1 For adults with high cholesterol levels: The AHA recommends an omega-3 fatty acid supplement (as fish oils), 2 to 4 grams daily of EPA and DHA. 2  It may take 2 to 3 weeks to experience benefits from fish oil supplements. 3  Supplements should be taken under the direction of a physician.nother type of omega-3 fatty acid, ALA (from flaxseed, for example) may not have the same benefit as fish oil. Some people with diabetes can't efficiently convert ALA to a form of omega-3 fatty acids that the body can use.