Hemp seed in Chinese medicine

In a Chinese herbal pharmacy, among the roots and barks, there is usually a drawer of small, glossy brown fruits: huomaren, 火麻仁, hemp seed. Physicians prescribe them as a moistening laxative, and they have done so for about 1,800 years. The best-known prescription, the Hemp Seed Pill, goes back to a physician of the second century AD and is still among the most widely used.

This is cannabis used without intoxication. The seeds contain at most traces of THC or CBD. That has not stopped them from becoming a legal question wherever the plant is a narcotic.

Fruit, seed or kernel

The names are older than the botany. What the trade calls hemp seed is, strictly, a fruit, with the seed inside a brown shell, and Chinese texts have never agreed which they meant.

Name	Literally	What it refers to
火麻仁 huomaren	“fire-hemp kernel”	The pharmacy name today; in the Chinese Pharmacopoeia of 2005 and 2015, the dried ripe fruit
麻子 mazi, 麻子仁 maziren	hemp seed, hemp-seed kernel	The usual names in older texts and formulas
麻實 mashi	hemp fruit	Another older term
麻蕡 mafen	—	The flowering or fruiting top of the plant; its exact meaning has been argued over for centuries

The 2010 edition of the Pharmacopoeia called the drug “Cannabis Semen”, the seed, while describing the fruit; the 2015 edition went back to “Cannabis Fructus”. The word má itself, hemp, runs through all of them.

From the flower to the seed

Hemp appears in the bencao, China’s books of materia medica, from about 200 AD onwards, and by 659 every part of the plant had been recorded: seed, flower, leaf, root and even the water in which the stalks were retted. The early books put the flowering top, mafen, at the head of the entry and the seed after it. One early source says the top should be gathered on the seventh day of the seventh month and the seeds in the ninth, and that the top is toxic while the seeds are not. The flowers’ power to make people “see spirits” is the subject of hemp in the Taoist censer.

Over the centuries the balance shifted. Li Shizhen’s great compendium of the late sixteenth century gives the seeds about three times as many words as the flowers. By the Qing dynasty many books had an entry for the seeds only, and modern textbooks follow them. A dictionary of nearly 97,000 historical formulas lists 69 with hemp seed as a main ingredient and no named formula built on the flower. The researchers Eric Brand and Zhao Zhongzhen of Hong Kong Baptist University, who traced this history, read it as a sign that the drug plant was little used in Chinese medicine, while the seed crop was everywhere: the bencao often filed hemp among the grains.

The Hemp Seed Pill

The physician Zhang Zhongjing recorded Ma Zi Ren Wan, the Hemp Seed Pill, around the second century AD, for constipation. It combines hemp seed with rhubarb, white peony root, bitter apricot kernel, immature bitter orange and magnolia bark, and it is still in the textbooks and the clinics. In Taiwan’s national health insurance data for 2003 it ranked fortieth of the 301 formulas most often prescribed, with over ten tonnes of concentrated extract, and hemp seed alone, added to other formulas, ranked 140th of 353 single herbs.

The pill has also been tested in the modern way. A trial at Hong Kong Baptist University gave it or a placebo to 120 people with functional constipation: 43 per cent of those on the pill responded during treatment, against 8 per cent on placebo, with no serious side effects.

Outside the pharmacy the seeds are simply food. In Hong Kong, hemp-seed drinks are sold at herbal-tea stalls and in bottles.

Where the law draws the line

China listed cannabis as a narcotic in 1985, and the seeds stayed in its pharmacopoeia. Elsewhere in the Chinese-speaking world the line has had to be drawn more precisely.

In Hong Kong the government’s Narcotics Division tells parents that huomaren, hulled and roasted, cannot germinate, contains no THC and is not a dangerous drug. Taiwan’s courts apply a ruling of the health ministry’s drug regulator: huomaren is the dried ripe fruit, processed so that it can no longer sprout, and as such falls outside the drug laws. A seed that can sprout is a cannabis seed. In 2023 a district court in Yilan heard a man who said he had sold huomaren. His buyer had planted the seeds, they had grown into plants, and the plants tested positive for THC. The court found that he had sold cannabis seeds. In both places the test is the same: whether the seed is still alive.^{[1][2][3][4][5]}