The small clinical trial was published in the open access journal BMJ Nutrition, Prevention & Health in March 2024 and its findings press released. The study findings generated widespread international attention at the time, and continue to be frequently referred to in media coverage.

The retraction was prompted by concerns raised about the quality of the work, including the approach to statistical analysis of the data; implausible statistical values; the reliability of the raw data; inadequate reporting of methods; and lack of prospective trial registration, which breaches BMJ Group’s editorial policy.

Initially, concerns were raised in critiques of the study, some of which were published as letters in the journal. But after review by BMJ Group’s content integrity team, the study was referred to statistical experts to evaluate its reliability. This included attempts to replicate the results and examine the authenticity of the underlying data supplied by the authors.

It wasn’t possible for the statisticians to replicate the results and multiple analytical errors were identified. There were also irregularities in the data set, and their report, which is appended to the retraction notice, concluded that the data collected from each participant would require further independent scrutiny.

The authors said that the identified errors were honest mistakes, but they agree with the decision to retract the study.

Dr Helen Macdonald, Publication Ethics and Content Integrity Editor at BMJ Group, said: “Tempting though it is to alert readers to an ostensibly simple and apparently helpful weight loss aid, at present the results of the study are unreliable, and journalists and others should no longer reference or use the results of this study in any future reporting.”

She added: “This retraction reflects our strategic and proactive approach to investigating concerns raised about the content we publish. We act where necessary in the interests of openness and the importance of correcting the scientific record.

“While we deal with allegations as swiftly as possible, it’s very important that due process is followed. Investigations are often complex. This one involved detailed scrutiny of data and correspondence with researchers, institutions, and other experts, for example. Reaching a sound and fair and final decision can therefore take several months.”

Commenting on the decision to publish the study despite the lack of trial registration, Professor Martin Kohlmeier, editor in chief of BMJ Nutrition Prevention & Health, explained: “In hindsight, this was the wrong decision to make. But the authors come from a scientific environment that is underrepresented in nutritional research and the journal aims to prioritise high quality evidence, which usually comes from clinical trials.

“These are relatively unusual in nutritional research as they can be challenging to undertake because of the numbers of participants and time needed to obtain meaningful results.”

“We were surprised to find that zeaxanthin, already known for its role in eye health, has a completely new function in boosting anti-tumor immunity,” said Jing Chen, PhD, Janet Davison Rowley Distinguished Service Professor of Medicine and senior author of the study. “Our study show that a simple dietary nutrient could complement and strengthen advanced cancer treatments like immunotherapy.”

How does this nutrient work?

The study builds on years of work by Chen’s lab to better understand how nutrients influence the immune system. By screening a large blood nutrient library, the team identified zeaxanthin as a compound that directly enhances the activity of CD8+ T cells, a crucial type of immune cell that kills tumor cells. These cells rely on a molecular structure called the T-cell receptor (TCR) to recognize and destroy abnormal cells.

The researchers found that zeaxanthin stabilizes and strengthens the formation of TCR complex on CD8+ T cells upon interacting with the cancer cells. This, in turn, triggers more robust intracellular signaling that boosts T-cell activation, cytokine production, and tumor-killing capacity.

Zeaxanthin improves immunotherapy effects

In mouse models, dietary supplementation with zeaxanthin slowed tumor growth. Importantly, when combined with immune checkpoint inhibitors – a type of immunotherapy that has transformed cancer treatment in recent years – zeaxanthin significantly enhanced anti-tumor effects compared to immunotherapy alone.

To extend the findings, the researchers tested human T cells engineered to recognize specific tumor antigens and found that zeaxanthin treatment improved these cells’ ability to kill melanoma, multiple myeloma, and glioblastoma cells in laboratory experiments.

“Our data show that zeaxanthin improves both natural and engineered T-cell responses, which suggests high translational potential for patients undergoing immunotherapies,” Chen said.

A safe and accessible candidate

Zeaxanthin is sold as an over-the-counter supplement for eye health, and is naturally found in vegetables like orange peppers, spinach, and kale. It’s inexpensive, widely available, well-tolerated and, most importantly, its safety profile is known – which means it can be safely tested as an adjunct to cancer therapies.

The study also reinforces the importance of a balanced diet. In their previous research, Chen’s group discovered that trans-vaccenic acid (TVA), a fatty acid derived from dairy and meat, also boosts T-cell activity – but through a different mechanism. Together, the findings suggest that nutrients from both plant and animal sources may provide complementary benefits to immune health.

