Nighttime light exposure may weaken the heart, increase the risk of cardiovascular disease

Experts have long recommended a dark, light-free bedroom for better sleep. New research shows that sleeping in near-total darkness may carry an added benefit: protecting the heart.

In a study published in the European Heart Journal, researchers at Tulane University’s Celia Scott Weatherhead School of Public Health and Tropical Medicine found that even small amounts of nighttime light exposure were linked to potentially harmful changes in the heart’s structure and function.

“Previous observational studies have linked nighttime light exposure with a higher risk of cardiovascular diseases, but little is known about the related cardiac structure and functional changes,” said lead author Lu Qi, HCA Regents Distinguished Chair and professor at Tulane. “We carried out this research to find out what happens to the heart over time when people are exposed to too much light at nighttime.”

The research team analyzed data from 11,017 participants, all of whom wore a sensor on their wrist for a week to measure levels of light exposure overnight. Some of the participants were exposed to 0 lux (near total darkness) and others were exposed to varying levels of light, with the highest group at more than 3 lux (roughly equivalent to a phone screen at low brightness on a nightstand or a hallway light left on outside a cracked door).

Three years later, each participant was given a cardiovascular magnetic resonance scan to examine any potential changes to the structure and function of their hearts. The results showed participants who were exposed to the highest levels of nighttime light saw the walls of the left chamber of their heart thicken, reducing the space inside the ventricle. There were also signs that the heart’s ability to flex during a heartbeat was reduced — an early indication of heart dysfunction.

“This is the first study of its kind, and it shows that exposure to higher levels of light at nighttime is linked to cardiac remodeling,” Qi said. “This is where the structure and function of the heart changes, and we typically see it in response to chronic stress or injury to the heart. It’s our body’s way of adapting to that stress, but ultimately it weakens the heart and can lead to heart failure.”

Cardiovascular disease, including heart disease and stroke, is the leading cause of death both in the United States and around the world. Nighttime light has been identified as a potential environmental risk factor for this deadly group of diseases. Unlike age or genetics, nighttime light exposure is a modifiable risk factor within most people’s control — simply by turning off screens, drawing curtains before bed or sleeping with an eye mask. 

“Light pollution has emerged as a new risk factor for cardiovascular disease,” Qi said. “Our findings, together with evidence from other studies, suggest that a reduction in nighttime light exposure should be considered as one of the potential strategies for preventing heart disease by clinicians and policymakers.”

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Journal

European Heart Journal

DOI

10.1093/eurheartj/ehag563 

 

Benefits of slow running: Just 10 minutes of very slow running improves mood and executive function

 

A growing body of evidence shows that exercise improves mood and cognitive function. However, much of this evidence comes from cycling, which allows researchers to precisely control exercise intensity in the laboratory. Running may play a special role in this story: it is a fundamental human movement, closely linked to our evolutionary history, and remains a popular form of exercise practiced by millions of people worldwide. This raises two basic questions about running: does it provide similar benefits, and if so, how little running is enough?

To address these questions, the researchers used a treadmill to precisely control exercise intensity and functional near-infrared spectroscopy (fNIRS) to measure prefrontal cortical activity following 10 min of very slow running at approximately 3-6 km/h, a pace close to walking. This comfortable pace corresponds to a very light exercise intensity of approximately 35% of peak oxygen uptake (V̇o2peak).

The results were clear: after just 10 min of very slow running, participants showed a shorter Stroop interference time—a measure of executive function—and reported a more pleasant mood. Activity also increased in prefrontal regions associated with executive function and mood regulation, most notably the left dorsolateral prefrontal and left frontopolar cortices. Interestingly, greater up-and-down movement of the runner's head—the gentle vertical oscillation characteristic of running—was associated with a greater improvement in mood.

These findings suggest that even very slow running, despite imposing little physiological demand, can simultaneously improve mood and executive function while providing insight into the brain mechanisms that may underlie these effects.

