Fruit flies can taste calcium: Does that mean humans can?

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Searching for the sixth sense of taste

“Scientists identify a sixth taste sense.” It’s a claim that has made headlines several times over the last few years — first for fat, then for starch and even for water.  Now the new candidate for the sixth taste is calcium, after scientists identified the first calcium taste receptors in fruit flies.

Researchers at the University of California studied fruit fly behaviour and discovered the flies could taste toxic levels of calcium and didn’t like it. Then they used genetics to show that the calcium taste sense is hardwired into the fruit fly brain.

Craig Montell

University of California professor Craig Montell believes humans might share the fruit fly’s taste sensor for calcium. (UC Santa Barbara)

And because fruit flies and humans share the other main taste senses — sweet, sour, bitter, salty and savoury (called “umami”) — the study’s lead author, Craig Montell, thinks there’s a good chance that humans also have specific calcium taste receptors.

“I would say there is very good reason that, given that all the other tastes have been well conserved between flies and humans, that there probably is,” said Montell.

But the science of taste is surprisingly complicated. Even the idea that there might be additional taste receptors is controversial. As far back as Aristotle’s time, scientists have been puzzling over the question.

“Since people have been doing scientific research on taste there’s been this disagreement over whether there are these fundamental or basic tastes,” said neurobiologist Gary Beauchamp, who is an expert in the science of taste and has been researching the question for years at the Monell Chemical Senses Center in Philadelphia.

Gary Beauchamp

Taste scientist Gary Beauchamp, from the Monell Chemical Senses Centre, believes all the human taste senses have been identified. (Monell Chemical Sciences Center)

The controversy revolves around the definition of “taste sense.”

“By that I mean something that is perceptually distinct and very clear,” Beauchamp said. As a test, he considers whether other cultures have also identified the taste.

“There’s no doubt that things like calcium, starch, fat interact with our taste system and modulate what we like and what we consume,” Beauchamp said. “But to me, calling this a sixth taste is nonsense, as far as humans go.”

Umami — commonly associated with savoury flavours including cheese, cooked meat and monosodium glutamate (MSG) — is the most recent addition to the list of human taste senses, but it was only officially accepted after scientists began discovering humans had specific receptors.

“To call something an actual type of taste requires not only seeing there’s a behavioural taste. But to show that it’s really innate, it’s helpful to be able to identify a receptor,” Montell said.

“There’s really still a lot of questions. Even for sour tastes there isn’t a receptor that’s been reported yet. The ones that have been really well characterized in humans are sweet, bitter and umami. Sodium has been a little bit more enigmatic.”

Both scientists agree that taste science matters.

“There’s a very important goal in understanding how taste works,” Beauchamp said. But despite the fruit fly findings, Beauchamp dismisses calcium as a distinct human taste sense.

“The discovery of a receptor for calcium in fruit flies is very interesting,” he said, but for humans it’s already covered by the five existing senses.

“You would just call this another bitter taste.”

Should we care what fruit flies can taste? Yes, Montell said.

That’s because the fruit fly has been a reliable model for understanding human physiology. Also, understanding what fruit flies and mosquitoes taste, can help fight human disease by identifying new methods of insect control.

“Insects, like mosquitoes that spread diseases like malaria and dengue and so forth, use all the senses including chemical senses to identify human hosts,” he said. “It’s valuable to humans either way.”


Perfectionism

Research has associated perfectionism with profound mental disorders, including depression, anxiety, anorexia and suicidal behaviour. (Gustavo Frazao/Shutterstock)

Perfectionism is on the rise — and that’s not good news

Today’s college and university students in Canada feel pressure to be perfect more than other generations before them, with potentially devastating mental health consequences,  researchers say.

“Clinicians have been talking about perfectionism as a vulnerability factor to severe psychological illness now for 50 years,” said Thomas Curran, a social psychologist at the University of Bath and co-author of a study recently published in the journal Psychological Bulletin.

Perfectionism is defined as “a combination of excessively high personal standards and overly critical self-evaluations,” the study says.

Although many people view it simply as a personality trait, research has associated it with profound mental disorders, including depression, anxiety, anorexia and suicidal behaviour.

Perfectionism differs significantly from simply being conscientious or hard-working, Curran emphasized.

“The conscientious person, the diligent person, is really trying to … do the very best job on a task or an action,” he said. “The perfectionist is striving to perfect themselves.”

Because everyone is human, that’s an inherently impossible goal — so perfectionists inevitably fail, which is “catastrophic” for their sense of self.  

But despite well-established knowledge that perfectionism is problematic, there hasn’t been adequate research to show whether it’s an increasing phenomenon —  so Curran and his co-author, psychologist Andrew Hill, decided to find out.

