated by chemicals. (The toxins are called "toxoids" once inactivated.) This protects the host—a.k.a. you, potentially—from developing clinical diphtheria and tetanus disease, even if you are exposed to the microorganisms. (Some viruses have toxins—Ebola appears to, for example—but they're not the key antigens, so they're not used for our current vaccines.)

As they do when developing live attenuated or inactivated vaccines, scientists who create these bacterial vaccines need some target bacteria to culture. But because the bacteria don't need a host cell to grow, they can be produced in simple nutrient broths by vaccine manufacturers. The toxins are then separated from the rest of the bacteria and growth media and inactivated for use as vaccines.

Similarly, some vaccines contain just a few antigens from a bacterial species. Vaccines for Streptococcus pneumoniae, Haemophilus influenzae type B, and Neisseria meningitidis all use sugars that are found on the outer part of the bacteria as antigens. These sugars are purified from the bacteria and then bound to another protein to enhance the immune response. The protein helps to recruit T cells in addition to B cells and create a more robust reaction.

Finally, we can also use genetic engineering to produce vaccines. We do this for Hepatitis B, a virus that can cause severe liver disease and liver cancer. The vaccine for it consists of a single antigen: the hepatitis B surface antigen, which is a protein on the outside of the virus. The gene that makes this antigen is inserted into yeast cells; these cells can then be grown in a medium similar to bacteria and without the need for cell culture. The hepatitis B surface antigen is then separated from the yeast and serves as the primary vaccine component.

OTHER INGREDIENTS IN VACCINES (AND WHY THEY'RE THERE)

Once you have the live or killed viruses, or purified antigens, sometimes chemicals need to be added to protect the vaccine or to make it work better. Adjuvants, such as aluminum salts, are a common additive; they help enhance the immune response to some antigens by keeping the antigen in contact with the cells of the immune system for a longer period of time. Vaccines for DTaP/Tdap, meningitis, pneumococcus, and hepatitis B all use aluminum salts as an adjuvant.

Other chemicals may be added as stabilizers, to help keep the vaccine working effectively even in extreme conditions (such as hot temperatures). Stabilizers can include sugars or monosodium glutamate (MSG). Preservatives can be added to prevent microbial growth in the finished product.

For many years, the most common preservative was a compound called thimerosal, which is 50 percent ethylmercury by weight. Ethylmercury doesn't stick around; your body quickly eliminates it via the gut and feces. (This is different from methylmercury, which accumulates in fish and can, at high doses, cause long-lasting damage in humans.) In 2001, thimerosal was removed from the vaccines given in childhood due to consumer concerns, but many studies have demonstrated its safety.

Finally, the vaccine is divided into vials for shipping to physicians, hospitals, public health departments, and some pharmacies. These can be single-dose or multi-dose vials, which can be used for multiple patients as long as they're prepared and stored away from patient treatment areas. Preservatives are important for multi-dose vials: bacteria and fungi are very opportunistic, and multiple uses increase the potential for contamination of the vaccine. This is why thimerosal is still used in some multi-dose influenza vaccines.

Though some of the vaccine ingredients sound worrisome, most of these chemicals are removed during multiple purification steps, and those that remain (such as adjuvants) are necessary for the vaccine's effectiveness, are present in very low levels, and have an excellent track record of safety.

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What Is Infinity?
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Albert Einstein famously said: “Two things are infinite: the universe and human stupidity. And I'm not sure about the universe.”

The notion of infinity has been pondered by the greatest minds over the ages, from Aristotle to German mathematician Georg Cantor. To most people today, it is something that is never-ending or has no limit. But if you really start to think about what that means, it might blow your mind. Is infinity just an abstract concept? Or can it exist in the real world?

THERE'S MORE THAN ONE KIND

Infinity is firmly rooted in mathematics. But according to Justin Moore, a math researcher at Cornell University in Ithaca, New York, even within the field there are slightly different uses of the word. “It's often referred to as a sort of virtual number at the end of the real number line,” he tells Mental Floss. “Or it can mean something too big to be counted by a whole number.”

There isn't just one type of infinity, either. Counting, for example, represents a type of infinity that is unbounded—what's known as a potential infinity. In theory, you can go on counting forever without ever reaching a largest number. However, infinity can be bounded, too, like the infinity symbol, for example. You can loop around it an unlimited number of times, but you must follow its contour—or boundary.

All infinities may not be equal, either. At the end of the 19th century, Cantor controversially proved that some collections of counting numbers are bigger than the counting numbers themselves. Since the counting numbers are already infinite, it means that some infinities are larger than others. He also showed that some types of infinities may be uncountable, as opposed to collections like the counting numbers.

"At the time, it was shocking—a real surprise," Oystein Linnebo, who researches philosophies of logic and mathematics at the University of Oslo, tells Mental Floss. "But over the course of a few decades, it got absorbed into mathematics."

Without infinity, many mathematical concepts would fall apart. The famous mathematical constant pi, for example, which is essential to many formulas involving the geometry of circles, spheres, and ellipses, is intrinsically linked to infinity. As an irrational number—a number that can't simply be expressed by a fraction—it's made up of an endless string of decimals.

And if infinity didn't exist, it would mean that there is a biggest number. "That would be a complete no-no," says Linnebo. Any number can be used to find an even bigger number, so it just wouldn't work, he says.

CAN YOU MEASURE THE IMMEASURABLE?

In the real world, though, infinity has yet to be pinned down. Perhaps you've seen infinite reflections in a pair of parallel mirrors on opposite sides of a room. But that's an optical effect—the objects themselves are not infinite, of course. "It's highly controversial and dubious whether you have infinities in the real world," says Linnebo. "Infinity has never been measured."

Trying to measure infinity to prove it exists might in itself be a futile task. Measurement implies a finite quantity, so the result would be the absence of a concrete amount. "The reading would be off the scale, and that's all you would be able to tell," says Linnebo.

The hunt for infinity in the real world has often turned to the universe—the biggest real thing that we know of. Yet there is no proof as to whether it is infinite or just very large. Einstein proposed that the universe is finite but unbounded—some sort of cross between the two. He described it as a variation of a sphere that is impossible to imagine.

We tend to think of infinity as being large, but some mathematicians have tried to seek out the infinitely small. In theory, if you take a segment between two points on a line, you should be able to divide it in two over and over again indefinitely. (This is the Xeno paradox known as dichotomy.) But if you try to apply the same logic to matter, you hit a roadblock. You can break down real-world objects into smaller and smaller pieces until you reach atoms and their elementary particles, such as electrons and the components of protons and neutrons. According to current knowledge, subatomic particles can't be broken down any further.

THE INFINITIES OF THE SINGULARITY

Black holes may be the closest we've come to detecting infinity in the real world. In the center of a black hole, a point called a singularity is a one-dimensional dot that is thought to contain a huge mass. Physicists theorize that at this bizarre location, some of the singularity's properties are infinite, such as density and curvature.

At the singularity, most of the laws of physics no longer work because these infinite quantities "break" many equations. Space and time, for example, are no longer two separate entities, and seem to merge.

According to Linnebo, though, black holes are far from being an example of a tangible infinity. "My impression is that the majority of physicists would say that is where our theory breaks down," he says. "When you get infinite curvature or density, you are beyond the area where the theory applies."

New theories may therefore be needed to describe this location, which seems to transcend what is possible in the physical world.

For now, infinity remains in the realm of the abstract. The human mind seems to have created the concept, yet can we even really picture what it looks like? Perhaps to truly envision it, our minds would need to be infinite as well.

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