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Yellow food dye can make living tissue transparent − these methods could one day improve cancer treatment, blood draws and even tattoo removal

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theconversation.com – Guosong Hong, Assistant Professor of Materials Science and Engineering, Stanford University – 2024-09-05 13:04:52

A dye called FD&C Yellow 5 could have some useful scientific properties.
Noppawat Tom Charoensinphon/Moment via Getty Images

Guosong Hong, Stanford University

Why isn’t your body transparent? Some animals such as jellyfish, zebra fish and some glass frogs have see-through bodies. But most mammals, including humans, aren’t transparent.

While the idea of a transparent body might seem odd or even a bit creepy, it could actually be really helpful for doctors. If our bodies were transparent, doctors could easily see inside to diagnose diseases in organs such as the liver, spleen and brain. They wouldn’t need invasive procedures such as biopsies or expensive machines such as CT scanners and MRIs.

I’m a materials scientist, and my team and I work on how new materials can aid biomedicine. My colleagues and I have wondered whether it’s possible to make living tissue transparent temporarily to aid in medical treatments and other uses.

We discovered that by dissolving certain dye molecules, including a food dye commonly used in snacks called FD&C Yellow 5, into water, we can change the way light travels through the water. We used this phenomenon to make organic tissue – specifically the thin skin of mice – transparent in our study, published in September 2024 in Science.

Refractive indices

Our bodies, like those of most mammals, aren’t transparent mainly because of how light interacts with our tissues. Normally, light travels in a straight line through the air. But when light hits the human body, it doesn’t go very far before its path gets scattered. The light bounces around in different directions instead of traveling straight through. If light passed through us without scattering, our tissue would be transparent.

This scattering happens because human tissues are made up of many different components, including water, fats and proteins. Each of these components slows down light differently, a property known as the refractive index.

For example, water has a refractive index of about 1.33, while fats and proteins have a higher refractive index of around 1.45 in the visible spectrum. So, light travels more slowly in lipids than in water.

The key to making living tissue transparent would be to reduce the differences in how light moves through different parts of the tissue – specifically between water and fats and proteins.

Kramers-Kronig relations

A principle in physics known as the Kramers-Kronig relations explains how if a material absorbs more light of one color, such as blue, this increased absorption will change how light of a different color, such as red, moves through it. Kramers-Kronig relations say that the colors of light are not independent of each other but connected.

FD&C Yellow 5 absorbs blue light strongly, which yields its characteristic orange-to-red color when dissolved in water. This happens because the blue part of the light is absorbed, leaving only the orange-to-red part visible. As a result of the Kramers-Kronig relations, this absorption of blue light increases the refractive index of water for red light. The water’s refractive index increases from 1.33 and matches that of fats and proteins, around 1.45.

When the refractive indices match, red light no longer scatters as much. It travels in water the same way that it does in fats in the tissue. So, the whole tissue appears as a single, uniform material. This process can make the tissue look transparent, even though it’s normally opaque.

Turning tissue transparent

My research team applied this idea in an experiment using a scattering phantom, which is a material designed to mimic the opaqueness of human skin. As we added more FD&C Yellow 5 dye to the phantom, it became more orange-red in color, just as we expected.

However, something else happened. It became more transparent to red light. This increased transparency allowed us to see the grid pattern on the table underneath the phantom.

We then decided to test this idea on a piece of chicken breast from the grocery store. Unless it’s sliced very thin, chicken meat usually looks opaque.

When we soaked the chicken breast in a solution containing FD&C Yellow 5 dye, something amazing happened. It became more transparent, allowing us to clearly see a Stanford sign placed underneath.

Finally, we used this idea to make the skin of a mouse optically transparent. We applied the FD&C Yellow 5 dye to different parts of the mouse’s body. When we added it to the mouse’s scalp, we could see the blood vessels in its brain. When we added it to the mouse’s belly, we could see its gut. When we added it to the mouse’s limbs, we could see its muscle fibers.

All this experiment took was gently massaging a solution of the dye into the mouse’s skin and a bit of patience.

