In the UK, the Department for Environment, Food and Rural Affairs treats hemp as a purely non-food crop, but with proper licensing and proof of less than 0.2% THC concentration, hemp seeds can be imported for sowing or for sale as a food or food ingredient. In the U.S., imported hemp can be used legally in food products and, as of 2000, was typically sold in health food stores or through mail order.
The oil contained in the hemp seed is 75-80% polyunsaturated fatty acids (the good fats) and only 9-11% of the lesser desired saturated fatty acids. Hemp seed oil is reputed to be the most unsaturated oil derived from the plant kingdom. The essential fatty acids (EFAs) contained in hemp seed oil are deemed essential because our bodies do not naturally produce them. This means that they must be obtained from the food we eat.
In the United Kingdom, cultivation licences are issued by the Home Office under the Misuse of Drugs Act 1971. When grown for nondrug purposes, hemp is referred to as industrial hemp, and a common product is fibre for use in a wide variety of products, as well as the seed for nutritional aspects and for the oil. Feral hemp or ditch weed is usually a naturalized fibre or oilseed strain of Cannabis that has escaped from cultivation and is self-seeding.
One of the most important aspects of hemp seed is its high mineral content, including magnesium, which creates a very soothing and relaxing sensation throughout the body. Magnesium has various stimulating qualities on enzymes and hormones that induce sleep. According to a report published in the Journal of the American Geriatrics Society, Serotonin is released when magnesium is administered, and it travels to the brain, where it becomes converted to melatonin. Melatonin is a powerful sleep aid, and insomnia patients have often claimed that magnesium supplementation is the reason. A single serving of hemp seed contains nearly 50% of the daily recommended dose of magnesium, so grab a handful and get guaranteed beneficial and restorative sleep.
Hemp can be used as a "mop crop" to clear impurities out of wastewater, such as sewage effluent, excessive phosphorus from chicken litter, or other unwanted substances or chemicals. Additionally, hemp is being used to clean contaminants at the Chernobyl nuclear disaster site, by way of a process which is known as phytoremediation—the process of clearing radioisotopes and a variety of other toxins from the soil, water, and air.
Concrete-like blocks made with hemp and lime have been used as an insulating material for construction. Such blocks are not strong enough to be used for structural elements; they must be supported by a brick, wood, or steel frame. However, hemp fibres are extremely strong and durable, and have been shown to be usable as a replacement for wood for many jobs, including creating very durable and breathable homes. The most common use of hemp lime in building is by casting the hemp and lime mix while wet around a timber frame with temporary shuttering, and tamping the mix to form a firm mass; after the removal of the temporary shuttering, the solidified hemp mix is then ready to be plastered with a lime plaster.
In the early 1990s, industrial hemp agriculture in North America began with the Hemp Awareness Committee at the University of Manitoba. The Committee worked with the provincial government to get research and development assistance, and was able to obtain test plot permits from the Canadian government. Their efforts led to the legalization of industrial hemp (hemp with only minute amounts of tetrahydrocannabinol) in Canada and the first harvest in 1998.
Although cannabis as a drug and industrial hemp both derive from the species Cannabis sativa and contain the psychoactive component tetrahydrocannabinol (THC), they are distinct strains with unique phytochemical compositions and uses. Hemp has lower concentrations of THC and higher concentrations of cannabidiol (CBD), which decreases or eliminates its psychoactive effects. The legality of industrial hemp varies widely between countries. Some governments regulate the concentration of THC and permit only hemp that is bred with an especially low THC content.
In the United States, the public's perception of hemp as marijuana has blocked hemp from becoming a useful crop and product," in spite of its vital importance prior to World War II. Ideally, according to Britain's Department for Environment, Food and Rural Affairs, the herb should be desiccated and harvested towards the end of flowering. This early cropping reduces the seed yield but improves the fiber yield and quality. In these strains of industrial hemp* the tetrahydrocannabinol (THC) content would have been very low.