Exploring the Benefits and Drawbacks of Caffeine Consumption
Waking up to a cup of coffee or tea has become our daily morning ritual, but does it do more than just give us a pick-me-up? Recent investigations suggest that our dependency on caffeine might be more dangerous than we think.
"The kick against the wall is that habitual use - even a single cup of tea daily - results in withdrawal after a period of abstinence. A primary symptom of withdrawal is drowsiness, which can be alleviated by ingesting the stimulant," asserts Michael Keane from Dublin City University.
Caffeine bears a striking resemblance to the molecule adenosine, a substance that suppresses activity in the central nervous system. Adenosine receptors can be found throughout the body, and when adenosine binds to them, it inhibits the release of neural transmitters, promoting sedation and having anti-convulsant activity. Caffeine, being an adenosine antagonist, binds to the receptors but without decreasing neural activity.
Caffeine's influence is not easy to study because individuals have varying levels of tolerance. If you indulge in medium to high amounts, your sensitivity to it plummets. Whilst caffeine helps keep us awake and offers minor improvements in physical performance, it results in jitteriness and anxiety in some people and raises blood pressure by narrowing blood vessels. During withdrawal, blood vessels widen again, leading to headaches when caffeine is absent. Symptoms of withdrawal improve within a few days and disappear after about a week.
Researchers from the University of Bristol found that by 10:30 am, individuals accustomed to a morning dose of caffeine were already beginning to experience mild withdrawal symptoms. By the afternoon, effects intensified, leading to sleepiness, lower mental alertness, and poorer performance on reaction and memory tasks.
Caffeine only enhanced reaction times but did not improve mental performance. The Bristol team argues that frequent consumption fails to enhance mental alertness and mental performance. Surprisingly, caffeine had minimal influence on non-consumers, other than making them feel less sleepy.
Lead researcher Prof Peter Rogers observes, "I debated for a long time why caffeine wasn't boosting alertness in non- and low-consumers - it seemed strange." The answer lay in distinguishing between focus and being alert. Rogers discovered that caffeine's positive effects on alertness were being neutralized by jitteriness and anxiety in non- and low-consumers.
Rogers abandoned caffeine several years ago, but he occasionally has a coffee to stay awake on long car trips. "Each time I go through withdrawal again," he says, "it still catches me off guard."
Is it just a harmless habit?
Excessive caffeine can accelerate the heart or cause abnormal heart rhythms. Extreme overdoses can even be fatal. Nevertheless, even smaller amounts can have negative consequences. A study by the University of Queensland, Australia, involving nearly 45,000 people between 1979 and 1998 found that men who consumed 28 cups of coffee per week were 56% more likely to die from all causes before the age of 55, while women running a similar risk doubled their chances of mortality. Researcher Carl Lavie admits that additional research is necessary, but for now, he advises moderation.
Both the US Food and Drug Administration (FDA) and the European Food Safety Authority (EFSA) are examining caffeine's safety. The FDA's efforts are prompted by the addition of caffeine to a growing number of products, while EFSA was asked by the European Commission to assess the risk of adverse health effects resulting from caffeine intake 'from all sources.' Although caffeine can be found in a variety of products, including chocolate, the greatest concerns revolve around energy drinks, the fastest-growing sector of the UK drinks market since 2004, according to a report for the UK Food Standards Agency by its Committee on Toxicity (COT). An average energy drink contains about 80 milligrams (mg) of caffeine per 250ml can. This compares with 60-80mg of caffeine in an average cup of instant coffee and up to 135mg per cup of filter coffee. A can of cola contains 30-45mg of caffeine.
Caffeine's half-life in the body is approximately five hours, yet it can linger in certain cases for up to 30 hours, such as in women taking oral contraceptives, pregnant women, and young children. These groups are more susceptible to caffeine toxicity, explains Alan Crozier from the University of Glasgow's School of Medicine.
Pregnant women in the UK and the US are advised to limit their daily caffeine consumption to 200mg, which equates to around three cups of instant coffee. Recent research at Sahlgrenska Academy, Sweden, based on data from over 59,000 women who participated in the Norwegian Mother and Child Cohort Study, suggests that caffeine may cause decreased birth weight.
Health Canada, the national public health organization, has recommended that children aged between 10 and 12 years maintain a maximum caffeine intake of 85mg per day. Considering that just one can of energy drink puts children at this level, concerns are mounting over their consumption. A Swiss study on rats indicates that caffeine delays brain development during puberty by reducing deep sleep.
Energy drinks aren't just harmful for children. They are frequently mixed with alcohol to produce a phenomenon known as 'wide-awake drunk,' reports the COT. The theory is that caffeine prevents people from realizing just how intoxicated they are, extending drinking time. In 2010, the FDA worked to withdraw caffeinated alcoholic beverages from the market due to studies suggesting that ingesting caffeine and alcohol together might lead to 'life-threatening situations.'
From December 2014, drinks containing more than 150mg per liter of caffeine - excluding tea and coffee - will be required to display a 'high caffeine content' warning in the European Union. There are no legal limits on the amount of caffeine that may be present.
How much is too much?
authority." People differ so much in their reactions to caffeine that a maximum figure could not be set, argues Richard Laming from the British Soft Drinks Association. "Even if there was a recommended intake, the proportion coming from soft drinks is small compared to that from tea and coffee." With tea and coffee, caffeine content varies widely from cup to cup, making it difficult to label accurately.
Glasgow's Alan Crozier has analyzed espresso coffees purchased in cafes to reveal a 6-fold difference in caffeine levels. The highest caffeine content in a single espresso was 322mg, while another three contained over 200mg. Variations stem from levels of roasting - more intense roasting lowers caffeine levels, says Crozier.
Some of us might find it easier to limit caffeine consumption than others. "We've known for a long time that people's consumption of drugs, including caffeine, has a genetic basis," says Marcus Munafo, a University of Bristol psychologist. The team is using new genetic technology to identify genetic variants that account for differing levels of consumption. "We've been looking at specific genetic variants and using more precise measures of how much caffeine people consume," he explains. The goal is to find genetic markers for caffeine consumption and to see if they predict the risk of conditions like cardiovascular disease or stroke.
"Questions remain about the effects of dietary caffeine - that is, what effects are present at normal levels of consumption," says Michael Keane. "For example, should caffeine be considered a risk factor in cardiovascular disease, given the evidence that we may not develop a tolerance to the blood pressure effects of the drug?"
While caffeine may not kill you, it is evidently detrimental to the body. If you're worried about potential negative effects, perhaps it's time to reconsider, or at least curb, your daily dose.
Emma Davies is a science journalist with a PhD in food science.
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- Despite its common use as a morning pick-me-up, excessive caffeine consumption can cause abnormal heart rhythms and accelerate the heart, potentially leading to fatal outcomes.
- A study conducted at the University of Queensland found that men who consumed 28 cups of coffee per week were 56% more likely to die from all causes before the age of 55, while women were twice as likely, highlighting the potential risks associated with caffeine.
- Caffeine affects people differently due to varying levels of tolerance, with moderate to high amounts diminishing sensitivity to its effects. However, caffeine can cause jitteriness, anxiety, and raise blood pressure in some individuals.
- Researchers from the University of Bristol discovered that by 10:30 am, individuals accustomed to a morning dose of caffeine were already experiencing mild withdrawal symptoms, leading to decreased mental alertness and poorer performance on tasks later in the day.
- Pregnant women and children are more susceptible to caffeine toxicity, and regular consumption can lead to decreased birth weight in children and delayed brain development during puberty. Furthermore, energy drinks are often mixed with alcohol, potentially leading to prolonged drinking times and life-threatening situations.
