The Iceman's last meal: goat

Researchers examine the stomach contents of a famous 5,300-year-old mummyWeb edition : Monday, August 22nd, 2011 Scientists have only now discovered the stomach of the 5,300-year-old Iceman mummy, because many of the internal organs had shrunk and moved from their original positions.South Tyrol Museum of Archaeology

Outside of the Nancy Grace show, few people have had their final hours as poked, prodded and scrutinized as much as Ötzi, the “Iceman” who died high in the Italian Alps 5,300 years ago.

Hikers discovered his frozen, mummified body in 1991. Two decades later, scientists have a good idea of what happened to Ötzi: Fleeing pursuers, he retreated to the mountains only to be shot in the back with an arrow. But even today, the Iceman is still giving up surprises.

New, more detailed radiological images of the mummy have revealed his stomach for the first time and shown that he didn’t die hungry. Within an hour of his murder, Ötzi ate a big meal mostly of the wild goat called ibex, reports a team led by Albert Zink, head of the Institute for Mummies and the Iceman in Bolzano, Italy.

“We now think that he must have felt quite safe, because otherwise he wouldn’t have had this big meal,” Zink says. “This was a really big surprise.” The work was published online August 17 in the Journal of Archaeological Science.

The Iceman may have eaten meat fairly regularly, the scientists suggest; the new scans also uncovered three gallstones, a sign that his diet could have been richer in animal products than researchers thought. And newfound signs of heavy strain in Ötzi’s knees may mean he walked a lot in mountainous terrain — as opposed to being a valley dweller who wandered up high just before his death.

In life, Ötzi was a brown-eyed, long-haired man in his mid-40s who stood 5 foot 3 inches tall, average height for the Copper Age. In death, he became one of the world’s best-preserved mummies, thanks to the ice that encased him soon after his murder. When climbers found Ötzi sticking out of a retreating glacier front in September 1991, scientists rushed his body into a climate- and humidity-controlled cell so he wouldn’t thaw.

Until now, the closest researchers had gotten to Ötzi’s last meal was locating and taking samples from his colon. It contained the remains of several meals, including the meat of red deer and ibex along with vegetables and grains like einkorn, a local wheat.

But in 2005 Zink’s team took new and more detailed X-ray computed tomography images of the mummy, quickly sliding the frozen corpse in and out of a hospital scanner. Those images revealed an organ once thought to be part of the colon but now recognizable as the long-sought stomach. After death, many of the Iceman’s organs shrank and moved from their original locations, and nobody had recognized the stomach because it had shifted into the upper abdomen, Zink says.

In November, the researchers pulled some of Ötzi’s stomach contents out through an incision in the abdominal wall. Preliminary DNA analysis of the fatty tissue shows it came from an ibex.

“What we have found is that he consumed an omnivorous diet,” says Klaus Oeggl, a paleobotanist at the University of Innsbruck in Austria who is analyzing the nonmeat parts of the stomach contents. The Iceman’s last several meals contained a mix of meat, vegetables and grains, but with a lot more meat in his final meal.

To Zink, a full stomach suggests that Ötzi wasn’t actively fleeing from his pursuers just before he died. Oeggl, however, speculates that the Iceman could have gotten a head start on those chasing him, then sat down for a break before an enemy surprised and shot him from behind.

“I’ve been on top of this particular mountain, and it’s an ideal place to stop and have a rest, maybe have something to eat,” adds Frank Rühli, head of the Center for Evolutionary Medicine at the University of Zurich in Switzerland. Once the arrow hit Ötzi, Rühli and other scientists reported in 2007, it tore open an artery and sent him into fatal hemorrhagic shock. He died on the spot.

Other evidence supports the theory that the Iceman had been under stress in the days before he died. In his last 33 hours, Ötzi moved from up near the timber line to down among the trees and up again into the realm of ice, as shown by pollen grains from various alpine plant species lodged in his body.  

Ötzi also had a deep laceration on his right hand that he received at least several days before he died.

One factor that may have made the Iceman’s life uncomfortable — though it certainly didn’t kill him — was the state of his teeth. Rühli and his colleagues recently took a close look at Ötzi’s teeth and found that the Iceman had a lot of cavities. “The whole oral health of the Iceman was much worse than we had thought before,” says Rühli.

