Most adults should eat at least 8 ounces of fish per week, which works out to about two average servings. That target, set by the Dietary Guidelines for Americans, delivers enough omega-3 fatty acids to meaningfully lower your risk of heart disease. But the type of fish matters almost as much as the amount, especially when mercury is part of the equation.
The 8-Ounce Weekly Target
Eight ounces is the minimum recommendation for adults eating a standard 2,000-calorie diet. A single serving is roughly the size and thickness of your palm, which comes to about 4 ounces cooked. So two palm-sized portions spread across the week hits the target. If you weigh significantly more or less than 160 pounds, adjust slightly: add or subtract about one ounce per serving for every 20 pounds of difference in body weight.
Keep in mind that fish shrinks when cooked. Eight ounces of raw fish yields roughly 6 ounces cooked. If you’re weighing portions before cooking, aim for closer to 10 ounces raw to end up with 8 ounces on your plate.
Why Two Servings Per Week Matters
Eating at least two servings of fish per week, particularly fatty fish rich in omega-3s, lowers the risk of heart disease and sudden cardiac death. Omega-3 fatty acids slightly reduce blood pressure and lower triglycerides, a type of fat in the blood linked to cardiovascular problems. These benefits come specifically from the omega-3s found in fish, which the body absorbs more effectively than those from supplements or plant sources like flaxseed.
The fish with the highest omega-3 content are salmon, mackerel, sardines, herring, and trout. You don’t need to eat these exclusively, but making them your go-to choices a couple of times a week delivers the most benefit per serving.
Mercury Levels in Common Fish
Mercury accumulates in fish over their lifetimes, so larger, longer-lived predatory species carry the highest concentrations. The differences are dramatic. Salmon averages just 0.022 parts per million (ppm) of mercury. Cod comes in at 0.111 ppm. Canned light tuna (usually skipjack) averages 0.126 ppm. All three are low enough to eat freely within the two-serving guideline.
Canned albacore (white) tuna is a step up at 0.350 ppm, nearly three times the level in canned light tuna. Fresh tuna steaks, depending on species, range from 0.354 ppm for yellowfin to 0.689 ppm for bigeye. Swordfish sits near the top at 0.995 ppm, with some samples exceeding 3 ppm.
This doesn’t mean you can never eat swordfish or tuna steaks. It means those species shouldn’t be the fish you eat every week. Rotating in lower-mercury options like salmon, shrimp, cod, and sardines lets you hit your weekly target without building up concerning mercury levels.
Canned Light Tuna vs. Albacore Tuna
Because so many people rely on canned tuna as their primary fish, the distinction between light and albacore matters. Canned light tuna contains species like skipjack and tongol that are smaller and shorter-lived, keeping mercury levels relatively low. You can comfortably eat two to three servings per week.
Canned albacore tuna carries roughly three times more mercury. Health Canada recommends that pregnant or breastfeeding women limit albacore to about 10.5 ounces (300 grams) per week. Children ages 5 to 11 should stay under about 5 ounces (150 grams) per week, and children ages 1 to 4 under about 2.5 ounces (75 grams). For the average adult without specific risk factors, keeping albacore to one serving per week and filling the rest with lower-mercury fish is a practical approach.
How Much Fish for Children
Children need less fish than adults, and the FDA recommends scaling portions to body size. A child’s serving is roughly the size of that child’s palm, which is naturally smaller than an adult’s. For a toddler, that might be just 1 to 2 ounces per serving. For an older child, 3 to 4 ounces. The goal is still about two servings per week, but with those smaller portions and a focus on low-mercury species like salmon, tilapia, pollock, and shrimp.
Mercury is a bigger concern for children than adults because their developing nervous systems are more vulnerable. Stick to fish in the lowest mercury category and avoid swordfish, shark, king mackerel, and bigeye tuna entirely for kids.
Farmed vs. Wild-Caught Fish
Both farmed and wild-caught fish are good sources of protein and omega-3s. The nutritional differences are modest for most species. Farmed salmon tends to have slightly more total fat (including omega-3s) because of the feed used in aquaculture operations. Wild-caught salmon is leaner.
The tradeoff involves contaminants. Some studies have found higher concentrations of persistent organic pollutants like PCBs and dioxins in certain farmed fish, likely reflecting what’s in the feed. However, the levels in commercially sold farmed fish generally remain below safety thresholds. For most people, the health benefits of eating either type of fish outweigh the risks of avoiding it altogether.
Microplastics in Seafood
About 25 to 28 percent of commercially sold fish contain detectable microplastic particles, based on studies of fish markets in the U.S. and Indonesia. Plastic particles tend to concentrate in the digestive tract, so fish you eat whole (like sardines or anchovies) and shellfish like mussels carry the highest exposure. Top European shellfish consumers eat an estimated 11,000 plastic particles per year.
No international food safety body has yet established limits on microplastic content in seafood, and the health effects of ingesting these particles at current levels remain unclear. This is not a reason to stop eating fish. The cardiovascular and nutritional benefits of regular fish consumption are well established, while the risks from microplastics at dietary exposure levels are still being studied.
Locally Caught Fish
If you catch your own fish from lakes, rivers, or coastal waters, check your state, territory, or tribal fish consumption advisories before eating them regularly. Local waterways can contain contaminants like mercury, PCBs, or industrial chemicals that vary widely by location. Your state environmental or health agency publishes specific guidance on which species are safe to eat and how often, broken down by water body. The EPA maintains links to these advisories at the federal level. Commercial fish sold in stores and restaurants is monitored separately and held to federal safety standards.