08 February 2000 --
Dr Ng Min Ching
The human body requires lipids (fats) in its daily functions. Most of these lipids are derived from or contain fatty acids. Fatty acids are either ingested or produced by the body itself. Omega-3 fatty acids are certain types of fatty acids that are not readily produced by the body and therefore need to be obtained from the diet.
Examples of omega-3 fatty acids are EPA (eicosapentanoeic acid) and DHA (docosahexanoeic acid).
Dietary Sources of Omega-3 Fatty Acids
Cold water fish such as sardines, tuna, mackerel, herring, salmon and cod are rich sources of omega-3 fatty acids. For example, there are 3.3 grams of omega-3 in three ounces of sardines and 2.5 grams in the same amount of mackerel.
These acids are also found in wild animals. Domesticated livestock is a poor dietary supply.
Rich plant sources include flaxseed, canola and certain marine algae.
How much is enough
International Food Nutrition Organisation's Daily Recommended Values for Omega-3 Fatty Acids (DHA and EPA)
|Food Nutrition Organisation
||Daily Recommended Values for Adults|
|COMA (UK's Committee on Medical
Aspects of Food Policy)
|200 mg of DHA/EPA|
|NATO (North American Treaty
Organisation) Workshop on
Omega-3/Omega-6 Fatty Acids
|800 mg of DHA/EPA|
|British Nutrition Foundation
||1000-2000 mg of DHA/EPA|
|Health and Welfare, Canada
Scientific Review Committee
|1000-1800 mg of DHA/EPA|
|Norway National Nutrition Council
||1000-2000 mg of Omega-3 fatty acids|
|Denmark/Finland Ministry of Health
||1000-2000 mg of Omega-3 fatty acids|
|Food Nutrition Organisation
||Daily Recommended Values for Infants|
|WHO (World Health Organisation)
and the FAO ( FOOD and Agriculture
Organisation of the United Nations)
|40 mg of DHA per kg body weight|
|ISSFAL (International Society for the
Study of Fatty Acids and Lipids)
|35-75 mg of DHA per kg body weight|
Most Singaporeans, especially pregnant females and breastfeeding mothers, do not consume adequate amounts of dietary omega-3 fatty acids. Omega-3 fatty acid supplements are thus required.
What does Scientific Research say about Omega-3 Fatty Acids
1) Growth and Development of the Human Brain
It is said that the human brain tripled in size over three million years. How did it occur? One key theory proposes that this was possible due to the increased ingestion of food rich in omega-3 fatty acids. Primitive man had a predominantly vegetarian diet. As they foraged for more food, fish and other meat rich in omega-3 fatty acids were added to their diet, resulting in the rapid advancement of evolution and progress.
In experiments, animals fed omega-3 fatty acids learn and perform better than those fed other fatty acids that have to be converted in the body to omega-3 fatty acids.
Modern man generally consumes much less of these essential fatty acids compared to his ancient ancestors. Hence, there are suggestions that we should increase the amount of omega-3 fatty acids ingested.
It has been proven scientifically that the proper development of the brain and retina of the foetus and the infant depends on an adequate supply of omega-3 fatty acids. Breast milk contains significant levels of DHA. In one study, infants who were breastfed had better neurological development and eyesight than those who were bottle-fed on milk with no DHA. Therefore, if bottle-feeding a baby, it is desirable to buy infant formulas that are supplemented with DHA.
Clinical research has provided evidence that an adequate intake of omega-3 fatty acids is important during pregnancy, lactation and infancy.
A recent study published in 1997 raised the possibility that a diet high in fish (high in omega-3 fatty acids) may improve cognitive function in elderly men. More studies need to be done to prove this issue conclusively.
2) Cardiovascular Protection
The Eskimos of Greenland consume large quantities of fish and cholesterol-rich seals. Yet, they have a very low rate of cardiovascular death. This has prompted scientists to speculate and subsequently prove that fish oil, which is a rich source of omega-3 fatty acids, has a protective effect on the heart.
Scientists reported that at least one fish meal a week is associated with a 52 percent lower risk of sudden cardiac death. Consumption of two fish meals weekly is associated with a 65 percent reduction in risk of heart diseases.
Besides lowering blood triglyceride (a specific type of fat) level, the ingestion of DHA significantly decreased the total cholesterol : HDL cholesterol ratio and the LDL cholesterol : HDL cholesterol ratio in the blood.
DPA and EPA from fish oil also reduced blood clotting by an average of 25% and DHA has been found to be effective in reducing the development of high blood pressure and the incidence of irregular heart rate.
These actions of omega-3 fatty acids not only reduce the risk of heart attacks, they lower the chances of having a stroke as well.
