Scientists noticed a curiously low incidence of heart disease among Greenland Eskimos, despite their high-fat diet. The reason? They were eating fish rich in omega-3 fatty acids. Later studies confirmed the cardioprotective effect of fish oils while uncovering other benefits as well.
What they are?
The fat in fish includes a form of polyunsaturated fatty acids called omega-3s. These differ from the polyunsaturated fatty acids found in vegetables oils (called omega-6s) and they have different effects on the body. (Fish don't manufacture such fats but get them from the plankton they eat – the colder the water, the more omega-3s the plankton contains.) The two most potent forms of omega-3s, eicosapentonoic acid (EPA) and docosahexanoic acid (DHA), are found in abundance in cold-water fish such as salmon, trout, mackerel and tuna (including, to a limited extent, the canned variety). The sources of a third type of omega-3, alpha-linolenic acid (ALA), are certain vegetable oils (such as flaxseed oil) and leafy, fleshy greens (such as purslane). However, ALA doesn't affect the body in the same way as EPA and DHA.
What they do?
Omega-3 fatty acids play a key role in a range of vital body processes, from regulating blood pressure and blood clotting to reducing inflammation and boosting the immune system. They may be useful for preventing or treating many conditions.
Fish oils appear to reduce the risk of heart disease in several ways. Most importantly, the presence of omega-3s makes platelets in the blood less likely to clump together and form the clots that lead to heart attacks. Next, omega-3s can reduce triglycerides (blood fats related to cholesterol) and may lower blood pressure. In addition, recent research has shown that omega-3s strengthen the heart's electrical system, preventing heart-rhythm abnormalities. However, the strongest evidence for the cardiovascular benefits of fish oils comes from studies in which the participants ate fish rather than taking fish oil supplements.
Within the artery walls, omega-3s inhibit inflammation, which is a factor in plaque build-up. As a result, therapeutic doses of fish oils are one of the few successful ways to prevent the reblockage of arteries that commonly occurs after angioplasty, in which a small balloon is guided through an artery to a blockage and then inflated to compress plaque, widen the vessel and improve blood flow to the heart. This effect on blood vessels makes fish oils helpful for Raynaud's disease as well.
Omega-3s are also effective general anti-inflammatories, useful for joint problems, lupus and psoriasis. Studies indicate that people with rheumatoid arthritis experience less joint swelling and stiffness when they take fish oil supplements, and may even be able to manage on lower doses of anti-inflammatory drugs. In a year-long study of people suffering from Crohn's disease (a painful type of inflammatory bowel disease), 69% of those taking enteric-coated fish oil supplements (about 3 g of fish oils a day) stayed symptom-free, compared with just 28% of those receiving a placebo. Fish oils may also help to ease menstrual cramps. In addition, omega-3s may play a role in mental health. Some experts believe there's a correlation between the increasing incidence of depression in many western countries and the declining consumption of fish. And a preliminary US study suggested that omega-3 fatty acids may reduce the severity of schizophrenia by about 25%. Omega-3 fatty acids have also been used to alleviate symptoms of asthma and eczema.
- Help to prevent cardiovascular disease; useful for other circulatory conditions as well.
- Block disease-related inflammatory responses in the body.
- May lower blood pressure and blood cholesterol.
- Because omega-3 fatty acids inhibit blood clotting, consult a doctor before using fish oil supplements if you have a blood disorder or if you are taking anticoagulant medications.
- Don't take fish oil supplements two days before or after surgery.
- Reminder: If you have a medical condition, talk to your doctor before taking supplements.
How to take it?
For heart disease, Raynaud's disease, lupus and psoriasis: Take 3000 mg of fish oils a day.
For rheumatoid arthritis: Take 6000 mg a day.
For inflammatory bowel diasease: Take 5000 mg a day.
Guidelines for use:
Fish oil supplements are not necessary for heart disease prevention or treatment if you eat fish at least three times a week. However, supplements are recommended for rheumatoid arthritis and other inflammatory conditions. Take capsules with meals. Supplements may be easier to tolerate if you take them in divided doses; for example, 1000 mg three times a day instead of 3000 mg in one sitting.
Possible side effects
Fish oil capsules may cause belching, flatulence, bloating, nausea and diarrhoea. Very high doses may result in a slightly fishy body odour. There's some concern that high doses can lead to internal bleeding, but a study of people with heart disease who took 8000 mg of fish oil supplements in addition to aspirin (which is an anticoagulant) found no increase in internal bleeding.
Some studies found that high doses of fish oils worsen blood sugar control in people with diabetes; others have shown no effect. To be safe, people with diabetes should not take more than 2000 mg of fish oil supplements a day except on their doctor's advise.
If a blood test has shown that you have high fasting triglycerides, you should be careful if you also have high LDL ('bad') cholesterol: therapeutic doses of fish oils can increase LDL. Garlic supplements, however, may counteract this effect; one study found that girls reversed the LDL-raising effect of fish oils. For rheumatoid arthritis and other inflammatory conditions, eating fish is probably not sufficient; fish oil supplements are recommended.
- If you find you can't tolerate one brand of fish oil supplements, try another. Side effects vary from brand to brand.
- Don't try to save money by buying fish oil supplements in bulk because they can go rancid very quickly. Always check the expiry date.
- Don't buy cod liver oil to get your omega-3s. It contains high amounts of vitamin A and vitamin D, both of which can be toxic in large doses.
- According to a preliminary study from the University of California, Los Angeles, omega-3s may help fight breast cancer and maintain healthy breast tissue. Animal studies also indicate that fewer breast tumors develop when fish oils are part of a healthy diet.
- Fish oils may help to prevent colon cancer. Participants in a recent study who took 4400 mg of fish oils a day produced much less of one potent carcinogen associated with colon cancer than those on a placebo.
- To get the most benefit from cold-water fish, it should be fresh, and preferably steamed or poached.