In October, Iceman scientists will gather in Bolzano for a 20th anniversary symposium to talk about what they’ve learned about the life and death of Ötzi. That will probably include the first complete analysis of the Iceman’s nuclear DNA, which has been finished but not yet formally published.

Found in: Humans

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The world's oldest profession: chef

CHEW, CHEW, SLEEP, CHEWThis chimp and other non-human primates spend nearly half their time eating, but new research demonstrates that the cooking skills of Homo erectus allowed the lineage to save time and extract more nutrients, paving the way for bigger brains.Ronan Donovan

Nearly 2 million years ago, it seems the original naked chef was cooking up a storm. Homo erectus, the extinct hominid that’s a mere branch or so away from humans on the family tree, was the first to master cooking, new evidence suggests. This seminal event had huge implications for hominid evolution, giving the ancestors of modern humans time and energy for activities such as running, thinking deep thoughts and inventing things like the wheel and beer-can chicken.

“In the big picture, eating cooked food has huge ramifications,” says Harvard’s Chris Organ, a coauthor of the new study. Cooking and other food-processing techniques aren’t just time-savers; they provide a bigger nutritional punch than a raw diet. The new work is further evidence that cooking literally provided food for thought, making it easier for the body to extract calories from the diet that could then be used to grow a nice, big brain.

Humans are the only animals who cook, and compared to our living primate relatives we spend very little time gathering and eating food. We also have smaller jaws and teeth.

Homo erectus also had small teeth relative to others in the human lineage, and the going idea was that hominids must have figured out how to soften up their food by the time that H. erectus evolved. But behavioral traits such as the ability to whip up a puree or barbecue ribs don’t fossilize, so a real rigorous test of the H. erectus-as-chef hypothesis was lacking.

Organ and his colleagues, including Harvard’s Richard Wrangham, an early champion of the cooking hypothesis, decided to quantify the time one would expect humans to spend eating by looking at body size and feeding time in our living primate relatives. After building a family tree of primates, the researchers found that people spend a tenth as much time eating relative to their body size compared with their evolutionary cousins — a mere 4.7 percent of daily activity rather than the expected 48 percent if humans fed like other primates.

Then the team looked at tooth size within the genus Homo. From H. erectus on down to H. sapiens, teeth are much smaller than would be predicted based on what is seen in other primates, the team reports online the week of August 22 in the Proceedings of the National Academy of Sciences.

“Tooth size becomes dramatically smaller than what we would expect,” says paleoanthropologist David Strait of the University at Albany in New York, who was not involved with the work. “This is really compelling indirect evidence the human lineage became adapted to and dependent on cooking their food by the time Homo erectus evolved.”

Found in: Humans

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Parkinson's protein comes in fours

Stabilizing the ties that bind a protein important in Parkinson’s disease to its buddies might help fend off the disease, a new study of the protein’s structure suggests.

Alpha-synuclein builds up in tough aggregates in the brains of patients with Parkinson’s disease. Researchers thought that this protein was normally a floppy, snakelike molecule.

But now, neuroscientist and neurologist Dennis Selkoe of Brigham and Women’s Hospital and Harvard Medical School and his colleagues show that alpha-synuclein normally forms bands of four molecules in living cells. These quartets (scientists call them tetramers) of alpha-synuclein molecules resist the clumping that leads single molecules of the protein down the path to brain cell destruction, Selkoe and colleagues report online August 14 in Nature.

Discovering that alpha-synuclein works in groups of four could be important in treating or preventing Parkinson’s disease, says Patrik Brundin, a neuroscientist at Lund University in Sweden. The findings suggest that loner alpha-synuclein molecules could be “part of the ‘bad guy’ pathway, and stabilizing it as a tetramer might help avoid the disease,” he says.

No one yet knows whether quartets of alpha-synuclein disintegrate into single molecules in the brains of people with Parkinson’s disease, leading to big brain-cell-killing plaques. Studies comparing normally aging brains with those of people with the disease may help answer those and other questions raised by the study, Brundin says.

