Swordfish offers impressive nutritional benefits—high protein, omega-3 fatty acids, and essential vitamins. But it also contains significant mercury levels that require careful consideration, especially for pregnant women and children. This guide examines the complete picture: nutrition facts, mercury content, health benefits, safety guidelines, and who should avoid or limit swordfish consumption.
Is Swordfish Healthy? The Quick Answer
Yes, swordfish is nutritious for most healthy adults when eaten occasionally (once per week maximum). It provides high-quality protein, heart-healthy omega-3s, vitamin D, and selenium. However, swordfish contains elevated mercury levels averaging 0.995 parts per million (PPM)—among the highest of commonly eaten fish.
Who should avoid swordfish: Pregnant women, women planning pregnancy, breastfeeding mothers, and children under 6 years should avoid swordfish entirely due to mercury’s effects on developing nervous systems.
Who can eat it safely: Healthy adults can enjoy swordfish once weekly as part of a balanced diet without significant health risks.
Swordfish Nutrition Facts
Per 6-Ounce Cooked Serving
Calories: 220
Protein: 34g (68% Daily Value)
Total Fat: 8g
├ Saturated Fat: 2g
├ Omega-3 Fatty Acids: 1.3g (EPA + DHA)
└ Omega-6 Fatty Acids: 0.2g
Cholesterol: 88mg (29% DV)
Sodium: 200mg (9% DV, without added salt)
Carbohydrates: 0g
Fiber: 0g
Sugar: 0g
Key Vitamins and Minerals
Vitamin B12: 2.7 mcg (113% DV) – Supports nerve function and red blood cell formation
Niacin (B3): 11mg (69% DV) – Energy metabolism, skin health
Vitamin B6: 0.8mg (47% DV) – Brain development, immune function
Vitamin D: 15.9 mcg (80% DV) – Bone health, immune system
Selenium: 100 mcg (182% DV) – Antioxidant protection, thyroid function
Phosphorus: 414mg (33% DV) – Bone and teeth health
Potassium: 620mg (13% DV) – Heart health, blood pressure
Magnesium: 45mg (11% DV) – Muscle and nerve function
Macronutrient Breakdown: 62% protein, 33% fat, 0% carbohydrates
Health Benefits of Swordfish
High-Quality Protein Source
With 34 grams per serving, swordfish provides more protein than most chicken breasts. This complete protein contains all nine essential amino acids needed for muscle building, tissue repair, and enzyme production. The lean profile (only 8g fat per serving) makes it suitable for weight management and muscle maintenance.
Omega-3 Fatty Acids for Heart Health
Swordfish delivers 1.3 grams of omega-3s (EPA and DHA), the most bioavailable forms. Research shows omega-3 fatty acids:
- Reduce triglycerides: Multiple studies demonstrate 15-30% reductions in blood triglyceride levels
- Support heart health: May reduce cardiovascular disease risk when consumed as part of a balanced diet
- Anti-inflammatory properties: Help manage chronic inflammation
- Brain function: DHA comprises 40% of brain fatty acids, supporting cognitive function
The American Heart Association recommends eating fatty fish twice weekly for cardiovascular benefits.
Vitamin D for Bone and Immune Health
A single serving provides 80% of daily vitamin D needs. This vitamin is crucial for:
- Calcium absorption and bone mineralization
- Immune system regulation
- Mood regulation (may help prevent seasonal depression)
- Reduced risk of certain autoimmune conditions
Vitamin D deficiency affects an estimated 42% of U.S. adults, making fish consumption valuable for meeting requirements.
Exceptional Selenium Content
Swordfish is remarkably high in selenium (182% DV), a trace mineral that:
- Acts as antioxidant: Protects cells from oxidative damage
- Supports thyroid function: Essential for thyroid hormone production
- May reduce cancer risk: Some research suggests protective effects against certain cancers
- Counters mercury: Selenium binds to mercury, potentially reducing its toxic effects
The selenium-mercury interaction is noteworthy—swordfish’s high selenium content may partially offset mercury concerns for adults (though not enough to make it safe during pregnancy).
Vitamin B12 for Nervous System Health
Exceeding daily B12 needs (113% DV), swordfish supports:
- Nerve cell health and myelin sheath formation
- Red blood cell production (prevents megaloblastic anemia)
- DNA synthesis
- Energy metabolism
B12 deficiency is common among older adults and vegetarians, making occasional fish consumption beneficial.
