The seed of Cannabis sativa L. has been an important source of nutrition for thousands of years in Old World cultures. Non-drug varieties of Cannabis, commonly referred to as hemp, have not been studied extensively for their nutritional potential in recent years, nor has hempseed been utilized to any great extent by the industrial processes and food markets that have developed during the 20th century. Technically a nut, hempseed typically contains over 30% oil and about 25% protein, with considerable amounts of dietary fiber, vitamins and minerals.
Hempseed oil is over 80% in polyunsaturated fatty acids (PUFAs), and is an exceptionally rich source of the two essential fatty acids (EFAs) linoleic acid (18:2 omega-6) and alpha-linolenic acid (18:3 omega-3). The omega-6 to omega-3 ratio (n6/n3) in hempseed oil is normally between 2:1 and 3:1, which is considered to be optimal for human health.
In addition, the biological metabolites of the two EFAs, gamma-linolenic acid (18:3 omega-6; ‘GLA’) and stearidonic acid (18:4 omega-3; ‘SDA’), are also present in hempseed oil.
The two main proteins in hempseed are edestin and albumin. Both of these high-quality storage proteins are easily digested and contain nutritionally significant amounts of all essential amino acids.
In addition, hempseed has exceptionally high levels of the amino acid arginine.
Hempseed has been used to treat various disorders for thousands of years in traditional oriental medicine. Recent clinical trials have identified hempseed oil as a functional food, and animal feeding studies demonstrate the long-standing utility of hempseed as an important food resource.
Abbreviations: AL: alpha-Linolenic acid (18:3 omega-3); GLA: gamma-Linolenic acid (18:3 omega-6); EFA: Essential fatty acid; LDL: Lowdensity lipoprotein; n6/n3: Ratio of omega-6/omega-3 fatty acids; PUFAs: Polyunsaturated fatty acids; SDA: Stearidonic acid (18:4 omega-3); THC: delta-9-Tetrahydrocannabinol
Cannabis sativa L. has been an important source of food, fiber and medicine for thousands of years in the Old World (Zias et al., 1993; Xiaozhai & Clarke, 1995; de Padua et al., 1999; Pringle, 1997).
The bast fiber from the stalk is still used in the modern production of durable fabrics and specialty papers in some countries; e.g., as canvas, linen, tea bags, paper money, cigarette papers and other strong, thin papers that are used to make thick books, such as the Holy Bible.
Both the ripened seed of hemp and seed meal are excellent sources of dietary oil, fiber and protein.
Seed-eating migratory birds and rodents are especially attracted to hemp fields at harvest time, which in turn attract raptors and other predatory animals. Eaten raw, or after long-term storage, this common seed was certainly used by prehistoric humans (Weiss et al., 2004), and probably earlier hominids as well (McPartland & Geoffrey, 2004).
This is both logical and in line with the prehistoric use of Cannabis as an important source of economic plant fiber in the fabrication of nets, for catching birds and other small animals (Pringle, 1997), in addition to the medical potential of useful cannabinoids in the leaves and flowers of the plant itself (Zias et al., 1993).
Hempseed has been documented as a source of food throughout recorded history – raw, cooked or roasted, and hempseed oil has been used as a food/medicine in China for at least 3000 years (de Padua et al., 1999). The seed, both crushed and whole, remains an important grain in traditional Asiatic foods and medicines.
In North America, hempseed has been used in the paint and varnish industries and imported as bird food.
Within the last 10 years, hempseed has been legally used as food for humans in both Canada and the United States, while the cultivation of hemp remains illegal in the latter.
Recent historical considerations
At over 90% in unsaturated fatty acids, hempseed oil once rivaled linseed (Linum usitatissi-mum L.) as a drying oil in paints, varnishes and other technical coatings. Hempseed was eventually replaced by linseed in the late 1930s, after a prohibition of the cultivation of all Cannabis varieties was affected in North America. Subsequently, the potential use and development of hempseed as a food for humans and domesticated animals was interrupted, and available seed in the west was restricted to the propagation of a few fiber varieties for the production of specialty papers in some European countries for the remainder of the 20th century, notably France. This is an important historical note, for without hemp fiber and pulp from a western source, the United States would have been dependent on Chinese or Russian sources for hemp pulp during the Cold War to make strategically important papers.
Onset of the Second World War quickly brought hemp production back to North America, but only until it could be replaced by other durable natural fibers, such as Manila hemp (i.e., ‘abaca’, Musa textiles). By the 1950s, petroleum-based fibers had captured most of the hemp fiber market in North America. By the 1960s, long bast fibers were no longer in great demand for the production of ropes, textiles and related products in Europe and other parts of the world as cheaper petroleum products began to capture a majority of the market share for such durable goods.
