Why Neglected Tropical Diseases Should Matter to Americans
Daisy Hernández was five years old when one of her favorite aunts was struck with a mysterious illness. Tía Dora had stayed behind in Colombia when Daisy's mother immigrated to Union City, New Jersey. A schoolteacher in her late 20s, she began suffering from fevers and abdominal pain, and her belly grew so big that people thought she was pregnant. Exploratory surgery revealed that her large intestine had swollen to ten times its normal size, and she was fitted with a colostomy bag. Doctors couldn't identify the underlying problem—but whatever it was, they said, it would likely kill her within a year or two.
Tía Dora's sisters in New Jersey—Hernández's mother and two other aunts—weren't about to let that happen. They pooled their savings and flew her to New York City, where a doctor at Columbia-Presbyterian Medical Center with a penchant for obscure ailments provided a diagnosis: Chagas disease. Transmitted by the bite of triatomine insects, commonly known as kissing bugs, Chagas is endemic in many parts of Latin America. It's caused by the parasite Trypanoma cruzi, which usually settles in the heart, where it feeds on muscle tissue. In some cases, however, it attacks the intestines or esophagus. Tía Dora belonged to that minority.
In 1980, U.S. immigration laws were more forgiving than they are today. Tía Dora was able to have surgery to remove a part of her colon, despite not being a citizen or having a green card. She eventually married a legal resident and began teaching Spanish at an elementary school. Over the next three decades, she earned a graduate degree, built a career, and was widowed. Meanwhile, Chagas continued its slow devastation. "Every couple of years, we were back in the hospital with her," Hernández recalls. "When I was in high school, she started feeling like she couldn't swallow anything. It was the parasite, destroying the muscles of her esophagus."
When Tía Dora died in 2010, at 59, her niece was among the family members at her bedside. By then, Hernández had become a journalist and fiction writer. Researching a short story about Chagas disease, she discovered that it affected an estimated 6 million people in South America, Central America, and Mexico—as well as 300,000 in the United States, most of whom were immigrants from those places. "I was shocked to learn it wasn't rare," she says. "That made me hungry to know more about this disease, and about the families grappling with it."
Hernández's curiosity led her to write The Kissing Bug, a lyrical hybrid of memoir and science reporting that was published in June. It also led her to another revelation: Chagas is not unique. It's among the many maladies that global health experts refer to as neglected tropical diseases—often-disabling illnesses that afflict 1.7 billion people worldwide, while getting notably less attention than the "big three" of HIV/AIDs, malaria, and tuberculosis. NTDs cause fewer deaths than those plagues, but they wreak untold suffering and economic loss.
Shortly before Hernández's book hit the shelves, the World Health Organization released its 2021-2030 roadmap for fighting NTDs. The plan sets targets for controlling, eliminating, or eradicating all the diseases on the WHO's list, through measures ranging from developing vaccines to improving healthcare infrastructure, sanitation, and access to clean water. Experts agree that for the campaign to succeed, leadership from wealthy nations—particularly the United States—is essential. But given the inward turn of many such countries in recent years (evidenced in movements ranging from America First to Brexit), and the continuing urgency of the COVID-19 crisis, public support is far from guaranteed.
As Hernández writes: "It is easier to forget a disease that cannot be seen." NTDs primarily affect residents of distant lands. They kill only 80,000 people a year, down from 204,000 in 1990. So why should Americans to bother to look?
Breaking the circle of poverty and disease
The World Health Organization counts 20 diseases as NTDs. Along with Chagas, they include dengue and chikungunya, which cause high fevers and agonizing pain; elephantiasis, which deforms victims' limbs and genitals; onchocerciasis, which causes blindness; schistosomiasis, which can damage the heart, lungs, brain, and genitourinary system; helminths such as roundworm and whipworm, which cause anemia, stunted growth, and cognitive disabilities; and a dozen more. Such ailments often co-occur in the same patient, exacerbating each other's effects and those of illnesses such as malaria.
