Omega fatty acids in your diet

Written by: 
Dr Sarah Brewer

You might have heard about omega-3 - a lot of supermarket foods are topped up with this fatty acid - but why is it important, and what is omega-6?

Omega-6 and omega-3 fatty acids are components of dietary fatOne of the three main food constituents (with carbohydrate and protein), and the main form in which energy is stored in the body.. They are called essential fatty acids because the body cannot make them, and so they must be taken in through the diet.

Essential fatty acids provide important health benefits.

A deficiency of essential fatty acids in the diet may lead to unpleasant symptoms. Humans evolved eating a very different diet to the one typically consumed today in Western countries, and many people in Western populations might feel healthier if they altered the ratio of omega-6 to omega-3 fatty acids in the diet.

Many thousands of years ago, humans evolved as hunter-gatherers on a diet of green plants, wild animals and fish.

Dietary sources of omega-6 and omega-3 fatty acids

Omega-3 and omega-6 fatty acids are polyunsaturated fats.  This means they tend to be liquid at room temperature, forming an oil - unlike saturated fatty acids such as butter and lard that are solid at room temperature.

Omega-6 fatty acids are mainly derived from vegetable oils such as sunflower, safflower and corn oils, and are often found in fried and processed foods.

One type of omega-3 fatty acid, alpha-linolenic acid (ALA), is also found in significant amounts in some vegetable oils (such as rapeseed and walnut oils). Other forms of omega-3 fatty acids such as eicosapentaenoic acidAn essential omega-3 fatty acid found in oily fish. (EPAAn essential omega-3 fatty acid found in oily fish.) and docosahexaenoic acid (DHA), which provide the greatest health benefits, are mainly derived from fish oils (having originally come from the plankton on which these fish feed).

Health benefits of essential fatty acids

Essential fatty acids are important for making cellThe basic unit of all living organisms. membranes as flexible as possible. Flexible membranes enable brain cells to communicate more easily, assist in maintaining a healthy circulation and help to keep skin soft and supple.

In addition, essential fatty acids act as building blocks for making sex hormones.

Regulating inflammation

Your body converts essential fatty acids into substances that regulate inflammatory reactions:

  • Most omega-6s are converted into substances (series 2 prostaglandinsOne of a group of hormone-like substances that have a wide variety of actions, including the dilation of blood vessels and contraction of smooth muscle. and series 4 leukotrienes) that promote inflammationThe body’s response to injury. and increase bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. stickiness
  • Omega-3s are converted into substances (series 3 prostaglandinsOne of a group of hormone-like substances that have a wide variety of actions, including the dilation of blood vessels and contraction of smooth muscle. and series 5 leukotrienes) that reduce inflammationThe body’s response to injury. and have a bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid.-thinning effect.1,2

An omega-6 fatty acid known as gammalinolenic acid (GLA, found in evening primrose and starflower oil) is one of the few omega-6s that can reduce inflammationThe body’s response to injury. if intake is sufficiently high.3

Because the body cannot convert excess omega-6s into omega-3s (or vice versa), it is important to obtain a balanced dietary intake of both types of polyunsaturated fatty acid to limit the formation of inflammatory substances in the body.

Fatty acid deficiency

A deficiency of essential fatty acids in the diet is associated with symptoms such as:

  • Feeling excessively thirsty
  • Needing to urinate very frequently
  • Dry, rough, pimply skin
  • Itchy skin
  • Dry, dull hair and soft or brittle nails
  • Lowered immunity, with frequent infections
  • Learning difficulties, including dyslexia, attention deficit hyperactivity and autism spectrum disorders.

Ratio of omega-6 to omega-3 fatty acids in the diet

Many thousands of years ago, humans evolved as hunter-gatherers on a diet of green plants, wild animals and fish. This diet contained a ratio of omega-6 fatty acids (from natural vegetable oils) to omega-3s (from oily fish) of around 2:1.5

In most modern populations, however, the intake of omega-6 fatty acids is now dramatically higher, due to increased consumption of processed vegetable oils, vegetable spreads and convenience foods. People today also generally eat fewer nuts and less oily fish than did our ancestors.

These dietary changes mean that the ratio of omega-6 to omega-3 fatty acids is currently closer to 10:1 or more.6 This pattern promotes inflammatory changes in the body and is suspected to contribute to the development of many chronicA disease of long duration generally involving slow changes. diseases including cardiovascular and autoimmuneAny condition caused by the body’s immune response against its own tissues. diseases and cancerAbnormal, uncontrolled cell division resulting in a malignant tumour that may invade surrounding tissues or spread to distant parts of the body..7

Improving your omega-6 to omega-3 ratio

To increase your intake of anti-inflammatoryAny drug that suppresses inflammation omega-3s, aim to eat more:

  • Oily fish (2 to 4 portions per week) such as mackerel, herring, salmon, trout, sardines, pilchards, fresh tuna (not tinned)
  • Wild game meat such as venison and buffalo
  • Grass-fed beef
  • Omega-3 enriched eggs.

Omega-3 fish oil supplements are also available.

To reduce intakes of inflammatory omega-6s, aim to consume less:

  • Omega-6 rich vegetable oils such as safflower oil, grape-seed oil, sunflower oil, corn oil, cottonseed oil or soybean oil - replace with healthier oils such as rapeseed, olive, walnut or macadamia nut oils
  • Margarine based on omega-6 oils such as sunflower or safflower oil
  • Convenience food
  • Fast food
  • Manufactured goods such as cakes, sweets and pastries.
References: 
  1. MacLean CH, Mojica WA, Morton SC, et al. 'Effects of omega-3 fatty acids on lipids and glycemic control in type II diabetes and the metabolic syndromeThe combination of insulin resistance, abdominal obesity, high blood pressure and disordered blood lipids that increases the risk of cardiovascular disease. and on inflammatory bowel diseaseA group of inflammatory conditions of the intestine. The two major forms are Crohn’s disease and ulcerative colitis., rheumatoid arthritisInflammation of one or more joints of the body., renal disease, systemic lupus erythematosus, and osteoporosis: Summary, evidence report/technology assessment No. 89.' 2004. (Prepared by the Southern California/RAND Evidence-based Practice Center, Los Angeles, CA.) AHRQ Publication No. 04-E012-1. Rockville, MD: Agency for Healthcare Research and Quality.  March 2004.
  2. Calder PC. 'N-3 polyunsaturated fatty acids, inflammationThe body’s response to injury. and inflammatory diseases.' American Journal of Clinical Nutrition. 2006; 83(6 Suppl): 1505S-1519S.
  3. Belch JJ, Hill A. 'Evening primrose oil and borage oil in rheumatologic conditions.' American Journal of Clinical Nutrition. 2000; 71(1 Suppl): 352S-6S.
  4. Food and Behaviour Research Factsheet 002 - Physical Signs of Fatty Acid Deficiency'. Food and Behaviour Research.
  5. Cordain L, Eaton SB, Sebastian A et al. 'Origins and evolution of the Western diet: health implications for the 21st century.' American Journal of Clinical Nutrition. 2005 Feb; 81(2): 341-354.
  6. Kris-Etherton PM, Taylor DS, Yu-Poth S et al. 'Polyunsaturated fatty acids in the food chain in the United States.' American Journal of Clinical Nutrition. 2000 Jan; 71(1): 179S-188S.
  7. Simopoulos AP. 'The importance of the omega-6/omega-3 fatty acid ratio in cardiovascular disease and other chronicA disease of long duration generally involving slow changes. diseases.' Exp Biol Med (Maywood). 2008 Jun; 233(6): 674-88.