Thus, with its limited availability, hempseed was not exposed to 20th century farming, food processing or marketing.
Hempseed as food
For various reasons, hemp has been reconsidered as a valuable industrial crop for both food and fiber in Canada and European countries during the last decade. As a result, hempseed and hempseed food products have become available to the general public in these countries.
While the human food potential for hempseed has not yet entered mass markets in the west, its nutritional properties have long been recognized and valued as food for both humans and domesticated animals throughout Asia, India, Russia and Eastern Europe. In China, roasted hempseed is still sold as snacks by street venders. In Russia, ‘black’ oil has been pressed from hempseed and used as a substitute for more expensive (and less healthy) sources of dietary fat, such as butter and hydrogenated margarines.
The natural dark color of hempseed oil is from chlorophyll within the mature seed, which can hasten auto-oxidation of oil that is exposed to light. Some traditional hempseed foods can still be found in the Baltic states, particularly Latvia, and in other east European countries. Such a long history and a variety of uses over a large geographic area, and throughout so many different cultures, are all strong reminders of hempseed’s utility as a useful source of nutrition.
Over the past few years, modern science has finally begun to catch up with this ancient knowledge through its own methodologies (Callaway, 2002; Callaway et al. 1997a, 2004; Kriese et al., 2004).
The recent availability and use of hempseed oil in Europe and North America has fostered anecdotal stories on improvements in health, over a wide range of acute and chronic conditions; e.g., from the rapid healing of simple cuts and burns to influenza, various skin problems, other allergic symptoms and inflammatory diseases. Most, if not all, of these claims can be understood by considering the unique fatty acid profile of hempseed oil (Deferne & Pate, 1996; Kriese et al., 2004), and its direct impact on the subsequent metabolism of dietary essential fatty acids (EFAs) to eicosanoids, which include prostaglandins and other important metabolites. Eicosanoids have been implicated in chronic disease states of the human immune system (Darshan & Rudolph, 2000). The difference in the fatty acid profiles between oil hempseed and fiber hempseed has already been reported (Callaway et al., 1997a).
The EFAs are fatty acids that cannot be made by humans and must be obtained through the diet. Their fundamental importance in the human diet was already recognized by the 1930s (Burr & Burr, 1929, 1930). Thus, dietary supplementation with oils that contain high levels of EFAs and other polyunsaturated fatty acids (PUFAs) certainly can be used to enhance human health and development (Simopoulos, 1991), especially when they are lacking in the diet. PUFAs are also incorporated more directly as phospholipids in cellular and organelle membranes (Manku et al., 1984; Oliwiecki et al., 1991). The incorporation of PUFAs in the formation of membrane phospholipid bilayers is essential for maintaining vital characteristics of cell membrane fluidity, especially in the construction of neuronal membranes within the central nervous system.
Dietary PUFAs and their biologic metabolites can favorably influence the fatty acid profile in low-density lipoproteins (LDL) when compared to saturated fats in the diet, which are strongly associated with coronary heart disease (Callow et al., 2002). Thus, a diet that has sufficient levels of PUFAs can lower both arterial levels of LDL-cholesterol and blood pressure in humans. PUFAs also increase bleeding times by decreasing platelet aggregation, which results in decreased peripheral blood pressure and clot formation.
Hempseed protein and other nutrients Albumin, a globular protein, and edestin, a legumin, are the two main proteins in hempseed and both are rich in the amino acids that are essential to human health. A direct comparison of protein amino acid profiles from egg white, hempseed and soy bean shows that hempseed protein is comparable to these other high quality proteins. Hempseed protein has good amounts of the sulfur-containing amino acids methionine and cystine (Odani & Odani, 1998), in addition to very high levels of arginine and glutamic acid. As an industrial source of vegetable nutrition, both hempseed and hempseed meals are rich sources of protein and polyunsaturated oils, in addition to considerable amounts of vitamins and useful minerals.
The individual tocopherols in hempseed (cv Finola), presented as vitamin E in Table 4, are alpha-tocopherol (5 mg/100 g) and gamma-tocopherol (85 mg/100 g), for a total of 90 mg/100 g of vitamin E. These levels are considerably higher than those reported for any other varieties of hemp (Kriese et al., 2004).
Empirical and clinical studies on hempseed oil
The system of traditional Chinese medicine maintains the oldest recorded source of information on hempseed, both as a traditional food and medicine (Xiaozhai & Clarke, 1995; de Padua et al., 1999). In recent times, a porridge of oats and hempseed was used as an important source of nutrition in the Czech Republic, and at least one published report has described the application of hempseed porridge, from folk medicine, in the treatment of tuberculosis without antibiotics (Sirek, 1955).