The Mercury Problem: What You Need to Know
Why Swordfish Contains High Mercury
Mercury enters oceans primarily from industrial emissions—coal-burning power plants, waste incineration, and mining operations release mercury into the atmosphere. Rainfall deposits mercury into water bodies, where microorganisms convert it to methylmercury, the highly toxic form that accumulates in fish.
Biomagnification process:
- Small organisms absorb methylmercury from water
- Small fish eat these organisms, accumulating mercury
- Larger predatory fish eat smaller fish, concentrating mercury further
- Swordfish, as apex predators living 9-15 years, accumulate the highest levels
Mercury Levels in Swordfish
Average mercury content: 0.995 parts per million (PPM)
Range: 0.10 – 3.22 PPM (varies by individual fish)
Comparison: 20 times higher than mackerel (0.05 PPM), 70 times higher than sardines (0.014 PPM)
The FDA categorizes swordfish in the “Avoid” category for pregnant women and young children, alongside shark, king mackerel, and tilefish.
Health Effects of Mercury Exposure
Methylmercury is neurotoxic, meaning it damages nervous system tissue. Effects vary by exposure level and individual vulnerability:
In developing fetuses and young children:
- Impaired brain development
- Delayed developmental milestones (walking, talking)
- Reduced cognitive function and IQ
- Attention deficits and learning disabilities
- Motor skill impairment
In adults (high exposure):
- Numbness or tingling in extremities
- Vision and hearing problems
- Memory and concentration difficulties
- Coordination issues
- In severe cases: kidney, lung, cardiovascular, or digestive system damage
Key distinction: Adults have more resilient nervous systems than developing fetuses. Occasional swordfish consumption (once weekly) is unlikely to cause measurable harm in healthy adults.
Is Swordfish Safe to Eat?
For Healthy Adults
Yes, in moderation. The FDA recommends:
- Maximum frequency: Once per week
- Serving size: 6 ounces cooked
- Weekly limit: One serving of high-mercury fish OR substitute with lower-mercury options
At this frequency, mercury intake remains below the EPA’s Reference Dose (RfD) of 0.1 micrograms per kilogram of body weight per day for most adults.
Factors that improve safety:
- Cooking: Reduces mercury content by up to 30% through fat dripping
- Selenium content: May partially neutralize mercury effects
- Variety: Alternating with lower-mercury fish reduces cumulative exposure
For Pregnant and Breastfeeding Women
No. Avoid entirely. Major health organizations unanimously recommend pregnant women, those planning pregnancy within six months, and breastfeeding mothers avoid swordfish due to:
- Critical brain development: The fetal brain is most vulnerable to mercury during pregnancy, particularly in the third and fourth months
- Mercury crosses placenta: Methylmercury readily transfers from mother to fetus
- Long-term effects: Studies in New Zealand, Faroe Islands, and Seychelles linked maternal high-mercury fish consumption to developmental delays in children
- No safe threshold: Developing nervous systems show sensitivity even at low mercury levels
FDA recommendation for pregnancy: Eat 8-12 ounces weekly of low-mercury fish (salmon, shrimp, pollock, catfish) for omega-3 benefits, but avoid all high-mercury species.
For Children
Age 1-6 years: Avoid completely. Young children’s developing brains are highly vulnerable to mercury.
Age 6-11 years: Limit to one 4-ounce serving per month maximum, though lower-mercury fish are better choices.
Age 12+: Follow adult guidelines (once per week maximum).
The FDA’s fish consumption chart categorizes fish into three groups: “Best Choices,” “Good Choices,” and “Choices to Avoid.” Swordfish falls into “Choices to Avoid” for vulnerable populations.
How Often Can You Eat Swordfish?
Consumption Frequency Guidelines
Healthy adults:
- Maximum: Once per week (6 oz serving)
- Better: Once every 2 weeks, alternating with lower-mercury fish
- Ideal: Occasional treat (monthly), with regular consumption of low-mercury options
Pregnant/breastfeeding women and children under 6:
- Recommendation: Never
Children 6-11 years:
- Maximum: Once per month (4 oz serving)
- Better: Avoid and choose lower-mercury alternatives
Older adults (65+):
- Follow adult guidelines
- Consider more frequent low-mercury fish for omega-3 benefits
Why Frequency Matters
Mercury accumulates in body tissues over time. The half-life of methylmercury in humans is 50-70 days—meaning it takes nearly two months for your body to eliminate half the mercury from one meal. Regular consumption of high-mercury fish prevents clearance, allowing buildup to potentially harmful levels.
