Summary Phytonutrients such as phenolics play important roles in health and well‐being. The main phenolic compounds include phenolic acid, tannins, stilbenes, lignans and flavonoids. Phenolic compounds in plants distributed in the tissues, cell walls and subcellular compartments have biological activities, including antioxidant, chemopreventive, neuroprotective, cardioprotective and immunomodulatory properties. Citrus fruits, herbs and cereals are a few examples of flavonoid sources with biological functions. This article reviews recent findings in some common groups of phenolics and their role beneficial to human effects. Regular consumption of various plant sources which possess phenolic acids, tannins, stilbenes, lignans and flavonoids can reduce oxidative stress, cancer, cardiovascular disease and slow the progression of memory loss. Role of phenolic acid, tannins, stilbenes, lignans and flavonoids in human health.