How Light at Night Disrupts the Body

Nelson’s research shows that artificial light at night interferes with the body’s internal clock, suppressing melatonin production and disrupting the natural light–dark cycle that governs many biological functions. This disruption affects multiple systems:

Brain and mood: Exposure to dim light during normal sleep hours has been shown in animal studies to increase brain inflammation, reduce levels of brain-derived neurotrophic factor (BDNF), and cause behaviors linked to depression.

Metabolism: Nighttime light alters circadian gene expression, which can impair insulin sensitivity, promote weight gain, and disturb glucose regulation.

Immune function: Irregular light exposure can suppress normal immune responses or cause chronic low-grade inflammation, increasing vulnerability to illness.

These effects can appear even with relatively low light levels—around 5 lux, similar to the glow from a dim bedside lamp. Research has linked such exposure to a greater risk of metabolic disorders, cardiovascular disease, and mood disorders.

From Laboratory Studies to Clinical Trials

While much of the foundational work comes from controlled lab experiments, Nelson’s team is translating these findings into real-world applications through clinical trials. In hospital intensive care units (ICUs), patients are often exposed to bright artificial light around the clock, which may slow recovery. Nelson’s group is testing interventions such as adjusting light wavelengths and timing to improve outcomes for stroke and cardiac surgery patients.

Another study focuses on night-shift nurses, who are at high risk for sleep problems and mood disturbances. By using blue-light visors at specific times, the research aims to help reset their circadian rhythms, potentially improving cognitive performance and overall well-being. These trials explore whether similar strategies could support shift workers in other industries, where irregular schedules make it hard to maintain natural sleep–wake cycles.

Nelson also points out that the time of day can affect research results. Experiments done in the morning might give different outcomes than those done in the evening, but many studies don’t record or control for this. Keeping track of when tests are done could make biomedical research more consistent and reliable.

Practical Steps for Protecting Circadian Health

Nelson’s work underscores that small lifestyle changes can help protect circadian rhythms and reduce the health risks of artificial light at night. Strategies supported by current evidence include:

Limit blue light exposure after sunset: Use warmer-toned light bulbs in the evening and enable night mode on screens.

Block ambient nighttime light: Blackout curtains or eye masks can reduce intrusion from streetlights and outdoor lighting.

Maintain regular sleep–wake cycles: Going to bed and waking up at consistent times helps reinforce natural rhythms.

Increase daylight exposure: Spending at least 30 minutes outside in the morning boosts alertness and helps anchor the circadian clock.

Nelson’s recent book, Dark Matters, offers a detailed guide for the public on aligning daily habits with biological timing to improve long-term health.

Artificial light at night is now recognized as a growing public health concern, with research linking it to chronic disease risk and mental health challenges. Nelson’s investigations—from molecular changes in the brain to patient care in the ICU—show that circadian disruption is not just a sleep issue but a multi-system health problem. Adopting circadian-friendly lighting practices and reducing nighttime light exposure could play a key role in preventing illness and improving well-being.

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Rewriting Gene Activity in the Diseased Brain

Alzheimer’s disease disrupts how genes operate in brain cells. To understand this better, scientists first mapped the patterns of gene activity in individual neurons and support cells (called glia) from brains affected by the disease. This process, known as gene expression profiling, shows which genes are active or dormant. The researchers then searched for drugs that could flip those patterns back toward normal.

They turned to a large public database called the Connectivity Map, which catalogs how thousands of drugs affect gene activity in human cells. Out of 1,300 drugs, just 10 reversed Alzheimer’s-linked gene patterns across different brain cell types, and only five were already approved by the U.S. Food and Drug Administration.

Using medical records from over 1.4 million patients across California’s university hospitals, the researchers looked for any real-world signs that those drugs might help prevent Alzheimer’s. The records showed that people who had taken some of these medications, mostly for cancer, appeared less likely to develop the disease later on.

