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  • Writer's pictureAlan Frischer, MD, MPH


Coffee – admit it; you love it. But it seems that every day there is a new study telling us that caffeine is good…or bad for us. Which is it? The best answer is both.

Caffeine is a stimulant that occurs naturally in the leaves, seeds, or fruit of more than 60 plant species, including coffee beans, tea leaves and buds, cacao beans, dola nuts, guarana seeds, and yerba mate leaf. It’s known as a central nervous system stimulant, and in some prescription and over-the-counter medicines, it’s used to lessen drowsiness and to improve the effect of pain relievers. In recent years, caffeine has been added to protein and energy bars, workout drinks, powders, gels, and even gum, jellybeans, waffles, oatmeal, water, syrup, sunflower seeds…and marshmallows! In the United States, more than 90% of adults consume caffeine regularly, at over 200 milligrams per day on average.

Caffeine raises our heart rate and blood pressure, increases energy levels, and improves mood. It acts within minutes, and has a half-life of about five hours, meaning that half of it will still be in our body five hours later. We can build up a tolerance as the body becomes resistant to the drug, and some barely even notice its effects. On the other hand, those who are very sensitive to caffeine may feel it for hours, and even into the next day. It depends upon the amount consumed and on individual factors, including age and body weight.

Many studies have demonstrated caffeine’s benefits. Here are just a few:

  • Just 75mg can increase attention and alertness, and higher doses may improve mental alertness, speed of reasoning, and memory.

  • Caffeine can increase endurance and reduce perceived exertion.

  • Drinking coffee may slow the mental decline that is often associated with age.

  • Some studies suggest that long-term caffeine consumption may reduce the risk of developing Alzheimer’s dementia, and higher levels of coffee consumption have been associated with a lower risk of developing Parkinson’s disease.

  • Caffeine may help with weight loss by suppressing appetite. It also may stimulate thermogenesis, so that the body generates more heat and energy from digesting food.

  • Caffeine may help protect people from blepharospasm, an eye disorder, and may help protect the lens of the eye against cataracts.

  • Caffeine may guard against some skin cancers. One study showed that the consumption of three cups of coffee a day led to a 21% lower risk of developing basal cell cancer for women, and a 10% lower risk for men.

  • A higher caffeine intake was associated with a lower risk of kidney stones.

  • Men and women who consumed four cups of coffee per day showed a 49% lower risk of death from oral cancers.

  • A study of Swedish women indicated that drinking more than one cup of coffee per day may lead to a 25% lower risk of stroke, and a recent German study found a lower risk of mortality from heart disease.

The negative side effects of caffeine are well known, including nervousness, restlessness, irritability, stomach ache, diarrhea, rapid or irregular heart beat, increased rate of breathing, insomnia, sweating, gout attacks, incontinence, exacerbation of hot flashes during menopause, migraines, heartburn, and even anxiety and panic attacks. Caffeine increases urinary volume and frequency, causing the body to lose water and electrolytes. High doses are associated with a small decrease in bone density, because caffeine affects the way in which our bodies absorb calcium.

The American Psychiatric Association does not label caffeine as an addictive drug. Still, caffeine withdrawal is a real syndrome. Symptoms, including fatigue, irritability, muscle pain, nausea, lack of focus, and headache typically subside within a few days. A gradual taper usually works best for those trying to quit their caffeine habit.

An important note about alcohol and caffeine: drinking coffee does not make us sober, or fit to drive. It does make us more alert, but does not reverse the poor judgment and other effects associated with alcohol.

My bottom line? The data coming at us is both positive and negative, and oftentimes directly conflicts. Consume caffeine if you enjoy it. Be attuned to undesirable side effects, and reduce your consumption as necessary. If your goal is to increase your energy level, consider other methods such as exercise, improved nutrition, better sleep, and stress reduction.

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