Guest blog contributed by Claire Saunders, a student at Oxford Brookes University, currently on placement at CABI.
Many people are not sure how omega oils feature in their diet and in what quantities they should be consuming them. Confounded by acronyms such as PUFA, ALA and DHA, it’s tempting just to eat a piece of fish and hope for the best. Considering that many of are not getting even the minimum levels in our diet that are deemed “critical” to health by the World Health Organization (WHO), maybe we should rethink our 'laissez faire' attitude. A 2016 systematic review revealed that 80% of the world has low or very low blood levels of DPA and EHA. When questioned, a third or consumers in Germany, UK and USA were unsure how much they should be consuming. There follows a practical guide to omega oils.
Why are they called Omega oils?
Omega (ω-), Greek for end or tail, denotes the end of the molecular structure of the oil. The number (as in omega 3, 6, 7 and 9) is determined by counting how far along this structure a double bond sits, and it is this that gives each oil its unique profile. These double bonds make omega oils liquid at room temperature, as opposed to saturated fats, which remain solid until heated.
Why are they so important?
The body can synthesize most of the fats it needs, but not all. There are some fats that are essential to health that we cannot make and can only obtain through the diet. The WHO recognises the unique biological properties of these essential fatty acids (EFA) and their importance to our health. Many conditions have been linked with a lack of these essential nutrients, from cardiovascular disease and arthritis to foetal development and nerve function.
How many of us are getting enough?
Most of us are falling short of the recommendations essential for our health; a recent global survey reported that people in North America, Central and South America, Europe, the Middle East, Southeast Asia, and Africa are just not eating enough. Only 20% of Australians are eating the recommended amounts.
How much should we be eating?
Trawling through the advice and guidelines, it is not surprising that the public are confused, and this may be part of the problem. In the UK the NHS advises us to eat at least two portions of fish a week (at least one oily) and that these have greater benefits than vegetable sources. Other advice is a little less user-friendly: the NHS Eatwell Guide merely says “choose unsaturated oils and in small amounts”. Most national guidelines (such as those for Denmark, Canada and Iceland) are filtered down from evidence collected and published by WHO, that say at least 0.5% of your total energy should be coming from Omega-3s (this equates to 0.25g/day, or 0.3g/day in pregnancy) and 2.5% from Omega-6 (1.25g/day) . Any less and you may be at risk of coronary heart disease, diabetes and metabolic syndrome and other diseases. WHO also says that children need between 0.5 and 1.6g of omega-3 per day, depending on age and size.
The best sources are mackerel, salmon, cod liver, flax, hemp, chia seeds, walnuts and soya bean oil. Fortified foods such as omega-3 eggs can be a useful addition. You may have heard the terms EPA, DHA and ALA. These are simply different types of omega-3s. The first two are fish-based sources (eicosapentaenoic acid and docosahexaenoic acid) while ALA (alpha-linolenic acid) is a plant-based omega-3.
Linoleic acid is the most common omega-6 oil. It may surprise you to know that if you searched Nutrition Data’s list of foods containing the highest levels of omega-6, the first 250 are all takeaway and fast foods, without a wholefood in sight. The top scorer, packing 24752 mg of omega-6 per serving is a ranch sauce (data from 2014); approximately ten times more than the recommendations. This is partly because the main sources of omega-6 are corn, safflower, sunflower and soya oil, many of which feature greatly in fast food manufacture.
Omega-7s and 9 are not essential for health, so there are no recommended daily intakes, but they are good for us. A recent review found that they reduce inflammation and protect against heart disease. Omega-7 can be found in oily fish, macadamia nuts and sea buckthorn berries. Omega-9 sources are nuts, sunflower and olive oils.
The lower the ratio, the better. 1:1 may be optimum (omega-6: omega-3). According to WHO in 2008, there was no compelling scientific rationale for the recommendation of a specific ratio of omega-6: omega-3. However, one could surmise by their guidelines of 2.5% and 0.5% of your daily energy coming from omegas-6 and 3 respectively, it would be 5:1. That said, these guidelines are based on evidence available in 2008. A 2013 review of omega-6 to omega-3 ratios and brain health found that intakes with a high ratio of omega-6 compared to omega-3 could be linked with cognitive decline. The authors conclude that a low ratio is recommended for brain health.
Many foods contain a combination of omegas-6 and 3 (such as nuts, seeds and oils) in optimum ratios. The general rule of thumb is the less processed the food, the healthier the ratio is likely to be.
Are we getting the ratios right?
The short answer is no. Developed countries in particular are eating far too much omega-6. The problem is that as well as being present in healthy food like nuts and seeds, Omega 6 is also abundant in meat and dairy, fast food, cakes, crackers and crisps, salad dressings and vegetable oils. “In the past three decades, intake of omega-6 fatty acid increased and intake of omega-3 fatty acid has decreased, causing changes in the omega-6/omega-3 ratio from 1:1 during evolution to 20:1 today or even higher” said Artemis Simopoulos in her recent paper An Increase in the Omega-3/Omega-6 Fatty Acid Ratio Increases the Risk for Obesity. Many supplements contain Omega-6 unnecessarily.
Stark, K., Van Elswyk, M., Higgins, R., Weatherford, C., Salem Jr., N. 2016. Global survey of the omega-3 fatty acids, docosahexaenoic acid and eicosapentaenoic acid in the blood stream of healthy adults., Progress in Lipid Research: Vol. 63, pp. 132-152. http://doi.org/10.1016/j.plipres.2016.05.001.
Bailey, R., Denby, Nigel R., Haycock, B., Sherif, K., Steinbaum, S., Von Schacky, C. 2015. Perceptions of a Healthy Diet: Insights From a 3-Country Survey., Progress in Lipid Research: Vol. 50, Issue 6, pp. 282-287. doi: 10.1097/NT.0000000000000119
Mateos, H., Lewandowski, P. A. Vaughan, V., Su, X. 2013. Health impacts of eicosapentaenoic acid and docosahexaenoic acid., CAB Reviews: 8, No. 007. doi: 10.1079/PAVSNNR20138007
Pompili, M., Longo, L., Dominici, G., Serafini, G., Lamis, D., Sarris, J., Amore, M., Girardi, P.2017. Polyunsaturated fatty acids and suicide risk in mood disorders: A systematic review., Progress in Neuro-Psychopharmacology and Biological Psychiatry. Vol. 74, pp. 43–56. doi:org/10.1016/j.pnpbp.2016.11.007
Ferguson, L., Caterina, R. de., Görman, U., Allayee, H., Kohlmeier, M., Prasad, C., Choi, M. S., Curi, R., Luis, D., de Gil, A., Kang, J., Martin, R., Milagro, F., Nicoletti, C., Nonino, C., Ordovas, J.,; Parslow, V., Portillo, M., Santos, J., Serhan, C., Simopoulos, A. P., Velázquez-Arellano, A., Zulet, M., Martinez, J. 2016. Journal of Nutrigenetics and Nutrigenomics: Vol 9, Issue 1, pp. 12-27. doi: 10.1159/000445350
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