Clinical applications of zeaxanthin

Although the results are promising, the researchers emphasize that the work is still at an early stage. Most of the findings come from laboratory experiments and animal studies. Thus, clinical trials will be needed to determine whether zeaxanthin supplements can improve outcomes for cancer patients.

“Our findings open a new field of nutritional immunology that looks at how specific dietary components interact with the immune system at the molecular level,” Chen said. “With more research, we may discover natural compounds that make today’s cancer therapies more effective and accessible.”

The study, “Zeaxanthin augments CD8+ effector T cell function and immunotherapy efficacy,” was supported by grants from the National Institutes of Health, the Ludwig Center at the University of Chicago, and the Harborview Foundation Gift Fund.

Additional authors include Freya Zhang, Jiacheng Li, Rukang Zhang, Jiayi Tu, Zhicheng Xie, Takemasa Tsuji, Hardik Shah, Matthew Ross, Ruitu Lyu, Junko Matsuzaki, Anna Tabor, Kelly Xue, Chunzhao Yin, Hamed R. Youshanlouei, Syed Shah, Michael W. Drazer, Yu-Ying He, Marc Bissonnette, Jun Huang, Chuan He, Kunle Odunsi, and Hao Fan from the University of Chicago; Fatima Choudhry from DePaul University, Chicago; Yuancheng Li and Hui Mao from Emory University School of Medicine, Atlanta; Lei Dong from University of Texas Southwestern Medical Center, Dallas; and Rui Su from Beckman Research Institute, City of Hope, Duarte, CA.

That would only be possible if an atmosphere is present – a big mystery the scientists are attempting to unravel and now even closer to solving using the largest telescope in Space.

Deploying NASA’s JWST, the researchers have reached these discoveries as part of a major international project which is probing the atmosphere and surface of TRAPPIST-1e, also more simply known as planet e in the system, orbiting within the habitable zone of red dwarf star TRAPPIST-1.

Exoplanets are highly varied planets which orbit stars outside the solar system. Planet e is of particular interest because the presence of liquid water – not too hot or cold – is theoretically viable, but only if the planet has an atmosphere.

Researchers aimed JWST’s powerful NIRSpec (Near-Infrared Spectrograph) instrument at the system as planet e passed in front of its star. Starlight passing through the planet’s atmosphere, if there is one, will be partially absorbed and the corresponding dips in the light spectrum that reaches JWST tell astronomers what chemicals are found there. With each additional transit, the atmospheric contents become clearer.

Initial results, published in two scientific papers in the journal Astrophysical Journal Letters, indicate several potential scenarios, including the possibility of an atmosphere.

Dr Hannah Wakeford, Associate Professor in Astrophysics at the University of Bristol, is a leading member of the JWST Transiting Exoplanet team who helped design the observational set-up for the telescope to ensure scientists obtain vital data.

Dr Wakeford said: “What we have found with JWST in these first four observations helps refine the earlier Hubble measurements and reveals there might now be hints of an atmosphere, but we cannot yet rule out the possibility there is nothing to detect.”

“JWST’s infrared instruments are providing unprecedented detail, helping us understand much more about what determines a planet’s atmosphere and surface environment, and what they’re composed of. It’s incredibly exciting to be peeling back the curtain of these fascinating other worlds, measuring the details of starlight around Earth-sized planets to ascertain what it might be like, and if life could be possible. Through a careful process of elimination and comparison we’re uncovering great new insights.”

Although various possibilities remain open for planet e, the researchers are confident the planet does not have its original atmosphere.

Co-author of both studies, Dr David Grant, a former Senior Research Associate at the University of Bristol, explained: “The findings also further rule out the presence of a primordial hydrogen-based atmosphere. This is the gaseous envelope, mainly comprising hydrogen, that surrounded a planet in its early stages of formation. Such atmospheres are believed to be common for both giant planets and terrestrial planets in the early solar system.”

Dr Wakeford added: “Since TRAPPIST-1 is a very active star, with frequent flares, it’s not surprising that any hydrogen-helium atmosphere the planet may have formed would be stripped off by stellar radiation. Many planets, including Earth, build up a heavier secondary atmosphere after losing their primary atmosphere. It is possible planet e was never able to do this and doesn’t have a secondary atmosphere, but there’s an equal chance one does exist.”

The presence of a secondary atmosphere means liquid water could also exist on the surface and if that’s the case, researchers understand it would be accompanied by a greenhouse effect, akin to that of planet Earth, in which various gases, especially carbon dioxide, keep the atmosphere stable and the planet warm.