Example calculation:
A 150-pound adult eating 6 oz swordfish weekly consumes approximately 6 micrograms of mercury per meal. At once-weekly frequency, mercury levels remain relatively stable as excretion roughly matches intake. More frequent consumption causes accumulation exceeding safe thresholds.
Swordfish vs. Other Fish: Mercury Comparison
High-Mercury Fish (Avoid or Limit Severely)
| Fish | Average Mercury (PPM) | Frequency Limit |
|---|---|---|
| King Mackerel | 0.730 | Avoid (pregnancy), Monthly (adults) |
| Marlin | 0.485 | Avoid (pregnancy), Monthly (adults) |
| Orange Roughy | 0.571 | Avoid (pregnancy), Monthly (adults) |
| Shark | 0.979 | Avoid (pregnancy), Monthly (adults) |
| Swordfish | 0.995 | Avoid (pregnancy), Weekly (adults) |
| Tilefish (Gulf) | 1.450 | Avoid (pregnancy), Avoid (adults) |
| Bigeye Tuna | 0.689 | Avoid (pregnancy), Monthly (adults) |
Moderate-Mercury Fish (Eat Occasionally)
| Fish | Average Mercury (PPM) | Frequency Limit |
|---|---|---|
| Albacore Tuna | 0.350 | 1x/week (adults), Avoid (pregnancy) |
| Mahi-Mahi | 0.178 | 2x/week |
| Halibut | 0.241 | 2x/week |
| Sea Bass | 0.219 | 2x/week |
Low-Mercury Fish (Eat Freely)
| Fish | Average Mercury (PPM) | Frequency |
|---|---|---|
| Salmon (wild) | 0.022 | 2-3x/week |
| Sardines | 0.014 | 2-3x/week |
| Anchovies | 0.017 | 2-3x/week |
| Herring | 0.084 | 2-3x/week |
| Trout | 0.071 | 2-3x/week |
| Mackerel (Atlantic) | 0.050 | 2-3x/week |
| Cod | 0.111 | 2-3x/week |
| Tilapia | 0.013 | 2-3x/week |
| Shrimp | 0.009 | 2-3x/week |
| Catfish | 0.025 | 2-3x/week |
Key insight: Low-mercury fish provide similar nutritional benefits (protein, omega-3s, vitamin D) without the mercury risk, making them superior choices for frequent consumption.
Safer Alternatives to Swordfish
If you’re seeking swordfish’s nutritional benefits without the mercury risk, consider these alternatives:
For High Protein
Wild Salmon: 39g protein per 6 oz, only 0.022 PPM mercury, higher omega-3 content (2.3g)
Sardines: 25g protein per 6 oz, 0.014 PPM mercury, calcium-rich (with bones)
Cod: 28g protein per 6 oz, 0.111 PPM mercury, extremely lean
For Omega-3 Fatty Acids
Salmon: 2.3g omega-3 per 6 oz (78% more than swordfish)
Sardines: 1.8g omega-3 per 6 oz
Herring: 2.4g omega-3 per 6 oz
Anchovies: 2.0g omega-3 per 6 oz
For Meaty Texture (Similar to Swordfish)
Mahi-Mahi: Firm, mild flavor, 0.178 PPM mercury (5x lower)
Halibut: Dense, steak-like texture, 0.241 PPM mercury (4x lower)
Tuna (Skipjack/Light): Meaty but much lower mercury (0.144 PPM)
For Selenium
Brazil Nuts: 544 mcg per ounce (not fish, but selenium powerhouse)
Oysters: 300 mcg per serving, very low mercury
Sardines: 87 mcg per serving, excellent mercury-to-selenium ratio
How to Reduce Mercury Exposure When Eating Swordfish
If you choose to eat swordfish occasionally, these strategies minimize mercury intake:
1. Cook Properly
Grilling, baking, or broiling: These methods allow fat to drip away, reducing mercury by up to 30%. Mercury binds to fat and protein—as fat melts and drips, some mercury leaves with it.
