Health-promoting oils

The term health-promoting oils refers to high-quality vegetable oils, which differ from other oils mainly due to their high quality and specific, health-promoting properties. In particular, the quality of the oils is in the foreground, which is achieved by using selected raw materials and gentle processing. The germination capacity of the freshly harvested oil seeds guarantees the preservation of valuable nutritional components (1). From a medical point of view, the high proportion of omega-3 fatty acids is particularly relevant, which have already demonstrated their preventive effect on various diseases in studies (2). Compared to other known vegetable oils, linseed oil in particular has one of the highest concentrations of omega-3 fatty acids, but camelina oil and hemp oil also contain significant amounts of these special fatty acids (3). In addition, oils with antibacterial properties such as peppermint oil, tea tree oil, thyme oil and clove oil can also be counted among the health-promoting oils and used in particular for inflammatory and oral diseases and for daily dental care and oral hygiene (4). Health-promoting oils are also used for the alleviation of symptoms, in the prevention of cardiovascular and chronic diseases and for the targeted supply of omega-3 fatty acids, e.g. during pregnancy and sometimes also as a culinary component (1)(2). In this context, oil extraction according to Ayurvedic teachings is also worth mentioning, which is mainly used in the field of oral health and, according to the art of healing, is also supposed to provide relief from diseases such as headaches and even migraines, skin problems as well as asthma and diabetes (5).

As already mentioned above, it is also the health-promoting properties, such as the omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which distinguish a health-oil from a simple vegetable oil. In human metabolism, fatty acids play an essential role as an energy source, as a component of the cell membrane and as a precursor for other substances (e.g. hormones). Due to their anti-inflammatory properties, they can alleviate inflammation and can thus be used to prevent and treat many chronic diseases, such as cardiovascular and neurodegenerative diseases (2). The omega-3 index, which represents the percentage of the two omega-3 fatty acids in the total fatty acid content of the serum, is a suitable laboratory diagnostic measure. If the omega-3 index is <4 %, the risk of sudden cardiac death is ten times higher than with an index > 8 % (6). Among the fatty acids, linoleic acid plays an important role in omega-6 fatty acids, while alpha-linolenic acid (ALA) is one of the most important representatives of omega-3 fatty acids. As an essential fatty acid, ALA cannot be synthesized by the body and must therefore be supplied by the diet (3).
 

A good source of ALA is linseed oil, which has one of the highest concentrations (between 50-70%) of the specific omega-3 fatty acid. This is the oil of common linseed (Linum usitatissimum), which belongs to the cruciferous family (Brassicaceae) and is one of the oldest cultivated plants in the world. Furthermore, the oil of Camelina sativa, which belongs to the same plant genus, has a significant ALA content (30-40%). The oil of hemp (Cannabis sativa), whose history as a crop plant also goes back a long time, can also be counted among the health oils with its high proportion of ALA (up to 30%) (3). Furthermore, linseed oil as well as gold of pleasure oil naturally contain gamma-tocopherol (vitamin E), which is not only beneficial to health due to its antioxidant effect, but also increases the stability and durability of the oil (7). In addition to omega-3 fatty acids, humans also needs omega-6 fatty acids, which serve as precursors for the endogenous synthesis of tissue hormones. Linoleic acid is a doubly unsaturated essential omega-6 fatty acid from which the body can synthesise the important gamma-linolenic acid (GLA). GLA is needed in the human body for the synthesis of prostaglandins and leukotrienes and is also a component of biological membranes (8).
 