This process is noninvasive because it doesn’t require tissue removal or surgery, and the skin returns to its normal opacity once you rinse off the dye with water. Although it’s a fascinating technique, we strongly advise against trying this on yourself.

While the use of Yellow 5 is approved by the FDA, some people have raised concerns about its potential health risks. These include allergic reactions – particularly in people with asthma – hyperactivity in children and potential links to cancer. But researchers will need to conduct more tests to determine whether there are any dangers.

Future uses

So what could this approach be used for? Right now, it works best on very thin layers of skin, like that of a mouse.

Unfortunately, human skin is much thicker, so this method isn’t quite ready for practical use on people yet. Also, the red color of the dye means that the color balance isn’t quite right and the transparency isn’t perfect across the entire visible spectrum. The dye still blocks blue light.

My colleagues and I are working on improving this technique to make it more effective for human tissues. We’re also trying to shift the dye’s absorption toward the ultraviolet spectrum, which would create a more balanced transparency effect across all visible colors.

Looking ahead, this technology one day could make veins more visible, making it easier to perform venipuncture – the process of drawing blood or injecting fluids through a needle – especially in elderly patients with hard-to-see veins.

A nurse drawing blood from a senior patient's arm.
Having a window of transparent skin could help make veins more visible during blood draws.
Yoshiyoshi Hirokawa/DigitalVision via Getty Images

It could also aid in the early detection of skin cancer, enhance light delivery into deep tissues for photodynamic and photothermal therapies and simplify laser-based tattoo removal.

In photodynamic and photothermal therapies, doctors use a laser to kill cancerous and precancerous cells. But light from the laser penetrates only so far into the tissue, so these therapies aren’t suitable for organs deeper in the body – yet.

All of these applications could benefit from a reversible, on-demand transparency window into the body.The Conversation

Guosong Hong, Assistant Professor of Materials Science and Engineering, Stanford University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Mark Zuckerberg thinks workplaces need to ‘man up’ − here’s why that’s bad for all employees, no matter their gender

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theconversation.com – Adam Stanaland, Assistant Professor of Psychology, University of Richmond – 2025-01-23 07:48:00

Meta CEO Mark Zuckerberg attends a UFC match on Feb. 17, 2024.

Sean M. Haffey/Getty Images

Adam Stanaland, University of Richmond

When Meta CEO Mark Zuckerberg appeared on a Jan. 10, 2025, episode of “The Joe Rogan Experience,” he lamented that corporate culture had become too “feminine,” suppressing its “masculine energy” and abandoning supposedly valuable traits such as aggression.

The workplace, he concluded, has been “neutered.”

Perhaps not surprisingly, Zuckerberg has also embraced stereotypically masculine pursuits in his personal life. He’s become a mixed martial arts aficionado and has shared his affinity for smoking meats. On his expansive Hawaii compound, he’s even taken up bow-and-arrow pig hunting.

He’s come a long way from the geeky image of his youth.

But is Zuckerberg right? Do workplaces in the U.S. need to embrace a more diesel-fueled, street-fighting, meat-eating mentality?

As a social psychologist who studies masculinity and aggression, I think it’s important to evaluate what the science says about Zuckerbeg’s claims – and to consider what it means for the future of workplace culture in the U.S.

Show no weakness

In 2018, sociologist Jennifer Berdahl and her colleagues coined the term “masculinity contest culture” to describe workplaces rife with cutthroat competition, toxic leadership, bullying and harassment.

Integrating decades of prior research on masculinity in the workplace, Berdahl and her collaborators were able to map how masculinity contest cultures operate, as well as show how they affect organizations and individual employees.

In her experiments, she had participants agree or disagree with statements such as “expressing any emotion other than anger or pride is seen as weak,” based on their perceptions of their own organization. Using advanced statistical techinques, Berdahl’s team was able to distill masculinity contest cultures down to four components: “showing no weakness,” “strength and stamina,” “putting work first” and “dog eat dog.”

Then they were able to show how these cultures are tied to a host of negative outcomes for workers and companies, such as burnout, turnover and poor well-being. And at the organization level, they can foment a dysfunctional office environment, toxic leadership and even bullying and harassment.