The new discovery may also help researchers figure out what alpha-synuclein’s day job is, says Joakim Bergström, a molecular biologist and biochemist at Uppsala University in Sweden. The protein was thought to be important in grasping lipids — fats and other molecules that make up membranes, carry messages and perform other functions in a cell — but earlier experiments have given mixed results. In the new study, the researchers found that the alpha-synuclein quartet can hold much more lipid than single molecules of the protein can.

The finding that the protein hangs out in groups of four “potentially explains a lot of contradictory information in the literature,” about alpha-synuclein’s behavior, says Chad Rienstra, a structural biologist at the University of Illinois at Urbana-Champaign.

Rienstra suggests that contradictory information may have come from the way scientists produce samples of the protein for study. Most researchers studying the protein induce bacteria to make large quantities of the molecule.

But the bacteria-produced version of the protein doesn’t fold up the same way as it does in human cells, Selkoe’s group found. In human red blood and brain cells, the protein winds up into spiral structures called alpha helices and then forms hardy four-man bands.

Even so, it’s far too soon to throw out decades of data suggesting that the protein is a loner, says Hilal Lashuel, a protein biochemist at the Swiss Federal Institute of Technology in Lausanne. The group’s claims “should be treated with caution until reproduced,” he says. That’s something he has tried to do without success since hearing about the study at a meeting earlier this year.

Lashuel is concerned about some of the experimental methods used in the study and the group’s interpretation of the results, which may have larger implications for Parkinson’s disease research. “I’m worried that people will start questioning all the previous data,” he says. Abandoning that previous work could prove costly if the new finding ultimately doesn’t pan out, he says. “My view is that any time we waste, we take away from patients and their families.”

Found in: Genes & Cells

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White dwarfs gobble Earthlike treats

Astronomers studying the atmospheres of planet-munching white dwarf stars have found that some stellar meals included the same ingredients as Earth.

Remains of rocky bodies that once circled the white dwarfs pepper the gas envelopes around the dead stars. The ratios of elements in these remains — called “pollution,” since it mars the star’s normally pristine hydrogen or helium atmosphere — tell astronomers what the bodies were made of and where they might have come from. Although about as common as normal stars in the Milky Way, white dwarfs aren’t the most obvious choice for astronomers looking for traces of extrasolar planets — but, it turns out, the dense, collapsed stars may be incredibly useful.

Each of two polluted white dwarf stars snarfed at least 10 sextillion grams of rocky dust, roughly equal to the mass of the dwarf planet Ceres (a sextillion equals 1 with 21 zeros after it). And, one of the stars ate something very similar in composition to the Earth, astronomers report online August 7 at arXiv.org and in an upcoming issue of the Astrophysical Journal.

“This means that planetlike rocky material is forming at Earthlike distances or temperatures from these stars,” says astronomer and study coauthor Ben Zuckerman of UCLA. Zuckerman notes that it’s still unclear whether the material is from a planet, planetlike bodies or an asteroid, but it is clear that there’s a lot of it.

For years, astronomers thought the dwarfs were simply catching dust during their interstellar travels. Now, scientists think the atmospheric debris signals the presence of ancient orbiting planetary systems. Zuckerman says that between 25 and 30 percent of white dwarfs have orbital systems that contain both large planets and smaller rocky bodies. After the dwarf forms, larger, Jupiter-mass planets can perturb the orbits of smaller bodies and bounce them toward the star.

“This is the first hint that despite all the oddball planetary systems we see, some of them must be more like our own,” says astronomer John Debes of NASA’s Goddard Space Flight Center in Greenbelt, Md., who was not involved in the study. “We think that most of these systems that show pollution must in some way approximate ours.”

Using the Keck I telescope on Mauna Kea in Hawaii, Zuckerman and his team peered closely at two helium-dominated white dwarfs and determined the ratios of the polluting elements. Star PG1225-079 has a mix of elements — including magnesium, iron and nickel — in ratios resembling those found in bulk Earth and some elements that are two or three times more abundant (calcium, for example).

The other star, HS2253+8023, munched material that contains more than 85 percent oxygen, magnesium, silicon and iron — very much like Earth. That’s indicative of a rocky parent body forming in an area with conditions similar to those where the Earth first formed.