More recent evidence has described how dietary fatty acids can be used in the treatment of this particular disease (Russell, 2003; Coghlan, 2003; Anes et al., 2003).
During the last decade, hempseed oil has become available in specialty food shops throughout Europe and North America (Leson et al., 1999, 2001). Anecdotal reports attribute improvements in skin quality, stronger finger nails and thicker hair to modest daily usage (ca. 15–30 ml/day) over time; e.g., improvements in skin quality: 2–4 weeks, nails: 2–4 months and hair: 6–8 months. In both allopathic and traditional forms of medicine, such improvements are considered as good indications of general health.
A recent clinical study with topically applied hempseed oil has already demonstrated its usefulness in healing mucosal skin wounds after eye, nose and throat surgery (Grigoriev, 2002). This finding is in line with numerous other clinical studies that have demonstrated the utility of EFAs and other PUFAs in healing and immune response (Manku et al., 1982, 1984; Bordoni et al., 1988; Oliwiecki et al., 1991; Sakai et al., 1994; Yu & Bj¨orkst´en, 1998; Derek & Meckling-Gill, 1999; Harbige et al., 2000; Harbige&Fisher, 2001; Horrobin, 2000; Simopoulos, 2002a,b).
The fatty acid profile of hempseed oil is remarkably similar to that of black currant seed oil, which also seems to have a beneficial impact on immunologic vigor (Wu et al., 1999; Barre, 2001). Borage, which is rich in GLA, but totally lacking in omega-3 PUFAs, is fairly well tolerated as a source of this fatty acid (Takwale et al., 2003), but perhaps more than just GLA is required in some disease states, such as atopy (Whitaker et al., 1996; van Gool et al., 2003). In a randomized, crossover study that compared hempseed oil and olive oil, improvements were seen in a population of patients with atopic dermatitis (eczema) within eight weeks after the ingestion of hempseed oil at 30 ml (2 tbs)/day (Callaway et al., 2004). In this preliminary study, statistically significant improvements were seen in both skin quality and in plasma fatty acid profiles.
Animal feeding trials
Recent feeding trials with chickens have confirmed that hempseed is an excellent source of nutrition for laying hens, where the omega fatty acid profile in egg was favorably influenced after feeding hempseed meal (Silversides et al., 2002). This is in agreement with empirical observations over thousands of years in China and other Asiatic nations. Another study on hempseed found it to be an excellent source of rumen undegraded protein in cows and sheep (Mustafa et al., 1999), and unpublished results from recently completed trials in Finland have demonstrated hempseed meal to be at least as good as soy meal in farmed fish feed.
THC and other Cannabinoids
Most scientific research on Cannabis over the last 40 years has focused on the putative toxicity of tetrahydrocannabinol (THC) and, to a lesser extent, other cannabinoids. Ironically, this effort has resulted in the identification of new medicines (Mechoulam, 1986; Mechoulam & Hanu, 2001; Mechoulam et al., 2002; Kassirer, 1997). THC and other cannabinoids are potent lipophilic antioxidants, which may explain some of the historic therapeutic potential associated with Cannabis (Hampson et al., 2000). Trace amounts of THC and other cannabionoids can be detected in foods that are made from hempseed, just as trace amounts of morphine are found in poppy seed. When oil is pressed from the poorly cleaned seed of hemp varieties that have >1% THC (e.g., Chinese hempseed), such trace amounts can have a significant impact on human drug testing (Callaway et al., 1997b). However, there is no significant effect of intoxication with such low levels of THC, and the hemp food industry has worked to reduce this potential in recent years. Such low levels of THC cannot be expected to have any significant negative impact on human health or drug testing with properly cleaned seed hempseed (Leson et al., 2001).
Hempseed is an excellent source of nutrition. Indications from traditional Chinese medicine, recent anecdotal reports and modern human clinical trials agree that hempseed has health promoting properties that are supported by results from nutritional analyses of the seed, oil and seed meal.
In particular, the healing properties of hempseed can be attributed to high levels of EFAs and other PUFAs in the oil, in addition to a rich source of important amino acids in an easily digested protein.
Recent feeding trials with fish, hens and ruminants, in addition to empirical observations over thousands of years, have effectively demonstrated that hempseed and its derivatives are useful in animal feed as well.
Subjective concerns over THC in hemp foods are not supported by scientific evidence.
Article Source: “Hempseed as a nutritional resource: An overview” by Dr. J.C. Callaway, Department of Pharmaceutical Chemistry, University of Kuopio, FIN-70211 Kuopio, Finland