Avoid: Frying in oil traps mercury-containing fat in the finished dish.
2. Trim Visible Fat
The dark, fatty portions of swordfish contain higher mercury concentrations. Remove before cooking.
3. Choose Smaller Fish
When possible, select smaller swordfish steaks. Younger, smaller swordfish have accumulated less mercury over their lifetimes.
4. Check Source
Ask where swordfish was caught. Some regions have lower mercury contamination. Atlantic swordfish from certain areas may have slightly lower levels than Pacific varieties.
5. Don’t Eat Swordfish Skin
Most swordfish is sold as boneless steaks without skin, but if present, remove it. Skin concentrates environmental contaminants.
6. Balance with Selenium-Rich Foods
Eat selenium-rich foods alongside swordfish:
- Brazil nuts (1-2 nuts provide 200+ mcg selenium)
- Sunflower seeds
- Whole grains
Selenium’s protective binding to mercury may reduce absorption, though this doesn’t eliminate risk entirely.
7. Increase Omega-3 from Other Sources
Since swordfish should be limited, get additional omega-3s from:
- Walnuts (plant-based ALA)
- Flaxseeds
- Chia seeds
- Algae-based supplements (vegan DHA/EPA)
- Lower-mercury fish
8. Stay Informed
Check the FDA’s updated fish advisory list regularly. Mercury levels can change based on environmental conditions and fishing locations.
Testing for Mercury Exposure
If you’ve consumed swordfish frequently or are concerned about mercury levels:
Blood Mercury Test:
- Measures recent exposure (past few months)
- Normal levels: <5 micrograms/liter
- Concerning levels: >10 micrograms/liter
Hair Mercury Test:
- Reflects long-term exposure (several months)
- Normal: <1 parts per million
- Concerning: >5 parts per million
When to test:
- Planning pregnancy (test 6 months before conception)
- Regular high-mercury fish consumption
- Symptoms suggesting mercury exposure
- Occupational exposure concerns
Consult your physician if results are elevated. Cessation of high-mercury fish typically allows levels to decline over 3-6 months.
The Bottom Line: Should You Eat Swordfish?
For most healthy adults: Yes, occasionally. Once-weekly consumption provides nutritional benefits (protein, omega-3s, vitamin D) while keeping mercury exposure below concerning thresholds. However, lower-mercury fish like salmon, sardines, and trout offer similar or superior nutrition without the risk, making them better everyday choices.
For pregnant women, women planning pregnancy, breastfeeding mothers, and children under 6: No. The mercury risk to developing brains outweighs any nutritional benefits. Choose lower-mercury alternatives exclusively.
The ideal approach: Enjoy swordfish as an occasional treat (once weekly maximum for adults), but build your regular fish consumption around low-mercury options that can be eaten 2-3 times weekly without concern.
Swordfish offers impressive nutrition, but it’s not irreplaceable. A diet rich in variety—emphasizing lower-mercury fish, plant-based omega-3 sources, and diverse protein—provides optimal nutrition without unnecessary mercury exposure.
Conclusion
Swordfish presents a nutritional paradox: excellent protein, omega-3s, vitamin D, and selenium, but concerning mercury levels that require careful consumption limits. The science is clear—pregnant women and young children should avoid swordfish entirely, while healthy adults can safely enjoy it once weekly.
The key to healthy fish consumption isn’t avoiding all fish with mercury, but rather making informed choices about frequency and variety. By understanding mercury levels across species and following FDA guidelines, you can enjoy swordfish’s unique flavor and nutritional benefits while protecting your health and that of your family.
For the best of both worlds—great nutrition without the mercury trade-off—make lower-mercury fish like salmon, sardines, and trout your staples, reserving swordfish for special occasions. Your body gets the omega-3s and protein it needs, without the cumulative mercury exposure that comes from frequent high-mercury fish consumption.
Frequently Asked Questions
Is swordfish healthy to eat?
Yes, for healthy adults when eaten in moderation (maximum once per week). Swordfish provides 34g protein, 1.3g omega-3 fatty acids, and 80% daily vitamin D per 6-ounce serving. However, it contains 0.995 PPM mercury—among the highest levels in commonly consumed fish. Pregnant women, breastfeeding mothers, and children under 6 should avoid swordfish completely due to mercury’s effects on developing nervous systems.
