Fish oil supplements are usually taken in the form of pills or capsules. They contain oils from fish, such as mackerel and herring, which are rich in monounsaturated and polyunsaturated fats. These fats are believed to protect the heart against disease by lowering blood cholesterol levels and triglyceride concentrations, and reducing the tendency of blood to clot. Chemicals, such as prostaglandins, derived from some of the fish-oil fats (e.g. arachidonic acid, an omega-3 fatty acid), help to regulate blood pressure, and play an important role in the inflammatory and immune responses. Although it is generally agreed that fish oils are beneficial, many dietitians advise that the oils should be obtained directly from fish and not from supplements because the effectiveness of supplementation is unproven. There is also doubt about the optimum dietary levels of the oils and it is easy to overdose on supplements. An excessive intake may prolong clotting time to a dangerous extent, increasing the risk of bleeding after accidents or during surgery. Also, pills containing cod liver oil are rich in vitamins A and D, which can be toxic in large amounts.
Subjects: Medicine and Health.