On January 18th, 2018 we learned about

Updating our spotty, rat-filled understanding of the 14th century plague epidemics

If there’s one thing we can learn from the Black Death in the 14th century, it’s the importance of record keeping in times of crisis. Granted, it was probably hard to focus on documenting what was going on when tens of millions of people were dropping dead for no obvious reason. However, piecing together exactly how the plague spread with the speed it did has been an ongoing question, even long after we’ve come to understand and successfully treat the Yersinia pestis bacteria that actually causes bubonic plague. While rats have long been thought to have carried fleas that carried the bacteria, new investigations are starting to cast doubt on what we thought we knew about these horrifying epidemics.

No rats required

To be clear, Y. pestis is still the cause of death that killed millions of Europeans on more than one occasion. The question is how big a role rats played in transmitting the bacteria to humans. Part of our evidence against the rodents is that they have often play a role in plague outbreaks today, which understandably makes a strong case for their guilt in the 14th century. However, there are some holes in the story of past epidemics, such as no reporting on dead rats turning up in large numbers (as the rodents can be killed by the plague just as we can.) Researchers have also questioned if the flow of infections that we do know about really required rats’ presence in the first place, so they ran some tests to find out.

These experiments obviously didn’t involve risking any human or rat lives. They were conducted as simulations in a computer, allowing changes in different variables to be run over and over, eventually revealing the likelihood of one scenario over another. Obviously, long-shots can still happen, but these simulations showed that fleas biting humans could be passed around quite efficiently with no help from furry friends. In fact, in seven out of nine cities’ virtual infections, the human-flea-human model was a better match for mortality records than scenarios that depended on the movement of rodents.

Looking at leprosy

While these simulations have tried to consider an array of data sources to build a more accurate picture of how the plague spread, some historical gaps have been filled erroneously. Many images that are now archived as contemporary depictions of plague victims are actually pictures of other diseases entirely, such as leprosy. This kind of mistake has become common enough that it’s likely reshaping people’s understanding of what symptoms the bubonic plague actually produces.

Medieval images of leprosy, later labeled as the plague, often include eye-catching lesions on the victims’ skin. It’s dramatic and easily understood as a sign of disease, making these mislabeled images all the more convince to audiences lucky enough to never encounter an actual bubo- the real calling card of the bubonic plague. While some victims could occasionally end up with dark red spots under their skin, most people would end up with a single swollen lymph node in the armpit or neck, depending on where the bacteria-carrying flea bit them. However, these buboes don’t turn up in any drawings or paintings from the 14th century outbreaks. Instead of showing the medical reality of the plague, the few contemporary images directly related to the epidemic focus on its effect on societies, such as a drawing of people burying coffins from 1349, or Jews being burned alive in the 1340s after they were blamed for the disease.

Seeing patterns in the symptoms

Even after the dramatic epidemic of the 14th century, the plague revisited Europe every few decades. Bit by bit, people started to put the pieces together, even making a point to record what an actual plague victim looked like. Images of swollen lymph nodes are directly connected to the plague in imagery from the 15th century, both in artwork and medical documents, some of which suggested lancing buboes to save infected patients.

It’s understandable that people didn’t know what to keep track of before they even knew what was making them sick. But it’s interesting to consider how much information about a curable disease is still hard to be sure of. As someone who was preemptively treated for bubonic plague once as a toddler, I guess I’m just grateful that someone around me knew what to look for at a time when it counted. For what it’s worth, in that case people blamed a flea-bitten cat.

Source: Maybe Rats Aren't to Blame for the Black Death by Michael Greshko, National Geographic

On January 11th, 2018 we learned about

Mammals keep our offspring on our left side so we can more easily identify their emotions

By the time my son was two-years-old, my left tricep was in great shape. Neither of my kids are petite, and they both loved to be carried around, giving my arms and shoulders plenty of exercise. Being right-handed, I tried to keep the kids perched on my left arm most of the time, leaving my “good” hand to interact with the rest of the world. There may have been a more tender side to this preference though, as researchers are building the case that the left-arm bias may have actually been about accommodating the right side of my brain, not my hand.

