Coffee is a high potassium food, included in a table of high potassium drinks here. But it also has advantages beyond its ability to provide large amounts of potassium and thus aid in the prevention of hypertension, osteoporosis and kidney stones.
Coffee has over 1000 compounds in it. Many of these compounds are protective against cancer. Two diterpenes in coffee are known to produce effects felt to be anticarcinogenic. Coffee's polyphenols also show anticarcinogenic activity. DNA methylation is felt to be an early step in cancer production, and is inhibited by caffeic acid in coffee. Multiple other compounds found in coffee have also been studied and found protective.
There have been hundreds of epidemiologic studies of coffee's effect on health, with over 500 on the association between coffee and cancer. Two common types of studies are case-control and prospective cohort. Recall bias and selection bias are two problems with case-control studies. To eliminate those biases, a metastudy published last November in BMC Cancer used only prospective cohort studies.
The study included over 2 million people and over 34,000 cancers in 40 different cohorts. The studies came from North America, Europe, and the Asia-Pacific area. Because the studies came from multiple geographic areas, the heterogeneity of the studies was large. The amount of coffee consumed, the concentration of the coffee, the coffee type, and the method of preparation all varied. They adjusted the differences to equivalents of 1 cup of coffee, and compared the amount consumed in a day, up to 6 cups, to the risk of cancer development.
The study showed a reduction in cancer for those who drank coffee compared to non-coffee drinkers. Furthermore it showed that the more coffee you drink the lower your cancer risk.
They also broke the study down into different individual cancers. The individual cancers that coffee helped prevent were pancreatic, colorectal, breast, endometrial, liver, prostate, male bladder, leukemia, esophageal, oral and pharyngeal. It had no effect on stomach, lung, kidney, ovarian or non-melanoma skin cancers.
So although there are many who discuss the evils of coffee and try to discourage you from drinking coffee, the scientific evidence at this point indicates that for most people the more you drink, the healthier you will be. You need to be careful with some of coffee's side effects though. Too much over too short a time can lead to a short period of heart beat irregularity. For some people, drinking it too late in the day will keep them awake. And it does cause a short lived increase in blood pressure shortly after it is drunk. But in the long run coffee will add to the potassium that will bring down your resting blood pressure. And there is the added bonus of less chance of cancer.
To find other tables showing the amount of potassium in various foods, look in the list of posts.