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What is metabolism? A biochemist explains how different people convert energy differently − and why that matters for your health

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theconversation.com – Travis Nemkov, Assistant Research Professor of Biochemistry and Molecular Genetics, of Colorado Anschutz Medical Campus – 2024-04-04 07:44:30

If you've spent any time scrolling through the and wellness corners of social , you've likely across many products claiming to improve your metabolism. But what exactly is your metabolism?

Everything you expose your body to – from lifestyle to an airborne virus – influences your physical characteristics, such as your blood pressure and energy levels. Together, these biological characteristics are referred to as your phenotype. And the biological system that most directly influences your phenotype is your metabolism.

So if you are eating something, take medications, smoke or exercise, your metabolism is responsible for transferring that biological information throughout your body for it to adapt.

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Metabolism is energy conversion

Your metabolism consists of a network of tens of thousands of molecules and proteins that convert the food you eat into the energy and building blocks your body uses to move, grow and repair itself. At the chemical level, energy metabolism begins when the three macronutrients – carbohydrates, fats and protein – are broken down atom by atom to release electrons from chemical bonds. These electrons charge components in cells called mitochondria.

Akin to how batteries work, mitochondria harness this electrical potential to create a different form of chemical energy that the rest of the cell can use.

Simply put, a primary role of metabolism is to convert chemical energy into electrical energy and back into chemical energy. How this energy is transferred throughout the body might play a central role in determining whether you're sick or healthy.

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Diagram consisting of dense, interconnected multicolored lines and dots

As illustrated by this simplified diagram of the human metabolome (where lines indicate chemical reactions and dots indicate reactants or products), your metabolic network is incredibly complex.
J3D3/Wikimedia Commons, CC BY-SA

I am a biochemist who studies the various networks of metabolism that are used as your body changes. My team and I have been able to define specific traits of metabolism, such as the presence and amount of certain metabolites – products made from breaking down macronutrients – across a wide range of conditions.

These conditions include diseases such as COVID-19, diabetes, multiple sclerosis and sickle cell anemia, to experiencing unique environments such as radiation exposure, high altitude, aging and sports performance. Each of these settings influences which parts of your metabolic network are used and how they communicate with one another.

Elite athletes define the upper limits

Given the alarming rise in obesity and its associated metabolic syndrome – about 1 in 8 people across the globe were living with obesity in 2022 – defining a healthy or impaired metabolism can identify what's gone wrong and how to address it.

Elite athletes offer a prime population to study metabolic function at its best, since their network of molecular and chemical reactions must be finely tuned to compete on the world stage.

Traditionally, lactate threshold has been a critical measure of athletic performance by pinpointing exercise intensity when lactate starts to rise in muscles and blood.

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Contrary to common belief, lactate is not merely a waste product but an energy source as well, and it accumulates when it's produced faster than mitochondria can use it. While a moderately active person might reach their threshold at an exercise intensity of around 2 watts per kilogram, elite cyclists can sustain an intensity up to nearly two to three times higher.

When comparing the lactate thresholds of a group of elite cyclists, we found that the cyclists with higher thresholds had markers of better mitochondrial function. One of these markers was higher production of coenzyme A, a molecule that shuttles carbon around cells and is important for breaking down carbs, amino acids and fat into chemical energy.

Higher-performing cyclists also appeared to burn more fat and burn fat longer during a multistage world tour compared with lower-performing cyclists.

Dysfunctional metabolism in diseases like COVID-19

Your metabolism also changes if you get an acute illness such as .

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In contrast to elite cyclists, COVID-19 patients have an impaired ability to burn fat that appears to persist with long COVID. The blood of these patients at rest is similar to that of an elite cyclist's at exhaustion. Considering that exercise intolerance frequently occurs with long COVID, this suggests mitochondrial dysfunction may play a role in COVID-related .

Person curled up on a couch, half-covered with a blanket

Long COVID patients have metabolic profiles that resemble that of an exhausted elite cyclist.
Maria Korneeva/Moment via Getty Images

Burning fat uses a lot of oxygen. COVID-19 damages the red blood cells that deliver oxygen to organs. Because red blood cells have a limited ability to repair themselves, they might not function as well during the remainder of their roughly 120-day span. This may partially explain why COVID symptoms last as long as they do in some people.

