Health News

New type of taste cell discovered in taste buds

Our mouths may be home to a newly discovered set of multi-tasking taste cells that — unlike most known taste cells, which detect individual tastes — are capable of detecting sour, sweet, bitter and umami stimuli. A research team led by Kathryn Medler at the University at Buffalo reports this discovery in a study published 13th August in PLOS Genetics.

Taste buds in the mouth are critical to our survival and help us to decide whether a food is a good source of nutrients or a potential poison. Taste buds employ three types of taste cells: Type I cells acts as support cells; Type II cells detect bitter, sweet and umami tastes; and Type III cells detect sour and salty flavors. To better understand how taste cells detect and signal the presence of different tastes, the researchers used an engineered mouse model to investigate the signaling pathways that the animals use to relay taste information to the brain. They discovered a previously unknown subset of Type III cells that were “broadly responsive” and could announce sour stimuli using one signaling pathway, and sweet, bitter and umami stimuli using another.

The idea that mammals might possess broadly responsive taste cells has been put forth by multiple lab groups, but previously, no one had isolated and identified these cells. The researchers suspect that broadly responsive cells make a significant contribution to our ability to taste. Their discovery provides new insight into how taste information is sent to the brain for processing, and suggests that taste buds are far more complex than we currently appreciate.

“Taste cells can be either selective or generally responsive to stimuli which is similar to the cells in the brain that process taste information,” commented author Kathryn Medler. “Future experiments will be focused on understanding how broadly responsive taste cells contribute to taste coding.”

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Materials provided by PLOS. Note: Content may be edited for style and length.

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Adding a meter between meals boosts vegetarian appeal

Meat-heavy diets not only risk our health but that of the planet, as livestock farming on a massive scale destroys habitats and generates greenhouse gases.

Conservationists at the University of Cambridge are investigating ways of “nudging” people towards eating more plants and less meat, to help curb the environmental damage caused by excessive consumption of animal products.

The researchers experimented on customers in the cafeterias of two Cambridge colleges to find out whether the position of vegetarian options influences the uptake of plant-based dining.

They collected and analysed data from 105,143 meal selections over a two-year period, alternating the placement of meat and veg dishes every week, and then changing the pattern to every month.

The size of the study is unprecedented. A previous review of various studies using “choice architecture” to reduce meat intake only reached a combined total of 11,290 observations.

The researchers found that simply placing veggie before meat in the order of meal options as people entered the serving area did little to boost green eating in one of the colleges.

In the other college, however, the sales of plant-based dishes shot up by a quarter (25.2%) in the weekly analysis, and by almost 40% (39.6) in the monthly comparison.

The difference: almost a metre of added distance between the vegetarian and meat options, with an 85cm gap in the first college compared to a 181cm gap in the second. The findings are published today in the journal Nature Food.

“Reducing meat and dairy consumption is one of the simplest and most impactful choices we can make to protect the climate, environment and other species,” said study lead author Emma Garnett, a conservationist from Cambridge’s Department of Zoology.

“We’ve got to make better choices easier for people. We hope to see these findings used by catering managers and indeed anyone interested in cafeteria and menu design that promotes more climate friendly diets.”

The latest research follows on from work by Garnett and colleagues published last autumn, which showed that adding an extra veggie option in cafeterias cuts meat consumption without denting overall sales.

Livestock and aquacultures behind meat, fish, dairy and eggs are responsible for some 58% of the greenhouse gas created by global food, and take up 83% of farmland despite contributing to just 18% of the world’s calorie intake.

Recently, Cambridge researchers recommended eating less meat to reduce the risk of future pandemics, and the UK’s public sector caterers pledged to cut the amount of meat used in schools and hospitals by 20%.

The experiments were conducted across two colleges — one with 600 students and one with 900 students — where cafeteria customers were presented with vegetarian and meat options in differing orders for weekday lunch and dinner.

College members take a tray, view the meals on offer, and then ask serving staff to dish up their preferred options. Food is purchased by swiping a university card, and the researchers gathered anonymised data on main meal selections only (sandwiches and salads went uncounted).

While the catering managers helped to set the experiments up, the diners remained unaware.

The researchers had expected to see a difference in vegetarian sales through order alone, but it was only in the college with the extra metre — the 181cm gap — between food options that recorded an uptick when arranged “Veg First.”

To confirm the findings, researchers reduced the gap in this cafeteria to just 67cm, and vegetarian sales fell sharply. In fact, with such a small gap, vegetarian dishes fared even worse when put first in line (falling almost 30% compared to “Meat First” days).

“We think the effect of the metre may be down to the additional effort required to seek out meat. If the first bite is with the eye, then many people seem perfectly happy with an appetising veggie option when meat is harder to spot,” said Garnett.