How much mercury is in swordfish?
Swordfish contains an average of 0.995 parts per million (PPM) mercury, with individual fish ranging from 0.10 to 3.22 PPM. This is approximately 20 times higher than mackerel (0.05 PPM) and 70 times higher than sardines (0.014 PPM). The FDA classifies swordfish in the “Choices to Avoid” category for pregnant women and young children due to these elevated levels.
Can pregnant women eat swordfish?
No. The FDA, EPA, and American College of Obstetricians and Gynecologists unanimously recommend pregnant women avoid swordfish entirely. Mercury crosses the placenta and can impair fetal brain development, particularly during the third and fourth months of pregnancy. Studies link maternal high-mercury fish consumption to developmental delays, reduced IQ, and learning disabilities in children. Pregnant women should eat 8-12 ounces weekly of low-mercury fish instead.
How often can I eat swordfish?
Healthy adults: Maximum once per week (6 oz serving). Children ages 6-11: Maximum once per month (4 oz serving). Children under 6, pregnant women, and breastfeeding mothers: Avoid completely. Mercury has a 50-70 day half-life in the body, so more frequent consumption causes accumulation. For optimal health, eat swordfish occasionally and choose lower-mercury fish (salmon, sardines, trout) for regular consumption 2-3 times weekly.
Is swordfish high in omega-3?
Yes, moderately high. A 6-ounce serving provides 1.3 grams of omega-3 fatty acids (EPA and DHA), meeting about 65% of recommended daily intake. However, other fish offer higher omega-3 content with lower mercury: wild salmon (2.3g), sardines (1.8g), and herring (2.4g) per 6-ounce serving. These alternatives provide superior omega-3 benefits without the mercury concerns.
What are the symptoms of mercury poisoning from fish?
In adults: numbness or tingling in hands and feet, vision problems, hearing loss, memory and concentration difficulties, coordination issues, tremors. In severe cases: kidney, lung, or cardiovascular damage. In children exposed during pregnancy: delayed developmental milestones (walking, talking), reduced cognitive function, learning disabilities, attention deficits. Symptoms develop gradually with regular high-mercury fish consumption over months or years.
Does cooking swordfish reduce mercury?
Yes, cooking reduces mercury content by up to 30%. Grilling, baking, and broiling allow fat to drip away, taking some mercury with it since mercury binds to fats and proteins. Trimming visible fat before cooking further reduces levels. However, a 30% reduction still leaves swordfish with high mercury content (approximately 0.70 PPM after cooking), so frequency limits remain important.
Is swordfish better than salmon?
No, salmon is nutritionally superior for regular consumption. Salmon provides more protein (39g vs 34g per 6 oz), nearly double the omega-3s (2.3g vs 1.3g), and similar vitamin D, but contains 45 times less mercury (0.022 PPM vs 0.995 PPM). Salmon can be safely eaten 2-3 times weekly, while swordfish should be limited to once weekly. Swordfish has a firmer, meatier texture that some prefer, making it worthwhile as an occasional alternative.
What fish has the lowest mercury?
Sardines, anchovies, and shrimp have the lowest mercury levels (0.009-0.017 PPM). Other excellent low-mercury choices include salmon (0.022 PPM), catfish (0.025 PPM), tilapia (0.013 PPM), Atlantic mackerel (0.050 PPM), and cod (0.111 PPM). These fish can be safely eaten 2-3 times weekly by everyone, including pregnant women and children, while providing similar nutritional benefits to swordfish.
Can I eat swordfish while breastfeeding?
No. The FDA recommends breastfeeding mothers avoid high-mercury fish including swordfish. Mercury consumed by the mother can pass through breast milk to the infant, potentially affecting the baby’s developing nervous system. While breast milk mercury levels are generally lower than maternal blood levels, the safest approach is avoiding high-mercury fish entirely during breastfeeding. Choose low-mercury alternatives like salmon, sardines, and cod for omega-3 benefits without risk.
Medical Disclaimer: This article provides general health information and is not a substitute for professional medical advice. Consult your physician or registered dietitian for personalized dietary recommendations, especially if pregnant, breastfeeding, or managing health conditions.