The wheatgrass diet was developed by Boston resident Ann Wigmore, who immigrated to the United States from Lithuania. Wigmore believed strongly in the healing power of nature. Wigmore's notion that fresh wheatgrass had value came from her interpretation of the Bible and observations that dogs and cats eat grass when they feel ill. Wigmore claimed that the wheatgrass diet could cure disease. 

In 1982, the Massachusetts Attorney General sued Wigmore for claiming that her program could reduce or eliminate the need for insulin in diabetics. Afterward, she retracted her claims. In 1988, the Massachusetts Attorney General sued Wigmore again, this time for claiming that an "energy enzyme soup" she invented could cure AIDS. Wigmore was ordered to stop representing herself as a physician or person licensed to treat disease. Although Wigmore died in 1993, her Creative Health Institute is still active. Wheatgrass is readily available, and her diet is still in use. 

The consumption of wheatgrass in the Western world began in the 1930s. 

Schnabel, an agricultural chemist, conducted his first experiments with young grasses in 1930, when he used fresh cut grass in an attempt to nurse dying hens back to health. The hens not only recovered, but they produced eggs at a higher rate than healthy hens. Encouraged by his results, he began drying and powdering grass for his family and neighbors to supplement their diets. The following year, Schnabel reproduced his experiment and achieved the same results. Hens consuming rations supplemented with grass doubled their egg production. Schnabel started promoting his discovery to feed mills, chemist and the food industry. Two large corporations, Quaker Oats and American Diaries Inc., invested millions of dollars in further research, development and production of products for animals and humans. By 1940, cans of Schnabel's powdered grass were on sale in major drug stores throughout the United States and Canada.