Hemp (Cannabis sativa) is one of the oldest crops cultivated by man. It has been grown for industrial fiber and seed for the last 5,000 years. There are indications that it was cultivated 20,000 years ago in China. Hemp was produced in North America until 1937, when the Marijuana Tax Act made it a forbidden crop; however, the import of hemp seeds for use in bird feed was permitted. During the Second World War, hemp production was revitalized as access to imported fiber had been curtailed. Prior to 1937, an active seed breeding program was ongoing at the USDA. After this point, such programs continued in only a few European countries. Only China continued the production of hemp seed to any extent.   

Over the past decade, hempseed and oil have experienced a revival, especially in the food and health area. Hemp seed and oil are increasingly used in natural food products, such as snacks, nutrition bars, hummus, non-dairy milks, breads, cereals, prepared foods and numerous other applications. The oil is available in capsules or bottles. The market for hemp oil as a topical ingredient in natural body care and cosmetic products is also growing.

Nutritional Composition

Hemp seed composition is quite interesting in that, unlike other oilseeds, it has near equivalent levels of oil, protein and carbohydrate. Intact hemp seed contains approximately 24% crude protein, 30% crude fat, and 32% neutral detergent fiber (a reflection of total fiber content) and 5% ash (a reflection of the total mineral content)¹. 

Table 1: Composition of Hemp Seed (%)

 a - Seed cover, husk, external part of the seed.

Fatty Acids

Hempseed oil is produced by pressing the hemp seed. The oil can be eaten on its own, blended into other food or used in body care products. 

As shown in Table 2, hempseed oil has a unique fatty acid profile, especially when compared to other oils. Hempseed oil contains over 90% PUFAs, of which 80% of the oil is comprised of the essential fatty acids linoleic acid (LA, C18:2 omega-6) and alpha-linolenic acid (ALA, C18:3 omega-3). Hempseed oil is rich in LA (over 55%) and contains, depending on plant variety, 15-20% ALA. The oil is low in saturated fat, which constitutes only 9% of total fatty acids.

Hempseed oil is a rare plant source of an omega-6 EFA called gamma linolenic acid or GLA (GLA, C18:3 omega-6). GLA may be as high as 5%, but is usually between 2-3%. The presence of upwards of 3% of another unique fatty acid called stearidonic acid (SDA, C18:4 omega-3) is a distinctive property of the oil.  Newer varieties of hemp have fatty acid compositions that are skewed towards higher levels of GLA, ALA and SDA2.

Table 2: Composition of Hemp and Selected Oils

Protein

Hempseed protein is of exceptional high quality in terms of total protein levels as shown below. Only soybeans are higher in total protein3.

Table 3:                Comparison of Hempseed and Other Protein Sources

As shown in Table 4, hempseed protein contains all 21 amino acids (AA), including the 8 essential amino acids (EAA) in a ratio that resembles “complete” protein sources such as meat, milk, and eggs³. 

Table 4: Hempseed Typical Amino Acid Profile

* Essential Amino Acids

Hempseed protein is a quality source of the AAs arginine and histidine, both important for growth during childhood. It is also a good source of sulphur-containing AAs methionine and cysteine, which are required for the production of vital enzymes and for the repair and growth of lean body tissue.  Relatively high levels of the branched chain AAs leucine, isoleucine and valine, which are deemed crucial in the repair and growth of lean body mass, are also present.

Hemp seed protein is also a relatively rich source of the non-essential AA, arginine (Figure 1)3. Arginine is important physiologically as the immediate precursor of nitric oxide, which relaxes blood vessels. In this respect, arginine is used in conditions where dilation of the blood vessels is considered required, as in peripheral arterial disease.

Figure 1:     Arginine content of hempseed protein products relative to other protein sources.

In fact, research is underway at Agriculture and Agri-food Canada to develop bioactive peptides enriched with arginine from hempseed that can lower blood pressure4. Through its conversion to nitric oxide, arginine also lowers the levels of homocysteine, a protein that is associated with heart disease and stroke. Nitric oxide reacts with homocysteine to form the non–toxic compound S-nitroso-homocysteine. Thus, there may be potential applications for hempseed AAs in specialty supplements geared toward blood pressure lowering.