Blood donors define the middle

Blood transfusions are one of the most common clinical procedures. Over 118 million pints of blood are donated by millions of people worldwide every year. Because blood donors undergo screening to ensure they are healthy enough to donate, they are typically moderately healthy, somewhere between acute illness and elite athletic performance. Blood donors, coming from every walk of life, also have a diverse range of biological traits as a study population.

My team and I looked at blood from over 13,000 blood donors to shed light on their metabolic diversity. We found specific traits that could predict how well a donor's blood would work in patients, which also has implications for how well that blood works in the donors themselves.

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We found that one of these traits is a metabolite called kynurenine, which is produced from the of the amino acid tryptophan. We found that blood from donors with higher levels of kynurenine was less likely to restore hemoglobin levels in transfusion recipients compared with donors with lower kynurenine levels.

Kynurenine levels are higher in older donors and donors with a higher BMI, and may potentially be tied to higher levels of inflammation. In , our group also found that kynurenine increases dramatically in runners participating in the 171-kilometer (106 miles) Ultra-Trail du Mont-Blanc. In addition, we also identified that kynurenine is a strong marker of COVID-19 severity.

The relationship between metabolites and health outcomes reinforces the important role metabolism plays in the body. Getting a better understanding of what healthy metabolism looks like can offer unique insights into how it deviates when someone gets sick and may offer new approaches to medical treatments.

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The Conversation

AI chatbots are intruding into online communities where people are trying to connect with other humans

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theconversation.com – Casey Fiesler, Associate Professor of Information Science, University of Colorado Boulder – 2024-05-20 07:27:05
AI chatbots are butting into human spaces.
gmast3r/iStock via Getty Images

Casey Fiesler, University of Colorado Boulder

A parent asked a question in a private Facebook group in April 2024: Does anyone with a child who is both gifted and disabled have any experience with New York City ? The parent received a seemingly helpful answer that laid out some characteristics of a specific school, beginning with the context that “I have a child who is also 2e,” meaning twice exceptional.

On a Facebook group for swapping unwanted items near Boston, a user looking for specific items received an offer of a “gently used” Canon camera and an “almost-new portable air conditioning unit that I never ended up using.”

Both of these responses were lies. That child does not exist and neither do the camera or air conditioner. The answers came from an artificial intelligence chatbot.

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According to a Meta help page, Meta AI will respond to a post in a group if someone explicitly tags it or if someone “asks a question in a post and no one responds within an hour.” The feature is not yet available in all regions or for all groups, according to the page. For groups where it is available, “admins can turn it off and back on at any time.”

Meta AI has also been integrated into search features on Facebook and Instagram, and users cannot turn it off.

As a researcher who studies both online communities and AI ethics, I find the idea of uninvited chatbots answering questions in Facebook groups to be dystopian for a number of reasons, starting with the fact that online communities are for people.

Human connections

In 1993, Howard Rheingold published the book “The Virtual Community: Homesteading on the Electronic Frontier” about the WELL, an early and culturally significant online community. The first chapter with a parenting question: What to do about a “blood-bloated thing sucking on our baby's scalp.”

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Rheingold received an answer from someone with firsthand knowledge of dealing with ticks and had resolved the problem before receiving a callback from the pediatrician's office. Of this experience, he wrote, “What amazed me wasn't just the speed with which we obtained precisely the information we needed to know, right when we needed to know it. It was also the immense inner sense of security that comes with discovering that real people – most of them parents, some of them nurses, , and midwives – are available, around the clock, if you need them.”

This “real people” aspect of online communities continues to be critical . Imagine why you might pose a question to a Facebook group rather than a search engine: because you want an answer from someone with real, lived experience or you want the human response that your question might elicit – sympathy, outrage, commiseration – or both.

Decades of research suggests that the human component of online communities is what makes them so valuable for both information-seeking and social support. For example, fathers who might otherwise feel uncomfortable asking for parenting advice have found a haven in private online spaces just for dads. LGBTQ+ youth often join online communities to safely find critical resources while reducing feelings of isolation. Mental health support forums provide young people with belonging and validation in addition to advice and social support.

Online communities are well-documented places of support for LGBTQ+ people.