Because it requires relatively little exertion, very slow running may be an accessible form of exercise, potentially benefiting people with low fitness levels or those who find conventional exercise challenging. A brief, comfortable run could provide a practical way to support physical and mental well-being while benefiting executive function. Notably, previous research has also shown that a 10-min bout of very light-intensity exercise can enhance hippocampal-dependent memory (Suwabe & Soya et al., PNAS, 2018), highlighting the broader potential of light-intensity exercise for cognitive function.

As probiotic use surges, microbiome-supportive food consumption stagnates

 New research finds that probiotic supplement use has surged in the United States, while the consumption of microbiome-supportive foods has remained virtually unchanged.

According to a study published in Clinical Gastroenterology and Hepatology, the consumption of probiotic supplements increased 287% among adults from 2009-2023 and 786% among young people (less than 20 years old).

Over the same span, fiber intake did not meaningfully change, while the average consumption of high microbial foods rose slightly.

“We have known that probiotic supplement use is increasing across all ages, but this is the first time we have looked closely at it in relation to other microbiome-focused health behaviors,” said Kira L. Newman M.D., Ph.D., Clinical Assistant Professor of Internal Medicine at the University of Michigan Medical School and lead author on the paper.

“Dietary fiber and fresh produce have well-established health benefits for the gut microbiome. However, our findings suggest that people are not making changes to what they eat, even though an increasing number are concerned enough about their microbiome to take a probiotic supplement.”

The study authors used data from the National Health and Nutrition Examination Survey.

From 2009 to 2023, the proportion of people under 20 taking a probiotic rose from 0.63% to 5.58%.

Among people over 20, the percentage increased from 1.8% to 6.96%.

Probiotic supplement users were found to consume more foods high in microbial quality and fiber content than non-users.

Researchers add, however, that these beneficial diet habits may be decreasing, as supplements are potentially used as a substitute for higher-quality diets.

Probiotic supplement use increased dramatically after 2014 despite official guidelines suggesting limited benefits.

The study authors note a variety of health benefits associated with high microbial foods.

They emphasize that these benefits are not necessarily related to microbial content.

“A diet with plenty of vegetables, fruits, legumes, and whole grains provides not just fiber, but also a wealth of other beneficial vitamins, minerals and plant-derived compounds,” Newman said.

“This helps support a diverse range of beneficial gut microbes. Prebiotic supplements alone do not contain the same variety or richness. It’s like picking one color out of a rainbow.”

The study authors hope these trends will highlight the need for more public health campaigns on the importance of diet in fostering microbiome health.

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Journal

Clinical Gastroenterology and Hepatology

DOI

10.1016/j.cgh.2026.08.02

Hormone therapy in peri- and early postmenopause linked to lower cardiovascular risk

 

 A study led by Virginia Commonwealth University and the University of Pittsburgh provides pivotal insights into one of the most debated questions in women’s health: how does hormone therapy for menopause symptoms affect cardiovascular disease risk when used in peri- or early postmenopause?

By analyzing 20 years of health data from women with vasomotor symptoms participating in the Study of Women’s Health Across the Nation (SWAN), the researchers found hormone therapy initiated during peri- or early postmenopause was linked to a reduced risk of cardiovascular disease events by 22% compared to those who did not use hormone therapy. The protective effect of hormone therapy was strongest among Black women and women who initiated therapy within 10 years of menopause onset.

The study is the first of its kind in the United States to assess risk of future cardiovascular events among women with vasomotor symptoms who use therapy during peri- and early postmenopause stages. The findings, published today in the JAMA Internal Medicine, help address an important gap in understanding how the timing of hormone therapy influences the likelihood of cardiovascular disease events like stroke or heart failure, among others.

“The menopause transition represents a critical window for understanding how hormone therapy may relate to cardiovascular disease risk,” said Samar R. El Khoudary, Ph.D., M.P.H., professor and chair of the Department of Epidemiology at the VCU School of Public Health, a SWAN investigator and scientific leader and one of the senior researchers who led the study. “Our findings suggest that timing of initiation may influence cardiovascular outcomes.”

