WHAT IT IS: Coix seeds come from an annual plant which originated in East Asia.
It spread widely and is now found in eastern India, China, Japan, the Philippines, northern Africa, the Caribbean, Central America, northern South America and the United States.
It is known as yiyiren in Chinese, and Chinese barley or Job's tears in English.
Ms Pansy Yeo, a traditional Chinese medicine (TCM) practitioner at Chong Hoe Health Products Chinese Medical Store, said the seeds are harvested when the plant ripens in the autumn. The husks are removed and the seeds are used either fresh, dry fried or baked.
Good quality coix seeds are big, full, white grains. A 500g packet is sold at $3.50 at the medical hall where Ms Yeo works.
HOW TCM USES IT: Coix seeds are bland in taste. They are considered slightly cold in nature, and are used in TCM to clear heat and resolve dampness, which can lead to many illnesses.
The herb is thought to move through the lung, spleen and kidney meridians - channels through which qi (vital energy) travels in the body. A good flow of qi in the body is required for good health.
In TCM, the spleen converts nutrients from food into blood and qi.
When the spleen is weak - due to a weak constitution, chronic illness, overeating, irregular meals or the consumption of spicy and raw food - dampness is said to be present in the body, which then obstructs the flow of qi.
The dampness gives rise to digestive ailments such as poor appetite, indigestion, bloatedness and loose stools, said Ms Yeo.
The person is also observed to have a thick coating on the tongue etched with teeth marks.
In addition, the dampness shows up as diarrhoea, fatigue or water retention in the lower limbs, she said.
It can also combine with heat to give rise to damp-heat syndrome, which makes digestive ailments and oedema - the abnormal accumulation of fluid beneath the skin - more pronounced.
People with damp-heat syndrome are susceptible to infections such as urinary tract infection, gout, rheumatoid arthritis and eczema.
Coix seeds are used to strengthen the spleen and act as a diuretic to remove fluids that have been retained.
WHO IT IS FOR: Ms Yeo says the exposure to hot, humid weather and a love of heaty food such as durians, mangoes, and fried and spicy food makes damp-heat syndrome a common problem of Singaporeans.
Coix seeds are frequently prescribed.
Those with swelling of the legs or gastrointestinal problems such as diarrhoea, poor digestion and abdominal bloating may also benefit from their use.
WHO SHOULD AVOID IT: Ms Yeo cautioned pregnant women against using herbs with a diuretic effect, such as coix seeds.
Those who are dehydrated - marked by a dry throat, bad constipation, excessive perspiration or urination - are said to have no dampness within their bodies, and should avoid this herb, which may aggravate their symptoms.
WHAT RESEARCH HAS SHOWN: In a study published in the Journal Of Ethnopharmacology in 2008, coix-seed extract was found to significantly inhibit the activity of fatty acid synthase, which is the key process for tumour cell growth and survival.
The authors from Tianjin University and Tianjin Institute of Pharmaceutical Research concluded that there may be "clinical application of coix-seed extract in cancer therapy".
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