In addition to similar findings in my own lab related to LGBTQ+ participants in online communities, as well as Black Twitter, two more recent studies, not yet peer-reviewed, have emphasized the importance of the human aspects of information-seeking in online communities.

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One, led by PhD student Blakeley Payne, focuses on fat people's experiences online. Many of our participants found a lifeline in access to an audience and community with similar experiences as they sought and shared information about topics such as navigating hostile systems, finding clothing and dealing with cultural biases and stereotypes.

Another, led by Ph.D student Faye Kollig, found that people who share content online about their chronic illnesses are motivated by the sense of community that comes with shared experiences, as well as the humanizing aspects of connecting with others to both seek and support and information.

Faux people

The most important of these online spaces as described by our participants could be drastically undermined by responses coming from chatbots instead of people.

As a type 1 diabetic, I follow a number of related Facebook groups that are frequented by many parents newly navigating the challenges of caring for a young child with diabetes. Questions are frequent: “What does this mean?” “How should I handle this?” “What are your experiences with this?” Answers from firsthand experience, but they also typically come with compassion: “This is hard.” “You're doing your best.” And of course: “We've all been there.”

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A response from a chatbot claiming to speak from the lived experience of caring for a diabetic child, offering empathy, would not only be inappropriate, but it would be borderline cruel.

However, it makes complete sense that these are the types of responses that a chatbot would offer. Large language models, simplistically, function more similarly to autocomplete than they do to search engines. For a model trained on the millions and millions of posts and comments in Facebook groups, the “autocomplete” answer to a question in a support community is definitely one that invokes personal experience and offers empathy – just as the “autocomplete” answer in a Buy Nothing Facebook group might be to offer someone a gently used camera.

Meta has rolled out an AI assistant across its social media and messaging apps.

Keeping chatbots in their lanes

This isn't to suggest that chatbots aren't useful for anything – they may even be quite useful in some online communities, in some contexts. The problem is that in the midst of the current generative AI rush, there is a tendency to think that chatbots can and should do everything.

There are plenty of downsides to using large language models as information retrieval systems, and these downsides point to inappropriate contexts for their use. One downside is when incorrect information could be dangerous: an eating disorder helpline or legal advice for small businesses, for example.

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Research is pointing to important considerations in how and when to design and deploy chatbots. For example, one recently published paper at a large human-computer interaction conference found that though LGBTQ+ individuals lacking social support were sometimes turning to chatbots for with mental health needs, those chatbots frequently fell short in grasping the nuance of LGBTQ+-specific challenges.

Another found that though a group of autistic participants found value in interacting with a chatbot for social communication advice, that chatbot was also dispensing questionable advice. And yet another found that though a chatbot was helpful as a preconsultation tool in a health context, sometimes found expressions of empathy to be insincere or offensive.

Responsible AI development and deployment means not only auditing for issues such as bias and misinformation, but also taking the time to understand in which contexts AI is appropriate and desirable for the humans who will be interacting with them. Right now, many companies are wielding generative AI as a hammer, and as a result, everything looks like a nail.

Many contexts, such as online support communities, are best left to humans.The Conversation

Casey Fiesler, Associate Professor of Information Science, University of Colorado Boulder

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The Conversation

Is hard water bad for you? 2 water quality engineers explain the potential benefits and pitfalls that come with having hard water

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theconversation.com – Sarah Blank, Master's Student in Civil Engineering, Iowa University – 2024-05-20 07:26:46
Do you know how hard your water is?
Tatiana Maksimova/Moment via Getty Images

Sarah Blank, Iowa State University and Timothy Ellis, Iowa State University

When you turn on your faucet to get a glass of water or wash your face, you're probably not thinking about what's in your water – besides water. Depending on where you and whether you have a water-softening system, your water might contain dissolved minerals such as calcium and magnesium. And these minerals can play a role in whether certain pollutants such as stay out of your water.

The more dissolved minerals, the “harder” your water. But is hard water actually good or bad for you?

As engineering researchers who study water quality, we have seen the effects – both good and bad – that soft and hard water can have on everything from plumbing systems to the human body.

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What is hard water?

Hard water is water that contains dissolved minerals such as calcium, magnesium, iron and manganese. Soft water contains lower concentrations of these minerals.

Hardness is measured in terms of calcium carbonate, CaCO₃, which is used as a reference point for comparing different minerals.