Looking closely from the left

According to this study, the key reason to hold a baby in your left arm is so their face will be more clearly visible to your left eye. That eye is connected to the right hemisphere of your brain, which is more directly associated with processing spatial and emotional information. You probably don’t notice any that gap in your day to day activity, but most of the stimuli you’re looking at isn’t being clutched right next to your face (and pulling on your glasses). So by picking up small changes in your baby’s emotional state more easily, a parent can either head off trouble or just provide emotional feedback a bit faster.

Now even if parents have been proven to more accurately assess their babies’ moods when relying on their left eye, that doesn’t prove that emotional communication is the root cause behind this pattern. Maybe our right hemispheres became attuned to facial expressions because so many of us were already right-handed, and needed to access the ancient equivalent of a cell-phone all day? To test this, researchers looked at other mammalian parents to see if they had a similar preference in how they viewed their kids. Non-primates in particular were of interest, as their forelimbs should make less of a difference in how they interact with their offspring.

Gauging the maternal gaze of bats and walruses

The two other mammal species didn’t have much in common, except for the fact that they were known to spend some time looking at the faces of their offspring. Walruses and flying fox fruit bats were both observed interacting with their young, and as expected, they were more likely to orient themselves to keep their kin in their left visual field. In the case of the walruses, researchers noted that interactions from the animals’ left side weren’t only more common, but they lasted longer than engagement from the right.

In all of these cases, this pattern turned up in the babies as well. Offspring tended to approach their parents from the left, and when facing a parent could watch with their left eyes, just like their mothers.

Looking and leaning when kissing

Looking back to humans, a separate study may have inadvertently found a similar connection between adult humans. Adult couples were asked to kiss their spouse, and then record their descriptions of how the kiss occurred. Among other trends, researchers found that most people prefer to avoid mirroring their partner’s head position, and will tilt their head in the opposite direction, usually to each person’s right.

This was attributed to the handedness of each participant, and who initiated the kiss (usually men in heterosexual couples.) However, it seems like the tension between handedness and emotional observation is relevant here, because tilting your head to the right means that you’re giving your left eye the best view of your partner’s face. It seems fair to say that reading the emotional state of the person you’re about to kiss would be important, giving people all the more reason to lean right as they smooch. Unfortunately, this study didn’t specifically mention how often folks were kissing with their eyes open or closed.

Source: Mammals prefer to cradle babies on the left, study demonstrates by Nicola Davis, The Guardian

On January 4th, 2018 we learned about

Fossilized microbes show surprising biodiversity from 3.4 billion years ago

Most rocks on the Earth’s surface don’t last more than 200 million years before erosion or other forces get the best of them. Sure, that’s older than any dinosaur, but it’s only a tiny slice of our planet’s 4.5-billion-year history. Thankfully, rocks and crystals from the Earth’s early days do turn up here and there, helping us understand what our planet once looked like, and even more intriguing, who first called it home. That latter point is being revealed by 3.4-billion-year-old rocks from Australia, which have been found to not only contain fossilized microorganisms, but evidence of a surprisingly diverse ecosystem at a time when our planet was just beginning to be habitable.

Combing through fossils for traces of chemistry

The fossilized microorganisms weren’t multicellular animals of course, so these ancient rocks offered no bones or organs to study. Instead, researchers studied each singled-celled organism with secondary ion mass spectroscopy (SIMS). This technology allowed researchers to compare variations of carbon atoms, or isotopes, in the fossils and surrounding stone. The ratios of carbon-12 to carbon-13 was then be used to determine how each microbe functioned when it was alive, as those isotopes will accumulate differently in different metabolic conditions.

Differences in these early prokaryotes‘ metabolisms suggest that even 3.4 billion years ago, life had evolved a few different ecological niches. One group was apparently a methane producer, while another powered its metabolism by consuming methane. A third fossil showed signs of primitive photosynthesis that, unlike today’s plants, didn’t produce oxygen (which would have been toxic to these organisms). A microbe from an earlier study rounds out the bunch, as it relied on sulfur as its primary food-source.

