The principles about the 5-7 tastes, including Bitter, go back thousands of years in eastern medicine (Chinese and Ayurveda) in written texts, and much longer than that within the oral tradition of pre-history. Also, in european traditional medicine, herbal âbittersâ go back to the 13th-14th century (Hildegard von Bingen and others) using a mix of roots such as Dandelion, Chicory, Burdock as well as herbal leaf blends like Dandelion greens, Parsley (used at Passover Seders to symbolize the bitterness of past enslavement - sometimes green onion tops or potato peels are used as well), Thyme, Oregano, Rosemary, Motherwort, and Sage. 
Bitter is wonderful for liver health and detox. Being that specific tastes on the palate have immediate neurological responses, bitter taste for nausea and general malaise has an immediate benefit followed by further biochemical/digestive aspects.
Bitter is esp good for the elderly palate which has some changes that come with age - and Indian elders swear by their love of weekly Bitter Gourd for digestive health and happiness. Itâs an acquired taste, the first time I had it when I was in my 30s I almost keeled over - itâs much stronger tasting than Dandelion leaves and root.
From the eastern science perspective, Bitter boosts digestive fire which in turn boosts immunity, assimilation, etc.
This is my current favorite Bitter fix for evening enjoyment, it energizes without caffeine and tastes very coffee-like when made strong. Because of the powers of Bitter, for people who need to stop coffee for whatever reason, they can switch to such root powder drinks without any of the awful caffeine withdrawal symptoms - I expect because of the liver support. Only 1g carb per cuppa.
Feel better with Bitter!