HEMP SEED OIL
A source of valuable essential fatty acids

Interest in Cannabis has largely focused on its content of psychoactive substances (cannabinoids) or its potential industrial use as a source of cellulose fibre. While the whole seed has long been used as a source of food, its potential health contribution has never gained much attention. Hemp seeds have a high content of easily digestible complete protein and a rich oil providing a favorable ratio of the linoleic (C18:2w6) and linolenic (C18:3w3) essential fatty acids required for proper human nutrition, in addition to a significant contribution of gamma-linolenic (C18:3w6) acid of potential therapeutic efficacy.

With a recently acquired knowledge concerning the importance of these fatty acids in the human diet, it is time to both intensify research on their variable occurrence among varieties of hemp seed, and investigate methods of oil extraction and storage suitable for their preservation.
Throughout history and in separate parts of the world, hemp has often been an important plant revered for its psycho activity and useful for medicine, as a source of fibre, and for the food provided by its seed.

The fruit of hemp is not a true seed, but an "achene", a tiny nut covered by a hard shell. These are consumed whole, used in food and folk medicinal preparations or employed as a feed for birds and fishes. Whole hemp seed contains approximately 20-25% protein, 20-30% carbohydrates and 10-15% insoluble fibre as well as a rich array of minerals, particularly phosphorous, potassium, magnesium, sulfur and calcium, along with modest amounts of iron and zinc the latter of which is an important enzyme co-factor for human fatty acid metabolism.

It is also a fair source of carotene, a "Vitamin A" precursor, and is a potentially important contributor of dietary fibre. Most hemp seed also contains approximately 25-35% oil, although one variety grown in Russia called "olifera" reportedly contains 40% and a Chinese variety was claimed to slightly exceed this figure.
This highly polyunsaturated oil has uses similar to that of linseed oil (e.g., fuel for lighting, printer¢s ink, wood preservative), but also has been employed as a raw material for soaps and detergents and as an emollient in body-care products.

However, it is the nutritional qualities of the oil that are particularly important. The crushed seed by-product is suitable for animal feed as well as a human staple due to its spectrum of amino acids, including all 8 of those essential to the human diet as well as carbohydrates and a small amount of residual oil. Its protein is primarily edestin, an easily assimilated globular protein of a type similar to the albumin found in egg whites and blood. However, heat-treating whole hemp seed denatures this protein and renders it insoluble, possibly affecting digestibility.
An ideal hemp seed variety would produce a high yield of seed (normally 0.5-1.0 t/ha) containing a high percentage of good quality oil. Highly branched varieties are usually preferred. For seed production, male plants are sometimes removed after pollination has occurred, in order to leave more space for female plants. The seed yield can be doubled using monoecious varieties, although this sexual type suffers some inbreeding depression. Cultivation of a monoecious strain in Switzerland yielded up to approximately 1.5 metric tons of seed per hectare in but lower yields are generally reported. Highest seed yields are obtainable with unisex female varieties, such as Uniko-B. The number of flowers per plant and, therefore, the quantity of seed produced, can be increased by "topping" the plants when they are 30-50 cm high. Maximum seed yield requires that hemp be sown at a much lower density than for fibre. However, weeds can prosper if planting density is too sparse (e.g., 25/m2 ).

Extraction methods
Extraction of oil from hemp seed is not being carried out on a large scale at the present time. That being processed is sometimes relatively inhomogeneous, mature seeds mixed with green ones. This is due to the difficulty of finding the optimal time for harvesting, since not all seeds reach maturity simultaneously, especially in hemp undeveloped for seed production. The presence of unripe seeds not only increases seed crop moisture content, it also lowers oil yield and modifies its taste.
After harvest, hemp seed undergoes a drying process that reduces its moisture content to 10% or less, so as to prevent sprouting during storage. Batches of this material are then fed into a hydraulic screw press and a pressure of 500 bars is progressively applied, resulting in only a minor elevation in temperature. Best quality oil is obtained from the first fractions recovered. Approximately 35% of the available oil remains in the seed cake. The pressing process is sometimes repeated with this crushed residue to obtain a small additional amount of oil, although quality is decreased.
This "cold pressing" does not allow an extraction yield equal to that of techniques employing solvents or high temperatures, but it has the advantage of minimizing degrading changes in the oil. A small amount of oil is also lost during the subsequent filtration process. Further refining procedures should be avoided in order to preserve the native qualities of this product. Bottling must occur quickly and filling under nitrogen into opaque bottles, then refrigerating, offers significant protection against oil degradation due to oxidation and the action of light, although freezing is necessary for long-term storage. Addition of anti-oxidants extends shelf life of the product at room temperature.