Is life less unusual than we assumed?

This version of Earth certainly wouldn’t be habitable by today’s standards, but it’s an amazing degree of sophistication for a planet that had probably only had solid ground for 600 million years. This suggests that either the Earth was intensely lucky at an early age, or that life may be a bit more tenacious than we once thought. If it’s the latter, researchers suspect that this aggressive microbial timeline may have played out on other planets as well. It wouldn’t mean that other planets have the same complex organisms we do here, but that getting some microbes growing in the first place isn’t such a long-shot.

Until we get probes out to places like Europa, Titan or Enceladus, the best location to find extraterrestrial microbes may be Mars. This wouldn’t be to find microbes alive today, but to look for traces of similar fossils from the days when Mars was likely a more habitable planet.


On January 2nd, 2018 we learned about

Mouse guts demonstrate the multi-generational impact of low-fiber diets on microbial diversity

The next time you’re in the grocery store, consider the idea that you’re not just shopping for yourself. In addition to the enjoyment and nutrients you might gain, what you eat also makes an impact on the multitudes of bacteria that live in your digestive tract. In addition to the nutritional needs of your microbiome, recent research has found that what you munch on might also make a difference in the guts of your children, as well as your grandchildren. So what are all these microbes interested in eating? Fiber, and lots of it.

Fiber isn’t easy for us to digest, at least not on our own. Unlike animals that have multiple stomachs to help break down tough bits of cellulose, dextrins or pectins, humans have to get what we can from dietary fiber in the first round of digestion. Fortunately, bacteria living in our guts can help with this, as they help break down fiber by targeting what are known as microbiota-accessible carbohydrates. By fermenting these carbs, the bacteria feed themselves, and make a bit of fuel that our bodies can reclaim as well. If that weren’t enough of an incentive, well-fed microbes have also been linked to lower rates of allergies, infections and autoimmune diseases.

Starving the microbiome in sterile mice

Researchers at Stanford University wanted to see how long a gut’s microbiome could last without its favorite foods, checking to see just how strict a diet these bacteria were on. This would be a difficult test to control in humans, so mice were raised in a sterile environment, and with no natural bacteria of their own. That way, the starting microbiome could be controlled by seeding the mice’s’ guts with bacteria laden feces from a healthy human. It doesn’t sound appealing, but it made for mice that could healthily digest meals without any problems.

After a few weeks of a healthy, high-fiber diet, half the mice were switched to meals lacking in fiber, which made a clear impact on their gut bacteria. Bacteria populations declined in 60 percent of the sampled species in just seven weeks. Unfortunately, putting giving those mice extra whole grains and veggies didn’t really undo the damage— returning to a high-fiber diet restored some bacterial diversity, but the mouse guts were still 33 percent more homogeneous than before.

This simplified gut ecology persisted, even in other mice. Researchers compared gut bacteria in multiple generations of mice, and continued to see the impact of even temporary low-fiber diets. Fourth-generation low-fiber mice showed 72 percent less microbial diversity, and could only recover five percent of their stunted microbiome when switched to a high-fiber diet. Aside from the loss of bacterial diversity, researchers also noted a decline in glycoside hydrolases, the proteins that bacteria use to help digest fiber in the first place.

Is your bacterial diversity doomed already?

It’s good to keep in mind that this study was in an unusually controlled environment with a small number of mice. It shouldn’t be taken as a perfect proxy for human digestion, as we generally get exposed to a variety of bacteria in our everyday life, and usually eat a wider variety of foods than mice do. So while the mice needed to be isolated from these factors in order to properly test the possible impact of food, the degree of isolation likely makes a difference. With that said, most Americans don’t eat their recommended helping of 25 grams of fiber a day, and so it probably couldn’t hurt to eat more fresh produce, beans and whole grains in our diets. We can’t say for sure if our great-great grandchildren will notice the effects, but we’ll probably feel better while we wait for them to be born.

