Fish is promoted for its beneficial effects on the heart, joints and brain, but the amount in a single serving can sometimes be confusing. Different organizations have differing definitions for the size of a serving, but the general recommendations of how much you should eat over the course of a week are fairly well-established. Your own health conditions can impact how much fish you should consume, so keep this in mind when calculating your own ideal serving size.
Typical Serving Size
A typical serving size of fish can range from 3 to 6 oz, depending on the type of fish and its preparation. The American Heart Association considers 3.5 oz. of cooked fish, or about 3/4 cup, to be a single serving. A can of tuna contains about 5 oz. and lists 2 oz., or 1/4 cup, as an appropriate single serving size on the nutrition label. The American Dietetic Association food exchange lists calculate using 1 oz. servings of fish. Many restaurants and home cooks serve more than one serving's worth in a single meal. To estimate a single serving without weighing or measuring it, 3 oz of fish is generally about the size of a woman's palm.
One oz. of fish contains approximately 35 calories and 1 g of fat, placing it into the category of a very lean protein, according to the Academy of Nutrition and Dietetics. A 3 oz serving of fish can have between 0.1 and 1.9 g of heart-healthy omega-3 fats, with Atlantic salmon, blue fin tuna and sardines topping the list.
The American Heart Association recommends eating about two servings of fish per week, 6 or 7 oz. of fish, to reap the benefits of high levels of omega-3 fats. Most people should try to keep fish consumption under 12 oz. per week, or about three to four servings, to avoid mercury contamination. A single serving of shark, swordfish, tilefish, and king mackerel has unhealthy levels of mercury, according to the Cleveland Clinic. Pregnant women, lactating mothers and young children should avoid consuming even a small amount of these fish and limit their two weekly servings to low-mercury fish such as salmon, catfish, pollock and canned light tuna.
Some people should get extra servings of fish each week. People with heart disease should aim to get 1 g or more of the fish-derived omega-3 fats EPA and DHA every day, and people with high triglycerides might need as much as 4 g per day, according to the Cleveland Clinic. Individuals who want to get the benefits of fish but eat fewer than the recommended servings per week might consider taking a fish oil supplement.