“All cafeterias and restaurants have a design that ‘nudges’ people towards something. So it is sensible to use designs that make the healthiest and most sustainable food options the easiest to pick without thinking about it,” she said.

“We know that information alone is generally not enough to get us to change damaging habits. More research is needed on how to set up our society so that the self-interested default decision is the best one for the climate.”

Garnett’s research has contributed to food policy at the University of Cambridge, where the catering service has worked to reduce the amount of meat it uses.

Last year, University cafeterias (separate from the colleges) announced a 33% reduction in carbon emissions per kilogram of food purchased, and a 28% reduction in land use per kilogram of food purchased.

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Fireflies shed light on the function of mitochondria

Tiny factories float inside our cells and provide them with almost all the energy they need: the mitochondria. Their effectiveness decreases when we get older, but also when we face many diseases such as diabetes, cancer or Parkinson’s. This is why scientists are increasingly interested in how they work. At EPFL, a team has developed a protocol to measure their activity live in living animals. Described in Nature Chemical Biology, the method relies on the molecule responsible for the firefly’s bioluminescence. In the most literal sense of the word, this study sheds light on how mitochondria work.

Mitochondria are almost like cells within the cell. Like their host, they have a membrane that protects their genetic material and, above all, filters exchanges with the outside. The difference in electrical charge between the inside and the outside of the mitochondria, called “membrane potential,” allow certain molecules to go through, while other remain at bay.

As between the two poles of a used electric battery, the membrane potential of the mitochondria can sometimes drop. For scientists, this is an unmistakable clue that its functions are impaired.

We know how to measure the phenomenon on cultured cells. But until now, you couldn’t really see it on live animals. “Cell cultures are not very effective in studying diseases linked to mitochondria,” explains Elena Goun, professor at EPFL.

Elena Goun and her colleagues have found a way to study the phenomenon in live mice. They use animals that are genetically modified to express luciferase — an enzyme that produces light when combined with another compound called luciferin. This is how fireflies sometimes light up our summer evenings.

Scientists have developed two molecules that, when injected into the rodent, pass into the mitochondria, where they activate a chemical reaction. The mitochondria then produce luciferin and eject it outwards. Luciferin combines with luciferase in the mice’s cells and produce light.

“In a completely darkened room, you can see the mice glowing, just like fireflies,” says Elena Goun.

Researchers need only measure light intensity to get a clear picture of how well the mitochondria are functioning. When they function less well, their membrane lets in less chemical compounds. The production of luciferin decreases, and therefore the luminosity too.

To demonstrate the potential of their method, the researchers carried out several experiments. For example, they observed that older rodents produce significantly less light. This drop in light reflects a drop in the activity of mitochondria — their membrane potential is much lower than in younger rodents. We know that age causes a decrease in the activity of mitochondria, but this is the first time that the phenomenon has been accurately measured directly in living animals.

The team also tested a chemical known to rejuvenate mitochondria: nicotinamide riboside. This molecule is non-toxic and commercially available as a dietary supplement. Mice given this compound produced more light, a sign of increased mitochondrial activity.

The researchers were also able to measure the same phenomenon in animal models of cancer. This could be of great help for anticancer drug research. In addition, they also successfully demonstrated monitoring of mitochondria membrane potential in cells of brown adipose tissue, rich in mitochondria. Its stimulation could help cure certain forms of obesity.

The method described by Elena Goun is primarily intended for scientists who want to better understand the role of mitochondria and who need an animal model. The field of application is wide: diabetes, oncology, aging, nutrition, neurogenerative diseases… “Our process can measure varying degrees of mitochondria activity, and not just an on / off signal,” explains Elena Goun. “It is extremely sensitive — much more than a PET scan — affordable and easy to implement.

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Materials provided by Ecole Polytechnique Fédérale de Lausanne. Original written by Emmanuel Barraud. Note: Content may be edited for style and length.

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Nutrition labelling is improving nation’s diet

Nutritional information displayed prominently on food products which give consumers information on salt, sugar and calorie content play a significant role in nudging people towards better dietary choices, according to new research.

The study, from health economists at the universities of Bath and Bristol published in the Journal of Health Economics, is the first to evaluate the impact of Front-of-Pack nutritional labelling on retailers’ store-branded products, which was first introduced back in 2006.

Their results find a reduction in the quantity of labelled store-branded food purchased (for example ready meals, pizzas, burgers, etc.) and an overall improvement in the nutritional composition of consumers’ shopping baskets where labelling was displayed. Significantly, these improvements in food shopping habits were most prominently observed across poorer households.

