The dangerous effects of caffeine

By Liz Meszaros, MDLinx
Published October 3, 2018

Key Takeaways

Many people need their morning cup o’ Joe to function, but is coffee really that safe for you? The benefits of coffee have been touted in recent research and include reducing the risks of cardiovascular disease, type 2 diabetes, and even Parkinson’s disease. But other studies have shown that coffee, and the caffeine it contains, can have some bad effects as well.

Caffeine is said to be the world’s most widely consumed psychoactive drug. According to the International Coffee Organization, roughly 1.6 billion cups of coffee are consumed each day throughout the world. In the United States, the Food and Drug Administration has reported the daily caffeine intake is roughly 300 mg/person/d, equivalent to 2-4 cups of coffee. This is considered moderate.

Some of the more deleterious effects of excessive caffeine consumption can include the following:

  • According to the Mayo Clinic, consumption of more than 500-600 mg/d of caffeine can cause insomnia, nervousness, restlessness, irritability, dyspepsia, an increased heart rate, and muscle tremors.
  • Caffeine may raise blood pressure, especially in hypertensives and those who do not normally consume caffeine.
  • Young hypertensive adults who consume caffeine equivalent to four cups of coffee per day may be at a four-fold risk of myocardial infarction (MI), and even more moderate consumption may increase their risk of MI by three fold (Presented at ESC Congress 2015).
  • Caffeine binges may increase the risk for a flare-up of gout.
  • The risk of fibrocystic breast disease may be slightly increased (1.5-fold) in women who drink 31-250 mg/d. Those who drank over 500 mg/d had a 2.3-fold increase in the odds of developing cysts.
  • Women who consume a lot of caffeine are 70% more likely to develop incontinence
  • Investigators from the Mayo Clinic found that men who drank more than four cups of coffee per day had a 21% increased risk of all-cause mortality compared with non-coffee drinkers. They also found that men and women who consumed excessive amounts of coffee were more likely to smoke and be in poor physical condition.

In light of the research, perhaps the old adage —“Everything in moderation”—would be the wisest approach to caffeine intake.

Caffeine-epilepsy link

The cause-and-effect relationship between caffeine and epileptic seizures has long been debated, as have the pros and cons of caffeine consumption in general.

Caffeine prevents drowsiness by blocking the action of adenosine, a drowsiness hormone, and simultaneously stimulates areas of the autonomic nervous system. Many Americans drink caffeine daily in the form of coffee, soda, and energy drinks. This includes 80% of those with epilepsy. Because caffeine stimulates brain activity, researchers have long sought to determine whether caffeine can trigger epileptic seizures.

Most of the scientific research on caffeine and epilepsy has focused on adenosine, a hormone present in all the cells in the body. Epileptic seizures trigger a surge of adenosine, which leaves people groggy. Caffeine, however, interferes with adenosine while simultaneously stimulating areas of the autonomic nervous system, making people more alert.

In other research, investigators have indicated that precipitating factors—and not caffeine—may be to blame for the seizures. Such factors include missing a dose of medication, drinking alcohol, and not getting enough sleep. It is only in the presence of one or more precipitating factors that the addition of caffeine may increase seizure risk in epileptic individuals.

An oft-cited study on the topic was conducted in 2013 by Samsonsen et al, who found no strong relationship between caffeine consumption and the risk of seizure.

In a more recent systematic review (2018), however, van Koert et al found that, while clinical studies on the link between seizures and caffeine were rare, there was a suggestion in preclinical studies that caffeine did increase seizure susceptibility. In some cases, however, it was protective. These researchers also found evidence that caffeine seems to lower the efficacy of several drugs, especially topiramate, in animal models. They concluded that caffeine intake should be carefully considered in patients with epilepsy who are trying to achieve and maintain control of their seizures.

But again, many variables may come into play, especially with coffee. The liver and the body’s metabolism may play a role. Even sugar and cream levels in a cup of coffee may have an effect. Larger variables can even include the geographic area in which coffee drinking occurred, the level of roast, and chemistry of the drink.

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