Omega-3 Q & A
What are the Omega-3 fatty acids and why are they necessary?
What is the use of Omega-3 fatty acids?
Omega-3 fatty acids have several such biological functioning mechanisms and effects that make them beneficial in the prevention of chronic diseases, such as adult-onset (type 2) diabetes, renal disease, rheumatoid arthritis, hypertension and coronary disease, thrombosis and certain kinds of cancers, (Connor 2000).How do the Omega-3 fatty acids function within the human system?
Alpha- linolenic acid has three biological main tasks that together bring about its effects beneficial to human health. ALA functions as the initial stage of EPA and DHA which also have independent roles in relation with the clotting of blood, development of foetus as well as the health of skin, nails and hair. Diet containing plenty of ALA increases the total amount of ALA, EPA and Omega-3 fatty acids in the cell membranes ‘ phospholipids increasing that way the elasticity of cell membranes and their ability to function flawlessly (Nair et al. 1997). This is extremely important for instance to the nerve cells’ ability to transmit messages, red cells’ ability to bind and deliver oxygen as well as blood vessels’ ability to expand and contract.ALA restrains inflammatory reactions by reducing the formation of compounds aggravating inflammation by means of several mechanisms. Among other things, via transformation into EPA, ALA
- increases the amount of eicosanoids fixing tissues, limits the transformation of linoleic acid via arachidon acid to eicosanoids aggravating inflammation (Garg et al. 1990, Healy et al. 2000, Magrum & Johnston 1983)
- prevents the formation of proteins (cytocins) causing inflammatory fatigue; and it may for its part prevent the coagulation of thrombocytes and the formation of phospholipids activating the synthesization of arachidon acid.
From where can you get Omega-3 fatty acids?
There are Omega-3 fatty acids particularly in green-leaved vegetables, leguminous plants as well as in fish and shellfish. Even 80 % of the fatty acids found in dark green salads are ALA, nevertheless, because those vegetables contain only minimally fat, they are not a significant source. Some fatty ocean fish contain lots of transformation products of ALA, called EPA and DHA; they however contain very little ALA, the ‘mother of all the Omega-3 fatty acids’. The best alpha- linolenic acid source in our diet and at the same time the most significant Omega-3 source in the vegetable world is the oil pressed from linseeds, where the alpha- linolenic acid content, slightly less than 60 %, is higher than in any other known vegetable oil. Even unprocessed linseeds contain more ALA per 100 g than rapeseed oil (Fineli) taking second place on the list. With regard to individual fatty acids, olive and rapeseed oils contain most monounsaturated oleic acid. On the other hand, in several other vegetable oils, such as sunflower, soy and maize oil, more than half fatty acids are linoleic acid belonging to the Omega-6 series. The linoleic acid content of linseed oil is approximately 16 %.How much Omega-3 fatty acids are needed?
We do not know the optimal intake level of alpha- linolenic acid. For men, the daily intake is believed to be sufficient on the level of 1.6 g and for women on the level of 1.1 g. In case of pregnant women, the sufficient amount is 1.4 g and for those breast-feeding 1.3 g. According to the leading fatty acids experts in the world, it, however, would be justified to increase the recommended ALA intake to 2.2 grams (Simopoulos et al. 1999a). A recent consensus publication sets an ideal range for the intake of certain critical nutrients, to support comprehensive nutritional planning. Based on it, the alpha- linolenic acid intake should vary in a person’s long-term diet between 0.6 – 1.2 % of the daily energy need. In case of a female person doing physically light work, with the energy need of 1800 kcal/day this means 1.2 – 2.4 g; and with regard to a man doing physically hard labour and with the energy need of 3500 kcal/day, this would for its part mean 2.3 – 4.6 g. It is mentioned at the same time that the share of EPA and/or DHA of this whole amount should not exceed 10 % (DRI 2002/2005).What significance does the ratio of Omega-3 and Omega-6 fatty acids have?
