However, the study did not detect these potential benefits when coffee consumption exceeded this level. The 3-4 cup limit aligns with the daily maximum recommended by several major health agencies, including the NHS and the US Food and Drug Administration.

Telomeres, Mental Illness, and Why They Matter

Telomeres are located at the ends of chromosomes and function much like the plastic tips on shoelaces that prevent fraying. Although telomeres naturally shorten with age, the process appears to happen faster in people with major psychiatric conditions such as psychosis, schizophrenia, and bipolar disorder, the researchers note.

Because telomeres respond to environmental influences, including diet, the team explored whether moderate coffee intake might slow telomere shortening in individuals with serious mental health disorders. Coffee has been linked to various health benefits when consumed in moderation, making it a logical area for investigation.

Study Participants and Coffee Habits

The study examined 436 adults who were part of the Norwegian Thematically Organised Psychosis (TOP) study between 2007 and 2018. Of these participants, 259 had schizophrenia and 177 had affective disorders that included bipolar disorder and major depressive disorder with psychosis.

Participants reported their daily coffee intake and were placed into 4 groups: zero (44 people), 1-2 cups, 3-4 cups (110 people), and 5 or more cups. They were also asked about their smoking habits and how long they had smoked.

Those drinking 5 or more cups a day tended to be older than people who drank none or only 1-2 cups. Participants with schizophrenia also consumed more coffee on average than participants with affective disorders.

Smoking affects how quickly the body processes caffeine. Approximately three quarters of the group (77%; 337 people) were smokers, with an average smoking history of 9 years. Participants who drank 5 or more cups had smoked for significantly longer than those in the other categories.

Telomere Measurements and Key Findings

Researchers measured telomere length using white blood cells (leucocytes) from blood samples. The results showed notable differences among the four coffee intake groups, forming what the researchers describe as a J shaped curve.

Compared with participants who drank no coffee, those who consumed 3-4 cups each day had longer telomeres. This association did not appear in the group that drank 5 or more cups.

Participants consuming 4 cups a day had telomere lengths that aligned with a biological age roughly 5 years younger than non-coffee drinkers. This assessment accounted for age, sex, ethnicity, tobacco use, type of mental disorder, and current treatments.

Biological Explanations and Study Limitations

Because this was an observational study, the authors emphasize that it cannot establish a direct cause-and-effect relationship. They also note that they lacked details about several potentially important factors such as the type of coffee consumed, when it was consumed, the exact caffeine content, and whether participants drank other caffeinated beverages.

Even so, the researchers point to several possible explanations. Coffee contains potent antioxidant and anti-inflammatory compounds that may help protect cells from aging-related damage.

"Telomeres are highly sensitive to both oxidative stress and inflammation, further highlighting how coffee intake could help preserve cellular aging in a population whose pathophysiology may be predisposing them to an accelerated rate of aging," they explain.

Global Coffee Consumption and Safety Considerations

Coffee remains one of the most widely consumed beverages worldwide, with an estimated 10.56 billion kilos consumed globally in 2021-2.

Despite its potential advantages, the researchers caution that "consuming more than the daily recommended amount of coffee may also cause cellular damage and [telomere] shortening through the formation of reactive oxygen species," reiterating that international health authorities advise keeping daily caffeine intake at or below 400 mg/day (4 cups of coffee).

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