NTDs may be spread by insects, animals, soil, or tainted water; they may be parasitic, bacterial, viral, or—in the case of snakebite envenoming—non-infectious. What they have in common is their longtime neglect by public health agencies and philanthropies. In part, this reflects their typically low mortality rates. But the biggest factor is undoubtedly their disempowered patient populations.
"These diseases occur in the setting of poverty, and they cause poverty, because of their chronic and debilitating effects," observes Peter Hotez, dean of the National School of Tropical Medicine at Baylor University and co-director of the Texas Children's Hospital for Vaccine Development. And historically, the everyday miseries of impoverished people have seldom been a priority for those who set the global health agenda.
That began to change about 20 years ago, when Hotez and others developed the conceptual framework for NTDs and early proposals for combating them. The WHO released its first roadmap in 2012, targeting 17 NTDs for control, elimination, or eradication by 2020. (Rabies, snakebite, and dengue were added later.) Since then, the number of people at risk for NTDs has fallen by 600 million, and 42 countries have eliminated at least one such disease. Cases of dracunculiasis—known as Guinea worm disease, for the parasite that creates painful blisters in a patient's skin—have dropped from the millions to just 27 in 2020.
Yet the battle is not over, and the COVID-19 pandemic has disrupted prevention and treatment programs around the globe.
A new direction — and longstanding obstacles
The WHO's new roadmap sets even more ambitious goals for 2030. Among them: reducing by 90 percent the number of people requiring treatment for NTDs; eliminating at least one NTD in another 100 countries; and fully eradicating dracunculiasis and yaws, a disfiguring skin infection.
The plan also places an increased focus on "country ownership," relying on nations with high incidence of NTDs to design their own plans based on local expertise. "I was so excited to see that," says Kristina Talbert-Slagle, director of the Yale College Global Health Studies program. "No one is a better expert on how to address these situations than the people who deal with it day by day."
Another fresh approach is what the roadmap calls "cross-cutting" targets. "One of the really cool things about the plan is how much it emphasizes coordination among different sectors of the health system," says Claire Standley, a faculty member at Georgetown University's Center for Global Health Science and Security. "For example, it explicitly takes into account the zoonotic nature of many neglected tropical diseases—the fact that we have to think about animal health as well as human health when we tackle NTDs."
Whether this grand vision can be realized, however, will depend largely on funding—and that, in turn, is a question of political will in the countries most able to provide it. On the upside, the U.S. has ended its Trump-era feud with the WHO. "One thing that's been really encouraging," says Standley, "has been the strong commitment toward global cooperation from the current administration." Even under the previous president, the U.S. remained the single largest contributor to the global health kitty, spending over $100 million annually on NTDs—six times the figure in 2006, when such financing started.
On the downside, America's outlay has remained flat for several years, and the Biden administration has so far not moved to increase it. A "back-of-the-envelope calculation," says Hotez, suggests that the current level of aid could buy medications for the most common NTDs for about 200 million people a year. But the number of people who need treatment, he notes, is at least 750 million.
Up to now, the United Kingdom—long the world's second-most generous health aid donor—has taken up a large portion of the slack. But the UK last month announced deep cuts in its portfolio, eliminating 102 previously supported countries and leaving only 34. "That really concerns me," Hotez says.
The struggle for funds, he notes, is always harder for projects involving NTDs than for those aimed at higher-profile diseases. His lab, which he co-directs with microbiologist Maria Elena Bottazzi, started developing a COVID-19 vaccine soon after the pandemic struck, for example, and is now in Phase 3 trials. The team has been working on vaccines for Chagas, hookworm, and schistosomiasis for much longer, but trials for those potential game-changers lag behind. "We struggle to get the level of resources needed to move quickly," Hotez explains.
Two million reasons to care
One way to prompt a government to open its pocketbook is for voters to clamor for action. A longtime challenge with NTDs, however, has been getting people outside the hardest-hit countries to pay attention.
