Coffee curiosities, part 1: facts and myths
The internet is full of information about coffee. We decided to collect some of the most interesting claims in one place.
1. Women who drink two or more cups of coffee a day are less likely to develop depression
An association reported in a study—not proof of prevention. The original article referred to Harvard researchers following 50,739 women without signs of depression between 1996 and 2006, using questionnaires to track caffeine intake.
Over that period, 2,607 cases of depression were reported. Compared with women drinking very little or no caffeinated coffee, the study reported a roughly 15% lower relative risk among those drinking two or three cups daily and around 20% lower among those drinking four or more. Decaffeinated coffee did not show the same association.
Caffeine affects brain signalling, including blocking adenosine receptors, which may influence alertness and mood. However, an observational association cannot establish that coffee caused the difference. Coffee is not a treatment for depression, and the results are not a recommendation to increase caffeine intake.
2. Arabica beans contain more caffeine than Robusta
Myth. Arabica generally contains less caffeine than Robusta. The exact difference varies by beans and growing conditions, but Robusta often has substantially more.
3. Caffeine content depends on the coffee
True, with qualifications. Species and variety matter, as do dose, brewing method and serving size. A laboratory test is needed to determine the actual amount in a particular cup.
The original article reproduced the following unverified internet estimates for a 175 ml serving. They are retained as historical examples, not reliable fixed values for coffees from these origins.
| Coffee origin | Quoted caffeine estimate |
|---|---|
| Ethiopia | 140 mg |
| Brazil Santos | 140 mg |
| Peru | 160 mg |
| Costa Rica | 160 mg |
| Guatemala | 177 mg |
| El Salvador | 177 mg |
| Hawaii | 180 mg |
4. Coffee can influence decisions
A finding from a specific experiment, not a universal rule. The original article described an Australian study involving 140 students. Researchers asked about their attitudes to euthanasia and abortion, gave them orange juice with or without caffeine and then presented arguments opposing their initial views.
Students who received caffeine were reportedly more likely to change their position afterwards. That does not mean a cup of coffee will make someone agree to a contract, a date or a trip: decisions depend on far more than caffeine.
5. Caffeine is what makes coffee bitter
Only part of the story. Caffeine contributes to bitterness, but many other compounds are involved. The original article quoted a contribution of about 15%; the proportion depends on the coffee and preparation.
Chlorogenic-acid lactones contribute to bitterness in lighter and medium roasts, while phenylindanes become more prominent with darker roasting. These compounds develop during roasting, helping explain why roast level changes the cup.
More coffee curiosities are coming soon!