“I’ve never seen so much detail in spectra,” says astronomer Jay Holberg of the University of Arizona in Tucson, who was not involved in the study. “People have seen iron and calcium and other things in these stars, but [this group has] gone off and found a whole slew of other elements.”

Incredibly dense, white dwarfs are about the size of Earth but as massive as the sun, and mark the final stage of stellar evolution for more than 90 percent of the stars in the Milky Way. But before reaching that stage, stars puff up into red giants, a process that can rearrange an orbiting system and gobble up any bodies too close-by. Then the stars collapse — and some survivors of that initial expansion and contraction might be chucked inward by larger bully planets.

Found in: Atom & Cosmos and Planetary Science

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Moms talk, daughters' hormones listen

A comforting voice packs a biological punch that instant messages lackWeb edition : Friday, August 12th, 2011

Now hear this: A mother’s encouraging words heard over the phone biologically aid her stressed-out daughter about as much as in-person comforting from mom and way more than receiving instant messages from her.

That’s consistent with the idea that people and many other animals have evolved to respond to caring, familiar voices with hormonal adjustments that prompt feelings of calm and closeness, say biological anthropologist Leslie Seltzer of the University of Wisconsin–Madison and her colleagues. Written exchanges such as instant messaging, texting and Facebook postings can’t apply biological balm to frazzled nerves, the researchers propose in a paper published online July 29 in Evolution and Human Behavior.

Seltzer’s group found that 7- to 12-year-old girls who talked to their mothers in person or over the phone after a stressful lab task displayed drops in levels of cortisol, a stress hormone, accompanied by the release of oxytocin, a hormone linked to love and trust between partners in good relationships. Girls who instant messaged with their mothers after the lab challenge showed no oxytocin response and their cortisol levels rose as high as those of girls who had no contact with their mothers.

“At least in our subjects, instant messaging falls short of the endocrine payoff of speech or physical contact with a loved one after a stressful event,” Seltzer says.

It makes sense that speech, with ancient evolutionary roots, can trigger biological markers of reassurance, comments psychologist Jeffry Simpson of the University of Minnesota in Minneapolis. Mothers may have expressed support better in speech than in writing, or the tone of their voices could have had a special impact on daughters, Simpson says.

Unfamiliarity with instant messaging, especially among mothers, may have undercut the ability of digital connections to alleviate daughters’ stress in the new study, suggests psychologist Sandra Calvert, director of Georgetown University’s Children’s Digital Media Center in Washington, D.C. Still, “mom’s voice is very important to all of us who are daughters,” Calvert says.

Seltzer’s team studied 68 girls who reported good relationships with their mothers. Each girl spoke about a preselected topic for five minutes and then tried to solve mental arithmetic problems for five minutes in front of two strangers who maintained neutral facial expressions. Youngsters said that these tasks caused them considerable stress. Researchers tracked cortisol in saliva samples and oxytocin in urine samples.

Afterward, girls were randomly assigned to talk with their mothers in person, over the phone, via instant messaging or not at all. Mothers were told to offer as much emotional support to their daughters as possible.

Although this study found no hormonal benefit for instant messaging between mothers and daughters, children may profit biologically when such messages come from peers, remarks psychologist Kaveri Subrahmanyam of California State University, Los Angeles. A 2009 study found that instant messaging with an unknown peer for 12 minutes eased the sting of rejection among teens excluded from a group game in the lab.