From a health point of view, not only the intake of omega-3 fatty acids is essential, but also the right balance between omega-6 fatty acids and omega-3 fatty acids. As both fatty acids compete with each other for incorporation into the cell membranes, the German Nutrition Society (DGE) recommends a fatty acid ratio of 5:1, although studies show that the ratio in Austria has shifted in favor of omega-6 fatty acids (9).  If the fatty acid ratio of omega-6 fatty acids to omega-3 fatty acids is within the recommended range, more omega-3 fatty acids are used for the production of prostaglandins, which have anti-inflammatory effects, reduce blood clotting and have a positive effect on blood pressure. An unfavorable ratio between the intake of omega-6 fatty acids and omega-3 fatty acids, on the other hand, leads to the production of pro-inflammatory substances which, for example, promote cardiovascular diseases. Among the health oils, linseed oil, camelina oil and hemp oil are among those oils with the most favourable ratio of omega-3 to omega-6 fatty acids (10).

Oil pulling is an Ayurvedic procedure traditionally used for oral health and detoxification (5. In order to improve oral hygiene, oils with antibacterial properties that inhibit harmful organisms such as bacteria or fungi are used in the oral cavity in addition to tasteless edible oils such as sunflower oil. In addition, oil pulling is also used to protect the teeth and gums and to strengthen the jaw and prevent bad breath, bleeding gums and dry lips (11). According to Ayurvedic medicine, the process of "pulling" the oil through the spaces between the teeth for several minutes is supposed to activate enzymes which should draw toxins from the blood. In general, oil pulling in combination with brushing and flossing is a simple and natural method to improve and maintain oral health and hygiene. Furthermore, Ayurvedic teachings attribute additional effects of oil pulling on various diseases such as headaches and migraines, as well as on chronic diseases such as diabetes and asthma. The oral cavity is in particular in focus in Ayurvedic teachings, which, if the mucous membrane is intact, represents the first barrier against the penetration of pathogenic organisms and thus prevents them from entering the systematic circulation (5). Furthermore, the lining of the oral cavity with an intact microbial biofilm is also important. If oral hygiene is neglected, the balance can shift and colonization with pathogenic organisms can increase. An intact biofilm is particularly important to prevent periodontal diseases such as gingivitis or periodontitis, but also to limit systemic secondary diseases caused by inflammation and the invasion of pathogenic organisms (12).
 

In a small intervention study, oil pulling with sunflower oil as a supplement to normal oral hygiene proved to be effective against plaque and gingitivis (13). This result is further supported by another study in which oil pulling reduced the plaque index, the degree of gingivitis and the number of Streptococcus mutans bacteria. According to this study, oil extraction was as effective against plaque-induced gingivitis as chlorhexidine. However, unlike the antiseptic, the oil does not discolour the teeth, has no persistent aftertaste and does not cause allergies (14). According to a study, halitosis (bad breath) can also be treated just as well with oil as with chlorhexidine. Here the oil was able to reduce halitosis and halitosis-causing microorganisms in the oral cavity equally well (15). Oil pulling with sunflower oil also proved to be effective against the mouth fungus Candida albicans. This is consistent with the results of other studies on the improvement of oral thrush (oral candidiasis). The effect of oil pulling is based on two mechanisms: on the one hand, the "pulling" removes toxins and pathogens from the oral cavity and, on the other hand, the antifungal properties of the oils contribute to the elimination of the fungus (12). There are many theories on the mechanism of action of oil pulling, but the exact function has not been fully scientifically determined. One theory is based on oil saponification: During saponification, oils emulsify through the alkaline hydrolysis of their fats, resulting in bicarbonate. The soap substances mix with the oil, enlarging the surface and thus increasing the cleaning effect. Another theory relates to the viscosity of the oils, which may reduce the adhesion of bacteria and plaque. The third theory assumes that the antioxidants present in the oil detoxify by preventing lipid peroxidation and thus have an antibiotic effect (5). Without any scientific evidence so far, but known in Ayurveda for a long time, is the detoxifying effect of oil pulling. According to traditional knowledge, it stimulates the glands of the oral mucosa and improves the blood circulation, whereby harmful substances and toxins are excreted more effectively. The oil also "draws" harmful substances from the organism and binds them in the mouth. The harmful substances can then be removed from the oral cavity by spitting them out. For this reason, this decades-old technique is also used in modern detoxification practices (16). In principle, oil pulling can be carried out with almost any edible oil, however, tasteless and easily available vegetable oils such as sunflower oil are recommended, which is also one of the oil pulling classics (3). Darker oils for oil pulling, such as pumpkin seed oil, are not recommended, as this can lead to discoloration of the teeth.
 

