Medical Bulletin 27/June/2026 - Video

New Trial Establishes Safe Daily L-Tyrosine Intake for Healthy Adults

A four-week course of L-tyrosine supplementation appears to be safe and well tolerated in healthy adult men, according to a new study published in the journal Nutrients.

L-tyrosine is an amino acid naturally found in protein-rich foods such as meat, dairy products, and soy. It plays an important role in the production of neurotransmitters involved in mood, attention, and stress responses. While previous studies have suggested potential cognitive and stress-related benefits of L-tyrosine, data on its long-term safety at different doses have been limited.

To address this gap, researchers in Japan conducted a randomized, double-blind, placebo-controlled trial involving 30 healthy men aged 20 to 60 years. Participants received placebo or L-tyrosine supplements at doses ranging from 1 to 4 grams per day for four weeks, with washout periods between treatment phases.

The researchers monitored a wide range of health measures, including liver and kidney function, blood cell counts, cholesterol levels, blood sugar, electrolytes, and other biochemical markers. They also tracked adverse events, dietary intake, body measurements, and blood amino acid levels throughout the study.

Results showed no significant differences between any L-tyrosine dose and placebo for clinical safety markers. Liver function, kidney function, blood counts, and metabolic measures remained stable across all treatment groups. Although 18 mild or moderate adverse events were reported during the study, no serious adverse events occurred, and researchers found no evidence of a dose-related increase in side effects.

Based on the findings, researchers concluded that daily L-tyrosine supplementation of up to 4 grams for four weeks produced no observable adverse effects in healthy adult men. However, they noted that larger studies involving women, individuals with medical conditions, higher doses, and longer follow-up periods are needed to fully evaluate its long-term safety.

REFERENCE: Matsumoto H, Miura N, Naito M, Elango R (2026). Evaluation of the Safety and Tolerability of L-Tyrosine Supplementation in Healthy Adult Men: A Randomized Crossover Trial. Nutrients, 18(12), 2020. DOI: 10.3390/nu18122020, https://www.mdpi.com/2072-6643/18/12/2020

GLP-1 Weight Loss Drugs Linked to Reduced Risk of Violent Behavior: Study

A class of medications commonly prescribed for diabetes and weight management may be linked to reduced violent behavior by weakening the connection between impulsive tendencies and aggressive actions, according to a new study published in Criminology.

Researchers from Rutgers University examined whether these medications influence behavioral factors that are strongly associated with violence, particularly impulsivity and alcohol consumption. Previous research has suggested that these treatments may affect brain pathways involved in reward, self-control, and decision-making, raising questions about their potential impact beyond metabolic health.

The study analyzed data from a nationwide U.S. survey involving 7,521 adults, with a primary focus on 821 individuals who had used these medications. Researchers compared current users with former users and assessed how medication use influenced the relationship between impulsivity, alcohol use, and self-reported violent behaviors such as fighting, assault, and robbery.

Consistent with previous research, higher levels of impulsivity and alcohol consumption were associated with a greater likelihood of violent behavior across the overall sample. However, these associations were significantly weaker among people who were currently taking the medications.

The researchers found that the link between impulsivity and violent behavior was approximately 62% weaker among current users compared with former users. The relationship between alcohol use and violent behavior was also reduced by about 52%, although those findings were less consistent across additional analyses.

According to the researchers, the results suggest that the medications may not eliminate impulsive tendencies but could weaken the process that turns impulses into actions. This effect resembles mechanisms seen in behavioral therapies that help people improve self-control and decision-making.

The authors caution that the study does not prove the medications directly reduce violent behavior. Because the research was observational and based on a single point in time, it can only identify associations rather than establish cause and effect.

REFERENCE: Daniel C. Semenza, Christopher Thomas. Glucagon-like peptide-1 receptor agonist use and violent crime among US adults. Criminology, 17 June 2026 DOI: 10.1111/1745-9125.70058

Scientists Say Most People Need More Protein Than Current Guidelines

A growing body of research suggests that current public health recommendations for exercise and protein intake may be sufficient to prevent deficiency, but may not be enough to support optimal health, healthy aging, and long-term independence.

A new paper published in Frontiers in Nutrition argues that many people could benefit from higher levels of physical activity and protein consumption than current guidelines typically recommend.

The review highlights evidence linking regular exercise to a wide range of health benefits, including lower risks of chronic disease and premature death, improved mental well-being, better cognitive function, and greater resistance to age-related decline.

According to the paper, combining aerobic activities such as walking, running, or cycling with resistance training may provide particularly strong benefits by helping preserve strength, mobility, and physical function as people age.

The paper also examines protein requirements beyond the minimum amounts needed to prevent deficiency. Current recommendations in many countries are largely based on sedentary adults, but newer research suggests that older adults, physically active individuals, and pregnant women may benefit from higher protein intakes.

The review further notes that higher-protein diets may aid body composition by increasing feelings of fullness and boosting the body's energy expenditure during digestion. Importantly, the author emphasizes that sufficient protein can be obtained through both animal-based and plant-based diets when meals are properly planned.

Rather than replacing existing public health recommendations, the paper calls for additional guidance focused on achieving optimal health outcomes rather than simply avoiding disease. The author argues that exercise and nutrition should be viewed as tools for maintaining physical strength, mental sharpness, and independence throughout life.

REFERENCE: Chris Macdonald. Beyond the bare minimum: the case for revised physical activity guidelines and protein intake recommendations that maximise healthspan. Frontiers in Nutrition, 2026; 13 DOI: 10.3389/fnut.2026.1853124