Found in: Humans and Psychology

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The color of controversy

When it comes to the safety of dyeing food, the one true shade is gray. Artificial colorings have been around for decades, and for just about as long, people have questioned whether tinted food is a good idea. In the 1800s, when merchants colored their products with outright poisons, critics had a pretty good case. Today’s safety questions, though, aren’t nearly so black and white — and neither are the answers. Take the conclusions reached by a recent government inquiry: Depending on your point of view, an official food advisory panel either affirmed that food dyes were safe, questioned whether they were safe enough or offered a conclusion that somehow merged the two. It was a glass of cherry Kool-Aid half full or half empty. About the only thing all sides agree on is that there would be no discussion if shoppers didn’t feast with their eyes. Left alone, margarine would be colorless, cola wouldn’t be dark, peas and pickles might not be so vibrantly green, and kids cereals would rarely end up with the neon hues of candy. But as the 1990s flop of Crystal Pepsi showed, consumers expect their food to look a certain way. Some of the earliest attempts to dye food used substances such as chalk or copper — or lead, once a favorite for candy — that turned out to be clearly harmful. Most of the added colors in use today were originally extracted from coal tar but now are mostly derived from petroleum. Overseeing the safety of artificial food color was one of the reasons the U.S. Food and Drug Administration was founded (with its current name, in 1930). And the issue of food dye safety has continued to attract government notice, sometimes in dramatic ways, such as the time investigators demanded to know why trick-or-treaters became ill in 1950 after eating Halloween candy dyed with orange No. 1. The most recent government attention came in March, when an FDA advisory panel made up of scientists, consumers and industry representatives held a two-day hearing to try to determine whether food dyes cause hyperactivity in children. It is a debate that has gone on, in some incarnation, more than 30 years. Though scientific attention has grown, the disagreement lingers, partly because the issue is complicated to study and partly because dyes, if harmful, probably affect only a subset of children who have some yet-undiscovered genetic sensitivity. Over the years, skeptics of any connection have seized on uncertainties and other logistical flaws in the research that could lead to misleading results. Still, many scientists say studies are strong enough to warrant some kind of government action. And some of them are now criticizing the FDA, saying that, in retrospect, questions about the hyperactivity-dye link were presented to the advisory panel in a way that meant inaction was almost a foregone conclusion. “To me, the whole process was defective,” says Bernard Weiss, a psychologist in the Department of Environmental Medicine at the University of Rochester School of Medicine and Dentistry in New York who was invited to speak before the panel. The main question that committee members were assigned was whether “a causal relationship between consumption of certified color additives in food and hyperactivity in children in the general population has not been established” (a conclusion ultimately supported by 11 of 14 voting panel members). Weiss calls that “a ridiculous question,” not only because of its tortured, negative wording, but also because even those concerned about food dyes acknowledge that the science has not shown a link to hyperactivity in all kids.

Untrue colors

Nine different artificial dyes are currently approved for use in the United States; many of these chemicals have been staples of the food industry for generations. While the FDA does not have data on consumption, it does keep track of how much dye of each type gets the OK for use in products; the amount per capita has increased fivefold since the 1950s. Dyes have never been without criticism — a “pure food” movement was well under way even by the late 1800s. But specific concern about hyperactivity and other neurological effects first arose in 1975, when Ben Feingold, former chief allergist at Kaiser Permanente Medical Center in San Francisco, hypothesized that food additives were contributing to hyperactivity. His book Why Your Child is Hyperactive drew largely on his own clinical observations.

In 1976 in the journal Pediatrics, researchers published a study that compared a regular diet with a diet that eliminated artificial flavors and colors in 15 hyperactive children. After eating what has since become known as the “Kaiser Permanente elimination diet” or the “Feingold diet,” children showed an improvement in symptoms such as difficulty paying attention.

Three decades of studies since then have accumulated evidence linking food dyes to an exacerbation of hyperactivity. But the controversy remains unsettled. Skeptics have a lot of ammunition, pointing out that findings often have been inconsistent and confusing. To set up a study of food dyes, researchers have to juggle a lot of variables at once — including how big a dose of dyes to give, which ones to give and the fine art of having parents and teachers document symptoms that aren’t easy to measure.

Other factors also complicate the research. Studies have used mixtures of dyes, making it difficult to tease out the possible effects of any individual color. Also, it may be that only an unknown subset of children are affected: In a scientific analysis, the children not affected might outnumber those who are, blunting the overall findings when data are lumped together.

Finally, evidence suggests that dyes may not be the lone culprit. Children who appear to be sensitive to dyes may also have neurological reactions to other ingredients, even naturally occurring components such as wheat and chocolate. In some studies, children were given the dyes in cookies; if the children react to wheat or milk as well, the “placebo” might not have been the placebo scientists thought.