Hempseed protein contains no detectable gluten proteins. The maximum level for a product to declare gluten-free is <20ppm5.  Hemp products are currently used in many gluten-free foods. It is very important that grains are not contaminated or co-mingled at any point during on-farm collection or in and processing. Great care is taken by the industry to ensure that the hemp products being used in gluten-free foods are clean and of high quality.

Dietary Fiber

About 92% of the total carbohydrate fraction of hempseed is represented by fiber1. To compare, fiber represents 56% in sunflower seeds, 82% in sesame seeds, 11% in cashews and up to 69% in pecans and walnuts.  Based on water solubility, dietary fiber is classified as either soluble (pectins, gums, mucilage and some hemicelluloses), or insoluble (celluloses, some hemicelluloses and lignin)6. Hempseed contains both wate- soluble and insoluble forms of fiber¹.

Antioxidants

Hempseed oil contains tocopherols (natural vitamin E) at higher levels than other oils containing GLA, such as borage, blackcurrant and evening primrose (Table 5). The composition of tocopherols in hempseed oil is similar to soybean oil, where the gamma isomer is dominant with smaller levels of the alpha form. Gamma tocopherol has the strongest antioxidant capacity in food systems such as oils1.
 

Table 5: Tocopherol Content in Hempseed and other Oils1

Phytosterols

A variety of phytosterols are found in hempseed oil, and as shown in Table 6, the greatest being beta sitosterol--the most common in almost all plants. Second in amount is campesterol, followed by stigmasterol1. This pattern is similar to that found in soybean oil, which is a major source of phytosterols for cholesterol lowering applications7. The phytosterols in hempseed oil may contribute to positive effects of blood lipids.

Table 6: Phytosterol Content in Hempseed and Other Oils1

Role in Cardiovascular Disease

Hempseed has had little research published on its physiological effects. This may have been because of the psychotropic properties attributed to its botanical cousins, the drug/medicinal varieties of Cannabis.  The two studies that have been performed on the cardiovascular effects of hemp oil in humans have yielded inconsistent results. Schwab and colleagues compared the role of hempseed oil and flaxseed oil on several biomarkers of lipid function in healthy humans⁸. The 14 subjects consumed hemp and flaxseed oils (30ml/day) for 4 weeks each in a randomized, double-blind crossover design. The hempseed oil period resulted in higher proportions of both LA and GLA in serum cholesterol esters (CE) and triglycerides (TG), as compared with the flaxseed oil period; in contrast, the flaxseed oil period resulted in a higher proportion of ALA in both serum CE and TG, as compared with the hempseed oil period. Serum total TG concentration decreased significantly during the flaxseed oil period. Reduction in serum total TG during the hempseed oil period approached statistical significance. The total-to-HDL cholesterol ratio, which has been suggested to better predict the risk of coronary heart disease than LDL cholesterol concentration alone, decreased significantly during the hempseed oil period compared with the flaxseed oil period.

In another clinical study, 86 healthy male and female volunteers completed a 12-week double-blinded, placebo controlled trial, in which oral supplementation of 2g of placebo, fish, flax or hempseed oils per day were provided⁹. Supplementation with hempseed oil did not significantly alter the concentration of any plasma fatty acid. The lipid parameters (total cholesterol, HDL-C, LDL-C and triglyceride) did not show any significant differences among the four groups. None of the dietary interventions induced any significant change in collagen or thrombin stimulated platelet aggregation and no changes in the level of inflammatory markers were observed.

Recent animal data suggests that hempseed can impact cardiovascular disease through reductions in thrombosis (lowering of platelet aggregation or clotting)1⁰. The supplementation for 12 weeks, of either 5% or 10% (wt/wt) hempseed in the diets of male rats significantly inhibited platelet aggregation in comparison to a control chow or palm oil-rich diet. Platelet aggregation was approximately 35% lower following the hempseed diets. The results were attributed to the fatty acid composition of the hempseed--in particular the high ALA levels.