Oil composition and properties
Non-refined hemp seed oil extracted by cold-pressing methods varies from off-yellow to dark green and has a pleasant nutty taste, sometimes accompanied by a touch of bitterness. The seed (and therefore the extracted oil) normally does not contain significant amounts of psychoactive substances. Trace amounts of THC, sometimes found upon analysis, are probably due to contamination of the seed by adherent resin or other plant residues although reports to the contrary exist.

Analytical data reported for the fatty acid composition of hemp seed oil reveals that it is unusually high in polyunsaturated fatty acids (70-80%), while its content in saturated fatty acids (below 10%) compares favorably with the least saturated commonly consumed vegetable oils. This high degree of instauration explains its extreme sensitivity to oxidative rancidity, as the chemical "double-bonds" that provide such instauration are vulnerable to attack by atmospheric oxygen. This degradation is accelerated by heat or light. For this reason, the oil is unsatisfactory for frying or baking, although moderate heat for short periods is probably tolerable. It is best consumed as table oil, on salads or as a butter/margarine substitute for dipping bread, similar in use to olive oil.

Proper steam sterilization of the seed probably does not cause significant damage to the oil, but does destroy the integrity of the seed, allowing penetration by air and molds. If this procedure is required, it should be done at a legally bonded facility immediately before release of the seed for further processing. By the same reasoning, one should avoid eating whole hemp seed that has been subjected to any cooking process, unless reasonably fresh.
The two polyunsaturated essential fatty acids, linoleic acid (C18:2w6) or "LA" and linolenic acid (C18:3w3) or "LNA", usually account for approximately 50-70% and 15-25% respectively, of the total seed fatty acid content. Such a 3:1 balance has been claimed optimal for human nutrition and is apparently unique among the common plant oils, although black currant seed oil approaches this figure. Cannabis seed from tropical environments seems to lack significant quantities of LNA. Temperate variety oils are less saturated, perhaps due to a natural selection in northern latitudes for oils with a higher energy storage capacity or which remain liquid at a lower temperature. It will be interesting to see if this trend continues for Nordic hemp varieties. The range of results found in some analyses may be attributable to differences in crop ripeness, since formation of polyunsaturated fatty acids is incomplete in immature Cannabis seed. This suggests that a maximum ripening of the seed and the culling of immature seed are important considerations for the production of quality oil. Likewise, proper seed sampling criteria are also crucial for representative analyses.

GLA sources and importance
Gamma-linolenic acid (C18:3w6) or "GLA" is found in minute quantities in most fats of animal origin. Oats and barley also contain small amounts. Human milk contains some GLA, but any significance is probably overshadowed by the greater presence of its metabolic derivative dihomo-gamma-linolenic acid or "DGLA" (C20:3w6).
Hemp seed oil from sterilized seed analyzed in the US contained 1.7% GLA but higher levels (3-6%) have been measured, although it is apparently rare in most tropical varieties of Cannabis. However, absolute amounts of GLA are not the only criteria for ranking the desirability of oil. The arrangement of fatty acids on glycerol, as the natural triglyceride, as well as differences in possible toxicity among the various oils, must be taken into consideration.
The potential physiological effects of GLA have been extensively investigated only recently. In the body, GLA is normally derived from LA and serves as an intermediary for the formation of longer-chain fatty acids and eicosanoids. Eicosanoids are short-lived hormone-like substances which fulfill numerous vital roles, ranging from control of inflammation processes and vascular tone to initiation of contractions during delivery. The metabolic conversion of LA to GLA is slow in mammals. Further, it has been suggested that due to stress, ageing or pathology (e.g., hypertension, diabetes, etc.), formation of a sufficient amount or balance of eicosanoids may be impaired. This problem may be relieved by direct GLA supplementation, although caution is warranted since over consumption could be harmful. Its alleviating action on psoriasis, atopic eczema, and mastalgia are already well documented and GLA preparations are now frequently prescribed for the treatment of the latter two disorders. GLA has also been under investigation for its beneficial effects in cardiovascular, psychiatric and immunological disorders.
If a favorable response to GLA supplementation does not occur, additional application of stearidonic acid (SDA) or use of black currant seed oil may be indicated, since the same enzyme (delta-6-desaturase) that converts LA to GLA is also responsible for converting LNA to SDA. However, relatively few people suffer from a defect in this enzyme compared to the nearly universal lack of adequate LNA levels in the diet. A chronic LNA deficit is best acutely treated with flax seed (fresh linseed) oil, although it is unsuitable for prolonged consumption due to an imbalance in its LA (14%) to LNA (58%) content, a ratio approximately equal, but inverse, to that of hemp.