The second paper details work on the theoretical interpretation and lead author Dr Ana Glidden, a post-doctoral researcher at Massachusetts Institute of Technology, explained: “It is unlikely the atmosphere of planet e is dominated by carbon dioxide, like the thick atmosphere of Venus and the thin atmosphere of Mars. But it’s also important to note there are no direct parallels with our solar system. TRAPPIST-1 is a very different star from our Sun, and the planetary system around it is also distinct.”

Dr Wakeford added: “A little greenhouse effect can go a long way and the new measurements do not rule out sufficient carbon dioxide to sustain some liquid water on the surface. The liquid water could take the form of a global ocean, or cover a smaller area of the planet where the star is at perpetual noon, surrounded by ice. This would be possible because, owing to TRAPPIST-1’s planets’ sizes and close orbits to their star, they are all tidally locked, with one side always facing the star and the other side in perpetual darkness.”

Next steps in the research will involve further detailed observations, comparing data from another exoplanet – planet b – orbiting closest to TRAPPIST-1 in order to make more revelations.

One of the principal investigators of the research team focused on TRAPPIST-1e Dr Néstor Espinoza, an Associate Astronomer and Mission Scientist for Exoplanet Science at the the Space Telescope Science Institute (STScI) in Baltimore, Maryland, said: “Webb’s infrared instruments are giving us more detail than we’ve ever had access to before, and the initial four observations we’ve been able to make of planet e are showing us what we will have to work with when the rest of the information comes in.”

The JWST is the world’s premier space science observatory, capable of observing distant worlds and stars, and probing the mysterious structures of our universe. It is an international programme led by NASA, the European Space Agency, and the Canadian Space Agency.

The project is part of the JWST-TST DREAMS program, led by Dr Nikole Lewis, Associate Professor of Astronomy at Cornell University in the US city Ithaca, New York. This international project involves more than 30 scientists from the UK, USA, and India, five of whom are members or former members of Dr Wakeford’s team. It includes the breakthrough detection of Quartz clouds in the atmosphere of a hot exoplanet, as shown in a recent study, led by Dr Grant and co-authored by Dr Wakeford.

The study systematically reviews existing literature, including randomized controlled trials, crossover trials, and non-randomized studies, comparing yoga and other exercise interventions in sedentary adults.

The researchers point out that their aim has been to assess the impact of these interventions on vascular function, as measured by ultrasound.

Vascular function refers to the ability of blood vessels to efficiently transport blood to tissues. The elasticity and responsiveness of these vessels are critical indicators of cardiovascular health.

Sedentary behavior and prolonged sitting are known to impair vascular function, increasing the risk of hypertension, cholesterol buildup, and thrombosis.

Co-author Dr. Leena David, a specialist in medical diagnostic imaging and lecturer at the University of Sharjah, says:

“Think of blood vessels like flexible garden hoses. If they stiffen, the risk of heart attacks and strokes increases. Our study shows that structured exercise keeps those hoses flexible, while yoga provides some benefits but not as reliably. Middle-aged and older adults often notice improvements from yoga, but younger adults might not.”

The findings are particularly relevant for the estimated 300 million people worldwide who practice yoga and the more than 620 million individuals affected by cardiovascular disease as of 2023.

The researchers conclude that traditional exercise modalities, such as Tai Chi, Pilates, and high-intensity interval training, consistently outperform yoga in improving vascular function among sedentary individuals.

Dr. David emphasizes that while movement is essential, the type, intensity, and consistency of physical activity are key determinants of vascular health.

“Even simple routines can make arteries more resilient. Blood vessels have a memory — and every workout helps them forget the damage of sitting all day,” she adds.

She also describes prolonged sitting as “the new smoking — silent, sneaky, and stealing years from your arteries,” adding that “movement is the perfect antidote.”

While yoga remains accessible and culturally significant, the study suggests that individuals seeking consistent cardiovascular benefits may need to supplement yoga with more vigorous forms of exercise.

The authors advocate for a nuanced approach to physical activity, especially in public health messaging.

“Yoga has deep cultural roots and shows promise as an inclusive, accessible health intervention,” Dr. David notes.

“At the same time, the fitness and digital health industries can leverage these insights to develop structured exercise programs and technology-driven solutions for sedentary populations.”

The researchers hope their findings will encourage healthcare providers to recommend exercise not only for weight management but also as a proven strategy for improving vascular health.

Although yoga may not consistently enhance vascular function, it remains a valuable option, particularly for older adults and those unable or unwilling to engage in high-intensity workouts.

“On a larger scale, public health campaigns could emphasize that movement is medicine,” Dr. David explains. “This may encourage a mix of exercise and yoga to make heart health more accessible and culturally appropriate.

Forget the fitness goals — this is about protecting your body’s internal GPS system that keeps you alive.”