Source: Low-fiber diets make gut microbes poop out by Bethany Brookshire, Scicurious

On December 13th, 2017 we learned about

Antarctic microbes scavenge their metabolic fuel from the air around them

On a planet where live evolved around access to water, living in a desert is a challenge. Plants and animals that call these arid locations home often require impressive adaptations, like thorns and thick skin, to make the most of the resources available. As impressive as any of those adaptations are, scientists recently discovered that microbes may be the true masters of inhospitable biomes, making their homes in the coldest, darkest desert on Earth— the Antarctic. The various bacteria living in the icy terrain not only contend with a lack of water, but very low levels of carbon in the soil and a lack of photosynthesis-powering sunlight for half the year. With all these common sources of nutrients missing, it almost seemed liked the microbes were magically pulling their sustenance out of thin air.

As it turns out, the microbes were doing exactly that. The most reliable source of carbon and energy in the Antarctic is apparently the air itself. The microbes have evolved mechanisms to harvest what they need from hydrogen and carbon monoxide circulating in the atmosphere. It’s obviously not the most robust way to spur growth, but it seems to be the primary source of nutrition and energy for the microbes growing in locations where no plant could even hope to live.

Applications beyond Antarctic bacteria

The surprising diet these bacteria live off of raises two new lines of inquiry. While scavenging the air itself doesn’t appear to be the most energy-rich way to live, understanding how the bacteria accomplish this task may open up new technologies that don’t require traditional power sources.

It also lowers the bar for what life needs to sustain itself, particularly on other planets. Our search for extraterrestrial life generally focuses on ingredients that are found across wide portions of the Earth. There’s been some understanding of the extreme environments microbes can live in, such as along hydrothermal vents, but surviving on wafting carbon monoxide certainly expands our notion of what qualifies as ‘habitable.’

Source: Living on thin air—microbe mystery solved, Phys.org

On December 4th, 2017 we learned about

Organisms prepare for danger by picking up on specific smells

Growing up, we’re taught to look and listen for dangers in the world around us, from oncoming traffic to fire alarms. As humans, we generally gloss over things like smell, because these other senses are just so central to our experience. Our experience, however, isn’t universal, and plenty of other organisms do use their sense of smell for these tasks, sniffing for signs of trouble before it’s upon them. It’s actually such popular way to survey one’s local environment that life forms that lack a proper nose even rely on smell as a way to stay safe, or at least prepare for the worst.

Preemptive protection for plants

The tall goldenrod (Solidago altissima) is a plant that, as the name would suggest, grows up to four feet high and sprouts small, yellow flowers at its top. It’s popular with populating insects, but also with bugs that can cause it harm, like goldenrod gall flies (Eurosta solidaginis). The flies like to lay their eggs in the stem of the goldenrod so the larvae can hatch surrounded by their first meal. Their munching might not kill the plant outright, but they induce the plant to grow a gall, or protective casing around the larvae, that can strain growth and reduce the flower’s seed production.

To protect against the flies larvae, tall goldenrod have evolved a very specific defense system. A plant under attack will produce jasmonic acid, a compound that can reduce the amount of nutrition the larvae can gain from eating the plant, constraining their growth and theoretically limiting their impact. Researchers have confirmed that this defense mechanism can be deployed to greater effect if the plant can prepare in advance, particularly after smelling danger in the air. The exact scent they pick up is the mating pheromones of male E. solidaginis flies. While the flies use this scent to communicate their intent to reproduce, tall goldenrod can use it as a way to minimize the damage for the eventual offspring.

Roundworms bolster themselves against bacteria

The tiny roundworm Caenorhabditis elegans is a bit more mobile than your average tall goldenrod, but they use smell to prepare for danger in a similar way. Instead of worrying about fly larvae, the microscopic nematodes keep a nose, or smell receptor, out for the scent of a strain of Pseudomonas aeruginosa bacteria called PA14. Even though the worms are technically mobile, they don’t bother fleeing a sniff of bacterial byproducts, and instead prime their cells’ immune response. When they do come in to contact with PA14, the prepared roundworms are much more likely to survive the encounter than peers that are caught off guard.

