Three to four cups of coffee a day may slow biological aging for those with severe mental illness, according to new research published in The BMJ. The key factor behind this effect is the lengthening of telomeres, a benchmark of cellular aging.
Authors of the paper suggest this daily habit may offer coffee drinkers the equivalent of five extra biological years, compared to abstainers.
However, this effect did not occur beyond four cups, which is the maximum recommended daily coffee intake threshold endorsed by several regulatory and health authorities including the UK’s National Health Service and the US FDA.
“Those participants getting a daily four-cup caffeine hit had telomere lengths comparable to a biological age five years younger than that of non-coffee drinkers after adjusting for age, sex, ethnicity, tobacco use, type of mental ill health, and drug treatment,” note the researchers.
Experts reacting to the observational study highlight key considerations about its findings.
Dr. Elizabeth Akam, senior teaching fellow in Biosciences, Loughborough University, UK, notes: “A noteworthy limitation of this study is that it treats ‘coffee’ as if it were a single substance. However, coffee contains many different compounds, and we don’t know which of these were administered, in what doses, or how much actually ended up in the bloodstream.”
“The evidence in this area is a mixed bag where many factors come into play like the efficacy of self-reporting — i.e. how accurately people report their coffee intake — and the blood concentration levels of the individual components of coffee, such as caffeine and associated metabolites. This matters because caffeine itself has been linked to telomere shortening.”
Coffee and mental health
Research backs coffee’s antidepressant effect, which another study recently found mirrors that of ketamine and electroconvulsive therapy.
Authors of the paper suggest three to four cups of coffee may offer the equivalent of five extra biological years, compared to for abstainers.Coffee’s longevity benefits at the cellular level are also backed by previous research in fission yeast — a single-celled organism similar to human cells — which found that caffeine “taps into an ancient cellular energy system” to help cells sustain life.
“Studies have indicated that individuals with psychiatric disorders ingest significantly higher caffeine levels compared with healthy controls,” note the study authors.
“Further differences have been found between different disorders, with some studies noting that individuals with bipolar disorder were found to drink more coffee compared with those with schizophrenia, with both psychiatric cohorts ingesting more coffee compared with healthy controls.”
The current BMJ study included 436 adult participants from the Norwegian Thematically Organised Psychosis study. Among them, 259 had schizophrenia, while the rest had affective disorders, including bipolar disorder and major depressive disorder with psychosis.
Based on how much coffee participants drank every day, researchers grouped them into four categories: zero (44), one to two cups (117), three to four cups (110), and five or more cups (133). They also indicated if participants smoked and for how long.
On average, participants who drank more than five cups a day were significantly older than those who drank none or one to two cups a day. Those with schizophrenia drank significantly more coffee than those with an affective disorder.
As a confounding factor, the authors note that smoking is associated with faster caffeine metabolism. Around three-quarters of participants (77%) smoked for nine years on average. Those drinking more than five cups a day had smoked for significantly longer than any of the other groups.
Effects on telomere shortening
Telomeres are found on the ends of chromosomes and perform a role “similar to the plastic tips on the end of shoelaces,” as the researchers put it. They note telomere shortening is a natural part of the aging process, but is accelerated in those with major psychiatric disorders, such as psychosis, schizophrenia, and bipolar disorder.
Telomeres are sensitive to environmental factors, possibly including diet. Coffee’s associated health benefits, when drunk in moderation, compelled the researchers to explore if it has any effect on the rate of telomere shortening among patients with major mental illnesses.
“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.
They measured the length of telomeres from white blood cells (leucocytes) taken from blood samples. This revealed a significant difference among the four groups.
Compared to those who did not drink coffee, participants who consumed up to three to four cups a day had longer telomeres on average. However, this was not the case among those drinking five or more daily.
The researchers underscore that no firm conclusions can be drawn about cause and effect from this observational study. They also acknowledge that the study did not include information on potentially influential factors, such as the type and timing of the coffee consumed, actual caffeine levels, or other sources of caffeinated drinks.
But, the researchers suggest there are plausible biological explanations for their findings. “These include the powerful antioxidant and anti-inflammatory compounds found in coffee.”
Despite coffee’s potential benefits, they warn 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.
Akam at Loughborough University adds: “To truly establish a link, positive or negative, between coffee, caffeine and antioxidant capacity for telomere length, future research should consider leukocyte telomere length and the levels of different compounds in coffee — such as caffeine — in the blood.”
