Question: “I am drinking a cup of coffee brewed from a French Press and made from Peruvian beans roasted by Coffee and Tea Exchange (local to me here in Chicago).  I can say that this coffee affects me differently than the coffee I buy (rarely) at work in the hospital. With my coffee at home, I don’t get jittery and I don’t get stomach upset. Also, I can drink a cup or two every day and I don’t get a headache if I stop. On the other hand, if I go through a period where I drink a lot of coffee at work, all of those things happen. Do you know the chemistry of why?” - Howard

Answer: I’m an amateur chemist, Howard but it’s a great question so I will do my best to share what I know on the chemistry of coffee.

First of all, coffee affects everybody differently.  While it’s a laxative for some people, it gives others an upset stomach.  There are two factors at play to answer your question, and they are acidity and caffeine.

On acidity, it’s a little known fact that coffee is actually not acidic.  In fact, it is considered low-acid and on the pH scale that measures how acidic a liquid, coffee measures between 4.5 and 6, with 7 being neutral.  Many sodas and juices are much more acidic, measuring between 2 and 3.  For the record, coffee is not acidic.  While any number of factors could cause a stomach ache, if you’re getting it from coffee and not sodas and juices, it is not likely related to acid content in the coffee.

When coffee connaisseurs refer to acidity, they are referring to something different.  Acidity in coffee is a characteristic of its flavor, its sharpness or tartness.  It is a prized characteristic in coffee, owing to high growing areas.  It’s a shame that it’s so confusing to talk of acidity in coffee without referring to its acid content – I know this had to be explained to me many times before it stuck.

And so, the real issue is probably the caffeine.  Howard, when you mention being jittery, this is almost certainly an effect of the caffeine so if it is occurring at the same time as the stomach ache, I would hazard a guess that your stomach is sensitive to caffeine.  The good news is that you obviously can enjoy some coffees without those side effects, so here’s my advice:

- Try dark roasted coffees.  The longer the roasting process, the more caffeine is lost, dispelling another myth that dark roasted coffees are “stronger” and that espresso is the strongest of all.  All other things being equal, there is LESS caffeine in espresso.

- Check if the hospital cafeteria is serving robusta coffee.  Robusta is a cheaper variant of coffee and luckily for us, most reasonable coffee we buy (even at grocery stores) is 100% of the arabica variant.  Not only is robusta cheaper, but it happens to contain more caffeine.  Your hospital may be choosing to cut cost or provide staff with much-needed wake-me-up.  Either way, look into it and don’t drink robusta coffee.

- Bring your own coffee to work.  You’re already doing it, as you mentioned elsewhere in your e-mail.  Good for you.  It’s easy to invest in a thermos, and bring coffee with you for the day that is less expensive than buying it by the cup, a nicer flavored coffee to drink, and in your case, that lets you comfortably get on with your day.