Future prospects
Questions remain concerning the reasons which have so far prevented a more extensive consumption of hemp seed oil. It is possible that the historically significant uses of hemp (i.e., fibre, medicine, whole seed and psychoactive drug) took priority over its potential utilization as a source of oil. Secondly, many other plant sources of oil have been found more adequate in terms of yield and chemical stability of their oil, and the nutritional value of hemp seed oil was little known. Finally, the relatively recent "anti-drug" ban on hemp cultivation in many countries has prevented food scientists from investigating in more depth the wide range of potential uses for this seed.
Probably no other single source of oil offers a more favorable human dietary balance of the two essential fatty acids, LA and LNA. Even though hemp seed oil contains only relatively small amounts of GLA when compared to more established sources, this is probably sufficient for many of those who cannot efficiently convert LNA to GLA, and helps to prevent GLA over consumption. In addition, because of its ease of cultivation, Cannabis may possess the potential to become an alternative raw material source for the production of isolated forms of GLA as a special dietary supplement.
Much work remains to be undertaken with the existing cultivars, as well as indigenous landraces and feral strains. A major research priority must be the full characterization of oils obtained from diverse hemp sources. There exists considerable potential for development of varieties providing larger yields of seed containing higher oil content with a consistent fatty acid profile. Knowledge of environmental influences on seed quality and the development of improved agricultural methods will also contribute to the future success of this plant. In addition, important questions remain concerning this oil's psycho-chemical properties, triglyceride structures, and physiological effect, as well as the methods of extraction and storage that are most economical and best suited to preserve its unique nutritional qualities.

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Therapeutic Hemp Oil by Andrew Weil, M.D.

The nutritional composition of oil from the marijuana plant could be beneficial to your health. To most people, Cannabis sativa is synonymous with marijuana, but the plant's Latin name means the "useful hemp." Species designated sativa (useful) are usually among the most important of all crops. In fact, the utility of hemp is manifold: the plant has provided human beings with fiber, edible seeds, an edible oil, and medicine, not just a notorious mind-altering drug.

In our part of the world, these other uses of hemp are no longer familiar. We rarely use hemp fiber and know little about hemp medicine. (Some cancer patients have found it to be a superior remedy for the nausea caused by chemotherapy, and some people with multiple sclerosis are grateful for its relaxant effects on spastic muscles.) Hemp seed is sometimes an ingredient in bird food; otherwise, edible products from Cannabis sativa are virtually unknown.

This may all change. In many parts of the country, promoters of hemp cultivation are working to educate people about the immense potential of this plant and to reintroduce it into commerce. They champion hemp as a renewable source of pulp for the manufacture of paper, as a superior fiber for making cloth, and as a new food that can be processed into everything from a milk substitute to a kind of tofu.

Hemp seeds contain 25% high quality protein and 40% fat in the form of an excellent quality oil. Hemp oil is just now coming on the market. Produced by the Ohio Hempery in Athens, Ohio, it will be sold through natural food stores in small, opaque bottles to be kept under refrigeration. It has a remarkable fatty acid profile, being high in the desirable omega-3s and also delivering some GLA (gamma-linolenic acid) that is absent from the fats we normally eat. Nutritionally oriented doctors believe all of these compounds to be beneficial to health.

Hemp oil contains 57% linoleic (LA) and 19% linolenic (LNA) acids, in the three-to-one ratio that matches our nutritional needs. These are the essential fatty acids (EFAs)-so called because the body cannot make them and must get them from external sources. The best sources are oils from freshly ground grains and whole seeds, but EFAs are fragile and quickly lost in processing. EFAs are the building blocks of longer chain fats, such as eicosapentaenoic (EPA) and docosahexaenoic acid (DHA) that occur naturally in the fat of cold-water fish like sardines, mackerel, salmon, bluefish, herring, and, to a lesser extent, tuna.

Adding these foods to the diet seems to lower risks of heart attacks because omega-3 fatty acids reduce the clotting tendency of the blood and improve cholesterol profiles. They also have a natural anti-inflammatory effect that makes them useful for people with arthritis and autoimmune disorders.

