Medical Bulletin 03/August/2026

Researchers found that reducing protein intake may slow biological aging by improving metabolism, lowering inflammation, reducing cellular damage, and preserving healthy cell function. Unlike calorie restriction, which can be difficult to maintain, protein restriction has shown benefits in animal studies without reducing overall calorie intake.

Previous research has demonstrated that lower protein intake can extend lifespan in flies and rodents. Human clinical trials have also found that protein-restricted diets can reduce body weight, fat mass, and fasting blood sugar, even when participants consume more total calories.

One of the main biological mechanisms involves fibroblast growth factor 21 (FGF21), a hormone that rises when protein intake is low. Higher FGF21 levels have been linked to increased energy expenditure, improved blood sugar regulation, and reduced inflammation. Studies in mice have also associated elevated FGF21 with longer lifespan.

The review further highlights specific amino acids—including methionine, isoleucine, and valine—that may contribute to aging-related processes when consumed in excess. High intake of these amino acids may stimulate growth-related pathways that increase the risk of obesity, chronic inflammation, and other age-related diseases.

The authors note that protein requirements are not the same for everyone. Pregnant women, highly active individuals, and some older adults may require higher protein intake. However, many sedentary adults already consume more protein than necessary and may not benefit from protein-fortified foods.

Although the review supports the potential benefits of moderate protein restriction for healthy aging, it does not recommend that everyone reduce protein intake. The authors emphasize that protein recommendations should be personalized based on factors such as age, health status, and physical activity, rather than applying a one-size-fits-all approach.

REFERENCE: Bailey A. Knopf, Dudley W. Lamming; The Hallmarks of Protein and Amino Acid Restriction in Aging and Longevity. Cell Press Blue. DOI: 10.1016/j.cpblue.2026.100079.

New Research Questions Whether Weight Loss Alone Can Prevent Type 2 Diabetes

Losing weight and maintaining a healthy lifestyle are well-established ways to lower the risk of type 2 diabetes. However, a new study published in Diabetes suggests that these measures may not provide the same level of protection for everyone, particularly those with a specific high-risk metabolic profile.

Researchers from the German Center for Diabetes Research (DZD), University Hospital Tübingen, and Helmholtz Munich found that people belonging to Tübingen's type 2 diabetes risk cluster 5 continued to experience worsening blood sugar control despite achieving significant long-term weight loss.

The study followed participants enrolled in the Tübingen Lifestyle Intervention Program (TULIP), a two-year lifestyle program involving healthy eating, weight loss, and increased physical activity. Participants were then monitored for approximately nine years.

The analysis focused on individuals who successfully lost around 8% of their body weight and maintained that weight loss over the long term.

Despite these sustained improvements, people in risk cluster 5 showed rising blood sugar levels, declining insulin production, and a persistently high likelihood of developing type 2 diabetes. In contrast, participants in other risk groups generally experienced greater metabolic benefits from lifestyle changes.

The researchers believe the reduced response may be driven by severe insulin resistance associated with fatty liver disease. Excess fat stored in the liver may impair the pancreas' ability to produce sufficient insulin, causing blood sugar levels to continue rising even after weight loss.

Previous research has already shown that cluster 5 is characterized by marked fatty liver and insulin resistance, placing individuals at particularly high risk of both type 2 diabetes and cardiovascular disease.

The findings suggest that a "one-size-fits-all" approach to diabetes prevention may not be effective. Instead, people with high-risk metabolic profiles may require personalized prevention strategies, including treatments that specifically target insulin resistance and fatty liver disease alongside lifestyle modification.

REFERENCE: Caroline Z. Meier, Robert Wagner, et al.; Different Metabolic Responses to Long-term Weight Loss After Lifestyle Intervention Among Type 2 Diabetes Risk Clusters: Results From the TULIP Study. Diabetes, 2026; 75 (6): 965 DOI: 10.2337/db25-0757

New Research Links Rice Bran Compound to Relief From Irritable Bowel Syndrome

A naturally occurring compound found in rice bran may help calm excessive intestinal contractions by blocking calcium signals that control gut muscle movement, according to a new study from Toho University. The findings suggest the compound could one day support dietary approaches for certain digestive disorders, including irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD).

Published by researchers from the university's Faculty of Pharmaceutical Sciences, the study investigated ferulic acid (FA), a plant-derived polyphenol commonly found in whole grains and rice bran. While ferulic acid is already recognized for its antioxidant and neuroprotective properties, its effects on intestinal movement had remained largely unexplored.

To examine its role, researchers tested ferulic acid on guinea pig intestinal smooth muscle. They found that the compound significantly reduced muscle contractions triggered by several naturally occurring signaling molecules, including acetylcholine, histamine, prostaglandin F2α, and serotonin.

The effect was both reversible and dose-dependent, meaning stronger inhibition occurred at higher concentrations, and normal muscle contractions returned once ferulic acid was removed.

Further experiments suggested that ferulic acid does not block the receptors for these signaling molecules directly. Instead, it appears to interfere with a shared mechanism required for muscle contraction.

The researchers found that ferulic acid reduced the movement of calcium into smooth muscle cells by inhibiting voltage-dependent calcium channels. Because calcium is essential for triggering muscle contraction, limiting calcium entry reduced the strength of intestinal contractions.

These findings suggest ferulic acid may help reduce excessive gut activity, potentially benefiting people with diarrhea-predominant IBS or IBD. However, the same effect could worsen symptoms in individuals with constipation-predominant IBS by slowing intestinal movement even further.

Although ferulic acid may reach higher levels inside the digestive tract after food consumption, clinical studies in humans are still needed to determine whether dietary intake or supplements can safely and effectively regulate intestinal motility.

REFERENCE: Keisuke Obara, Kento Yoshioka, et al.; Ferulic acid suppresses guinea pig ileal longitudinal smooth muscle contractions by inhibiting voltage-dependent Ca2 channels. Journal of Pharmacological Sciences, 2025; 158 (4): 289 DOI: 10.1016/j.jphs.2025.05.012