What's in your cup?
Coffee and tea are both rich dietary sources of polyphenols--antioxidant compounds found in plant foods that help offset free radical-damage. People who drink the beverages regularly tend to have lower rates of certain cancers (including liver, colon, skin, ovarian, and breast cancer), cardiovascular disease, diabetes, obesity, and neurodegenerative disorders like Parkinson's disease and Alzheimer's disease.
Catechins are the main type of polyphenols found in tea. The four major kinds of catechins in green and black teas include epicatechin, epigallocatechin, epicatechin gallate, and epigallocatechin gallate.
Coffee is one of the richest sources of polyphenols in the Western diet, outpacing fruits and vegetables. Chlorogenic acids are the most abundant class of phenolic compounds found in coffee.
Since these health-promoting beverages are so popular, scientists wanted to gain a better understanding of what factors affect the absorption and metabolism of the good stuff found in them. To do that, they compiled the results of dozens of studies.
Here's what they found about tea:
Tea polyphenols are generally poorly absorbed.
Drinking green tea regularly throughout the day for extended periods (several weeks) can help boost blood levels of catechins.
Adding ascorbic acid (a form of vitamin C) or citrus juice to tea can help improve catechin absorption.
Catechins are best absorbed when consumed away from food.
Adding milk to tea doesn't seem to affect catechin absorption.
If tea is your thing, green and black teas boast a treasure trove of health benefits. Green tea increases metabolism, aiding in weight loss, and regular consumption can help build stronger bones and prevent osteoporosis.
Black tea may decrease the risk of developing kidney stones, protect against lung cancer, and inhibit the growth of cavity-causing bacteria in the mouth.
Less is known about how phenolic compounds found in coffee are absorbed. From the available research, it appears that:
Longer roasting times decrease the polyphenol content of coffee. Light- and medium-roast coffees contain the most polyphenols.
Adding milk or creamer to coffee doesn't appear to affect polyphenol absorption.
Besides lowering the risk of several diseases, regular coffee consumption may protect against liver cirrhosis and non-alcoholic fatty liver disease, decrease the risk of depression, especially in older women, and enhance exercise performance.
Worried about your blood pressure? Most experts agree that while coffee may temporarily raise blood pressure, drinking it regularly won't cause a problem for most people.
(Physiol Behav 2010;doi:10.1016/j.physbeh.2010.01.035)