Swordfish is a nutrient-dense fish packed with protein, selenium, and vitamin D, but it carries one of the highest mercury levels of any commercially available seafood. Whether it’s “good for you” depends on how often you eat it and whether you fall into a higher-risk group for mercury exposure.
What’s in a Serving of Swordfish
A 3-ounce (85-gram) serving of cooked swordfish delivers 146 calories and 20 grams of protein, making it a lean, filling source of animal protein. But the real standout nutrients are selenium and vitamin D. That same serving provides 106% of your daily selenium needs and 71% of your daily vitamin D, two nutrients many people don’t get enough of. Selenium supports thyroid function and acts as an antioxidant, while vitamin D plays a key role in calcium absorption and bone health.
Swordfish also supplies meaningful amounts of minerals that are harder to track. Per 100 grams, it contains 506 mg of phosphorus and 57 mg of magnesium, both important for bone density and muscle function. Phosphorus works alongside calcium to maintain bone structure, and magnesium is involved in hundreds of enzymatic reactions throughout your body, including those that govern muscle contraction and energy production.
Omega-3 Content Compared to Other Fish
Swordfish contains omega-3 fatty acids, but less than you might expect from a large ocean fish. Per 100 grams of raw flesh, swordfish provides roughly 100 mg of EPA and 100 mg of DHA. That’s a combined 200 mg per 100 grams, which is modest compared to salmon (which can deliver over 1,500 mg in the same amount) or sardines and mackerel.
Those omega-3s still contribute to heart health. They help lower triglycerides, slightly reduce blood pressure, and combat the kind of chronic inflammation that damages blood vessels over time. But if you’re eating fish primarily for omega-3 benefits, swordfish isn’t your most efficient source. Fattier fish like salmon, herring, and anchovies deliver far more per serving.
The Mercury Problem
This is the trade-off that defines swordfish. According to FDA testing data, swordfish has a mean mercury concentration of 0.995 parts per million (ppm), with some samples reaching as high as 3.22 ppm. To put that in context, the FDA considers anything above about 0.46 ppm to be in the “high mercury” range. Swordfish nearly doubles that threshold on average.
Mercury accumulates in large, long-lived predatory fish because they spend years eating smaller fish that each contain trace amounts. Swordfish live for a decade or more and sit near the top of the ocean food chain, so the mercury concentrates in their flesh over time. Once you eat it, your body absorbs the mercury and eliminates it slowly, primarily through the kidneys and hair. At high enough levels, mercury damages the nervous system, impairs cognitive function, and can harm developing brains.
The FDA places swordfish in its “Choices to Avoid” category for pregnant or breastfeeding women and young children. This is the agency’s most restrictive classification, shared with only a handful of other species like shark, king mackerel, and tilefish. For these groups, the FDA recommends not eating swordfish at all.
How Much Is Safe for Most Adults
The FDA’s “Choices to Avoid” label is specifically aimed at pregnant women, breastfeeding women, and children. For other adults, occasional swordfish consumption is generally considered acceptable. Most nutrition experts suggest limiting high-mercury fish to no more than one serving per week, and less if you’re eating other mercury-containing seafood that same week.
Your total mercury exposure is what matters, not any single meal. If you eat swordfish on Monday and tuna on Thursday, both contribute to your weekly load. Spacing out your consumption and alternating with lower-mercury fish like salmon, cod, tilapia, or shrimp keeps your exposure well within safe limits while still letting you enjoy swordfish occasionally.
Swordfish does contain very high levels of selenium, and some researchers have explored whether selenium might offer a degree of protection against mercury’s effects, since the two elements interact at a molecular level. However, this relationship isn’t well enough understood to change the practical advice: treat swordfish as a high-mercury fish and eat it in moderation.
Who Benefits Most From Swordfish
If you’re someone who struggles to get enough vitamin D (and most people in northern climates do), a single serving of swordfish delivers more than two-thirds of your daily requirement without a supplement. That makes it one of the richest food sources of vitamin D available, alongside fatty fish and fortified dairy products. It’s also an excellent option if you’re focused on hitting high protein targets without excess calories or fat.
The selenium content is another practical benefit. Selenium deficiency is linked to thyroid problems and weakened immune function, and many people hover near the low end of adequate intake. One serving of swordfish more than covers your daily needs.
For adults without mercury-related risk factors, swordfish eaten once or twice a month offers a strong nutritional payoff. It’s a dense package of protein, vitamin D, selenium, phosphorus, and magnesium in a relatively low-calorie format. The key is treating it as an occasional choice rather than a weekly staple, and filling the rest of your seafood rotation with lower-mercury options that deliver more omega-3s per bite.