An imagined grievance

Based on this research, then, it seems like promoting rigid masculinity in the workplace is not the best solution for an arguably already struggling Meta.

What, then, led Zuckerberg to claim that the workplace has been neutered and must be infused with masculine energy? Has the American office really gone full “Legally Blonde”?

Zuckerberg’s own company isn’t exactly a paragon of parity: Its total workforce, as of 2022, was nearly two-thirds male, while its tech workforce was three-quarters male. Furthermore, according to psychologists Sapna Cheryan and Hazel Markus, workplaces in the U.S. still reflect what they call “masculine defaults” – cultures that reward characteristics or behaviors generally associated with men.

This can range from how companies describe themselves – for example, as places that are “aggressive” and “unrestrained” – to hosting events catering to traditionally male pursuits, such as golf outings.

A group of men observe another man participating in a golf simulator.

Many workplaces in the U.S. still promote and prize traditionally masculine traits and pursuits.

Daniel Boczarski/Getty Images for PXG

Although Cheryan and Markus’ analysis centers on how masculine defaults make it harder for women to carve out their professional paths, they can harm everybody, including men.

My research, for example, has shown that when men feel pressured to fulfill certain masculine expectations, they can develop fragile masculine identities, which are linked with aggression and anxiety.

Although the pervasiveness of masculinity norms can give men an upper hand in the workplace, I wonder whether men are contorting themselves to fit into outdated molds of who succeeds at work. Indeed, research shows that successful organizations promote a healthy mix of stereotypically masculine and feminine qualities.

In other words, it’s best when people of all genders feel comfortable showcasing traits such as cooperation and agency, qualities that don’t necessarily fall into one gender camp.

The rise of the fragile billionaire

If many workplaces still possess dog-eat-dog cultures and celebrate masculinity – with evidently poor outcomes – you might wonder why billionaire corporate leaders would advocate for them.

The most generous explanation is ignorance. Zuckerberg could simply be unaware that most offices in the U.S. still possess competitive environments and traits associated with traditional masculinity.

Although this could be the case, I think there could be two other explanations for Zuckerberg’s promotion of rigid masculinity norms.

There could be an economic motive. Perhaps Zuckerberg thinks that promoting his company as an arena of high-stakes competition and aggression is the best way to attract talent and spur innovation in a field already dominated by men. It’s often thought that competition drives innovation. So “Meta needs to be more masculine” could actually be code for “Meta needs to breed more internal competition, which will spur innovation and turn a profit.” This assumption is also misguided: Recent research has shown that internal competition may actually stifle innovation.

There could also be a psychological motive. I’ve found in my research that men are most likely to cling to notions of rigid masculinity when they feel pressure to “man up” and are insecure about themselves.

Perhaps Zuckerberg sees diversity efforts as a challenge to his power. Maybe he thinks aligning himself with President Donald Trump’s version of masculinity will help him gain and retain power, especially as he faces challenges from other tech giants. So his promotion of an aggressive workplace, along with his slashing of policies that could make him look “weak,” are moves to reinforce his status as a leader, as an innovator and as a man.

This isn’t to say that activities such as hunting and mixed martial arts are inherently bad, or even inherently masculine: There are plenty of female hunters and UFC fighters. Nor is it to say that certain masculine characteristics in the workplace are inherently bad.

But when I see middle-aged billionaires – Zuckerberg isn’t the only one – exhibiting the signs of fragile masculinity that I’ve observed among young adult men and adolescent boys, I can’t help but wonder what the country’s future holds.The Conversation

Adam Stanaland, Assistant Professor of Psychology, University of Richmond

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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FDA bans Red 3 dye from food and drugs – a scientist explains the artificial color’s health risks and long history

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theconversation.com – Lorne J. Hofseth, Professor and Associate Dean for Research, College of Pharmacy, University of South Carolina – 2025-01-23 07:45:00

Look out for Red 3, FD&C Red No. 3, erythrosine or E127 in the ingredients list of your favorite processed foods.

