Every good guide includes an example if relevant. This one’s for all you coffee lovers (myself included)…

Ode to Coffee:

  • If you’re like me, you love the coffee ritual just as the effect
  • You love the aroma, the warmth and characteristic smell. The aftertaste.
  • You anticipate jumping into consciousness. You appreciate the rush of drinking a fast cup just as much as sipping slowly, as needed.
  • The dark liquid brightens things, promises a reward for becoming animate for one more day.
  • We get out of bed knowing that our ally will soon arrive
  • Soon we find work automatic, a piece of mind

Caffeine is a mild stimulant. It blocks adenosine, a chemical associated with fatigue, which in turn increases stimulating chemicals. All drugs that make people euphoric somehow increase dopamine levels.

Few people ask about the health of coffee because it’s so widely used. But we want to find out independently.

This is our research question:

What amount (if any) of coffee is safe for an adult?

Research must be specific, but not too much so. We want to know the truth behind a reasonable amount of coffee. Anything can be deadly in excess, even water.

Let’s focus on caffeine. Other chemicals in coffee affect our brains. Ideally, we’d figure these into the equation, but that much specificity isn’t called for here. This caffeine calculator might give a good, rough estimate of how much coffee is safe, based on type of coffee, and weight of drinker. Mayo Clinic, the FDA, and other authorities lists 400mg as generally safe.

We then ask how much coffee would have 400mg of caffeine in it. The Mayo Clinic has their own thoughts on it.

But we need more sources, even if the first is highly qualified. One of the first search results is a comprehensive chart: an eight-ounce cup of caffeinated joe (the standard “cup” amount) can have anywhere between 65 mg and 165 mg caffeine. Likely, your form of coffee is listed in that table. If it isn’t or you’re not sure what category it falls under, then a little math can help us get a more general, inclusive idea.

A standard espresso is listed as containing 100mg caffeine. The other three types (drip, brewed, and instant) have ranges

  • Drip: 115mg-175mg
  • Brewed: 80mg-135mg
  • Instant: 65mg-100mg
  1. We should take an average of those ranges to get a solid number
    1. Drip: 115mg+175mg=290; 290/2=…
      1. 145mg
    2. Brewed: 80mg+135mg=215; 215/2=…
      1. 107.5 mg
    3. Instant: 65mg+100mg=165; 165/2=…
      1. 82.5 mg
  2. Those three averages, plus the espresso amount: 145+107.5+82.5+100=435
  3. 435/4=108.75 mg
  4. So one cup of average coffee might have about 108.75 mg of caffeine in it.

Notice that the amount of caffeine in a cup was not rounded. If the research ended there, that is to say, if our ultimate question was to find out how much caffeine is in a typical cup of coffee, rounding would have been fine. As it is, rounding now would throw off future calculations. Only round at the end.

Most people drink between two and three cups per day. Let’s take the average for 2015, 2.1 cups. That, multiplied by our 108.75 mg per cup, gives us 228.375 mg caffeine, per day. This is well-within our previously established, healthy range. But we could search further, garnering more qualified sources to support our findings. It’s way highly unlikely that researchers conducted a study on 228.375 mg of caffeine per day. Instead of searching “Is 228.375 mg of caffeine unhealthy?”, we search for “caffeine health”, or “max caffeine health”, or “mg caffeine health”, or  “caffeine damage mg”. Then we compare our 228.375mg to those results.

Google scholar  is a good place to start searching for studies. So is pubmed. Let’s go with google scholar. So we type in “mg caffeine health” on the google scholar page. Results based on green tea aren’t relevant, as there is another significant chemical in green tea, l-theanine. Similarly, studies on energy drinks can be discarded.

Here’s a bit of practice being a statistics sleuth:

Here are valid sources, along with traits satisfying the three main aspects of qualified sources:

  1. “potential health benefits including prevention of several chronic and degenerative diseases, such as cancer, cardiovascular disorders, diabetes, and Parkinson’s disease”
    1. 2014
    2. None
    3. Received 01/20/2014; Accepted 03/28/2014
  2. “Consumption of caffeine was…associated with a reduced risk of depression”
    1. 2008
    2. None
    3. Received 04/06/2008; Accepted 10/02/2008;

A comprehensive review revealed a range of positive effects, including

  • Physical endurance
  • Greater physical efficiency
  • Otherwise greater physical performance
  • Greater blood flow to the brain
  • Better working memory
  • More vigilance
  • Better concentration
  • Enhanced attention
  • More efficiency in the functioning of the cerberal cortex
  • Wakefulness
  • Ability to problem-solve
  • Mental clarity
  • More energy
  • Greater reasoning and vigor in solving problems
  • Faster responses when tested for speed
  • Faster reaction time
  • Significantly improves the performance of the armed forces when sleep-deprived
  • Improves mood
  • Reduces anxiety
  • Less hostility
  • More contentment
  • Greater head clarity
  • Lower risk of dying prematurely

The same review furthermore considered dose, and provided the conclusions of many other studies

  • Up to 1,000 mg, or more than nine cups of our 108.375 mg per cup of coffee, is safe
  • Up to 400 mg leads to a lower mortality rate
  • No association, even at very high doses, with heart disease or cardiovascular disease
  • The rate of stroke, and death from a variety of cardiovascular diseases, decreased as caffeine consumption increased
  • 500 mg in one study, and 1,000 mg in another, didn’t lead to more heart attacks
  • Caffeine intake is not associated with hypertension, even 1,000 mg per day for 11 years
  • 500 mg to 600 mg daily caffeine for four weeks decreased blood pressure
  • Blood pressure increases until two weeks of daily consumption
  • Any amount of caffeine decreased death of inflammatory diseases by 30%
  • Gout was halved by 1,000 mg or more of caffeine consumption
  • Caffeine does not increase the chance of glaucoma
  • Ovarian and breast cancer decrease
  • 1,000 mg to 1,500 caffeine consumption per day in pregnant women led to less gestational diabetes
  •  As caffeine consumption increases, the risk for diabetes type two decreases
  • Caffeine consumption while pregnant remains a debatable topic, best to play it safe
  • Up to 3,000 mg per day, doesn’t lead to drug or alcohol abuse, depression, antisocial disorder, generalized anxiety disorder, not panic disorder
  • Three cups daily decreases age-related losses in verbal and visuospatial memory
  • 400 mg to 650 mg per day leads to much less of a chance of dementia
  • Risk of Parkinson’s disease decreases as regular caffeine intake increases
  • At least ten cups of coffee routinely drank, among those 50-79 years old, lowers risk of Parkinson’s disease very significantly
  • 400 mg or more of caffeine does not increase the rate of seizures
  1. 2010
  2. None
  3. Received 08/06/2010; Accepted 08/07/2010

Warning: just because caffeine is a very safe drug, and a stimulant, that does not mean other stimulants are safe. For example, methamphetamine is neurotoxic (damages the brain) at any dose. Amphetamine is safer, but unless used as prescribed, can also readily damage the brain and heart. Methylphenidate is a safer drug than meth/amphetamine, but by no means as much as caffeine.

This chart details a few potential pros and cons of caffeine

Again, just because so many people use it regularly, that does not mean it can’t cause problems. Here’s a more complete list…

Sources: Caffeine-Not just a stimulant, http://www.caffeineinformer.com, http://zar777.github.io/biomedic/, Mayoclinic.com, FDA