The researchers note that these findings do not support using hormone therapy for cardiovascular disease prevention. As with any treatment, potential benefits must be weighed against risks, including the increased breast cancer risk observed with a longer duration of use. Further, this study was not a randomized controlled trial, the gold standard method to test biomedical treatments.

“These findings point to women with vasomotor symptoms as those who may show cardiovascular benefit from hormone therapy initiated during the perimenopause and postmenopausal years,” said Rebecca C. Thurston, Ph.D., associate dean for Women’s Health Research at the University of Pittsburgh School of Medicine, a SWAN principal investigator and one of the senior researchers who led the study. “However, conclusions should be tempered by the observational nature of the study, and findings should not guide clinical practice.”

Clearing confusion on menopause hormone therapy and cardiovascular disease

Vasomotor symptoms, also known as hot flashes and night sweats, affect up to 80% of women during their menopause transition. These symptoms last an average of seven to ten years, with their frequency and severity building up through perimenopause and typically peaking in early postmenopause.

Hormone therapy, which replaces estrogen and progesterone that women’s bodies stop producing after menopause, is currently the most effective treatment for mitigating these sensations of intense heat. However, clinical trials led by the Women’s Health Initiative in the early 2000s raised initial alarm over this therapy’s impact on heart diseases, stroke, breast cancer and other risks. This led to years of reluctance from both patients and providers in using this therapy.

“Hot flashes and night sweats have a significant impact on a woman’s quality of life and ability to work productively,” El Khoudary said. “While hormone therapy is an effective treatment for these symptoms, questions have remained about its cardiovascular effects, particularly the importance of when treatment is initiated during the menopause transition.”

More recent research suggests that the effect hormone therapy has on women's hearts and vascular systems may vary depending on age and timing of treatment, with women younger than 60 who begin treatment closer to menopause onset having different levels of risk.

In 2026, the U.S. Food and Drug Administration removed “black box” warnings from hormone therapy products, reflecting evolving evidence on the benefits and risks of treatment.

How early intervention with menopause hormone therapy affects women’s risk for cardiovascular disease events

There has been a growing number of studies over the past 20 years focusing on hormone therapy and cardiovascular risk. However, no clinical trials have specifically evaluated the risk of cardiovascular events from taking hormone therapy for vasomotor symptoms during the menopause transition.

To fill this knowledge gap, researchers from VCU and the University of Pittsburgh analyzed long-term data from the SWAN project, which is the largest and longest observational study of its kind in the United States to better understand the health impacts of the menopause transition in women.

The team used clinical data collected between 1997 and 2017 from more than 2,700 women who reported vasomotor symptoms and who had not previously experienced any cardiovascular events. Based on self-reported patient data, researchers then examined whether women who started hormone therapy for vasomotor symptoms were more or less likely to experience cardiovascular events, such as stroke, congestive heart failure, heart attack and revascularization procedures, than women who did not begin treatment.

“By using data from the SWAN study, we essentially were able to emulate a series of hypothetical clinical trials to gain a deeper understanding into how hormone therapy taken to mitigate vasomotor symptoms during peri- and early postmenopause influences cardiovascular risk over time,” El Khoudary said. “It allowed us to examine clinically meaningful cardiovascular disease events over long-term follow-up in a population and treatment window that has been challenging to study prospectively.”

The analysis suggested that initiating hormone therapy in peri- or early postmenopause among women with vasomotor symptoms reduced the risk of cardiovascular disease events by 22% compared with not starting therapy.

The cardiovascular effect of hormone therapy initiation also varied by timing, race and ethnicity, such as:

• Women who initiated hormone therapy within 10 years of menopause onset had an estimated 27% lower risk of cardiovascular disease events compared with women who did not initiate therapy.
• Among Black women, hormone therapy initiation during peri- and early postmenopause was associated with an estimated 49% lower risk of cardiovascular disease events compared with those who did not initiative therapy.
• No clear risk reduction was observed among women who initiated therapy more than 10 years after menopause onset or among White women and other racial/ethnic groups.