Targeting Two Cell Types with a Two-Drug Combo

From this shortlist, the team selected two drugs: letrozole, typically used to treat breast cancer, and irinotecan, used against colon and lung cancers. They believed each drug would target a different cell type — letrozole for neurons and irinotecan for glia — like a two-part key unlocking different doors in the brain.

When given to mice with advanced Alzheimer’s-like symptoms, the drug duo had striking effects. It stopped further damage, reduced toxic protein buildup, and even restored the animals’ ability to remember how to navigate mazes. Memory, in this case, was not just protected, it was brought back from the edge.

The researchers compare the process to rewiring a city after a blackout, where different crews work on separate grid sections, but the lights only come back when efforts are synchronized. Similarly, targeting both neurons and glia may be the missing link that single-drug strategies have overlooked.

A Possible Turning Point for Alzheimer’s Treatment

“This study opens a new door using drugs we already have,” said lead researcher Yadong Huang. His team emphasizes that although results in mice are promising, human trials are essential to confirm safety and effectiveness.

Letrozole and irinotecan, though widely used in cancer treatment, can come with serious side effects. If repurposed for Alzheimer’s, their doses and delivery methods will likely need major adjustments. The upside? Since the drugs are already approved, clinical trials could begin sooner than if researchers had to start from scratch.

With over 55 million people living with Alzheimer’s worldwide and that number set to double in the next two decades.

As co-author Marina Sirota puts it, “When two completely different kinds of data — from cells and from real patients — lead to the same drug, and it works in a model of the disease, we may finally be onto something.”

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Found in Thousands of Low-Calorie Products

Erythritol appears in everything from protein bars to flavored water, offering about 80% the sweetness of sugar without the calories or spikes in insulin. Its widespread use has grown with the popularity of low-sugar and diabetic-friendly diets.

But this sweetener, often labeled as natural due to its presence in some fruits and fermentation processes, may carry hidden risks.

The new study examined how erythritol affects the blood-brain barrier—the brain’s critical filtering system. Researchers exposed brain blood vessel cells to amounts of erythritol comparable to what’s found in a single sugar-free beverage. They observed a damaging cascade: increased oxidative stress, reduced antioxidant activity, and even cell death.

These changes also disrupted the delicate balance between two key molecules: nitric oxide and endothelin-1. Nitric oxide relaxes blood vessels, promoting healthy blood flow, while endothelin-1 causes them to constrict. Erythritol lowered levels of nitric oxide while boosting endothelin-1, causing blood vessels to stay narrowed. This narrowing can limit the brain’s access to oxygen and nutrients, increasing the risk of ischaemic stroke.

It also weakened the cells’ natural capacity to break down blood clots. Normally, they release a compound called tissue plasminogen activator (t-PA) to break down clots. But erythritol suppressed this mechanism, potentially leaving clots to accumulate and increase the risk of stroke.

Echoes of Earlier Human Studies

The laboratory results align with previous human studies. One 2023 investigation that tracked over 4,000 individuals across the US and Europe found that those with elevated erythritol levels in their blood had nearly double the risk of experiencing a heart attack or stroke within three years.

Another study showed that 30 grams of erythritol—a typical serving in sugar-free ice cream—can make blood platelets more likely to clump, setting the stage for clot formation.

Erythritol is often promoted as a “natural” alternative to artificial sweeteners like aspartame or sucralose, and its chemistry makes it easier to substitute for sugar in recipes. Because it’s technically a sugar alcohol and produced in small amounts by the body, it has largely avoided the negative attention directed at other synthetic sweeteners.

However, experts warn that its natural origin does not guarantee safety. The U.S. Food and Drug Administration and European Food Safety Authority have approved it for consumption, but the new data suggest long-term effects may not be fully understood.

What This Means for Consumers

Researchers emphasize that their experiments were conducted on isolated cells in laboratory conditions. Human bodies are more complex, and more research—especially studies involving whole-body responses or advanced vascular models—is needed to draw final conclusions.