In the end, the disagreement comes down to this: How much evidence is necessary to add product warnings about (or ban, as some consumer groups want) chemicals that offer no nutritional benefit and are consumed each day by millions of healthy children?

GOING NATURALNatural food dyes include betanin (derived from beetroot), compounds from the seeds of the achiote tree and curcumin (from turmeric).from top: oksana2010/ShutterStock; Dr. Morley Read/ShutterStock; Le Do/ShutterStock

Europe gets the blues

Food safety advocates believe the substantial suggestion of harm, even without proof, is enough to take action. So does the European Parliament, which in 2008 dictated that foods with certain dyes had to contain warnings that the chemicals “may have an adverse effect on activity and attention in children.” Neither the FDA nor American lawmakers have gone that far, saying that the levels of dye currently in foods are safe.

Most dyes have no set cap on the amount that can be used, just stipulations requiring manufacturers to use only enough to reach their desired color, and no more. “When the FDA established legal limits on dyes, they did not consider children,” says Laura Anderko, a researcher in public health at Georgetown University Medical Center in Washington, D.C. And it is not known, she says, what the lasting effects from constant exposure might be. “Kids, they have a long shelf life. If they are exposed at an early age — depending on those kinds of petrochemicals that are consumed — it could mean lifelong impacts,” she says.

The color industry says any link between food coloring and hyperactivity remains unproven. “We don’t see any strong compelling data at this point that there is a neurological effect,” says Sean Taylor, a chemist at Verto Solutions in Washington, D.C., and a representative of the International Association of Color Manufacturers. He notes that the dyes on the market today have been consumed in populations worldwide, without any apparent harm, for decades. In animal toxicity tests, Taylor says, most of the dyes in food are excreted, and the small amounts absorbed are broken down by the liver.

More than a dozen clinical studies have tried to investigate the relationship between food dyes and hyperactivity. In 2004, psychiatrists David Schwab from Columbia University and Nhi-Ha Trinh of Harvard University published a meta-analysis of all 15 known double-blind placebo-controlled trials — meaning those in which neither the researchers nor the participants knew who was getting the dyes. That study, in the Journal of Developmental & Behavioral Pediatrics, reported that the results “strongly suggest an association” between food dyes and hyperactivity, though the researchers included a long list of caveats.

Following the 2004 meta-analysis, the British Food Standards Agency (the equivalent of the U.S. FDA) commissioned large studies to further examine whether food dyes, along with a common food preservative, affected children’s behavior. Unlike most previous investigations, these new experiments included children from the general population who had no history of hyperactivity.

In those studies, researchers from the University of Southampton gave two groups of children (one toddler group, and one school age) beverages with one of two mixes of food dyes and the preservative sodium benzoate or a placebo, and asked parents and educators to note any behavior changes. The older children also took a computerized test designed to measure attention.

The results, published in 2007 in the Lancet, “lend strong support for the case that food additives exacerbate hyperactive behaviors,” the researchers write. “Our results are consistent with those from previous studies and extend the findings to show significant effects in the general population.” The scientists recognized the potential political impact of their findings: “The implications of these results for the regulation of food additive use could be substantial.”

And in Europe, they were. While the European Food Safety Authority did not think the evidence was strong enough to prompt action, the European Parliament was convinced. Dyes are not banned outright, but warning labels alone have been enough to change the way many products are made. A strawberry sundae at McDonald’s in the United States gets a boost of crimson from red No. 40. In Great Britain, a McDonald’s strawberry sundae gets its red only from strawberries.

In 2008, the year warning labels took effect in Europe, the D.C.-based Center for Science in the Public Interest (the same food watchdogs known to denounce the nutritional wasteland of convenience foods and movie popcorn) petitioned the FDA to ban the dyes. A long list of scientists and researchers signed on to the center’s appeal. “Food manufacturers voluntarily could substitute safe natural colors or other ingredients (such as fruit or fruit juices) for dyes, but that’s unlikely to happen throughout the food supply without the level playing field provided by government regulation,” the document stated. “Accordingly, the Food and Drug Administration ... should ban the use of dyes in all foods; until such action takes effect, the FDA should require a prominent warning notice on product labels.”

