Medical Bulletin 21/February/2026

Here are the top medical news for today:

Low-Fiber Diets Rapidly Impair Emotional Memory in Aging Brains, Study Finds

Just three days of poor eating may be enough to disrupt memory in the ageing brain. New research suggests that it’s not just fat or sugar that poses a problem—but a lack of fiber. In a recent animal study from The Ohio State University, scientists found that refined, low-fiber diets rapidly impaired emotional memory in older rats, even before obesity developed. The findings were published in Brain, Behavior, and Immunity.

As people age, the brain becomes more vulnerable to inflammation and metabolic stress. Highly processed diets have previously been linked to memory decline, but researchers wanted to pinpoint which dietary components were most harmful. To investigate, the team fed young and aged male rats either standard chow or one of five refined experimental diets for three days. These diets varied in fat and sugar content—ranging from low-fat/low-sugar to high-fat combinations—but all shared one feature: they lacked fiber.

Behavioral testing revealed a striking pattern. Older rats consuming any of the refined diets showed impaired long-term emotional memory linked to the amygdala, the brain region responsible for processing fear and risk-related learning. In contrast, hippocampal memory—associated with spatial and episodic recall—was disrupted only in aged rats on a high-fat, low-sugar diet. This pointed researchers toward a common denominator beyond fat or sugar.

Gut and blood analyses provided a clue. All fiber-deficient diets led to significantly lower levels of butyrate, a molecule produced when gut microbes break down dietary fiber. Butyrate is known to have anti-inflammatory properties and can cross the blood-brain barrier. Reduced butyrate levels may therefore promote unchecked brain inflammation, particularly in vulnerable ageing regions like the amygdala.

At the cellular level, the team observed impaired mitochondrial function in microglia from aged brains. Unlike cells from young animals, these mitochondria showed reduced respiration and limited ability to respond to energy demands—signs of compromised resilience.

Importantly, these cognitive effects occurred rapidly and were not primarily driven by weight gain. The researchers now plan to explore whether fiber or butyrate supplementation can reverse diet-related memory deficits, highlighting the potential brain benefits of a fiber-rich diet in older adults.

REFERENCE: Butler, M. J., et al. (2025). The aged amygdala’s unique sensitivity to refined diets, independent of fat or sugar content: A brain region and cell type-specific analysis. Brain, Behavior, and Immunity. DOI: 10.1016/j.bbi.2025.106220. https://www.sciencedirect.com/science/article/abs/pii/S0889159125004623?via=ihub

Ultra-Processed Foods Show Addiction Patterns Similar to Tobacco, Study Finds

That bag of chips you meant to stop eating. The soda that turns into refills. The late-night fast-food order that feels automatic. A new analysis suggests these choices may not be just about self-control—but about design. Researchers from the University of Michigan, Harvard University and Duke University argue that many ultraprocessed foods are engineered to drive repeat consumption in ways that resemble strategies once used by tobacco companies. Their findings appear in The Milbank Quarterly.

Ultraprocessed foods include packaged snacks, sugary drinks, ready-to-eat meals and many fast-food items. Unlike minimally processed foods, these products are formulated with combinations of refined carbohydrates, added fats, salt and flavor enhancers that maximize “hyper-palatability”—a level of taste and texture designed to strongly stimulate the brain’s reward system. According to the researchers, this formulation can encourage habitual use, increase cravings and make moderation difficult.

Methodologically, the team conducted a policy-focused analysis drawing from addiction science, nutrition research and historical tobacco industry documents. They compared how tobacco companies engineered cigarettes to enhance nicotine delivery with how food manufacturers optimize products for rapid reward and repeat consumption. The review also examined marketing tactics, pricing strategies and public messaging that frame overconsumption as an issue of personal responsibility rather than product design.

Lead author Ashley Gearhardt, a professor of clinical psychology at the University of Michigan, notes that the goal is not to equate eating with smoking. Instead, the researchers highlight structural similarities: both industries have developed products that amplify brain reward pathways while shaping public narratives to minimize corporate accountability.

The authors argue that current public health messaging places too much emphasis on willpower. They suggest shifting attention toward food environments—what products are affordable, aggressively marketed and widely accessible, especially to young adults.

By reframing ultraprocessed food consumption as a systemic issue rather than solely an individual failure, the researchers hope to spark discussion about regulatory approaches similar to those used in tobacco control.

REFERENCE: Ashley N. Gearhardt et al, From Tobacco to Ultraprocessed Food: How Industry Engineering Fuels the Epidemic of Preventable Disease, The Milbank Quarterly (2026). DOI: 10.1111/1468-0009.70066

Chronic Kidney Disease Associated With Higher Risk of Cognitive Decline: Study

As chronic kidney disease worsens, the brain may quietly suffer alongside it. A new study suggests that advancing kidney dysfunction is linked to measurable declines in cognitive abilities—including attention, processing speed and executive function. The findings, published in JAMA Network Open, highlight disease severity as a potential risk factor for cognitive impairment.

Chronic kidney disease (CKD) is a long-term condition marked by the gradual loss of the kidneys’ ability to filter waste from the blood. It typically persists for more than three months and can progress over years. While CKD is known to increase cardiovascular risk, growing evidence suggests it may also affect brain health.

In this cohort study, researchers—including a team from Tulane University—analyzed data from 5,607 adults aged 21 to 79 with CKD. Participants underwent blood and urine testing to measure kidney function, along with standardized cognitive assessments over a six-year follow-up period. A key measure was the urinary protein-to-creatinine ratio, an indicator of kidney damage.

The results showed that higher levels of urinary protein were significantly associated with poorer performance in attention, processing speed and executive function—the mental skills involved in planning, organizing and decision-making. Even after adjusting for clinical factors such as hypertension, the association between kidney disease severity and cognitive decline remained.

Researchers suggest several possible mechanisms. CKD can worsen high blood pressure, which in turn may damage small blood vessels in the brain. Vascular injury is a well-known contributor to cognitive impairment and dementia. However, hypertension alone did not fully explain the observed link.

Other CKD-related conditions may also play a role. Chronic inflammation, oxidative stress, anemia, sleep disturbances and abnormal bone mineral metabolism—common in advanced kidney disease—have all been implicated in brain dysfunction in prior research.

The findings underscore the importance of monitoring cognitive health in patients with chronic kidney disease. As kidney function declines, clinicians may need to consider the brain as another organ at risk, emphasizing early intervention strategies that address both renal and cognitive health together.

REFERENCE: Huang Z, Yaffe K, Li C, et al. Chronic Kidney Disease Severity and Risk of Cognitive Impairment. JAMA Netw Open. 2026;9(2):e2559834. doi:10.1001/jamanetworkopen.2025.59834