“Reishi” is the Japanese name for the fruiting body of Ganoderma lucidum, one of the most well-known herbal remedies in traditional Chinese medicine. This species of the Polyporaceae family of fungus is also commonly referred to as Ling zhi, or "God's Herb".

Companies in Japan are particularly heralded for developing cultivation and manufacturing techniques that yield the highest quality Reishi in the world, a reputation that has been strengthened by the Japanese government’s strict regulation of the domestic Reishi industry.

The use of Reishi as a dietary supplement has been documented in Chinese pharmacopoeia since approximately second century B.C. However, its rarity and long cultivation period meant that Reishi's health benefits were historically limited to royalty or aristocracy. In the 1970s, several successful methods of cultivating Reishi were finally developed and as a result, the natural supplement that was once exclusive to the wealthy is now readily available to the general public. Based on numerous cases of improvement shown in patients with serious illnesses such as cancer and hepatitis who used Reishi products, a number of countries including China and the UK are now researching the medical applications of Reishi more extensively.

Of particular interest to researchers is the exceptional concentration of polysaccharides – which have been linked to aiding cancer remission, normalizing blood-sugar levels, and strengthening the immune system – in high quality red Reishi specimens. In fact, many of the most potent Reishi products in the market today are created from red Reishi.

In contrast with conventional symptom-based treatment methods that depend heavily on medications with significant side effects, Reishi’s proponents claim that it bears the characteristics of a preventative adaptogen which serves to improve general health and body functions with no side-effects. Ginseng is currently more widely-used as an adaptogen in Western medicine than Reishi, but both are categorized in traditional Chinese medicine texts as supplements with the greatest potential for medical efficacy.