Coffee: The good, the bad and the ugly

coffee healthy habits

We all get frustrated when we listen to a news report touting all the health benefits of a certain food, and then the following month another news report describes all the ways that same food is trying to kill us. Most of the time, we receive conflicting advice because the answer is not straightforward. Such is the case with coffee.

 A new study from the New England Journal of Medicine tries to put the issue of coffee and our health to rest. The authors’ take home message: caffeinated coffee doesn’t increase your risk for heart disease or cancer, and in fact, three to five cups a day can actually reduce your risk of certain diseases.

Coffee itself is loaded with phytochemicals, vitamins and minerals that help reduce oxidative stress in the body, improve the gut microbiome, and regulate glucose and fat metabolism. This where all the health benefits of coffee come from.

But the caffeine found in coffee is where many of its problems lie. Caffeine affects nearly all of our body systems:

  • It has many benefits to the brain and nervous system, including increased alertness and improving mental performance, it reduces the risk of depression, and may even reduce the risk of Parkinson’s disease. However, it also contributes to insomnia and can induce anxiety.
  • It also affects the cardiovascular system, increasing blood pressure in the short-term.
  • Caffeine is used to treat breathing problems in premature infants, and it can improve lung function in adults as well.
  • It reduces the risk of liver fibrosis, cirrhosis and cancer.
  • It can reduce fetal growth and increase the risk of pregnancy loss in pregnant women.
  • It reduces the sensitivity of your muscles to insulin.
  • Finally, it can have a diuretic effect on your kidneys.

 It’s important to understand that coffee can affect people differently. About 50% of the population are “slow” caffeine metabolizers. This means the caffeine stays around longer in the body than people who are “fast” caffeine metabolizers. And although this make sound like a perk, in reality, if you’re a slow metabolizer, consuming a lot of coffee can actually increase your risk of heart disease. The speed at which you metabolize caffeine is largely genetic. The good news, though, is that slow metabolizers naturally drink less caffeine. Body wisdom tends to win out!

Having said that, for most people, coffee is just fine. The researchers from this study suggest that high doses, which means 200 mg in one sitting, or 400 mg throughout the day, can induce anxiety in some people. Those who are slow metabolizers will experience this at lower intakes. This obviously doesn’t happen to everyone, but if you experience the jitters, anxiety or agitation when you drink coffee, that’s a good sign you’ve had too much. To put this into perspective, a typical cup of coffee brewed at home has about 100 mg of caffeine.

There are a few things that will affect how caffeine affects you. For example, pregnancy slows down caffeine metabolism. By the third trimester, it can time 15 times longer to metabolize caffeine. And newborns will experience the effects of caffeine for days. Taking the birth control pill will double the time it takes to metabolize caffeine. Smoking has the opposite effect – it will cut the time it takes to metabolize the caffeine in half.

We all know that coffee can give you an energy lift in the moment. But it is no substitute for a good night’s rest. Your body needs a decent amount of sleep to recover, rebuild muscles, and reset your brain. If you are relying on coffee to stay awake and alert during the day, that’s probably a good sign that you need to take a look at your sleep habits and make some changes.

If you’re looking to decrease your caffeine intake, here are a few quick tips for you:

  • Try replacing some of your coffee with decaf – you’ll still great the great benefits of all the phytochemicals in the coffee itself
  • Decrease your intake by one cup
  • Try replacing some of your coffees with herbal tea
  • Order a tall or grande instead of a vente at Starbucks
  • Have one shot of espresso instead of two


Van Dam RM, Hu FB, Willett WC.Coffee, Caffeine, and Health. N Engl J Med . 2020 Jul 23;383(4):369–78.