The human body cannot transform Omega-6 and Omega-3 fatty acids to one another. Furthermore, the same enzymes are being needed in their metabolism, which means that they are all the time in a competitive situation. Excess supply of one category may obstruct the metabolism of the other group. While the stone-age diet offered Omega-6 and Omega-3 fatty acids equally i.e. in ratio 1:1, in today’s Western diet this ratio is for Americans typically 9:1 (Simopoulos 1999b,c), and in Western diet in general, even 17:1 (Simopoulos 2001). According to the Finnutrition 2002 study, adult Finns’ intake of those Omega-6 and Omega-3 categories’ fatty acids is on an average in ratio 4:1. The ratio of the essential fatty acids in our diet (LA: ALA) for its part is among the Finnish population 5:1. Nevertheless, the variation of intake between individuals is considerably big with regard to the absolute average, which means that the population level average intake describes somewhat poorly the situation of individuals. The abundant intake of Omega-6 fatty acids in relation to that of the Omega-3 acids is not beneficial to one’s health, because the ’sixes’ may obstruct the transformation of ALA into EPA and DHA. Furthermore, the high content of Omega-6 fatty acids in a person’s diet may cause the increase of arachidon acid within the phospholipids in the cell membranes, which lead in the course of time to the overproduction of eicosanoids aggravating inflammations. The excess supply of those eicosanoids may for its part contribute to the arteriosclerosis and other slowly advancing chronic inflammatory diseases. The reduced intake of Omega-6 fatty acids and the increased intake of Omega-3 acids for its part reduce the risk of chronic diseases such as heart disease and cancer. Based on nutrition experts’ consensus recommendation, the appropriate ratio between the intake of Omega-6 and Omega-3 fatty acids is between 5:1 and 10:1 (DRI, 2002/2005). Nevertheless, an international group of leading experts in the field of fatty acids has defined 2:1 (Simopoulos et al. 1999a) for the ideal ratio of those fatty acids.What special roles does EPA have?
Eicosapentaenoic acid is essential e.g. for the regulation of brain functions, for the transmission of signals between nerve cells and the circulation in the nervous system. Furthermore, it controls the enzymes dissolving other polyunsaturated fatty acids and functions as raw material for the prostaglandin hormones that have a significant role in the prevention of inflammation and in the immune system. Because of these functions, there has recently been very active research on the effects of EPA, and it has been found to be beneficial e.g. in the treatment of learning and behaviour disturbances, severe mental illnesses and depression in particular.What special roles does DHA have?
Docosahexaenoic acid is the constituent of plasma membranes in the nerve cells, and its share in the fatty acids found in the grey matter within brain amounts to 25 % and in retina even to 50 %. Therefore, DHA is absolutely necessary for the early development of sight, particularly during pregnancy and in babyhood. There has been found a direct relation between babies’ DHA intake and sharp eyesight (Birch et al. 2002).Nutrition or food supplements?
In an ideal situation everyone has all the essential nutrients in correct ratios in the nutrition he or she takes. The diet in developed countries, however, has been so refined and varied that it is not that simple to reach and maintain the ideal situation. Everyone compiles his or her diet in a way he or she prefers and/or considers the best. Even though the alpha- linolenic acid taken in within the nutrition is absorbed almost completely, the final intake may deviate significantly from the amount calculated for the nutrient. There are hints that e.g. the frying of fish destroys some of the Omega-3 fatty acids (Mozzafarian et al. 2003), because of temperatures possibly rising too high.References
Birch, E.E., Hoffman, D.R., Castañeda, Y.S. et al. 2002. A randomized controlled trial of long-chain polyunsaturated fatty acid supplementation of formula in term infants after weaning at 6 weeks of age. American Journal of Clinical Nutrition 75(3): 570-580.Connor, W.E. 2000. Importance of n-3 fatty acids in health and disease. Am. J. Clin. Nutr. 71: 171S-175S.
Fineli, Kansanterveyslaitos, ravitsemusyksikkö. Elintarvikkeiden koostumustietokanta.Versio 6. Helsinki 2006. www.ktl.fi/fineli.
Finravinto 2002 -tutkimus. Satu Männistö, Marja-Leena Ovaskainen ja Liisa Valsta (toim.). Kansanterveyslaitoksen julkaisuja B3/2003. Kansanterveyslaitos, Ravitsemusyksikkö. Helsinki 2003.
Mozzafarian, D., Lemaitre, R.N., Kuller, L.H., Burke, G.L., Tracy, R.P., Siscovick, D.S. 2003. Cardiac Benefits of Fish Consumption May Depend on the Type of Fish Meal Consumed. The Cardiovascular Health Study. J Fam Pract. 52(6): 438-41.
Simopoulos, A.P., Leaf, A.& Salem, N.Jr. 1999a. Workshop on the Essentiality of and Recommended Dietary Intakes for Omega-6 and Omega-3 Fatty Acids. J Am Coll Nutr 18: 487-489.
Simopoulos, A.P. 1999b. New products from the agri-food industry: The return of n-3 fatty acids into the food supply. Lipids 34: S297-S301.
Simopoulos, A.P. 1999c. Evolutionary aspects of omega-3 fatty acids in the food supply. Prostaglandins Leukot Essent Fatty Acids 60: 421-429.
Simopoulos, A.P. 2001. n-3 Fatty acids and human health: Defining strategies for public policy. Lipids 36: S83-S89.
DRI – Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. 2002/2005. (toim.) Panel on Macronutrients, Panel on the Definition of Dietary Fiber, Subcommittee on Upper Reference Levels of Nutrients, Subcommittee on Interpretation and Uses of Dietary Reference Intakes, and the Standing Committee on the Scientific Evaluation of Dietary Reference Intakes. Food and Nutrition Board. Institute of Medicine of the National Academies. 1351 s. National Academies Press. Washington DC. USA.
