There are good fats and there are bad fats.
Artificially produced trans-fatty acids are bad in any amount. Saturated fats from animal products should be kept to a minimum. The best fats (or oils rather, since they are liquid at room temperature) are those that contain essential fatty acids so named because without them we die.
Essential fatty acids are polyunsaturated and grouped into two families: the omega-6 EFAs and the omega-3 EFAs.
Seemingly minor differences in their molecular structure make the two EFA families act very differently in the body. While the metabolic products of omega-6 acids promote inflammation, blood clotting and tumour growth, the omega-3 acids act entirely opposite. Although we do need both omega-3s and omega-6s, it is becoming increasingly clear that an excess of omega-6 fatty acids can have dire consequences. Many scientists believe that a major reason for the high incidence of heart disease, hypertension, diabetes, obesity, premature ageing, and some forms of cancer is the profound imbalance between our intake of omega-6 and omega-3 fatty acids. Our ancestors evolved on a diet with a ratio of omega-6 to omega-3 of about 1:1. A massive change of dietary habits over the last few centuries has changed this ratio to something closer to 20:1 and this spells trouble.
The main sources of omega-6 fatty acids are vegetable oils such as corn oil and soy oil that contain a high proportion of linoleic acid. Omega-3 acids are found in flaxseed oil, walnut oil, marine plankton and fatty fish. The main component of flaxseed and walnut oils is alpha-linoleic acid (ALA) while the predominant fatty acids found in fatty fish and fish oils are eicosapentaenoic acid (EPA) and docosahaenoic acid (DHA). The most beneficial and active of these fatty acids are EPA and DHA. Alpha-linoleic acid (ALA) can be converted to EPA and DHA in the body, but the conversion is quite inefficient especially in older people.
Scientists were first alerted to the many benefits of EPA and DHA in the early 1970s when Danish physicians observed that Greenland Eskimos had an exceptionally low incidence of heart disease and arthritis despite the fact that they consumed a high fat diet. Intensive research soon discovered that two of the fats (oils) they consumed in large quantities, EPA and DHA, were actually quite beneficial. More recent research has established that fish oils (EPA and DHA) play a crucial role in the prevention of atherosclerosis, heart attack, depression and cancer. Clinical trials have shown that fish oil supplementation is effective in the treatment of many disorders including rheumatoid arthritis, diabetes, ulcerative colitis and Reynaud’s disease.
The human brain is one of the largest consumers of DHA. A high intake of fish has been linked to significant decrease in age-related memory loss and cognitive function impairment and a lower risk of developing Alzheimer’s disease. A recent study found that Alzheimer’s patients given an omega-3 rich supplement experienced a significant improvement in their quality of life. Other studies have shown that countries with a high level of fish consumption have fewer cases of depression.
An adequate intake of DHA and EPA is particularly important during pregnancy and lactation. During this time the mother must supply all the baby’s needs for DHA and EPA because it is unable to synthesize these essential fatty acids. There is also emerging evidence that low levels of omega-3 acids are associated with hyperactivity in children.
Researchers at the University of Sydney have found that children who regularly eat fresh, oily fish have at least a four times lower risk of developing asthma than do children who rarely eat such fish. They speculate that EPA present in the fish may prevent the development of asthma or reduce its severity by reducing airway inflammation and responsiveness.
An enormous amount of medical literature testifies to the fact that fish oils prevent and may help to ameliorate or reverse atherosclerosis, angina, heart attack, congestive heart failure, arrhythmias, stroke and peripheral vascular disease. Fish oils help maintain the elasticity of artery walls, prevent blood clotting, reduce blood pressure and stabilize heart rhythm.
Danish researchers have concluded that fish oil supplementation may help arrhythmias and sudden cardiac death in healthy men. An Italian study of 11,000 heart attack survivors found that patients supplementing with fish oils markedly reduced their risk of another heart attack, stroke or death.
Fish oils are particularly effective in reducing inflammation and can be of great benefit to people suffering from rheumatoid arthritis or ulcerative colitis. There is now considerable evidence that fish oil consumption can delay or reduce tumour development in breast cancer.