In basic terms, omega-3 is a polyunsaturated fatty acid that is essential to numerous functions throughout the body.  It aids in brain development and functioning, and has overall anti-inflammatory properties.  It helps lubricate your arteries to inhibit plaque buildup and can help treat or prevent conditions including heart disease, high blood pressure, cancer, diabetes, and arrhythmia. The current recommended intake of omega-3 for women is 1.1 g / day, and 1.6 g / day for men.  However, increased levels of 2-3 g / day seem to have additional benefits. The average amount of omega-3 in a variety of fish depends upon its physiology, diet, and environment.  Fish that consume algae (or other fish that eat it), which is high in DHA (a component of omega-3), and store it in fat needed as insulation from cold waters, are the best storehouses of omega-3.  All omega-3 amounts listed below refer to a standard 6 ounce serving. wild salmon -- 3.2 g anchovies -- 3.4 g Pacific sardines -- 2.8 g Pacific mackerel -- 3.2 g Atlantic mackerel -- 2.0 g whitefish -- 3.0 g bluefin tuna -- 2.8 g rainbow trout -- 2.0 g You should strive to eat 8-12 oz of high omega-3 fish a week. Adding in a variety of seafood will contribute additional omega-3 and help keep your dining experience from becoming too predictable and dull. Depending on calorie needs, one serving can be 4-6 oz.  canned albacore tuna in water -- 1.4 g Blue crab or Alaskan King crab -- 0.8 g halibut -- 1.0 g shrimp or scallops -- 0.6 g ocean perch or cod -- 0.4 g lobster -- 0.2 g You are what you eat, and so are fish.  (They also “are” where they live.)  Fish that grow in a cleaner, healthier environment and are caught and prepared with care provide omega-3 without bringing along as many undesirable elements like toxins.  Many people also think they taste better, which makes eating more easier.  If possible, buy your fish from someone who can tell you about where it came from and when and how it was caught.  It doesn't have to be a small, specialty shop; that person...

TL;DR in Vietnamese:
Bạn phải hiểu rõ cơ thể bạn cần bao nhiều omega-3. Chọn loại cá nước lạnh có nhiều mỡ. Chế biến chung với hải sản khác. Biết rõ nguồn gốc của cá, cách nuôi cũng như cách đánh bắt. Hạn chế tiêu thụ cá chứa nhiều thủy ngân và chất độc khác.