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Der ernährungsphysiologische Wert von Hanfsamen

Franjo Grotenhermen

Both ripe hemp seed and hemp seed meal, as well as hemp oil, are useful sources of oils and fatty acids, proteins and amino acids, and fibres and dietary fibres respectively. Technically, hemp seed is a nut that typically contains over 30% oil and about 25% protein, with significant amounts of fibre, vitamins and minerals.

Hemp oil contains over 80% polyunsaturated fatty acids and is an exceptionally rich source of the two essential fatty acids linoleic acid (18:2 omega-6) and alpha-linolenic acid (18:3 omega-3). The ratio of omega-6 to omega-3 in hemp oil is usually between 2:1 and 3:1. In addition, the two essential fatty acids, gamma-linolenic acid (18:3 omega-6) and stearidonic acid (18:4 omega-3), are also present in hemp oil.

In addition to its use as a food, hemp oil is suitable for use in cosmetic skin care products (ointments, skin oils) because of its favourable fatty acid ratios. Other vegetable oils containing gamma-linolenic acid such as evening primrose or borage oil have an unfavourable omega-6 to omega-3 ratio of about 30 to 1, which does not correspond to the fatty acid spectrum of human skin (4 to 1).

Finally, hemp oil contains medium to high concentrations of antioxidants of the vitamin E complex (100-150 milligrams per 100 grams of oil, mainly gamma-tocopherol) and smaller amounts of various other beneficial or essential components (phytosterols, phospholipids, carotene and several minerals).

The two main proteins in hemp seeds are edestin and albumin. These two high-quality storage proteins are easily digestible and contain nutritionally significant amounts of all essential amino acids. In addition, hemp seed has an exceptionally high content of the amino acid arginine.

Table: Important vegetable oils and their content of the most important unsaturated fatty acids

Vegetable oil Oleic acid Linoleic acid (Omega-6) Alpha-linolenic acid (omega-3) Gamma-linolenic acid (omega-6)
Hemp 10-16 50-70 15-25 2-4
Flax 13-23 17-31 44-54 -
Olives 64-86 4-15 1 -
Rapeseed 54-60 24-28 9-11 -
Sunflower 30-40 50-64 Spuren -
Soy 20-34 49-55 4-12 -
Evening Primrose 12-20 55-65 - 6-14
Borage 14-18 25-40 >1 21-25

Essential fatty acids cannot be synthesised by our body and must therefore be present in the diet. The triple unsaturated alpha-linolenic acid makes up a large proportion, typically 15 to 25 percent, of the total hemp fatty acids. Hemp oil contains various "higher fatty acids", i.e. those that the human body forms from the two essential fatty acids respectively. The most important are gamma-linolenic acid and stearidonic acid.

Most oils used in everyday life (e.g. sunflower, soy, rapeseed and maize) contain enough linoleic acid. However, only soybean and rapeseed oil also provide small amounts of alpha-linolenic acid. Flaxseed, which is rich in alpha-linolenic acid, is not suitable for cooking because of its fatty acids and the bitter substances in its oil. Since meat and cereals are also not important sources of alpha-linolenic acid or higher omega-3 fatty acids, Western countries often lack omega-3 fatty acids in their daily diet. There is evidence that a deficiency of omega-3 fatty acids contributes to several common acute and chronic diseases. The typical ratio of linoleic acid to alpha-linolenic acid in hemp oil is close to a ratio of 4:1 to 6:1, which is considered by nutritionists to be optimal for the human organism. This ratio is much more optimal than in all other vegetable oils conventionally used for cooking - with the exception of rapeseed oil, which has similarly optimal ratios.

The presence of gamma-linolenic acid and stearidonic acid in hemp oil offers an additional benefit over and above the favourable composition of the fatty acids linoleic acid and alpha-linolenic acid for people in whom the conversion of the two essential fatty acids to these higher fatty acids does not occur or does not occur to a sufficient extent via the metabolism due to genetic, nutritional or other life circumstances.

Normally, the healthy organism does not need gamma-linolenic acid because it is formed from linoleic acid by an enzyme, delta-6-desaturase. However, in order to be fully used by the body, linoleic acid must be metabolised into a number of other substances. If the delta-6-desaturase activity is reduced for any reason, then health disorders, such as skin problems, can occur. The direct supply of gamma-linolenic acid can then be an adequate measure to ensure normal function again.

A comparison of the composition of hemp oil with other oils shows that the proportion of gamma-linolenic acid in hemp oil is not particularly high. Borage and evening primrose oil, for example, each contain higher concentrations of gamma-linolenic acid. However, their instability, the unpleasant taste, but also the higher costs make these oils unsuitable as edible oils - they are mainly offered on the market in the form of capsules.