Anhelina Chumak/iStock via Getty Images Plus

Lorne J. Hofseth, University of South Carolina

Red 3 – also called FD&C Red No. 3, erythrosine or E127 – has been widely used in food, cosmetics and pharmaceuticals since its FDA approval in 1969. You’ve likely encountered Red 3 before. It’s a common additive to many candies, beverages, baked goods, cereals, maraschino cherries and gelatin desserts, as well as certain medications, syrups and cosmetics.

However, mounting scientific evidence suggests that consuming Red 3 poses significant health risks. These risks prompted California to ban its use in food in 2023 and the Food and Drug Administration to ban its use in both food and pharmaceuticals nationwide on Jan. 15, 2025.

As a researcher studying inflammation and cancer, I investigate how synthetic food dyes affect human health. Stricter regulations reflect growing concerns over the negative physiological effects of Red 3 and other synthetic dyes on your body, including causing cancer.

Health risks of Red 3

Over the past 35 years, an increasing amount of scientific evidence has identified the negative health effects of Red 3. While researchers haven’t yet established a direct link between Red 3 and cancer in people, substantial evidence from animal studies points to its carcinogenic potential.

First, Red 3 disrupts thyroid hormone regulation through several mechanisms. It inhibits the thyroid gland’s ability to absorb iodine, a key component for synthesizing thyroid hormones, and blocks an enzyme essential for converting one thyroid hormone to another, contributing to thyroid dysfunction. Along with other impairments in thyroid hormone function, Red 3 increases the risk of thyroid-related disorders.

Second, Red 3 may promote thyroid tumor formation. Several studies exposing rats and pigs to Red 3 observed enlarged tumorous thyroid glands and abnormalities in hormone regulation.

Third, Red 3 can have toxic effects on the brain in multiple ways. Rat studies have found that this synthetic dye increases oxidative stress, which damages tissues, and reduces the antioxidants that control oxidative stress, impairing communication between neurons. Studies in rodents also found that Red 3 triggers neuroinflammation that leads to neuronal damage and dysfunction. Additionally, Red 3 may interact with the amyloid-beta peptides linked to neurodegenerative conditions like Alzheimer’s disease and worsen those conditions.

Regulatory momentum

Red 3 first faced scrutiny in the 1980s when several animal studies linked it to thyroid tumors in male rats. This led to its 1990 ban in cosmetics in the U.S., although its use in food persisted under industry pressure. While the European Union restricted the use of Red 3 to only certain types of processed cherries in 1994, the U.S. has lagged behind.

California’s 2023 ban of Red 3 in foods, effective in 2027, reignited debate on Red 3 and its link to cancer and spurred 24 organizations to advocate for federal action.

Several countries have banned the use of Red 3 in food. Until January 2025, the U.S. had only banned it in cosmetics and topical drugs.

This debate culminated in the FDA’s nationwide ban in January 2025. While the FDA cites no direct evidence of Red 3’s carcinogenic effect in people, it acknowledges that animal studies provide sufficient basis for regulatory action. The FDA’s decision aligns with the 1958 Delaney Clause of the Federal Food, Drug and Cosmetic Act, mandating a ban on additives shown to cause cancer in humans or animals.

Notably, it took over 35 years from the initial findings of thyroid cancer in rodents to the eventual ban in 2025.

A path forward

The progression from Red 3’s approval to its prohibition highlights the conflict between industrial interests and public health. Continued vigilance over Red 3 could help the nation prioritize consumer safety.

Under the FDA’s mandate, manufacturers must reformulate food products and ingested drugs to leave out Red 3 by January 2027 and January 2028, respectively. While some countries still permit use of Red 3, U.S. imports must meet domestic safety standards. Harmonizing global standards on regulating and evaluating synthetic dyes is essential to protect consumer health.

Close-up of colorful cereal loops

Stronger, more standardized regulation of synthetic food dyes would help protect consumer health.

choness/iStock via Getty Images

Several companies selling ultra-processed foods have begun the shift away from synthetic dyes. In 2016, Mars announced plans to remove all artificial colors from its human food products over a five-year period. In 2024, General Mills announced that it would eliminate artificial colors and flavors from its products.

