Stroll through any drugstore, and you’ll see an array of fish oil supplements. You’ve heard that fish oil — or more specifically, the omega-3 fatty acids it contains — may combat many health problems, including heart disease, chronic pain and inflammation, asthma and depression.

But which one should you buy? The fancy-looking 100-capsule bottle for $25… the plain-looking store brand with twice as many capsules for $8.99… or something in between?

In general, with fish oil supplements, you get what you pay for. Less expensive products may contain as much “fish oil” as more expensive ones, but they typically contain less eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), the most biologically active and beneficial components.

Why it matters: The American Heart Association recommends supplementation with about 1,000 mg of combined EPA/DHA per day for people with known heart disease. It recommends 2,000 mg to 4,000 mg for people who need to lower triglycerides (a type of blood fat). I recommend a starting dose of 2,000 mg to 2,500 mg to all of my patients for general good health. Fish oil supplements are not a good choice for those taking warfarin (Coumadin) or other blood-thinning medications — consult your doctor. Because the typical low-priced “1,000-mg” fish oil capsule contains only 180 mg of EPA and 120 mg of DHA, you would have to take six to eight capsules each day to reach the recommended dose of EPA/DHA. With each capsule, you’re getting 700 mg of oil that is not EPA or DHA. Day after day, that’s a lot of oil you don’t really need — and it can cause loose stools and other unpleasant gastric effects.

Best: Buy a fish oil product that will require you to take the fewest capsules per day to reach your desired dose of EPA/DHA. This is better for your health than a less concentrated product and may not be as expensive as it seems when you consider that you’ll consume fewer capsules.