The reasons to care, global health experts argue, go beyond compassion. "When we have high NTD burden," says Talbert-Slagle, "it can prevent economic growth, prevent innovation, lead to more political instability." That, in turn, can lead to wars and mass migration, affecting economic and political events far beyond an affected country's borders.
Like Hernández's aunt Dora, many people driven out of NTD-wracked regions wind up living elsewhere. And that points to another reason to care about these diseases: Some of your neighbors might have them. In the U.S., up to 14 million people suffer from neglected parasitic infections—including 70,000 with Chagas in California alone.
When Hernández was researching The Kissing Bug, she worried that such statistics would provide ammunition to racists and xenophobes who claim that immigrants "bring disease" or exploit overburdened healthcare systems. (This may help explain some of the stigma around NTDs, which led Tía Dora to hide her condition from most people outside her family.) But as the book makes clear, these infections know no borders; they flourish wherever large numbers of people lack access to resources that most residents of rich countries take for granted.
Indeed, far from gaming U.S. healthcare systems, millions of low-income immigrants can't access them—or must wait until they're sick enough to go to an emergency room. Since Congress changed the rules in 1996, green card holders have to wait five years before they can enroll in Medicaid. Undocumented immigrants can never qualify.
Closing the great divide
Hernández uses a phrase borrowed from global health crusader Paul Farmer to describe this access gap: "the great epi divide." On one side, she explains, "people will die from cancer, from diabetes, from chronic illnesses later in life. On the other side of the epidemiological divide, people are dying because they can't get to the doctor, or they can't get medication. They don't have a hospital anywhere near them. When I read Dr. Farmer's work, I realized how much that applied to neglected diseases as well."
When it comes to Chagas disease, she says, the epi divide is embodied in the lack of a federal mandate for prenatal or newborn screening. Each year, according to the Centers for Disease Control and Prevention, up to 300 babies in the U.S. are born with Chagas, which can be passed from the mother in utero. The disease can be cured with medication if treated in infancy. (It can also be cured in adults in the acute stage, but is seldom detected in time.) Yet the CDC does not require screening for Chagas—even though newborns are tested for 15 diseases that are less common. According to one study, it would be 10 times cheaper to screen and treat babies and their mothers than to cover the costs related to the illness in later years. Few states make the effort.
The gap that enables NTDs to persist, Hernández argues, is the same one that has led to COVID-19 death rates in Black and Latinx communities that are double those elsewhere in America. To close it, she suggests, caring is not enough.
"When I was working on my book," she says, "I thought about HIV in the '80s, when it had so much stigma that no one wanted to talk about it. Then activists stepped up and changed the conversation. I thought a lot about breast cancer, which was stigmatized for years, until people stepped forward and started speaking out. I thought about Lyme disease. And it wasn't only patients—it was also allies, right? The same thing needs to happen with neglected diseases around the world. Allies need to step up and make demands on policymakers. We need to make some noise."
Interview with Jamie Metzl: We need a global OS upgrade
In this Q&A, leading technology and healthcare futurist Jamie Metzl discusses a range of topics and trend lines that will unfold over the next several decades: whether a version of Moore's Law applies to genetic technologies, the ethics of genetic engineering, the dangers of gene hacking, the end of sex, and much more.
Metzl is a member of the WHO expert advisory committee on human genome editing and the bestselling author of Hacking Darwin.
The conversation was lightly edited by Leaps.org for style and length.
In Hacking Darwin, you describe how we may modify the human body with CRISPR technologies, initially to obtain unsurpassed sports performance and then to enhance other human characteristics. What would such power over human biology mean for the future of our civilization?
After nearly four billion years of evolution, our one species suddenly has the increasing ability to read, write, and hack the code of life. This will have massive implications across the board, including in human health and reproduction, plant and animal agriculture, energy and advanced materials, and data storage and computing, just to name a few. My book Hacking Darwin: Genetic Engineering and the Future of Humanity primarly explored how we are currently deploying and will increasingly use our capabilities to transform human life in novel ways. My next book, The Great Biohack: Recasting Life in an Age of Revolutionary Technology, coming out in May 2024, will examine the broader implications for all of life on Earth.
