Phenolic acids are abundant in a balanced diet. You should get plenty of them as long as you consume adequate amounts of fruits, vegetables and whole grains. Examples of foods rich in phenolic acids include mangos, berries, apples, citrus fruits, plums, cherries, kiwis, onions, tea, coffee, red wine, and flour made from whole wheat, rice, corn or oats.
There are many different phenolic acids found in nature and they can be divided into two categories: benzoic acid derivatives, such as gallic acid; and cinnamic acid derivatives, including caffeic acid and ferulic acid. The cinnamiac acids are more common.
Gallic acid is found in tea and grape seeds. Coffee contains caffeic acid and chlorogenic acid. Blueberries, kiwis, plums, cherries and apples contain large amounts of caffeic acid. Red wine and citrus fruits contain cinnamic acid. Ferulic acid is found in the outer coverings of cereal grains. Corn flour has the most ferulic acid, and whole grain wheat, rice, and oat flours are good sources of ferulic acid as well.
Foods rich in phenolic acids may be beneficial for your health, but it's difficult to understand how much of that benefit is actually due to the phenolic acids, or to the nutrients, fiber and other phytochemicals also found in those foods. Here are a few examples. Flavonoids (another category of polyphenol) are often found in the same foods as the phenolic acids, and most fruits and vegetables are rich in nutrients and fiber. Drinking coffee has been associated with a decreased risk of cancer and other chronic diseases. It contains caffeic acid and chlorogenic acid, but it also contains caffeine, and other potentially beneficial compounds. Red wine has phenolic acids, but it also has resveratrol, which is another type of polyphenol that has potential health benefits.
Phenolic acids may be available commercially in the form of dietary supplements, such as grape seed extract or green tea extract, which contain gallic acid. These supplements are usually marketed as antioxidants, but current research evidence suggests that eating fruits, vegetables and whole grains is more beneficial than taking any type of antioxidant supplements.
Liu RH. "Potential synergy of phytochemicals in cancer prevention: mechanism of action." J Nutr. 2004 Dec;134(12 Suppl):3479S-3485S.
Manach C, Scalbert A, Morand C, Rémésy C, Jiménez L. "Polyphenols: food sources and bioavailability." Am J Clin Nutr. 2004 May;79(5):727-47.
Morton LW, Abu-Amsha Caccetta R, Puddey IB, Croft KD. "Chemistry and biological effects of dietary phenolic compounds: relevance to cardiovascular disease." Clin Exp Pharmacol Physiol. 2000 Mar;27(3):152-9.
Nkondjock A. "Coffee consumption and the risk of cancer: an overview." Cancer Lett. 2009 May 18;277(2):121-5.