“The differences in cardiovascular outcomes by race and ethnicity are notable, particularly because Black women are more likely to experience severe vasomotor symptoms,” El Khoudary said. “These findings highlight the need to better understand how hormone therapy timing may influence cardiovascular outcomes across diverse populations.”

It’s unclear why cardiovascular disease risk differs based on the timing of hormone therapy use, but the team believes it may be linked to differences in blood vessel health as we age.

“We hope these findings help inform conversations between women and their healthcare providers about the potential benefits and risks of hormone therapy for vasomotor symptoms,” El Khoudary said. “Studies like this can provide useful information, but the results should be interpreted carefully because other factors that were not measured may have influenced the findings. The findings also highlight the need for future clinical trials focused specifically on women during the menopause transition.”

“Our findings are thought provoking. However, caution should be exercised in their interpretation,” Thurston said. “Women who elect to use hormone therapy differ from women who do not on multiple characteristics, such as race, ethnicity, socioeconomic position, and access to healthcare that this study cannot fully address. These data point to the need for a clinical trial specifically designed among midlife women with vasomotor symptoms.”

The SWAN study is supported by grants from the Department of Health and Human Services and National Institutes of Health, including the National Institute of Aging, the National Institute of Nursing Research, and the NIH Office of Research on Women’s Health.

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Journal

JAMA Internal Medicine

DOI

10.1001/jamainternmed.2026.2922 

Walking at a brisker pace may be the sweet spot for those with sedentary lifestyles

 Taking fewer daily steps but at a faster pace or more steps at a slower pace may substantially lower the risk of early death by up to 43 per cent, new research from Monash University and the University of Sydney has found.

Published today in the British Journal of Sports Medicine, the research also found that walking at a brisker pace may be the sweet spot for those with sedentary lifestyles.

While evidence suggests a higher daily step count is key to preventing an early death, it was unclear until now what role stepping intensity might have or how different combinations of step counts and intensity might influence this risk, particularly among sedentary adults.

Lead author Professor Emmanuel Stamatakis, Director of the Monash Brain Park at the Turner Institute for Brain and Mental Health in the Monash School of Psychological Sciences, who led the research at the University of Sydney Charles Perkins Centre, said the findings may be particularly helpful for people who can’t accrue an adequate daily step count due to lack of time, disability or environmental restraints.

“We found that the risk was substantially lower among those achieving a higher stepping pace but fewer than 5000 daily steps,” Professor Stamatakis said.

“Similarly, the risk of early death was substantially reduced among those clocking up 5000 to 7500 daily steps but at a lower stepping pace.

“Our findings contribute to the evidence base for step-based approaches targeting daily step counts and stepping intensity to lower mortality risk, and may inform step-based interventions for middle-aged and older adults, particularly individuals with barriers to increasing daily step counts or stepping intensity.”

The research analysed data from 64,743 middle aged participants in the UK Biobank  who wore an activity tracker for seven consecutive days between 2013 and 2015 to monitor the number and intensity of daily steps taken.

During an average tracking period of around eight years, 1697 of the participants died from any cause and 502 from cardiovascular disease. 

Co-author Dr Nicholas Koemel, Senior Research Fellow at the Monash School of Psychological Sciences, said the research does not support the popular theory that everyone must take at least 10,000 steps a day to get fit.

“That heavily quoted step target actually came from a 1960s Japanese pedometer campaign rather than from evidence,” Dr Koemel said.

“For a 65-year-old managing a knee issue, a carer with fragmented time, or a shift worker, a high step target can be a reason to give up rather than a reason to start.