The scientific investigations have indicated that DHA was more effective than EPA in conferring cardiovascular protection.
3) Immune and Inflammatory Diseases
The immune system in the human body sometimes goes awry and attacks its own body. This leads to autoimmune and inflammatory conditions, e.g. rheumatoid arthritis, inflammatory bowel diseases such as ulcerativie colitis and Crohn's disease.
These diseases may require steroids that have accompanying side effects like peptic ulcer, osteoporosis, increased susceptibility to infections, high blood pressure and diabetes. Hence, if omega-3 fatty acids can be found to have a therapeutic effect on these illnesses, patients may be spared the side-effects of steroids and other medications.
So far, studies have shown that the consumption of two or more servings per week of fish high in DHA is associated with a decreased risk or reduced severity of rheumatoid arthritis.
Other clinical trials also reported a beneficial effect of omega-3 fatty acids in patients with inflammatory bowel diseases.
4) Depression and Aggression
It has been demonstrated that increased risk of depression, aggression and suicide is associated with low concentrations of omega-3 fatty acid in the blood and cerebrospinal fluid.
Consistently, the incidence of depression and violence appear to be lower in countries where the populations consume more fish (e.g. Japan, Korea) compared to those where less fish is eaten (e.g. United States, France).
Of course, cultural and other epidemiological factors cannot be discounted in the prevalence of depression and violence in these countries. However, it does appear that omega-3 fatty acids do have a role to play in the occurrence of such behaviour.
A study done among a population of South African West Coast fishing villagers has suggested that their low rate of colorectal (large intestine and rectum) cancer may be explained by the protective effects of omega-3 fatty acids.
There is cause for optimism in this aspect but more studies need to be done.
6) Children with Recurrent Respiratory Infections
Children with atopic eczema who were given omega-3 and omega-6 supplements were found to have fewer episodes of recurrent respiratory infections.
Again, this finding requires more clinical trials for greater validity.
1. Albert,C.M., Gennekens, C.H., O'Donnell, C.J., Aajani, U.A., Carey, V.J., Willet, W.C., Ruskin J.N., and Manson, J.E. (1998). Fish consumption and sudden cardiac death. The Journal of the American Medical Assocation, 279:23-28.
2. Belluzzi A., Brignola c., Campieri M., Pera A., Boschi S., Miglioli M. (1996). Effect of an enteric-coated fish-oil preparation on relapses in Crohn's disease. New England Journal of Medicine, 334:1557-1560.
3. Conquer, J.A., and Holub, B.J. (1996). Supplementation with an algae source of HAincreases n-3 fatty acid status and alters selected risk factors for heart disease in vegetarian subjects. Journal of Nutrition,126:3032-3039.
4. Hughes, D., Southern, S., and Pinder. (1996). Polyunsaturated fatty acids modulate the expression of functionally associated molecules on human monocytes in vitro. American Journal of Nutrition, 26:603-610.
5. Kalmijn et al. (1997). Polyunsaturated Fatty Acids improve cognitive function in elderly men. American journal of Epidemiology, 145, 1:33-41.
6. Mahrides, M., Simmer, K., Goggin, M., and Gibson, R.A. (1993). Erythrocyte DHA correlates with the visual response of healthy, term infants. Paediatric Research, 34:425-427.
7. Mclennan, Howe, Abeywardena, Muggli, Raedaestorff, Mano Rayner and Head. (1996). The cardiovascular protective role of DHA. European Journal of Pharmacology, 300:83-98.
8. Mori, T.A., Vandongen, R., Mahanian, F., and Douglas, A. (1992). Plasma lipid levels and platelet neutrophil function in patients with vascular disease following fish oil and olive oil supplementation. Metabolism, 41:1059-1069.
9. Schloss, Kidd, Tichelaar, Young, and O'Keefe, S. (1997) Dietary factors associated with a low risk of colon cancer in coloured West Coast fishermen. South African Medical journal, 87:152-158.
10. Shapiroo, Koepsell, Voigt, Dugowson, Kestin, and Nelson. (1996). Diet and rheumatoid arthritis in women: a possible protective effect of fish consumption. Epidemiology , 7(3):256-263.
11. Thompson. (1993). A randomised controlled study of evening primrose oil and fish oil in ulcerative colitis. Ailment Pharmacol Ther, 7:159-166.
12. Uauy, Peirano, Hoffman, Mena, Birch and Birch. (1996). Role of essential fatty acids in the function of the developinf nervous system. Lipids 31 (suppl.): S167-S176. Venuta A, and coworkers. (1996). Children with recurrent respiratory infections. Journal of Internal Medicine Res, 24:325-330.