While no large trials have been published since 2007, the government took the Center for Science in the Public Interest petition seriously enough to hold the hearings in March, asking members of its Food Advisory Committee to decide whether the evidence establishes a link between food dyes and hyperactivity in children in the general population.

Even Michael Jacobson, executive director of the Center for Science in the Public Interest, says he would answer “no.” To him and others, it was not the valid question to address. Better, he said, would have been to assess whether food dyes pose a danger to certain children, in the same way that allergens affect only susceptible people. Few products, no matter how dangerous, affect everyone in the population. “Even smoking does not affect everybody,” he says.

Metabolic black box

No one knows which children may be at risk, because the biology behind any potential neurological effect associated with hyperactivity isn’t clear. Taylor, the color industry biochemist, says that animal studies find that the molecules do not easily get through intestinal cell walls, and most of the dye passes through the body without leaving the digestive system.

Laura Stevens, a nutrition researcher at Purdue University in Indiana, acknowledges that this is the case. “In animals, very little of it is absorbed,” she says. “It is excreted in the feces.” But that doesn’t necessarily negate the idea of any effects on the body, she says; effects could come through metabolites, or through indirect mechanisms.

As examples, she cites two studies by British researchers. In one, published in the Journal of Nutritional Medicine in 1990, the scientists investigated how the yellow dye tartrazine affected the zinc levels of 10 hyperactive boys, compared with 10 nonhyperactive peers. (Zinc is a mineral important for proper brain function.) The team found that zinc levels dropped in the blood and increased in the urine among the hyperactive kids after tartrazine consumption. Another study, published in the Journal of Nutritional and Environmental Medicine in 1997, found a similar drop in zinc levels, and an increase in hyperactivity, in some children consuming tartrazine.

Newer research suggests that dyes trigger the release of histamines, which are part of the body’s immune system. An experiment reported last year in the American Journal of Psychiatry suggested that differences in genes that control histamines might explain why some children are affected and others are not.

But studies are few. In truth, Stevens says, aside from extrapolations from animal studies, the metabolic fate of dyes in humans is a black box. She and her colleagues at Purdue are among those trying to look at food dye metabolism in humans. “If there’s any chance at all there’s a problem, this should be addressed,” she says.

Ultimately, the future of food dyes may not rest with scientists or government regulators, but with consumers, says Ron Wrolstad, an agricultural chemist at Oregon State University in Corvallis.

“A lot of times now, particularly with natural colorants, it will be a marketing decision rather than a regulatory ruling,” he says. The snack food giant Frito-Lay, for instance, has announced, and heavily publicized, a commitment to use fewer artificial dyes in its products. A company spokeswoman said in December that the move was in response to consumers wanting more snacks “made with real food ingredients.”

“My personal opinion is that the synthetics don’t cause you any harm, but I don’t think they do you any good,” Wrolstad says. While other researchers are looking for harmful effects of synthetic dyes, Wrolstad is looking for beneficial effects of natural, plant-derived colors. “A lot of these compounds have antioxidant properties,” he says.

Though just as the idea of harm by synthetic colors isn’t universally accepted, neither is the suggestion of benefit from dyes extracted from plants. “I would feel a lot more comfortable if we had some data on those, too,” Weiss says.

In the meantime, dyes of all kinds will continue to dominate the grocery aisle unless shoppers demand otherwise. In the food business, the most influential color is green.

In the limelight

Though concern over a link to hyperactivity has prompted the latest attacks on food dyes, artificial colorings have caught the public’s attention for other economic and health reasons for more than a century.

1850s A Victorian-era domestic standby Enquire Within Upon Everything described how bread could be tested at home for the presence of alum, a metallic salt used to create a more preferable, whiter color in the dietary staple. As early as the Middle Ages, some bread manufacturers were rumored to make very white bread on the cheap by adding chalk.

1890s One effort used by the dairy industry to prevent newly invented and relatively cheap margarine from undercutting the popularity of butter was the push for regulations that would tax or ban margarine with the yellow tint of butter. (Naturally, margarine is colorless.) Anticoloring laws were adopted in 30 states, and some legislatures went so far as to demand that margarine be dyed pink. Because of the restrictions, some margarine manufacturers sold yellow dye packets with their products, so consumers could color their own margarine at home.