We humans will, over time, use these technologies on ourselves to solve problems and eventually to enhance our capabilities. We need to be extremely conservative, cautious, and careful in doing so, but doing so will almost certainly be part of our future as a species.
In electronics, Moore's law is an established theory that computing power doubles every 18 months. Is there any parallel to be drawn with genetic technologies?
The increase in speed and decrease in costs of genome sequencing have progressed far faster than Moore’s law. It took thirteen years and cost about a billion dollars to sequence the first human genome. Today it takes just a few hours and can cost as little as a hundred dollars to do a far better job. In 2012, Jennifer Doudna and Emmanuel Charpentier published the basic science paper outlining the CRISPR-cas9 genome editing tool that would eventually win them the Nobel prize. Only six years later, the first CRISPR babies were born in China. If it feels like technology is moving ever-faster, that’s because it is.
Let's turn to the topic of aging. Do you think that the field of genetics will advance fast enough to eventually increase maximal lifespan for a child born this year? How about for a person who is currently age 50?
The science of aging is definitely real, but that doesn’t mean we will live forever. Aging is a biological process subject to human manipulation. Decades of animal research shows that. This does not mean we will live forever, but it does me we will be able to do more to expand our healthspans, the period of our lives where we are able to live most vigorously.
The first thing we need to do is make sure everyone on earth has access to the resources necessary to live up to their potential. I live in New York City, and I can take a ten minute subway ride to a neighborhood where the average lifespan is over a decade shorter than in mine. This is true within societies and between countries as well. Secondly, we all can live more like people in the Blue Zones, parts of the world where people live longer, on average, than the rest of us. They get regular exercise, eat healthy foods, have strong social connections, etc. Finally, we will all benefit, over time, from more scientific interventions to extend our healthspan. This may include small molecule drugs like metformin, rapamycin, and NAD+ boosters, blood serum infusions, and many other things.
Science fiction has depicted a future where we will never get sick again, stay young longer or become immortal. Assuming that any of this is remotely possible, should we be afraid of such changes, even if they seem positive in some regards, because we can’t understand the full implications at this point?
Not all of these promises will be realized in full, but we will use these technologies to help us live healthier, longer lives. We will never become immortal becasue nothing lasts forever. We will always get sick, even if the balance of diseases we face shifts over time, as it has always done. It is healthy, and absolutely necessary, that we feel both hope and fear about this future. If we only feel hope, we will blind ourselves to the very real potential downsides. If we only feel fear, we will deny ourselves the very meaningful benefits these technologies have the potential to provide.
A fascinating chapter in Hacking Darwin is entitled The End of Sex. And you see that as a good thing?
We humans will always be a sexually reproducing species, it’s just that we’ll reproduce increasingly less through the physical act of sex. We’re already seeing this with IVF. As the benefits of technology assisted reproduction increase relative to reproduction through the act of sex, many people will come to see assisted reproduction as a better way to reduce risk and, over time, possibly increase benefits. We’ll still have sex for all the other wonderful reasons we have it today, just less for reproduction. There will always be a critical place in our world for Italian romantics!
What are dangers of genetic hackers, perhaps especially if everyone’s DNA is eventually transcribed for medical purposes and available on the internet and in the cloud?
The sky is really the limit for how we can use gentic technologies to do things we may want, and the sky is also the limit for potential harms. It’s quite easy to imagine scenarios in which malevolent actors create synthetic pathogens designed to wreak havoc, or where people steal and abuse other people’s genetic information. It wouldn’t even need to be malevolent actors. Even well-intentioned researchers making unintended mistakes could cause real harm, as we may have seen with COVID-19 if, as appears likely to me, the pandemic stems for a research related incident]. That’s why we need strong governance and regulatory systems to optimize benefits and minimize potential harms. I was honored to have served on the World Health Organization Expert Advisory Committee on Human Genome Editing, were we developed a proposed framework for how this might best be achieved.