The amount of these minerals in a 's water supply varies by region. It depends on both where the water is coming from and how the water is treated.

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Communities that source their water from wells rather than surface water such as lakes, streams, rivers and reservoirs often start with hard water pretreatment. As groundwater moves through the soil to a well, it picks up minerals. At the same time, areas where the types of rock and sediment are more prone to dissolving in water may have harder water.

A map showing water hardness across the U.S., with the hardest water in the Midwest, West and Southwest.
Streamflow water hardness across the U.S., where purple and blue indicate softer water and white and red indicate harder water. This map was updated in 2005 by the U.S. EPA.
U.S. Geological Survey

Effects on water lines and distribution

Water that's too hard or too soft could damage pipes and lead to health and aesthetic concerns.

Since hard water has a higher mineral concentration, minerals can build up in pipes, which to clogged pipes in homes and public water systems. Hardness also creates more deposits at higher temperatures, so hot water heaters are prone to mineral buildup. In areas with hard water, water heaters have a shorter span.

A pipe with gray material around the inside.
A pipe that has a thick layer of mineral deposits inside of it.
Mevedech/Wikimedia Commons

But hard water can , too. While minerals from hard water can clog pipes, a thin layer of mineral deposition in water lines can protect you from ingesting toxins that could seep in from the pipe itself. Water without any minerals can play a role in pipe corrosion, because without a thin, protective layer of minerals, the water may start to eat away at the pipes, releasing metals from the pipes into the water. Drinking this water might mean ingesting metals such as lead, copper and iron.

While water that is too soft or too hard can have different effects on water lines, there is more chemistry than just hardness that plays a role in pipe corrosion and clogging. So, there's no specific hardness level that is a cause for concern. Water treatment plants take the appropriate measures to adjust for different hardness levels.

A large tank of water, with fences around the top.
Drinking water normally undergoes treatment at a plant before it makes its way to your home.
Florida Water Daily, CC BY

Effects on skin and hair

Whether you use hard or soft water to wash up can also have noticeable effects on your skin and hair.

Hard water is more likely to leave your skin dry. The minerals in hard water strip moisture from skin and create deposits that clog pores.

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Hard water can also strip the hair of moisture, leaving it dry and coarse. Dry hair is more prone to frizz, tangles and breakage. Mineral deposits can also build up on the hair and scalp, clogging your hair follicles and leading to dandruff and slowed hair growth.

Many households have their own water-softening systems. A water-softening system may help hair and skin dryness and buildup. But many of these systems trap and replace calcium and magnesium with sodium, a mineral that does not contribute to water hardness, to lower overall hardness. Increasing the water's sodium content may be a concern for anyone on a low-sodium diet.

Overall health benefits

Other than aesthetic and water heater concerns, drinking hard water is actually good for you and doesn't come with any serious adverse side effects.

For example, the extra magnesium and calcium you consume in hard water may a gentle solution to digestive issues and constipation.

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Also, researchers have found positive correlations between the hardness of drinking water and bone health. Since calcium is an essential mineral in bones, individuals in areas with drinking water that has more calcium may have higher bone mineral density and may be less prone to osteoporosis.

Researchers have also found that drinking hard water has been associated with a decrease in cardiovascular disease-related mortality. Magnesium helps regulate your cardiac muscles, while calcium keeps the sodium-potassium balance in your cardiac muscles in check, which they need to function.

Whether you have hard or soft water, don't worry too much. Water treatment plants take appropriate measures to ensure safe water for the communities they .

To learn more about the water hardness in your area, you can contact your local water treatment plant about its specific water treatment process. Private well owners can contact their state to find out the testing recommendations for their area.The Conversation

Sarah Blank, Master's Student in Civil Engineering, Iowa State University and Timothy Ellis, Associate Professor of Civil, Construction and Environmental Engineering, Iowa State University

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Black holes are mysterious, yet also deceptively simple − a new space mission may help physicists answer hairy questions about these astronomical objects

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theconversation.com – Gaurav Khanna, Professor of Physics, of Rhode Island – 2024-05-15 07:16:18

An illustration of a supermassive black hole.