“The important message is that every step counts, and how you take those steps can also matter. Someone walking 4000 steps a day who walks them with more purpose is doing something worthwhile, and someone who cannot walk quickly can still benefit by gradually accumulating more steps at a slower pace.”

Co-author Associate Professor Matthew Ahmadi said anyone wanting to implement the findings in their own lives should focus on consistency. 

“The body responds to habitual patterns, not to irregular and infrequent effort, so what counts is what you do on most days over months and years, not a motivated fortnight,” Associate Professor Ahmadi said.

“There is no single pace that suits everyone. A speed that feels very comfortable to a fit walker in their forties may be maximal intensity for a 70-year-old. 

“The most practical test is also the simplest, which is to pay attention to your breathing: at a brisk pace that is maintained for at least a minute or so you should be breathing noticeably harder, feeling warmer, and still able to hold a conversation in short sentences, but you should not be able to sing comfortably.”

Read the research paper: http://doi.org/10.1136/bjsports-2025-111173

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Journal

British Journal of Sports Medicine

DOI

10.1136/bjsports-2025-111173

Differences in eating schedules and the risk of cardiovascular disease

 Work often requires people to adjust their eating patterns during the week, resulting in differences in eating schedules between weekdays and weekends or days off—when meal timing tends to be more closely aligned with their internal biological clocks. This shift, known as eating jetlag, may disrupt the body’s biological rhythm. Previous studies have already shown that disruptions to the biological clock linked to night work or late mealtimes can lead to cardiovascular complications.

The research team chose to assess the link between eating jetlag and the risk of cardiovascular disease within the NutriNet-Santé cohort. They analysed data from 104,806 adult NutriNet-Santé participants between 2009 and 2023. The severity of eating jetlag was calculated based on the timing of participants’ first and last meals of the day on weekdays and weekends. The association between eating jetlag and the risk of cardiovascular disease was assessed using appropriate statistical models, which also took into account other factors such as age, marital status and the number of children living in the household, socio-occupational factors, smoking, alcohol consumption, physical activity, diet, sleep, etc. By comparing meal timing on weekdays and weekends, the researchers classified eating jetlag according to the magnitude of the difference into three categories:

• ‘Advance’, where mealtimes are earlier at the weekend than on weekdays, with an average of 2 hours’ advance in the eating window;
• ‘Regular’, where the eating windows are similar;
• ‘Delay’, where mealtimes are later at the weekend than on weekdays, with an average delay of 1 hour 40 minutes in the eating window.

Eating jetlag associated with a higher risk of cardiovascular disease in men

For men, the results suggest that each additional hour of eating jetlag—be it earlier or later—is associated with an average 14% increased risk of cardiovascular disease and an average 21% increased risk of coronary heart disease. Both the ‘Advance’ and ‘Delay’ groups showed a higher risk compared with the ‘Regular’ group. The researchers did not find any significant difference among women. Several hypotheses may account for this finding. The first relates to sexual dimorphism, that is, differences in physiological functioning between the two biological sexes. The second relates to differences in lifestyle and socio-occupational circumstances between women and men in society, which could lead to different circadian rhythms. Finally, the absolute risk of cardiovascular disease is higher in men. 

This initial study suggests that changes in mealtimes between weekdays and weekends may play a role in the development of cardiovascular disease, regardless of sleep and diet, particularly in men. Further studies are needed to build on this initial observational study and establish the causality of these links.

A few years ago, we suggested that eating late was associated with an increased risk of cardiovascular disease. This new study suggests that, beyond simply eating late, maintaining consistent meal times between weekdays and weekends may be just as important. These associations appear to be independent of how long people sleep, suggesting that regular meal times could, in themselves, help resynchronise our biological rhythm. We are continuing our research to better understand this phenomenon.”
Bernard Srour, Research Director at INRAE

The body reacts to a plant-based diet by adjusting to replace missing proteins

 A new peer-reviewed review published in the journal Biology argues that much of the debate over whether plant-based diets deliver enough iron, protein, creatine, and other nutrients rests on a flawed assumption: that eating less of something automatically means the body has less of it available. Drawing on human intervention and observational studies across five biological systems, the review concludes that the body actively adapts to sustained dietary change, absorbing iron more efficiently, synthesizing more of its own creatine and carnosine, using protein more economically, and remodeling gut bacteria to better ferment fiber, and that these adaptations, not just intake numbers, determine long-term nutritional status.

