Caffeine & PH in Coffee

Your cup of coffee contains acidic compounds, in addition to the caffeine that helps to keep you alert. The caffeine content and amount of acids in coffee varies depending on the type of bean and how it is roasted. While the acids and caffeine in your coffee may not affect its flavor, they may impact things such as heartburn and your iron levels.

Background

The pH of a liquid represents how easily it can dissolve solids. A liquid's pH can range from 0 to 14, according to the U.S. Environmental Protection Agency. A pH of 7 means that a liquid is non-corrosive, or neutral. Acidic compounds have pHs of less than 7. Coffee has a pH of around 5, according to Thecoffeefaq.com website. For comparison, the pH of lemonade ranges from 2.2 to 3.0.

Effects

While a pH of approximately 5 does not mean that coffee is very acidic, some of coffees ingredients, including caffeine, can give you a stomach ache or heartburn. A March 2010 article from Eurekalert.org says that researchers Veronika Somoza and Thomas Hofmann showed that the caffeine in coffee along with other ingredients cause cells in some people's stomachs to overproduce acids, which leads to irritation. Somoza and Hofmann also found that another compound called N-methylpyrdium, or NMD, actually reduces the amount of acid your stomach produces. NMD is found in greater quantities in darkly roasted coffee beans.

Roast Affects pH and Caffeine

Darkly roasted coffees, sometimes called French or city roast, contain less caffeine and less acidic compounds than coffee from lightly roasted beans. In a March 2010 study for the "Journal of Agricultural Food Chemistry," J.K. Moon and colleagues showed that coffee beans that are roasted longer contain less acidic compounds, which relates to a lower pH. Similarly, in a 2006 report for National Public Radio, Allison Aubrey stated that darker roasted coffee contains less caffeine.

Concerns

Coffees with lower pHs or greater acidity may lower your iron levels. In a February 2005 article in the "Journal of Agricultural and Food Chemistry," Daniel Moreira and colleagues examined the iron-reducing effects of caffeine and chlorogenic acid content of coffee. Coffee that contained more chlorogenic acids had greater iron-reducing effects. Moreira and colleagues say that the caffeine in coffee had no effect on iron levels.

Misconceptions

While coffee does contain acidic compounds, when people refer to coffee as acidic, they are usually referring to the bright and sharp flavors of coffee, rather than a low pH level. According to Thecoffeefaq.com, more darkly roasted coffees have less of an acidic taste than lightly roasted coffees. The caffeine in coffee does not contribute to its flavor.