Medical Bulletin 16/December/2025

Biological age is different from the number of candles on your birthday cake—it reflects how your cells and DNA are functioning. Scientists measure it using DNA methylation, tiny chemical marks on our genes that shift as we age. The research team analyzed blood samples from over 1,600 adults, including participants in the TwinsUK study and the KORA cohort in Germany, to see how circulating levels of cocoa-related compounds correlated with biological aging markers.

The analysis revealed that those with more theobromine tended to have a younger biological age, even after adjusting for chronological age and lifestyle differences. Interestingly, no other compounds found in cocoa or coffee—such as caffeine—showed a similar effect. Researchers also found that higher theobromine levels correlated with longer telomeres, the protective ends of chromosomes that naturally shorten as we get older, signaling healthier cellular aging.

Theobromine belongs to a family of plant alkaloids that can influence gene activity and cell repair. While it’s toxic to dogs, in humans it may support vascular health and metabolism. Lead author Dr. Ramy Saad notes that these findings open new avenues for studying how diet-derived molecules interact with the epigenome, potentially shaping aging at a cellular level.

Still, the researchers caution against stocking up on chocolate bars. Theobromine might be beneficial, but chocolate often comes packaged with sugar and saturated fats. Instead, they suggest focusing on a balanced diet rich in natural plant compounds, many of which—like theobromine—may quietly work to keep our bodies younger for longer.

REFERENCE: Ramy Saad, Ricardo Costeira, Pamela R. Matías-García , Sergio Villicaña, Christian Gieger, Karsten Suhre, Annette Peters, Gabi Kastenmüller, Ana Rodriguez-Mateos, Cristina Dias, Cristina Menni, Melanie Waldenberger, Jordana T. Bell. Theobromine is associated with slower epigenetic ageing. Aging, 10 December 2025

Study finds tea may boost bone strength in older women; coffee linked to weakening

A warm cup might be doing more for you than just bringing comfort. A decade-long study from Flinders University has revealed that while moderate coffee is safe, daily tea consumption may help protect bones and slow age-related bone loss in older women. Published in the journal Nutrients, the findings draw from one of the largest long-term investigations of how caffeine-based beverages affect bone strength, emphasizing that what we drink each day could subtly influence our skeletal health.

Osteoporosis—a condition that weakens bones and increases fracture risk—affects about one in three women over fifty. Given how common coffee and tea are across daily diets, researchers sought to clarify their impact on bone mineral density (BMD), a key measure of bone strength. Using data from nearly 10,000 women aged 65 and older, the Flinders team tracked beverage intake patterns and repeated bone scans for ten years as part of the Study of Osteoporotic Fractures. The scans focused on the hip and femoral neck, the regions most prone to fractures later in life.

The results were surprisingly clear. Women who drank tea regularly had slightly higher BMD than non-tea drinkers. Though the difference was small, it was statistically significant—enough to suggest a population-level benefit. “Even small improvements in bone density can mean fewer fractures across large groups,” explained Associate Professor Enwu Liu, the study’s senior author.

Coffee, however, told a more complex story. Drinking up to two or three cups a day appeared harmless, but over five cups daily was linked to lower BMD, indicating potential bone depletion with excessive intake. The negative effects were strongest among women who also consumed more alcohol, while tea’s benefits were most evident in participants with obesity—a group often at higher risk of bone fragility.

Tea’s protective edge may come from catechins, natural plant compounds that help promote bone formation and reduce breakdown. Coffee’s high caffeine content, meanwhile, can slightly reduce calcium absorption, though adding milk appears to offset this effect.

The study’s authors emphasize moderation, not restriction. “You don’t need to give up coffee or drink endless cups of tea,” says Liu. “But enjoying a daily cup of tea could be a simple, enjoyable step toward stronger bones.”

REFERENCE: Ryan Yan Liu, Enwu Liu. Longitudinal Association of Coffee and Tea Consumption with Bone Mineral Density in Older Women: A 10-Year Repeated-Measures Analysis in the Study of Osteoporotic Fractures. Nutrients, 2025; 17 (23): 3660 DOI: 10.3390/nu17233660

Harvard researchers uncover gut link that may transform obesity and diabetes treatment

The gut may hold the keys to how our bodies manage energy and blood sugar. In a groundbreaking international study published in Cell Metabolism, scientists uncovered a group of gut-derived molecules that travel from the intestine to the liver and then to the heart, influencing how the body regulates metabolism and insulin sensitivity. The discovery suggests that these microscopic chemical messengers could one day help develop new treatments for obesity and type 2 diabetes.

The research, led by Harvard University in collaboration with the University of São Paulo (USP) and the University of Eastern Finland, explored how nutrients processed by gut bacteria interact with the liver—our central metabolic hub. When food is digested, it releases microbial byproducts into the hepatic portal vein, a blood vessel that directly connects the gut and the liver. This pathway makes the liver the body’s first responder to signals from the microbiome.

Using sophisticated metabolic profiling, scientists compared blood samples from healthy mice and those genetically prone to obesity and diabetes. Samples were taken from both the hepatic portal vein (blood exiting the intestine) and peripheral circulation (blood moving through the body). In healthy mice, researchers found 111 unique metabolites enriched in the hepatic vein, but this number dropped dramatically to 48 when the animals were fed a high-fat diet. The sharp decline suggests that poor diet alters which gut-produced chemicals reach the liver—and how effectively the body handles energy.

To test whether these molecules affect metabolism, the team looked at one standout compound: mesaconate, a metabolite involved in the Krebs cycle, the fundamental energy-producing process in cells. When liver cells were exposed to mesaconate in the lab, insulin signaling improved, and genes that regulate fat production and oxidation were better balanced.

The study also revealed that both genetics and environment shape how microbes produce these metabolites. When susceptible mice were treated with antibiotics to disrupt gut bacteria, metabolite profiles changed again, confirming the microbiome’s critical influence.

Lead author Dr. Vitor Rosetto Muñoz explains, “This is the first evidence that specific gut-to-liver metabolites directly influence insulin sensitivity.” The team is now identifying which bacterial strains generate these molecules. Their ultimate goal: to use these findings to design microbiome-based therapies that restore healthy metabolic function and prevent diseases such as diabetes.

REFERENCE: Vitor Rosetto Muñoz, Francois Moreau, Marion Soto, Yoshiyuki Watanabe, Loc-Duyen Pham, Jimmy Zhong, Sam Zimmerman, Bruna B. Brandao, Khyati Girdhar, Julian Avila, Hui Pan, Jonathan M. Dreyfuss, Michael Y. Mi, Robert E. Gerszten, Emrah Altindis, Aleksandar Kostic, Clary B. Clish, C. Ronald Kahn. Portal vein-enriched metabolites as intermediate regulators of the gut microbiome in insulin resistance. Cell Metabolism, 2025; 37 (10): 2048 DOI: 10.1016/j.cmet.2025.08.005