You foresee the equivalent of a genetic arms race between the world's most powerful countries. In what sense are genetic technologies similar to weapons?
Genetic technologies could be used to create incredibly powerful bioweapons or to build gene drives with the potential to crash entire ecosystems. That’s why thoughtful regulation is in order. Because the benefits of mastering and deploying these technologies are so great, there’s also a real danger of a genetics arms race. This could be extremely dangerous and will need to be prevented.
In your book, you express concern that states lacking Western conceptions of human rights are especially prone to misusing the science of genetics. Does this same concern apply to private companies? How much can we trust them to control and wield these technologies?
This is a conversation about science and technology but it’s really a conversation about values. If we don’t agree on what core values should be promoted, it will be nearly impossible to agree on what actions do and do not make sense. We need norms, laws, and values frameworks that apply to everyone, including governments, corporations, researchers, healthcare providers, DiY bio hobbyists, and everyone else.
We have co-evolved with our technology for a very long time. Many of our deepest beliefs have formed in that context and will continue to do so. But as we take for ourselves the powers we have attributed to our various gods, many of these beliefs will be challenged. We can not and must not jettison our beliefs in the face of technology, and must instead make sure our most cherished values guide the application of our most powerful technologies.
A conversation on international norms is in full swing in the field of AI, prompted by the release of ChatGPT4 earlier this year. Are there ways in which it’s inefficient, shortsighted or otherwise problematic for these discussions on gene technologies, AI and other advances to be occurring in silos? In addition to more specific guidelines, is there something to be gained from developing a universal set of norms and values that applies more broadly to all innovation?
AI is yet another technology where the potential to do great good is tied to the potential to inflict signifcant harm. It makes no sense that we tend to treat each technology on its own rather than looking at the entire category of challenges. For sure, we need to very rapidly ramp up our efforts with regard to AI norm-setting, regulations, and governance at all levels. But just doing that will be kind of like generating a flu vaccine for each individual flu strain. Far better to build a universal flu vaccine addressing common elements of all flu viruses of concern.
That’s why we also need to be far more deliberate in both building a global operating systems based around the mutual responsibilities of our global interdependence and, under that umbrella, a broader system for helping us govern and regulate revolutionary technologies. Such a process might begin with a large international conference, the equivalent of Rio 1992 for climate change, but then quickly work to establish and share best practices, help build parallel institutions in all countries so people and governamts can talk with each other, and do everything possible to maximize benefits and minimize risks at all levels in an ongoing and dynamic way.
At what point might genetic enhancements lead to a reclassfication of modified humans as another species?
We’ll still all be fellow humans for a very, very long time. We already have lots of variation between us. That is the essence of biology. Will some humans, at some point in the future, leave Earth and spend generations elsewhere? I believe so. In those new environments, humans will evolve, over time, differently than those if us who remain on this planet? This may sound like science fiction, but the sci-fi future is coming at us faster than most people realize.
Is the concept of human being changing?
Yes. It always has and always will.
Another big question raised in your book: what limits should we impose on the freedom to manipulate genetics?
Different societies will come to different conclusion on this critical question. I am sympathetic to the argument that people should have lots of say over their own bodies, which why I support abortion rights even though I recognize that an abortion can be a violent procedure. But it would be insane and self-defeating to say that individuals have an unlimited right to manipulate their own or their future children’s heritable genetics. The future of human life is all of our concern and must be regulated, albeit wisely.
In some cases, such as when we have the ability to prevent a deadly genetic disroder, it might be highly ethical to manipulate other human beings. In other circumstances, the genetic engineering of humans might be highly unethical. The key point is to avoid asking this question in a binary manner. We need to weigh the costs and benefits of each type of intervention. We need societal and global infrastrucutres to do that well. We don’t yet have those but we need them badly.