NASA/JPL

Gaurav Khanna, University of Rhode Island

Physicists consider black holes one of the most mysterious objects that exist. Ironically, they're also considered one of the simplest. For years, physicists like me have been looking to prove that black holes are more complex than they seem. And a newly approved European space mission called LISA will us with this hunt.

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Research from the 1970s suggests that you can comprehensively describe a black hole using only three physical attributes – their mass, charge and spin. All the other properties of these massive dying , like their detailed composition, density and temperature profiles, disappear as they transform into a black hole. That is how simple they are.

The idea that black holes have only three attributes is called the “no-hair” theorem, implying that they don't have any “hairy” details that make them complicated.

Black holes are massive, mysterious astronomical objects.

Hairy black holes?

For decades, researchers in the astrophysics community have exploited loopholes or work-arounds within the no-hair theorem's assumptions to up with potential hairy black hole scenarios. A hairy black hole has a physical property that scientists can measure – in principle – that's beyond its mass, charge or spin. This property has to be a permanent part of its structure.

About a decade ago, Stefanos Aretakis, a physicist currently at the University of Toronto, showed mathematically that a black hole containing the maximum charge it could hold – called an extremal charged black hole – would develop “hair” at its horizon. A black hole's horizon is the boundary where anything that crosses it, even light, can't escape.

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Aretakis' analysis was more of a thought experiment using a highly simplified physical scenario, so it's not something scientists expect to observe astrophysically. But supercharged black holes might not be the only kind that could have hair.

Since astrophysical objects such as stars and planets are known to spin, scientists expect that black holes would spin as well, based on how they form. Astronomical evidence has shown that black holes do have spin, though researchers don't know what the typical spin value is for an astrophysical black hole.

Using computer simulations, my team has recently discovered similar types of hair in black holes that are spinning at the maximum rate. This hair has to do with the rate of change, or the gradient, of -time's curvature at the horizon. We also discovered that a black hole wouldn't actually have to be maximally spinning to have hair, which is significant because these maximally spinning black holes probably don't form in nature.

Detecting and measuring hair

My team wanted to develop a way to potentially measure this hair – a new fixed property that might characterize a black hole beyond its mass, spin and charge. We started looking into how such a new property might a signature on a gravitational wave emitted from a fast-spinning black hole.

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A gravitational wave is a tiny disturbance in space-time typically caused by violent astrophysical in the universe. The collisions of compact astrophysical objects such as black holes and neutron stars emit strong gravitational waves. An international network of gravitational observatories, the Laser Interferometer Gravitational-wave Observatory in the United States, routinely detects these waves.

Our recent studies suggest that one can measure these hairy attributes from gravitational wave data for fast-spinning black holes. Looking at the gravitational wave data offers an for a signature of sorts that could indicate whether the black hole has this type of hair.

Our ongoing studies and recent progress made by Som Bishoyi, a student on the team, are based on a blend of theoretical and computational models of fast-spinning black holes. Our findings have not been tested in the field yet or observed in real black holes out in space. But we hope that will soon change.

LISA gets a go-ahead

In January 2024, the European Space Agency formally adopted the space-based Laser Interferometer Space Antenna, or LISA, mission. LISA will look for gravitational waves, and the data from the mission could help my team with our hairy black hole questions.

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Three spacecrafts spaced apart sending light beams towards each other while orbiting the Sun

The LISA spacecrafts observing gravitational waves from a distant source while orbiting the Sun.

Simon Barke/Univ. Florida, CC BY

Formal adoption means that the has the go-ahead to move to the construction phase, with a planned 2035 launch. LISA consists of three spacecrafts configured in a perfect equilateral triangle that will trail behind the Earth around the Sun. The spacecrafts will each be 1.6 million miles (2.5 million kilometers) apart, and they will exchange laser beams to measure the distance between each other down to about a billionth of an inch.

LISA will detect gravitational waves from supermassive black holes that are millions or even billions of times more massive than our Sun. It will build a map of the space-time around rotating black holes, which will help physicists understand how gravity works in the close vicinity of black holes to an unprecedented level of accuracy. Physicists hope that LISA will also be able to measure any hairy attributes that black holes might have.

With LIGO making new observations every day and LISA to offer a glimpse into the space-time around black holes, now is one of the most exciting times to be a black hole physicist.The Conversation

Gaurav Khanna, Professor of Physics, University of Rhode Island

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