While roundworm safety is great, research into this dynamic has been more focused on understanding exactly how it works on cellular and chemical level. Scientists first had to confirm that the worms were able to truly prepare in reaction to the smell of bacteria, and not just reacting to any stimuli. They exposed the roundworms to smells from various bacteria, and found that their “noses” were discriminating enough to only react to odors from more dangerous sources.

The mechanism that drives the preparation is called heat shock response, and is common to both plant and animal cells. When a stress, like changes in heat, salinity or other stimuli, is encountered, the cell creates specific proteins to do extra repair work in any damage that cell already has. That way it will be more likely to withstand new damage caused by the new threat when it starts causing trouble. While humans aren’t necessarily concerned about the same strains of P. aeruginosa the nematodes are, we might like to imitate their cell’s sense of smell to fight off other diseases or even symptoms of aging that do affect us.

Source: Worms learn to smell danger, EurekAlert!

On November 27th, 2017 we learned about

High-speed dust could help spread life throughout outer space

What are the odds that we’re all alien life forms? Even if your family has been in your home town for generations, there’s a chance that all life on Earth originated elsewhere, and was somehow transported to this planet billions of years ago. The idea is known as panspermia, and is usually based around the notion that a large asteroid broken off or expelled from a planet carried some hearty organisms along through space, eventually crashing into Earth where those organisms spread and diversified. A new wrinkle in this model is being suggested now, as simulations have found that a large rock may not have been a necessary component for life to travel— biological particles in a planet’s upper atmosphere may have been able to be launched by dust alone.

While there’s not enough air to breath in space, it’s not a complete vacuum either. In addition to larger and smaller asteroids, there’s a fair amount of dust that either never coalesced into a larger object, or was broken off a larger object in a collision. Researchers from the University of Edinburgh found that some of that dust is zipping along at a brisk 156,586 miles per hour, giving them a significant amount of energy to shove other particles that might be suspended high above a biologically active planet’s surface. For example, if a microscopic organism was suspended 93 miles over the Earth’s surface, around the altitude of auroras, a collision with space dust could knock it past the planet’s gravitational pull towards a new home (assuming it survived the collision.)

What life could survive in space?

Once biological material was on its way, the trip might be easier to survive than you’d think. Some bacteria have been found to survive in the generally hostile environment of outer space, and plants and animals do better than expected as well. However, a living creature wouldn’t be strictly necessary to seed life on a new planet. Even the delivery of organic molecules like amino acids would make a huge difference in kick-starting an ecosystem, some of which have already been linked to meteorites found on Earth. If these molecules could be sent sailing from mere dust as well, then the possibilities really open up for interstellar pollination.

Source: Space dust may transport life between worlds, University of Edinburgh News

On November 16th, 2017 we learned about

Bacteria swim and sense their surroundings with a single piece of anatomy

To walk down the street, your body employs over 25 muscle groups to control your gait and keep you upright. If you happen to bump into something, your foot has between 100,000 to 200,000 nerve endings in the sole alone to capture an enormous amount of detail about what you just hit. This works for us, but there are simpler ways to get around. After all, even lone bacteria can propel themselves through the world, making due with minimal sensory information. Exactly how that was all done with a single cell actually been a bit of a mystery, but researchers from the University of Basel have finally found how these tiny organisms interact with their environment.

The key feature in bacterial navigation is a long tendril extending from the cell membrane called the flagellum. As long as the bacteria is in some kind of liquid, from saliva to water to mucus, the flagellum spins, pushing the bacterium around like a stringy propeller on an outboard motorboat engine. It’s movement is powered by a stream of protons entering the cell, at least until it hits something.