Consumers can protect themselves from Red 3 exposure by reading ingredient labels for “FD&C Red No. 3” or “E127” and choosing products that use natural dyes. Preparing homemade foods with natural color alternatives like beet juice or turmeric is another option. Supporting dye-free brands and staying informed about regulatory changes can further reduce your exposure while promoting safer food practices.

Ongoing research and policy reforms focused on public safety could help ensure that food additives like Red 3 no longer put consumer health at risk.The Conversation

Lorne J. Hofseth, Professor and Associate Dean for Research, College of Pharmacy, University of South Carolina

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As Gaza ceasefire takes hold, Israeli forces turn to Jenin – a regular target seen as a center of Palestinian resistance

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theconversation.com – Maha Nassar, Associate Professor in the School of Middle Eastern and North African Studies, University of Arizona – 2025-01-22 17:42:00

Maha Nassar, University of Arizona

Just two days after a shaky ceasefire took hold in the Gaza Strip, Israel on Jan. 21, 2025, launched a large-scale incursion of the Jenin refugee camp in the West Bank.

Soldiers raided hundreds of homes in the West Bank city in what the Israeli military called a “counterterrorism” operation, aiming to reassert control there. Many analysts have suggested the raid is an attempt by Israeli Prime Minister Benjamin Netanyahu to appease far-right members of his coalition who oppose the ceasefire deal.

Whatever the motive, the offensive has been devastating for many of the camp’s residents. The Israeli military has destroyed infrastructure, closed entrances to local hospitals and forcibly displaced about 2,000 families, according to reports on the raids. As it was, life for inhabitants of the densely populated camp – home to some 24,000 Palestinian refugees – was hard. The West Bank director of UNRWA, the U.N. agency overseeing refugees, recently described camp conditions as “nearly uninhabitable.”

The focus of the latest Israeli operation is not new. The Jenin refugee camp, on the western edge of the town of Jenin in the north of the occupied West Bank, has often experienced violence between Israeli soldiers and Palestinian militants.

That violence has escalated since the Oct. 7, 2023, attacks, when Hamas gunmen led an incursion into Israel in which around 1,200 people were killed. The camp has faced repeated large-scale military operations by Israeli forces, including drone strikes, ground raids, and airstrikes that have caused widespread destruction. Meanwhile, Israeli settlers have torched Palestinian cars and properties, with 64 such attacks in the Jenin area alone since Oct. 7, 2023. Last December, the Palestinian Authority, which coordinates with Israel to oversee security in parts of the West Bank, also attacked local militants.

These events have deepened political tensions and worsened the economic and humanitarian crises in the West Bank. According to the U.N., more than a quarter of the 800-plus Palestinians killed in the West Bank since Oct. 7 attack have come from the Jenin district; several Israeli civilians have also been killed in the West Bank during the same period.

As a scholar of Palestinian history, I see this recent episode as the latest chapter in a much longer history of Palestinian displacement and defiance of Israeli occupation. Understanding this history helps explain why the Jenin camp in particular has become a target of Israeli offensives and a center of Palestinian militant resistance.

Camp conditions

Jenin, an agricultural town that dates back to ancient times, has long been a center of Palestinian resistance. During the 1948 Arab-Israeli War, Arab fighters successfully pushed back Israeli attempts to capture the town.

At the end of that war, the town became a refuge for some of the hundreds of thousands of Palestinian refugees who fled or were expelled from lands that became part of Israel. Jenin, along with the hilly interior of Palestine known as the West Bank, was annexed by Jordan.

The U.N. Relief and Works Agency established the Jenin camp in 1953, just west of the city. Since then, the agency has provided basic services to the camp’s residents, including food, housing and education.

Camp conditions have always been difficult. In the early years of the camp, refugees had to stand in long lines to receive food rations, and for decades their cramped homes lacked electricity or running water.

