[China] Fat choy (Nostoc flagelliforme), also known as fat choy, fa cai, black moss, hair moss or hair weed is a terrestrial cyanobacterium (a type of photosynthetic bacteria) that is used as a vegetable in Chinese cuisine. When dried, the product has the appearance of black hair. For that reason, its name in Chinese means “hair vegetable.” When soaked, this vegetable has a very soft texture which is like very fine vermicelli.
“Fat Choy” is available in Asian markets as dried cell biomass for use in a variety of meals, for their nutritional, organoleptic and functional (thickening) properties.
Native to northern China and nearby region, Fat Choy is used during the Chinese Lunar New Year as a delicacy. Fat choy grows on the ground in the Gobi Desert and the Qinghai Plateau. Over-harvesting on the Mongolian steppes has furthered erosion and desertification in those areas. The Chinese government has limited its harvesting, which has caused its price to increase. This may be one reason why some commercially available fat choy has been found to be adulterated with strands of a non-cellular starchy material, with other additives and dyes. Real fat choy is dark green in color, while the counterfeit fat choy appears black.
The last two syllables of this name in Cantonese sound the same as another Cantonese saying meaning “struck it rich” (though the second syllable, coi, has a different tone) — this is found, for example, in the Cantonese saying, “Gung1 hei2 faat3 coi4” (恭喜發財, meaning “wishing you prosperity”), which is often proclaimed during Chinese New Year. For that reason, this product is a popular ingredient in dishes used for the Chinese New Year. It is enjoyed as an alternative to cellophane noodles. It is mostly used in Cantonese cuisine and Buddhist cuisine. It is sometimes used as a hot pot ingredient.
Fat choy is also used in Vietnamese cuisine. It is called tóc tiên or tóc thiên (literally “angel’s hair”) in Vietnamese.
A research team from the biochemistry department of the Chinese University of Hong Kong said that international research has shown that Fat choy, besides having no nutritional value, has also been found to contain Beta-methylamino L-alanine (BMAA), a toxic amino acid that could affect the normal functions of nerve cells. Professor Chan King-ming of the team told the media that eating Fat Choy could lead to degenerative diseases such as Alzheimer’s, Parkinson’s, and dementia.
There is also a study by Takenaka which shows no significant difference between laboratory rats fed Nostoc flagelliforme and the control group.