Health news - Doubts raised over health benefits of omega-3 fats
31 March 2006 - written by Michael Paterson for Bupa's health information team
Omega-3 fats may not be as beneficial to health as previously thought, according to a study published online by the British Medical Journal.1 Consumption of omega-3 fatty acids, which are found in oily fish and some plant oils, is thought to protect against certain types of disease.
How was the study carried out?
Researchers examined the results of 89 recent studies of omega-3 fatty acids. This type of research is called a 'systematic review'. They looked at the health effects of omega-3 fatty acids in relation to death rates, heart attacks, cancers and strokes. They only reviewed studies that had lasted at least six months, pooling the results to get a comprehensive overview.1
What did the study show?
The study could find no strong evidence that eating omega-3 fatty acids lowered the chance of having a heart attack, getting cancer, suffering a stroke or living longer. Some studies have suggested that eating higher levels of omega-3 fatty acids can decrease mortality, but a recent large trial did not show any benefit.1
Did they find that omega-3 fatty acids have any harmful effects?
None of the 89 studies under review showed that people with a higher intake of omega-3 fatty acids were more at risk of cancer or stroke. The researchers thought that more studies needed to be done to look for possible harmful effects.
Did the researchers rule out the benefits of omega-3 fatty acids?
No. These findings do not mean that omega-3 fatty acids do not have health benefits. They simply say that more detailed research needs to be done.1
What did the researchers suggest?
The researchers said that the government should stick to its current health guidelines, which encourage us to eat oily fish. Higher amounts are advised after a heart attack. But the researchers said that angina sufferers should not eat more omega-3 fatty acids if they haven't had a heart attack. The study's overall conclusion was that scientific evidence should be reviewed regularly to see if health guidelines should change.1
How might omega-3 help protect against various serious illnesses?
Among their many benefits, omega-3 fatty acids can help to stop blood clots, which can lead to a stroke or heart attack. They may also help the body's immune system fight illness. A diet without omega-3 fatty acids is thought to make long-term illnesses more likely.2
How can you get omega-3 in your diet?
Omega-3 fatty acids are found in oily fish, such as salmon, trout, mackerel, sardines, pilchards, herring, kipper, eel and whitebait. All of these count as oily fish when canned, fresh or frozen. While fresh tuna is an oily fish, canned tuna isn't.3 You can get also omega-3 fatty acids from flaxseed (linseed) oil, nuts, green leafy vegetables and red meat. Alternatively, you can take an omega-3 supplement - with the advice of your doctor.4
Are there limits to how much omega-3 fat I should consume?
Girls and women who are pregnant or breast-feeding, or who plan to get pregnant, should eat no more than two portions of oily fish a week. (One portion is considered to be 140g.) This is because there are often tiny amounts of pollutants in fish that, taken in large quantities, could be dangerous for babies. Women who don't plan to get pregnant can eat up to four portions a week - as can boys and men.3 Experts generally recommend that we try and eat around 100g a day of omega-3 fatty acids.4
It can be difficult to monitor how much omega-3 you consume, unless you are taking it in diet-supplement form. But many foods will display the omega-3 content on an ingredients label.
For more information, see Bupa's health-news article:
How much fish can we eat safely?
Omega-3 is a 'fatty acid'. Isn't fat harmful?
Fats are an important part of a balanced diet and help to provide the body with energy. They can be divided into three types - saturates, monounsaturates and polyunsaturates. Omega-3 is a polyunsaturate, which is essential for a healthy diet, but which isn't made by the body and must be absorbed through the food you eat.
The British Nutrition Foundation advises limiting our consumption of saturates - found in animal products, cakes, biscuits and pastries - to reduce the risk of heart disease. Try cutting off the visible fat from meat and poultry, choosing lower-fat meat and dairy products, and using less oil when you cook. By law, foods marked 'low fat' must contain no more than 3 percent fat.
Monounsaturates, found in products like olive and rapeseed oil, are considered healthier than saturates.5
What other health benefits do omega-3 fatty acids have?
There is some evidence that omega-3 fatty acids can help brain development. Children with development disorders improve their reading, spelling and behaviour at school when they have more fish oils in their diets.6
What makes up a healthy balanced diet?
The British Nutrition Foundation's eight guidelines for a healthy diet are:5
- enjoy your food
- eat a variety of different foods
- eat the right amount to be a healthy weight
- eat plenty of foods rich in starch and fibre
- eat plenty of fruit and vegetables
- don't eat too many foods that contain a lot of fat
- don't have sugary foods and drinks too often
- drink alcohol sensibly
Bupa Information:
- Bupa factsheet: Healthy eating
http://hcd2.bupa.co.uk/fact_sheets/html/healthy_eating.html - Bupa factsheet: Diet and weight
http://hcd2.bupa.co.uk/fact_sheets/html/Diet_and_weight.html
Further information:
- British Nutrition Foundation
www.nutrition.org.uk - Food Standards Agency
www.food.gov.uk
References
- Hooper L, Thompson R, Harrison R, Summerbell C, Ness A, Moore H et al. Risks and benefits of omega 3 fats for mortality, cardiovascular disease, and cancer: systematic review. British Medical Journal online 2006. BMJ, doi:10.1136/bmj.38755.366331.2F
- What role do EFAs play in the body? Omega-3 information service.
www.omega-3info.com - Oily fish advice: your questions answered. Food Standards Agency.
www.food.gov.uk - The Modern Diet. Omega-3 information service.
www.omega-3info.com - Healthy Eating. A Whole Diet Approach. British Nutrition Foundation.
www.nutrition.org.uk - Richardson AJ, Montgomery P. The Oxford-Durham study: a randomized, controlled trial of dietary supplementation with fatty acids in children with developmental coordination disorder. Pediatrics 2005: 1115; 1360-1366.
All pages were accessed on 27 March 2006