Sticking a landing

When the bacterium comes in contact with a solid surface, the flagellum reveals its secondary function: a sensory “organ.” When the flagellum hits something, the the wall of your sinuses, the flow of protons is disrupted, which triggers further reactions inside the cell. Aside from the flimsy propeller being slowed down, the change in proton movement tells the bacterium to create an adhesive, which it then uses to anchor itself to that solid surface. In just a few seconds of contact, the bacterium is setting itself up to potentially launch an infection in the tissue it just bumped into.

Researchers hope that by understanding how bacteria initiate infections, we may be able to develop the means to disrupt them. This study was done with harmless Caulobacter bacteria, but the method of propulsion and mechanical sensitivity is probably used by many species of bacteria, including those that cause health problems in humans. With any luck, further research will allow us to prevent or at least slow this anchoring process, offering new forms of treatment as an alternative to our weakening library of antibiotics.

Source: Bacteria have a sense of touch

On October 11th, 2017 we learned about

What makes smoke from wildfires so bad to breathe in?

My neighborhood, while thankfully a safe distance from being actually immolated in the fires spread across northern California, is starting to look a little scary. The skies are darkened with the red tint of smoke, and trees just two blocks away are starting to be obscured by the thickening particulate. My third grader is… not taking it well. She’s nervously asking how close we are to the fires, if her aunt further north is safe, and if she should start expecting ash to start falling out of the sky, a scenario she only knows from stories about when a baby in southern California. Parental instinct leads me to try and calm her, but with at least 160,000 acres burned this week, how worried should we be about all this smoke?

Byproducts of burning plants

The smoke from forest fires has a lot of different ingredients. Trees’ and other plants’ exact combinations of cellulose, tannins, oils, waxes and more can create a wide range of chemical byproducts of a fire. Smoke from a burning forest is likely to contain carbon dioxide, carbon monoxide, water vapor, hydrocarbons, nitrogen oxides, benzene, formaldehyde, trace minerals and other particulate matter. While that may sound like a big scary list, your body can bounce back from the bigger molecules it inhales pretty well, with only temporary irritation to sensitive tissues in the eyes and respiratory tract. The items that are more worrisome are the tiny particles less than 2.5 micrometers in diameter, around 30 times thinner than a human hair. These minuscule particles can get lodged deep in your lungs, where they can cause more lasting damage to cells.

Avoiding inhalation

There are, unfortunately, a lot of health concerns with breathing in too much smoke. Older people, people with compromised hearts or lungs, and of course, growing kids, are all considered to be especially at risk when the air is too polluted. Kids with asthma are probably at the most risk, as irritation can cause their airways to close enough to completely restrict breathing, but anyone who’s lungs are either sensitive or still growing should really avoid breathing hard outdoors if at all possible. Breathing in some particulate is unavoidable— the goal is just to minimize exposure and impact.

Some folks wear dust or surgeons’ masks to try to stay safe, but most of those masks aren’t designed to block the tiny particulate that is of the most concern. Even if you do have an N-95 or P-100 respirator, it needs to fit against your face without gaps, otherwise you’ll end up sucking in particulate you were trying to filter out. Staying inside is probably a safer bet, using air conditioners to help filter the air. If that’s not an option, you may want to look for Clean Air shelters, or even climate controlled malls and businesses, as a way to avoid sucking in too much smoke.

Hazards from flaming houses

The fact that 3,500 buildings have burned down in these wildfires complicates things a bit. Houses these days are packed with a lot of plastics, which burn hot and fast, releasing more toxic and corrosive gasses like hydrogen chloride, phosgene and even hydrochloric acid. Thankfully, most of these won’t be released in high enough concentrations to affect the surrounding areas, and are more commonly issues for firefighters entering burning buildings. In those scenarios, the to big worries are carbon monoxide and cyanide, both of which are odorless, colorless and most dangerous in hot areas with restricted airflows, like a structure fire. Both chemicals restrict your body’s access and use of oxygen, and can be lethal in under ten minutes’ exposure. Again, this isn’t something you need to worry about in a smokey neighborhood downwind of a fire because concentrations each compound will probably be too low to cause that much harm, but it’s something to consider if you’re ever asked to evacuate, as staying in your home may put you and firefighters in much more risk if you need rescuing later on.