Further research by the same group has demonstrated that hempseed can significantly alter the levels of ALA in the heart and leads to beneficial cardioprotective effects in hearts subjected to ischemia-reperfusion challenge¹¹. This test refers to the restoration of blood flow to an area that had previously experienced deficient blood flow. Oxidative stresses associated with this situation may cause damage to the affected tissues or organs. In this study, a group of 40 male Sprague-Dawley rats were distributed evenly into four groups that were fed for 12 weeks; a normal rat chow supplemented with hempseed (5% and 10%), palm oil (1%), or a 10% partially delipidated hempseed served as a control.  Plasma ALA and GLA levels were significantly elevated in the rats that were fed a 5% or 10% hempseed-supplemented diet. Only ALA levels were significantly elevated in the hearts of rats fed these diets compared with control. Hearts from hempseed fed rats exhibited significantly better post-ischemic recovery of maximal contractile function and enhanced rates of tension development and relaxation during reperfusion than hearts from the other groups. The investigators suggest that dietary hempseed appears to provide significant cardioprotective effects during post-ischemic reperfusion, due to its highly enriched PUFA content.

Hempseed is a novel functional food and nutraceutical that contains several health-promoting bioactive ingredients that show promise in disease prevention and reduction.  Due to its positive nutritional characteristics, there is potentially a large market for its use in food products and dietary supplements. Hempseed oil, for example, is gaining widespread approval by the nutrition community because it contains a very well-balanced mixture of essential fatty acids, which have a number of physiological benefits for humans and animals. Human research, however, is required to clarify the role of hempseed and oil in cardiovascular disease and other chronic conditions.  NS

References

[1]Przybylski R. 2006. Validating and Disseminating the Presence of Micronutrients in Hemp Food Commodities. Report submitted to the Canadian Hemp Trade Association and Saskatchewan Agricultural Development Fund. November.

2Przybylski R. 2005. Hemp as Source of Nutraceutical Oil. Abstract LOQ 3/SOA 3.1. 96^th AOCS Annual Meeting. Salt Lake City, Utah. 

3House JD, Neufeld J. et al. 2007. Proximate analysis and protein digestibility-corrected amino acid score (PDCAAS) of hemp seed and hemp seed products. Canadian Nutrition Congress, Winnipeg, Manitoba, Canada, June 18-21, 2007 (Abstract)

4Muir A. 2007. Agriculture and Agri-Food Canada. Saskatoon, Canada.

5Codex Standard for foods for special dietary uses for persons intolerant to gluten. CODEX STAN 118 – 1979 (amended 1983; revised 2008). 

6Brown L, Rosner B, et al.  1999.  Cholesterol-lowering effects of dietary fiber: a meta-analysis. Am J Clin Nutr; 69(1): 30-42.

7Lichtenstein, AH, Deckelbaum, DK et al. 2001. Stanol/Sterol Ester-containing foods and blood cholesterol levels - A statement for healthcare professionals from the Nutrition Committee of the Council on Nutrition, Physical Activity, and Metabolism of the American Heart Association. Circulation. 103:1177-1179.

8Schwab US, Callaway JC, et al. 2006. Effects of hempseed and flaxseed oils on the profile of serum lipids, serum total and lipoprotein lipid concentrations and haemostatic factors. Eur. J. Nutr.45(8):470-7.

9Kaul N, Kreml R, et al. 2008. A comparison of fish oil, flaxseed oil and hempseed oil supplementation on selected parameters of cardiovascular health in healthy volunteers.  J. Amer. College Nutr. 27(1):51–58.

1⁰Richard MN, Ganguly R, et al. 2007. Dietary hempseed reduces platelet aggregation.  J. Thromb. Haemost. 5: 424–5

¹[1]Al-Khalifa A, Maddaford TG, et al. 2007. Effect of dietary hempseed intake on cardiac ischemia-reperfusion injury. Am. J. Physiol. Regul.  Integr. Comp. Physiol.292(3):R1198-203.