Health food stores stock many brands of EPA/DHA supplements in the form of fish oil capsules. I usually do not recommend them because I think it's better to get your essential fatty acids in foods, and I worry about toxic contaminants in fish oil supplements. But what can you do if you choose, for one reason or another, not to eat fish? You can get some omega-3s in expeller pressed canola oil, the only common vegetable oil that contains them.

A much richer source is flax oil. Flax oil is pressed from the seeds of Linum utilitatissimum, the source of linen fiber and an oil better known in this country as linseed oil, the base for oil paints.

Linseed oil is usually classified as a "drying oil" rather than a food oil because its chemical characteristics cause it to combine readily with oxygen and become thick and hard. This tendency to harden on exposure to air quickly turns linseed oil rancid and unfit to eat, but makes it useful as a vehicle for pigment on canvas. (The word "canvas" by the way is a relative of "Cannabis," because true canvas is made from hemp fiber.)

For dietary purposes flax oil must be pressed at low temperatures, protected from light, heat, and air, stored at cool temperatures, and used quickly once the containers are opened. Most flax oil is not delicious. There is great variation in taste among the brands currently sold in natural food stores, but the best of them still leaves much to be desired.

I have been recommending flax oil as a dietary supplement to patients with autoimmune disorders, arthritis, and other inflammatory conditions, but about half of them cannot tolerate it. Some say it makes them gag, even when concealed in salad dressing or mashed into a baked potato. These people have to resort to taking flax oil capsules, which are large and expensive.

Udo Erasmus, author of the classic book, Fats and Oils (Alive, 1986), [and Fats that Heal, Fats that Kill, The Complete Guide to fats, oils, cholesterol and human health, Second Printing of Fats and Oils, (Alive, 1996). This book is a fabulous resource on nutrition --ratitor] says that the problem is freshness. Unless you get flax oil right from the processor and freeze it until you start using it, it will already have deteriorated by the time you buy it. Hemp oil contains more EFAs than flax and actually tastes good. It is nutty and free from the objectionable undertones of flax oil. I use it on salads, baked potatoes, and other foods and would not consider putting it in capsules.

Like flax oil, hemp oil should be stored in the refrigerator, used quickly, and never heated. Unlike flax oil, hemp oil also provides 1.7% gamma-linolenic acid (GLA). There is controversy about the value of adding this fatty acid to the diet, but many people take supplements of it in the form of capsules of evening primrose oil, black currant oil, and borage oil. My experience is that it simulates growth of hair and nails, improves the health of the skin, and can reduce inflammation. I like the idea of having one good oil that supplies both omega-3s and GLA, without the need to take more capsules.

One of the questions that people are sure to ask about hemp oil is whether it has any psychoactivity. The answer is no. The intoxicating properties of Cannabis sativa reside in a sticky resin produced most abundantly in the flowering tops of female plants before the seeds mature. The main psychoactive compound in this resin is tetrahydrocannabinol (THC).

Strains of hemp grown for oil production have a low resin content to begin with, and by the time the seeds are ready for harvest, resin production has dropped even further. Finally, the seeds must be cleaned and washed before they are pressed. As a result, no THC is found in the final product.

A second question that people may ask is, "Is hemp oil illegal?" The oil itself is perfectly legal. Hemp seeds are allowed in commerce if they have been sterilized in some way to prevent germination. This is usually done by subjecting them to heat. At the moment, the Ohio Hempery is importing sterilized seeds from Canada and extracting the oil here, but it hopes to get some sort of exemption from this requirement in order to be able to use the freshest seeds possible in the future.

Obviously, there is a political dimension to the appearance of this product. For many years, Cannabis sativa has been stigmatized as a satanic plant and its cultivation has been prohibited. As an ethnobotanist interested in the relationships between plants and human beings, I have always felt that making plants illegal was stupid, especially when the objects of these actions are supremely useful plants like hemp. The plant is not responsible for human misuse of it.

The efforts of the Ohio Hempery and other groups to promote hemp cultivation are part of a campaign to rehabilitate this plant and change society's view of it. Whether or not you wish to join that campaign, it must seem counterproductive to deny ourselves access to the many benefits that hemp offers. Of those, the gift of an edible oil with superior nutritional and therapeutic properties is one of the most important.

If you have a chance to try hemp oil, a long forgotten, newly rediscovered food, I think you will see why I am enthusiastic about it.

Andrew Weil teaches at the University of Arizona College of Medicine, has a private medical practice, and is the author of Natural Health, Natural Medicine.

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