Pulling oil can act as a so-called dental oil in combination with antibacterial, essential oils such as thyme oil, sage oil, clove oil, tea tree oil and peppermint oil and also contribute to oral hygiene. Due to its high thymol content, thyme not only has antibacterial properties but also acts as an antioxidant and radical scavenger (17). Sage with its camphor, thujone and cineol components is effective against both gram-positive and gram-negative bacteria as well as fungi such as Candida albicans. The compounds in clove oil destroy microbial cell membranes and penetrate cytoplasmic membranes. The main component of clove oil is eugenol, which is mainly responsible for its antiviral and antibacterial properties. Tea tree oil has long been used for dermatological applications and dental hygiene due to its antibacterial properties and inhibition of the growth of the bacteria Porphyromonas gingivalis and Porphyromonas endodontalis, which are responsible for bad breath. However, it not only suppresses their growth, but also limits the production of the unpleasant smelling free sulphur compounds. Terpineol and cineol in tea tree oil also inhibit C. albicans. Peppermint oil is valued for its pleasant fresh taste and its strong anti-inflammatory properties. Like clove oil, it has shown antiviral properties against the herpes simplex virus (HSV-1 and HSV-2) in studies, whereas its antimicrobial activity is strongly dependent on the menthol content (4). Lemon balm oil with its citrus note is refreshing in taste and also has antimicrobial and antioxidant properties (18).
 

The anti-inflammatory properties of omega-3 fatty acids and their metabolites play a major role, particularly in protective functions. They reduce circulating inflammatory cytokines, chemokines and pro-inflammatory metabolites of arachidonic acid (2). Immunomodulatory effects of omega-3 fatty acids are currently being studied in detail, as over-activation of the innate immune system can lead to harmful effects. Here, omega-3 fatty acids can have a beneficial effect by changing the cell membrane composition, modifying signaling pathways and gene expression, and shifting the pattern of lipid metabolites produced under stress conditions towards a more anti-inflammatory metabolite profile. Due to the high content of ALA, linseed oil in particular can support a broad spectrum of mainly preventive - but also therapeutic - measures. The accompanying intake of linseed oil supports e.g. the maintenance of healthy blood lipid values and the prevention of cardiovascular diseases. Studies show that linseed oil supplements modulate the body's immune response (19). A recent study compared the effects of linseed oil and fish oil supplementation on cardiovascular risk parameters of diabetic patients with coronary heart disease. The results of the study suggest that linseed oil reduces insulin and increases the total capacity for nitrite and antioxidants to a similar extent as fish oil. In contrast to placebo, both oil treatments significantly lowered insulin levels and significantly increased antioxidant capacity (20). ALA-rich vegetable oils are also considered beneficial for the serum lipid profile and glucose metabolism. This is believed to contribute to protective action against type 2 diabetes and cardiovascular disease. In one study, the consumption of camelina oil showed more positive effects on blood cholesterol levels compared to fish. While total and LDL cholesterol concentrations decreased with the daily intake of camelina oil, the consumption of fish did not achieve this effect (21). The effect of camelina oil on the lipid profile was also confirmed in comparison with rapeseed and olive oil. Camelina oil not only increased the amount of ALA and its metabolites in the serum, but also reduced the LDL cholesterol by 12.2%. The cholesterol lowering effect of camelina oil was comparable to that of rapeseed and olive oil (22). The beneficial effects of camelina oil could be due to a molecular mechanism in the immune regulation: A 12-week diet enriched with camelina oil showed a reduced mRNA expression of interferon gamma, a macrophage activator with important immunoregulatory tasks and involvement in the inflammatory process (23).