They analyzed data from 41,641 post-secondary students who had completed a test for perfectionism between 1989 and 2016. About half the students were Canadian and the rest were from the U.S. and the U.K.

The test measured three types of perfectionism: self-oriented (an unachievable desire to be perfect), socially prescribed (perceiving that there’s an expectation from others to be perfect), and other-oriented (having unrealistic expectations that other people should be perfect).   

The study found that over the last 27 years, self-oriented perfectionism increased by 10 per cent and the expectation that others should be perfect rose by 16 per cent.

But the most significant finding, Curran said, was a 32 per cent increase in the number of students driven to perfectionism by social pressure.  

‘[This study] suggests that, OK, well, we are seeing these increases and maybe we need to pay more attention’– Paul Hewitt, University of British Columbia

Curran believes societal, cultural and economic changes over the last three decades have placed increasing pressure on young people, driving them to perfectionistic tendencies.

For example, it’s become more important than ever before to get a college or university education to secure employment and survive financially — and at the same time, getting into post-secondary schools is increasingly competitive.

And before students even reach college age, there’s been an “explosion of standardized testing” in schools, Curran said, putting even more pressure on kids.  

Parents’ anxiety about their children’s future can  — intentionally or not — feed into their children’s drive toward perfectionism.

Young people also compare many aspects of themselves — from appearance to achievements to position in the “social hierarchy” — with each other.  Social media may “amplify” that, Curran said.

Psychologist Paul Hewitt, who specializes in perfectionism at the University of British Columbia, sees “dramatic” consequences of the condition in his patients, including both psychological and physical disorders.

“There’s always questions of, ‘OK, well, is this on the increase?'” Hewitt said. “[This study] really addresses that and suggests that, ‘OK, well, we are seeing these increases and maybe we need to pay more attention.'”   


Comics a way to express ideas about health

Wam! Kapow! Boom!

Diabetes comic

Diabetes comic is a way of engaging and educating people about health issues. (CBC)

Who doesn’t love comics?  From Batman to Wonder Woman, the colourful images and text have been entertaining readers of all ages since the early 1800s.

“Comics are a popular source of entertainment, activism, education and subversion,” writes British social psychologist Petra Boynton in the Lancet.

She remembers, in the early 1980s, sending a coupon she’d clipped from a Superman comic for a smoking prevention information pamphlet. In that comic, Superman was on the winning side of a battle with Nick O’Teen, all part of an anti-smoking story created by DC Comics and the U.S.-based Health Education Council. .

Speaking by phone from her home near Brighton in the U.K., Boynton told CBC’s Kas Roussy that use of  comics and graphic novels within health care has been steadily growing for the past 50 years.

“You can go back across most cultures, they’ve used comics, or poster art or cartoon reels to inform. It might be about immunization, or it might be about health rights. I think increasingly within healthcare, it’s been recognized for what value they have for reaching patients, and more recently to inform clinicians,” she says.

And in this digital age, comics are easier to share than ever before, says Boynton. Because of that, a new group of health stories have emerged, she says, including comics created by doctors to help patients understand diseases like diabetes or depression, or social topics like gender and sexuality.

‘Comics allow you to tell way more complex stories with text and image’– Cameron Nye, Simon Fraser University

“That’s exciting for practitioners”, says Boynton. “They feel like they can connect either with their colleagues, or with their students, or with their patients.”  

“The cool thing about comics, there are a lot of different layers,” says American anthropologist Cameron Nye, who currently teaches at Simon Fraser University in Vancouver.

She co-authored a graphic novel called Lissa.  It’s part comic, part teaching tool and tells the story of two young women, one Egyptian, and one American. Both have family members who are sick. The comic interweaves stories of health and illness, set against the backdrop of the Egyptian Revolution in 2011 in Tahrir Square.

Lissa

Lissa, a comic about medical problems, also contrasts life for an American girl and one in Egypt. (CBC)

“Comics allow you to tell way more complex stories with text and image,” Nye said.

For example, the story of Lissa covers a variety of subjects, from politics to health conditions, to culture and geography. “I think they [doctors] would be motivated to read this because it would give them insight into what is it like to treat people in a context of extreme political violence and you get insights into that from our coverage of doctors treating protesters in Tahrir Square.”

Petra Boynton is a fan.

“Whether you read Lissa to educate yourself about health issues or research methods, or you just want to find out what happens to Layla and Anna, this graphic novel shows the huge and still untapped potential of comics for use in medicine and global.”  

Wam! Kapow! Boom! That’s the power of comics.

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