This blog is written by our clinicians and aims to keep patients informed with up to date information on medical conditions.
As people are becoming more and more health conscious, nutrition and supplementation are often topics that come up during GP consultations. “So what about oil fish – how much and how often?” they will ask. Well, for a start, fish is a good source of protein and, relative to other protein foods such as red meat, poultry and eggs, is generally lower in saturated fatty acids and higher in polyunsaturated Omega 3 fatty acids and selenium than other protein foods such as red meat and eggs. Oil fish also contains vitamin A and vitamin D.
What are fatty acids?
Omega 3 and Omega 6 are the two main forms of fatty acids which are essential, meaning they cannot be made by the body. Omega 3 in particular refers to a group of 3 fatty acids :- alpha-Linolenic acid (ALA), Eicosapentaenoic acid (EPA) and Docosahexaenoic acid (DHA). The parent fatty acid of this group is ALA has a short chain and is converted within our bodies to the more important long chain fatty acid EPA, which in turn is converted into the most crucial fatty acid DHA. This conversion process is very inefficient (especially in men), so obtaining long-chain Omega 3 directly from our food is much more effective.
Where do we get it from?
EPA and DHA are found in cold water oily fish such as salmon, herring, mackerel, anchovies, and sardines. Some foods, such as eggs, milk, bread and margarine are fortified with Omega 3. The parent fatty acid ALA is found in seed oils such as kiwifruit, perilla, walnut and linseed.
History of Omega 3
Omega 3 came to the forefront in the ‘70’s following a study of Greenland’s Inuit people who consume a lot of fat from fish and have very low levels of cardiovascular disease. The high levels of long chain fatty acids obtained from their diet reduced heart rate, blood pressure and atherosclerosis (fatty thickening of the arteries) in the population.
Why do we need fatty acids?
Fatty acids form the building blocks for a huge number of compounds involved in regulating blood clotting, body temperature, blood pressure, reproduction and immune function. They are therefore important for healthy functioning of the brain (a fat-rich organ, and around half of the fat content is DHA), eyes, heart and the growing foetus to name a few.
Omega 3 lowers cholesterol levels by slowing the liver’s production of bad fats (Very Low Density Lipoproteins/VLDL and triglycerides), increasing it’s break down of VLDL and improving the body’s clearance of triglycerides after eating.
EPA and DHA have also been shown to decrease the production of compounds involved in clotting and inflammation thereby lower the risk of heart attacks and improving inflammatory disorders such as rheumatoid arthritis and psoriasis.
Omega 6 fatty acids compete with Omega 3 for storage and conversion into other substances within cell membranes and therefore have a direct bearing on the type of hormone produced and the level of inflammation in the cell – Omega 3 being anti-inflammatory and Omega 6 being pro-inflammatory. Therefore a balance must be struck between both, but trying to achieve a 1:1 balance of Omega 3 to 6 is impossible and most experts consider the optimal ratio to be 1:2 but this is not easy to produce by diet alone. The only Westernized society that reaches close to that goal is the Japanese at around 1:4. The population of the United States consumes 19 times more Omega 6 than Omega 3!
Can I check whether I should be taking supplements?
The private medical sector, including ROC Private Clinic, is now able to offer a simple blood test that measures your Omega 3/Omega 6 ratio from red cells which allows us to recommend accurate supplementation.
Current guidance on fish oil intake
To summarise large governing bodies’ recommendations 3,4,5, patients who have had a heart attack should consume 7 grams/week of Omega 3 from 2-4 portions of oily fish (limited in pregnant or lactating women), and should only consider Omega 3 supplements within the first 3 months following a heart attack if they can not achieve adequate dietary intake of oily fish. Patients with high triglycerides unable to achieve adequate levels on cholesterol-lowering medications alone should take a 1g Omega 3 capsule every day.
Recent press about prostate cancer
A study on prostate cancer conducted by researchers at cancer centres across the US has found a link between Omega 3 and an increased risk of prostate cancer. The study, published online on 10th July ‘13 in the Journal of the National Cancer Institute2, looked at blood levels of Omega 3 fatty acids in 834 randomly selected men from 35,000 men over 50 from the US, Puerto Rico and Canada who were already enrolled in the Selenium and Vitamin E Cancer Prevention Trial (SELECT). Researchers measured blood levels of fatty acids and analysed the association with prostate cancer risk. Men with the highest levels of Omega 3 showed a 44% increased risk of low grade prostate cancer, a 71% increased risk of high grade prostate cancer making an overall 43% increased risk of total prostate cancer. However the study did not collect information on the men’s diets and it is likely that the very high levels of Omega 3 found in some participants’ blood came from supplements. It is unclear from this study why high levels of Omega 3 would increase prostate cancer risk. Therefore if you are man over 50 who is fit and well, there is no need to take Omega 3 supplements as you should be getting enough EPA and DHA from your diet of oily fish.
1 Dyerberg J, Bang HO, Hjorne N (1975). Fatty acid composition of the plasma lipids in Greenland Eskimos. Am J Clin Nutr 28(9): 958–66
3 National Institute for Health and Clinical Excellence. NICE, 2007. www.nice.org.uk/CG48
4 Scottish Intercollegiate Guidelines Network. SIGN, 2007. www.sign.ac.uk/guidelines/fulltext/97/index.html
5 Antman EM, Hand M, Armstrong PW et al. 2007 focused update of the ACC/AHA 2004 guidelines for the management of patients with ST-elevation myocardial infarction. Circulation 2008 (117):296–329.