Can you tell us more about your next book?
The Great Biohack: Recasting Lifee in an Age of Revolutionary Technology, will come out in May 2024. It explores what the intersecting AI, genetics, and biotechnology revolutions will mean for the future of life on earth, including our healthcare, agriculture, industry, computing, and everything else. We are at a transitional moment for life on earth, equivalent to the dawn of agriculture, electricity, and industrialization. The key differentiator between better and worse outcomes is what we do today, at this early stage of this new transformation. The book describes what’s happening, what’s at stake, and what we each and all can and, frankly, must do to build the type of future we’d like to inhabit.
You’ve been a leader of international efforts calling for a full investigation into COVID-19 origins and are the founder of the global movement OneShared.World. What problem are you trying to solve through OneShared.World?
The biggest challenge we face today is the mismatch between the nature of our biggest problems, global and common, and the absence of a sufficient framework for addressing that entire category of challenges. The totally avoidable COVID-19 pandemic is one example of the extremet costs of the status quo. OneShared.World is our effort to fight for an upgrade in our world’s global operating system, based around the mutual responsibilities of interdependence. We’ve had global OS upgrades before after the Thirty Years War and after World War II, but wouldn’t it be better to make the necessary changes now to prevent a crisis of that level stemming from a nuclear war, ecosystem collapse, or deadlier synthetic biology pandemic rather than waiting until after? Revolutionary science is a global issue that must be wisely managed at every level if it is to be wisely managed at all.
How do we ensure that revolutionary technologies benefit humanity instead of undermining it?
That is the essential question. It’s why I’ve written Hacking Darwin, am writing The Great Biohack, and doing the rest of my work. If we want scietific revolutions to help, rather than hurt, us, we must all play a role building that future. This isn’t just a conversation about science, it’s about how we can draw on our most cherished values to guide the optimal development of science and technology for the common good. That must be everyone’s business.
Portions of this interview were first published in Grassia (Italy) and Zen Portugal.
Jamie Metzl is one of the world’s leading technology and healthcare futurists and author of the bestselling book, Hacking Darwin: Genetic Engineering and the Future of Humanity, which has been translated into 15 languages. In 2019, he was appointed to the World Health Organization expert advisory committee on human genome editing. Jamie is a faculty member of Singularity University and NextMed Health, a Senior Fellow of the Atlantic Council, and Founder and Chair of the global social movement, OneShared.World.
Called “the original COVID-19 whistleblower,” his pioneering role advocating for a full investigation into the origins of the COVID-19 pandemic has been featured in 60 Minutes, the New York Times, and most major media across the globe, and he was the lead witness in the first congressional hearings on this topic. Jamie previously served in the U.S. National Security Council, State Department, and Senate Foreign Relations Committee and with the United Nations in Cambodia. Jamie appears regularly on national and international media and his syndicated columns and other writing in science, technology, and global affairs are featured in publications around the world.
Jamie sits on advisory boards for multiple biotechnology and other companies and is Special Strategist to the WisdomTree BioRevolution Exchange Traded Fund. In addition to Hacking Darwin, he is author of a history of the Cambodian genocide, the historical novel The Depths of the Sea, and the genetics sci-fi thrillers Genesis Code and Eternal Sonata. His next book, The Great Biohack: Recasting Life in an age of Revolutionary Technology, will be published by Hachette in May 2024. Jamie holds a Ph.D. from Oxford, a law degree from Harvard, and an undergraduate degree from Brown and is an avid ironman triathlete and ultramarathon runner.
Creamy milk with velvety texture. Dark with sprinkles of sea salt. Crunchy hazelnut-studded chunks. Chocolate is a treat that appeals to billions of people worldwide, no matter the age. And it’s not only the taste, but the feel of a chocolate morsel slowly melting in our mouths—the smoothness and slipperiness—that’s part of the overwhelming satisfaction. Why is it so enjoyable?