Extended influence

If all this weren’t enough, there’s a chance that wildfires are affecting you even if you can’t see the smoke. Global surveys of air quality have found that large forest fires release enough smoke to be detectable on a large scale, even beyond areas where the smoke is visible. In some cases, there are things that can be done to try to mitigate the impact of forest fires, from direct prevention to reducing carbon emissions that raise the world’s temperatures and make fires more likely in the first place.

For now, everyone’s rubbing their eyes, doing a bit more sneezing, and hoping that the fires can be contained before things get too much worse. If waiting things out feels too passive,  making donations to the people whose lives have been more directly uprooted by the fires has felt helpful as well.

Source: Wildfire Smoke: A Guide for Public Health Officials by Harriet Ammann, Robert Blaisdell, Michael Lipsett, et al., Environmental Protection Agency

On October 4th, 2017 we learned about

Pinning down the causes and effects of overly picky eaters

“Do I have eat all of it?”

My daughter looked at me, trying her best to look sad and tortured over the possibility of eating three more forkfuls of salad. The effect was slightly diminished though by her hand, which was still pinching her nose to stop herself from actually tasting her food.

“Yes, eat all of it.”

For all the groaning and whining, she did finish the serving of vegetables. Like most kids her age, she’d greatly prefer a diet strictly composed of starches and sugars, and so this melodrama wasn’t that surprising. However, it also wasn’t that bad- she’s been slowly expanding her range of palatable foods. I can’t really say that she’s a picky eater, because she will try new foods, occasionally even admitting to like them. What may seem “picky” one night might not on another, or to another parent. Because having a limited diet can have an impact on one’s health, scientists are trying to figure out what metrics can be used to classify a truly picky eater.

Figuring out what makes kids finicky

There are a lot of factors involved in a kid’s attitude towards food. Environmental feedback from parents and caregivers counts for a lot, but there’s evidence that kids all have an underlying predisposition for certain foods over others. One distinction that’s being made is cases where kids object to a meal because they don’t like the food, or if they’re objecting as a way to gain control over a situation. That’s sometimes easier said than done, as some kids seem to swing back and forth in their reactions to anything that’s not their favorite macaroni and cheese.

One truly measurable criteria may turn out to be genetics. Kids identified as “picky” by the adults in their lives had their DNA tested, with particular attention given to five genes related to taste. Out of those five, two genes were more likely to have variations in kids that turned their noses up to everything. Kids with very limited palates were most likely to have an unusual nucleotide on the TAS2R38 gene, and kids that turned meals into power struggles showed differences on their CA6 gene. Incidentally, both genes are associated with bitter taste perception, and so these kids’ objects may be tied to feeling extra sensitive to bitter flavors. Since evolution has used bitterness as a toxic defense mechanism in many species of plants, it’s not surprising that it would be an issue kids would fight about.

Minimal menu leads to damaged eyes

This doesn’t mean that picky eaters aren’t worth working with. Most veggies aren’t going to give them a dangerous dose of toxins, but it may just save them from serious vitamin deficiencies. A boy in Canada was recently brought to a hospital because his vision was deteriorating at an alarming rate, and could only make out a blur of movement if objects were dangled a foot in front of his face. Dry patches were found around the edge of his iris, and his cornea was somewhat disfigured.

Doctors eventually realized that he was severely vitamin A deficient, thanks to an extremely limited diet of lamb, pork, potatoes, apples, cucumbers and Cheerios. Without a trace of carrots, sweet potatoes, spinach or fish in his diet, the boy had essentially starved himself of a nutrient most of us don’t need to worry much about. Instead of eating his vitamin A, he was left to receive multiple doses of it intravenously, which restored much of his vision, but not all of it. At least the apples and Cheerios are helping the poor kid get some fiber.

Source: Got a picky eater? How 'nature and nurture' may be influencing eating behavior in young children, MedicalXpress.com