1950s In 1950, children became ill after eating Halloween candy containing orange No. 1, which had been approved for use in food by the U.S. Food and Drug Administration. The reports led to a public outcry, and along with other concerns, led the FDA to re-evaluate the safety of food colorings. Several dyes were delisted, and the Color Additive Amendments of 1960 established the current regulatory protocol.

1970s In the 1970s, it was red No. 2’s turn to cause a stir. Russian studies had suggested that the dye caused rats to develop intestinal tumors and was toxic to the gonads and embryos. Though the tests were largely debunked, when combined with earlier studies showing breast tumors in female rats fed the dye, the findings were enough to lead to a public health scare. The FDA banned red No. 2, and many manufacturers removed red products regardless of whether they contained the dye. Mars didn’t bring back red M&Ms until the late ’80s.

1990s Natural food dyes have caused controversy too. The reddish cochineal extract and carmine came to the attention of the Center for Science in the Public Interest in 1998. The dyes, made from a type of female beetle, had been used for hundreds of years, exempt from certification because they are natural. Recorded allergic reactions as well as anecdotal reports of outrage among vegetarians and kosher-keeping Jewish people who were unknowingly consuming insect products prompted demands for labeling. The FDA agreed to require manufacturers to list the dyes as ingredients on the product label, but consumers have to figure out for themselves that the products come from animals.

Added color 

The U.S. Food and Drug Administration currently certifies nine synthetically produced food dyes (three popular colorings are described below). Such dyes can transform colorless products, giving faded veggies a more vibrant hue and making children’s candies more fun.

Brilliant blue  Designated as blue No. 1 by the FDA, this dye is found in ice creams, ice pops, baked goods and a host of blue raspberry–flavored beverages. It shows up in ranch-flavored chips, prepared guacamole and mixed-berry applesauce. The dye was approved by the FDA in 1969.

Allura red Red No. 40 is found in strawberry-flavored drinks, ice creams and cream cheeses; some Nutri-Grain bars; licorice; and most other red sweets. It was approved by the FDA in 1971 and, in terms of consumption, is currently the most-used food dye.

Tartrazine  Yellow No. 5 is in products such as Mountain Dew, Peeps, Doritos and Cheez Doodles. It’s commonly found in relish, pickles, lemon-flavored seasonings and boxed macaroni and cheese. The dye was approved by the FDA in 1969.

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Book Review : BOOK REVIEW: The Man of Numbers: Fibonacci’s Arithmetic Revolution by Keith Devlin

Leonardo of Pisa, also known as Fibonacci, is best remembered today for introducing a sequence of numbers: 0, 1, 1, 2, 3, 5 and so on, each number after 0 and 1 equaling the sum of the two before it. The Fibonacci sequence is closely connected to the “golden ratio” used in art and architecture and turns up frequently in mathematics and nature.

For Devlin, NPR’s “Math Guy,” Leonardo of Pisa is much more:  he’s the man who brought arithmetic to the West — a celebrity of 13th century Italy.

“The likes of Apple Computer’s Steve Jobs and Microsoft’s Bill Gates will always be linked to the rise of the personal computer, and in this way Leonardo should be linked to the rise

of modern arithmetic,” Devlin writes.

The book, which draws heavily on academic sources, pieces together the little that is known about Leonardo’s life. As a young man, he traveled to North Africa and learned Hindu-Arabic numerals and al-jabr, the basis of modern algebra. At the time, merchants and traders in Italy still used Roman numerals, which were impractical for multiplication or division.

Leonardo’s Liber Abbaci was the first comprehensive arithmetic textbook in Europe. It helped change the way business was done, with hundreds of math problems based on everyday commerce such as converting currency or calculating profits.

A mathematician himself, Devlin demonstrates Leonardo’s original methods by walking the reader through copious calculations that read like cooking recipes. Readers with the patience to tackle the math, though, will discover a legacy that extends across eight centuries to the textbooks of schoolchildren today and the numbers that run the modern world. 

Walker & Co., 2011, 183 p., $25

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