Still, scientists advise consumers to read labels and be mindful of erythritol intake, especially if they consume multiple servings of sugar-free products daily. Given the links to vascular dysfunction and stroke risk, moderation may be a wise approach.

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The researchers analyzed dietary habits using data gathered from the Nurses’ Health Study and the Health Professionals Follow-Up Study. Food-frequency questionnaires were administered every two to four years, asking participants how often they consumed various foods, including processed red meats like bacon, hot dogs, and lunch meats, as well as nuts and legumes. Over the study period, 11,173 participants developed dementia.

Each additional daily serving of processed red meat was linked to an extra 1.6 years of cognitive aging, particularly affecting language ability and executive function. The high levels of saturated fats and cholesterol in processed red meats can lead to the buildup of cholesterol plaques in arteries, impairing blood flow to the brain and accelerating cognitive decline. Dr. Sham Singh, a psychiatrist at Winit Clinic who was not involved in the study, observed similar findings. He explained that excessive intake of saturated fats could contribute to atherosclerosis, which reduces blood flow and oxygen delivery to brain cells, potentially accelerating cognitive decline.

Moreover, cooking methods such as grilling, frying, or broiling processed red meats can produce harmful compounds like heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs). These compounds induce oxidative stress and inflammation, further contributing to neurodegenerative diseases like dementia. Processed red meats often contain nitrates and nitrites, which are preservatives that can form harmful compounds in the body, increasing dementia risk.

The research also underscored the advantages of substituting processed red meat with nuts, beans, or legumes. Participants who made this substitution had a 20% lower risk of dementia. Nuts and legumes are rich in healthy fats, fiber, vitamins, and minerals that support brain health and improve cardiovascular function. They contain omega-3 fatty acids, which are anti-inflammatory and help maintain healthy cell membranes in the brain.

Varsha Khatri, a certified nutritionist at Prowise Healthcare, pointed out that the fiber, vitamins, and minerals found in nuts and beans contribute to better heart and blood vessel health, reducing dementia risk by promoting improved blood flow to the brain. Additionally, these plant-based foods are abundant in polyphenols and other antioxidants that combat oxidative stress, a key factor in dementia development.

To reduce the risk of dementia, experts recommend gradually incorporating more nuts, beans, and legumes into the diet. Some practical approaches are to substitute beans for red meat in recipes, snack on nuts, and incorporate more plant-based meals into your weekly diet plan. Starting slowly and being prepared to use these ingredients in food preparation can help individuals make sustainable dietary changes.

Dr. Heather Snyder, vice president of medical and scientific relations at the Alzheimer’s Association, stressed the significance of maintaining a varied diet to support brain health. She noted that diets lower in fat and sugar and higher in vegetables are generally better for cognitive function. This aligns with findings from other studies showing that processed foods are linked to poorer health outcomes across the board, including increased risks of cancer, heart disease, and diabetes.

This research highlights how crucial dietary choices are for supporting brain health and lowering the risk of cognitive decline. While the findings show a strong association between processed red meat consumption and dementia risk, it is important to note that they do not prove a direct cause-and-effect relationship. Further research is needed to fully understand the mechanisms behind this link and to explore the potential benefits of plant-based diets.

In conclusion, adopting a diet rich in nuts, beans, and legumes while reducing processed red meat intake may be a viable strategy to mitigate dementia risk and promote overall brain health. This research adds to the growing body of evidence supporting the benefits of plant-based diets for long-term cognitive health.

References:

1. Alzheimer’s Society (2024). “Eating processed red meat could be significant risk factor for dementia”. Available at: https://www.alzheimers.org.uk/news/2024-07-31/eating-processed-red-meat-could-be-significant-risk-factor-dementia.
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2. Alzheimer’s Association (2024). “Processed red meat raises risk of dementia”. Available at: https://aaic.alz.org/releases-2024/processed-red-meat-raises-risk-of-dementia.asp

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