The review was co-authored by Hana Kahleova, MD, PhD, director of clinical research at the Physicians Committee for Responsible Medicine, alongside lead author Miguel López-Moreno of the Universidad Francisco de Vitoria in Madrid and colleagues from the University of British Columbia, the University of Granada, and the Instituto de Investigación Nutricional in Lima.

“For years, nutrition science has treated dietary intake as if it were a straight line to physiological status—eat less iron, absorb less iron; eat less creatine, have less creatine,” said Dr. Kahleova. “That's not how human physiology works. The body is not a passive pipe. When intake changes and stays changed, regulatory systems like the hepcidin-ferroportin axis in the gut, or the enzymes that make our own creatine and carnosine, adjust to hold function steady. As a clinician, I see this in my patients: The digestive symptoms that come with a new plant-based diet in week one are rarely the same story at month three, and a single blood draw or a single test meal doesn't tell you what a person's physiology looks like after they've actually adapted.”

The review synthesizes evidence across five areas where plant-based diets are most often flagged as “nutrients of concern”:

Iron. Vegans and vegetarians rely on less efficiently absorbed non-heme iron, but longer-term studies show the gut compensates by absorbing a greater fraction of it, partly explained by lower circulating hepcidin, the hormone that gates iron absorption. Total iron intake among vegetarians and vegans is also often as high as, or higher than, that of omnivores, since staple plant foods such as legumes, whole grains, and fortified cereals are iron-dense.

Creatine and carnosine. These compounds, found almost exclusively in animal foods, are also made by the body from amino acid precursors. Vegetarians run lower baseline muscle stores but generally maintain normal function and respond more robustly to creatine supplementation when it's used, evidence the authors say reflects lower baseline saturation rather than deficiency.

Protein. Well-planned plant-based diets that meet total protein recommendations preserve lean mass and strength comparably to omnivorous diets in controlled trials.

Fermentable fiber. Early bloating and gas from a higher-fiber diet typically ease over weeks as gut bacteria shift toward taxa that ferment complex carbohydrates more efficiently, a pattern documented since early controlled feeding studies of legume consumption.

Polyphenols. Gut bacteria convert plant compounds, from soy isoflavones to walnut ellagitannins, into more bioactive metabolites; long-term vegans show markedly higher levels of several of these microbial byproducts than people eating a standard omnivorous diet.

The authors are careful to note that adaptation has limits. Pregnancy, chronic inflammation, inflammatory bowel disease, celiac disease, and severe or prolonged dietary insufficiency can all outpace the body's regulatory capacity, which is why the review calls for individualized counseling rather than either blanket reassurance or blanket concern.

“This isn't an argument that nutrient composition doesn't matter, it clearly does, especially for patients whose adaptive capacity is already stretched thin,” Dr. Kahleova said. “It's an argument for asking a better clinical question: not just what is this person eating, but how long have they been eating this way, and does their physiology show signs of having adapted? In my own randomized trial of a fiber-rich, plant-based diet in adults with type 1 diabetes, we saw insulin requirements fall in ways that track with exactly this kind of adaptive, whole-body response rather than a simple nutrient swap. That's the kind of clinical population where testing the limits of adaptation matters most, and where I think this framework will do the most good.”

The review calls for longitudinal studies that track adaptation as it unfolds, rather than comparing only a baseline and endpoint, and for biomarkers that can distinguish a temporary response to dietary change from a stable, adapted state. The authors argue the same physiological principle extends well beyond plant-based diets, to any nutrition research that infers long-term status from short-term intake data.