The Jenin camp soon became the poorest and most densely populated of the West Bank’s 19 refugee camps. And given its location near the “Green Line” – the armistice line that serves as Israel’s de facto border – camp residents who were expelled from northern Palestine could actually see the homes and villages from which they were expelled. But they were prevented from returning to them.

The rise of militancy

Since 1967, Jenin, along with the rest of the West Bank, has been occupied by the Israeli military.

The Israeli occupation of Jenin compounded the difficulties of these refugees. As stateless Palestinians, they couldn’t return home. But under Israeli occupation, they couldn’t live freely in Jenin, either. Human rights groups have long documented what has been described as “systematic oppression,” which includes discriminatory land seizures, forced evictions and travel restrictions.

Seeing no other path forward, many of the camp’s young refugees turned to armed resistance.

In the 1980s, groups such as the Black Panthers, which was affiliated with the Palestinian nationalist Fatah organization, launched attacks on Israeli targets in an effort to end the occupation and liberate their ancestral lands. Throughout the first intifada – a Palestinian uprising lasting from 1987 to 1993 – the Israeli army raided the Jenin camp many times, seeking to arrest members of militant groups. In the process, Israeli forces also sometimes demolished family members’ homes and arrested relatives. Such acts of apparent collective punishment reinforced the idea for many Palestinians that the Israeli occupation could only be ended by force.

A group of men in headscarves stand in front of flags and banners. One holds a pistol up in the air.
Members of the militant group Fatah in Jenin in 1991.
Esaias Baitel/Gamma-Rapho via Getty Images)

The Oslo peace process of the 1990s – which consisted of a series of meetings between Israeli government and Palestinian representatives – led some former militants to hope that the occupation could be ended through negotiations instead. But Jenin’s camp residents remained marginalized in the West Bank and sealed off from Israel, seeing little improvement in their lives, even after the transfer of administrative powers from Israel to the Palestinian Authority in 1995.

Independent projects like the The Freedom Theatre provided some relief to the camp’s refugee children, but it was not enough to overcome the grinding poverty or the violence they faced from Israeli soldiers and settlers. By the time the second intifada broke out in 2000, many of the camp’s teenagers joined militant groups. That included Freedom Theatre co-founder Zakaria Zubeidi, who joined the Fatah-affiliated Al-Aqsa Martyrs Brigade. Like the youth of the 1980s, they, too, concluded that only armed resistance would bring an end to the occupation.

A cycle of violence?

In April 2002, the Israeli army invaded the Jenin camp, hoping to put an end to such armed groups. There were fierce clashes between Israeli soldiers and young Palestinian men in the camp, solidifying Jenin’s reputation among Palestinians as “the capital of the resistance.”

The lack of progress on peace talks since then, Israel’s settlement building on occupied land – deemed illegal under international law – and the inclusion of hard-line Israeli politicians in the government have exacerbated resentment in the camp. Polls show Palestinians increasingly support armed resistance.

Seeking to protect the camp from Israeli incursions, in 2021 a group of local residents formed the Jenin Brigades. While its founder was affiliated with Palestinian Islamic Jihad, the group quickly drew in militants from various political factions. Members acquired weapons, patrolled the streets and fought off Israeli military incursions. By 2022, they had declared parts of the camp to be “liberated” from the Israeli occupation.

Seemingly alarmed by the increase in militancy and the stockpiling of weapons in the camp, Israel dramatically stepped up its raids in 2022. It was during such a raid that Palestinian American journalist Shireen Abu Akleh was killed by an Israeli soldier.

On July 3, 2023, the Israeli military again invaded Jenin, withdrawing after two days of heavy aerial bombardment and a ground invasion that killed 12 Palestinians and wounded over 100.

The latest offensive could well surpass that death toll, with at least 10 killed in the first day of fighting. But the militancy associated with the camp was built on decades of resistance and defiance to occupation that Israel has had little success in extinguishing. Similarly this time, I believe, such militancy within the camp will only increase with the latest deaths and destruction.

This article is an updated version of a story that was first published by The Conversation on July 5, 2023.The Conversation

Maha Nassar, Associate Professor in the School of Middle Eastern and North African Studies, University of Arizona

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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