That’s what an interdisciplinary research team of chocolate lovers from the University of Leeds School of Food Science and Nutrition and School of Mechanical Engineering in the U.K. resolved to study in 2021. They wanted to know, “What is making chocolate that desirable?” says Siavash Soltanahmadi, one of the lead authors of a new study about chocolates hedonistic quality.
Besides addressing the researchers’ general curiosity, their answers might help chocolate manufacturers make the delicacy even more enjoyable and potentially healthier. After all, chocolate is a billion-dollar industry. Revenue from chocolate sales, whether milk or dark, is forecasted to grow 13 percent by 2027 in the U.K. In the U.S., chocolate and candy sales increased by 11 percent from 2020 to 2021, on track to reach $44.9 billion by 2026. Figuring out how chocolate affects the human palate could up the ante even more.
Building a 3D tongue
The team began by building a 3D tongue to analyze the physical process by which chocolate breaks down inside the mouth.
As part of the effort, reported earlier this year in the scientific journal ACS Applied Materials and Interfaces, the team studied a large variety of human tongues with the intention to build an “average” 3D model, says Soltanahmadi, a lubrication scientist. When it comes to edible substances, lubrication science looks at how food feels in the mouth and can help design foods that taste better and have more satisfying texture or health benefits.
There are variations in how people enjoy chocolate; some chew it while others “lick it” inside their mouths.
Tongue impressions from human participants studied using optical imaging helped the team build a tongue with key characteristics. “Our tongue is not a smooth muscle, it’s got some texture, it has got some roughness,” Soltanahmadi says. From those images, the team came up with a digital design of an average tongue and, using 3D printed molds, built a “mimic tongue.” They also added elastomers—such as silicone or polyurethane—to mimic the roughness, the texture and the mechanical properties of a real tongue. “Wettability" was another key component of the 3D tongue, Soltanahmadi says, referring to whether a surface mixes with water (hydrophilic) or, in the case of oil, resists it (hydrophobic).
Notably, the resulting artificial 3D-tongues looked nothing like the human version, but they were good mimics. The scientists also created “testing kits” that produced data on various physical parameters. One such parameter was viscosity, the measure of how gooey a food or liquid is — honey is more viscous compared to water, for example. Another was tribology, which defines how slippery something is — high fat yogurt is more slippery than low fat yogurt; milk can be more slippery than water. The researchers then mixed chocolate with artificial saliva and spread it on the 3D tongue to measure the tribology and the viscosity. From there they were able to study what happens inside the mouth when we eat chocolate.
The team focused on the stages of lubrication and the location of the fat in the chocolate, a process that has rarely been researched.
The artificial 3D-tongues look nothing like human tongues, but they function well enough to do the job.
Courtesy Anwesha Sarkar and University of Leeds
The oral processing of chocolate
We process food in our mouths in several stages, Soltanahmadi says. And there is variation in these stages depending on the type of food. So, the oral processing of a piece of meat would be different from, say, the processing of jelly or popcorn.
There are variations with chocolate, in particular; some people chew it while others use their tongues to explore it (within their mouths), Soltanahmadi explains. “Usually, from a consumer perspective, what we find is that if you have a luxury kind of a chocolate, then people tend to start with licking the chocolate rather than chewing it.” The researchers used a luxury brand of dark chocolate and focused on the process of licking rather than chewing.
As solid cocoa particles and fat are released, the emulsion envelops the tongue and coats the palette creating a smooth feeling of chocolate all over the mouth. That tactile sensation is part of the chocolate’s hedonistic appeal we crave.
Understanding the make-up of the chocolate was also an important step in the study. “Chocolate is a composite material. So, it has cocoa butter, which is oil, it has some particles in it, which is cocoa solid, and it has sugars," Soltanahmadi says. "Dark chocolate has less oil, for example, and less sugar in it, most of the time."