In 2006, the UK Food Standards Agency (FSA) recommended retailers to introduce Front-of-Pack (FOP) labelling on their store-brand products on seven types of foods (ready meals, burgers/sausages, pies, breaded/coated meats, pizzas, sandwiches and cereal). The recommendation was taken up by several UK retailers (Waitrose, Co-Op, Marks & Spencer, and Asda) who each introduced it at different times between March 2006 and September 2007.

Retailers introduced two types of nutritional labelling. Some introduced a Traffic Light System, a colour-coded scheme denoting the amount of nutrients by the colours red (high), amber (medium) and green (low), whilst some others introduced a hybrid system incorporating both a traffic light system and Guideline Daily Amounts (GDAs), where both colours and the contribution that each of these nutrients make towards the adult GDA were displayed.

By drawing on differences observed in the food choices of consumers who shopped in stores where labelling was displayed, to changes for consumers shopping elsewhere, the results from the new study show that on average, as a result of labelling, households improved the quality of their diet by reducing the total monthly calories from labelled store-brand foods by 588 Kcal, saturated fats by 14g, sugars by 7g, and sodium by 0.8mg. Hybrid labelling was found to be most effective at shifting choices.

The research comes as the UK government sets out its new obesity strategy in response to covid-19, unveiling as part of it a number of measures including menu calorie labelling to help people make healthier choices when eating out. The team behind the study say these new results can help inform future policies in this area.

Lead researcher, Dr Eleonora Fichera from the Department of Economics at the University of Bath explains: “Our results suggest that nutritional labelling on food products can play an important role in starting to shift behaviours towards more healthier food choices whether that be during the weekly shop in a supermarket, or potentially through new healthier menu choice options. Labelling has a dual effect in better informing consumers about the nutritional value of the products they put in their shopping basket, but it may also incentivise manufactures towards better quality food products.

“This of course is not a panacea to solve the obesity problem, which is multi-faceted and needs to be tackled with a much more systemic approach. But these results provide policymakers with further evidence that such measures can make an important contribution.”

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Materials provided by University of Bath. Note: Content may be edited for style and length.

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TV-watching snackers beware: You won’t notice you’re full if your attention is elsewhere

Eating while doing something perceptually-demanding makes it more difficult to notice when you feel full, shows new research from the University of Sussex.

Professor Martin Yeomans, Dr Sophie Forster and colleagues found that when your senses are taken up by an engaging task, you are less likely to be able to adjust how much extra food or drink you consume. The team tested 120 participants, giving them lower and higher calorie drinks and giving them tasks which demanded both low and high amounts of their attention. The paper “Ingested but not perceived: response to satiety cues disrupted by perceptual load” is published today 12 August 2020 in the journal Appetite.

The team found that participants who were fully engaged in a perceptually-demanding task ate roughly the same amount of follow-up crisps regardless of whether or not they were initially given a high or low calorie drink. But the people who were engaged in a task which demanded less of them could adjust how much of the additional snack they ate. The people in this group ate 45% fewer crisps after the higher energy drink than after the lower energy drink.

Previous research has shown that when perceptual demand is high — so that’s where the senses are engaged fully — then the brain filters out some of the sensory information. This is the first time that research has shown that sensory and nutrient cues associated with becoming full (satiety) could be filtered out in a similar way.

Professor Martin Yeomans from the School of Psychology at the University of Sussex, said:

“Our study suggests that if you’re eating or drinking while your attention is distracted by a highly engaging task, you’re less likely to be able to tell how full you feel. You’re more likely to keep snacking than if you’d been eating while doing something less engaging. This is important for anyone wanting to stay a healthy weight: if you’re a habitual TV-watching snacker — watching, say, an engaging thriller or mystery, or a film with a lot of audio or visual effects — you’re not likely to notice when you feel full. Video-gamers and crossword solvers should also take note!

“We already knew that feeling full could be affected by the texture and appearance of food, as well as pre-existing expectations about how full we think a type of food should make us feel. Now we also know that feeling full depends on how much sensory information our brains are processing at the time.”

About the research

One-hundred and twenty participants consumed either a low-satiety (75kcal) or high-satiety (272kcal and thicker texture) drink while simultaneously completing a task which was either low or high in perceptual demand. The participants who were given the low perceptual load task, and were given the high-satiety drink felt more full and ate 45% less of the snack offered to them afterwards. However, the participants who were given the higher load perception task were less able to tell when they felt full, and ate more of the snacks offered to them. The researchers conclude that a person’s ability to notice when the body feels full depends on how much available attention there is ‘left’ in the brain.

The results provide the first evidence that Load Theory of attention (the idea that a person has a limited amount of sensory information they can notice) can be successfully applied to eating habits.

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Materials provided by University of Sussex. Original written by Anna Ford. Note: Content may be edited for style and length.

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