The researchers determined that the oral processing of chocolate begins as soon as it enters a person’s mouth; it starts melting upon exposure to one’s body temperature, even before the tongue starts moving, Soltanahmadi says. Then, lubrication begins. “[Saliva] mixes with the oily chocolate and it makes an emulsion." An emulsion is a fluid with a watery (or aqueous) phase and an oily phase. As chocolate breaks down in the mouth, that solid piece turns into a smooth emulsion with a fatty film. “The oil from the chocolate becomes droplets in a continuous aqueous phase,” says Soltanahmadi. In other words, as solid cocoa particles and fat are released, the emulsion envelops the tongue and coats the palette, creating a smooth feeling of chocolate all over the mouth. That tactile sensation is part of the chocolate’s hedonistic appeal we crave, says Soltanahmadi.
Finding the sweet spot
After determining how chocolate is orally processed, the research team wanted to find the exact sweet spot of the breakdown of solid cocoa particles and fat as they are released into the mouth. They determined that the epicurean pleasure comes only from the chocolate's outer layer of fat; the secondary fatty layers inside the chocolate don’t add to the sensation. It was this final discovery that helped the team determine that it might be possible to produce healthier chocolate that would contain less oil, says Soltanahmadi. And therefore, less fat.
Rongjia Tao, a physicist at Temple University in Philadelphia, thinks the Leeds study and the concept behind it is “very interesting.” Tao, himself, did a study in 2016 and found he could reduce fat in milk chocolate by 20 percent. He believes that the Leeds researchers’ discovery about the first layer of fat being more important for taste than the other layer can inform future chocolate manufacturing. “As a scientist I consider this significant and an important starting point,” he says.
Chocolate is rich in polyphenols, naturally occurring compounds also found in fruits and vegetables, such as grapes, apples and berries. Research found that plant polyphenols can protect against cancer, diabetes and osteoporosis as well as cardiovascular ad neurodegenerative diseases.
Not everyone thinks it’s a good idea, such as chef Michael Antonorsi, founder and owner of Chuao Chocolatier, one of the leading chocolate makers in the U.S. First, he says, “cacao fat is definitely a good fat.” Second, he’s not thrilled that science is trying to interfere with nature. “Every time we've tried to intervene and change nature, we get things out of balance,” says Antonorsi. “There’s a reason cacao is botanically known as food of the gods. The botanical name is the Theobroma cacao: Theobroma in ancient Greek, Theo is God and Brahma is food. So it's a food of the gods,” Antonorsi explains. He’s doubtful that a chocolate made only with a top layer of fat will produce the same epicurean satisfaction. “You're not going to achieve the same sensation because that surface fat is going to dissipate and there is no fat from behind coming to take over,” he says.
Without layers of fat, Antonorsi fears the deeply satisfying experiential part of savoring chocolate will be lost. The University of Leeds team, however, thinks that it may be possible to make chocolate healthier - when consumed in limited amounts - without sacrificing its taste. They believe the concept of less fatty but no less slick chocolate will resonate with at least some chocolate-makers and consumers, too.
Chocolate already contains some healthful compounds. Its cocoa particles have “loads of health benefits,” says Soltanahmadi. Dark chocolate usually has more cocoa than milk chocolate. Some experts recommend that dark chocolate should contain at least 70 percent cocoa in order for it to offer some health benefit. Research has shown that the cocoa in chocolate is rich in polyphenols, naturally occurring compounds also found in fruits and vegetables, such as grapes, apples and berries. Research has shown that consuming plant polyphenols can be protective against cancer, diabetes and osteoporosis as well as cardiovascular and neurodegenerative diseases.
“So keeping the healthy part of it and reducing the oily part of it, which is not healthy, but is giving you that indulgence of it … that was the final aim,” Soltanahmadi says. He adds that the team has been approached by individuals in the chocolate industry about their research. “Everyone wants to have a healthy chocolate, which at the same time tastes brilliant and gives you that self-indulging experience.”