🐟 Mercury Levels & Health Comparison: Salmon vs. Sardines
Mercury Content
- Both sardines and salmon are considered low‐mercury fish, largely because they are small, short‐lived species that eat plankton rather than accumulating mercury through the food chain Livestrong.com+2Wikipedia+2Leigh Torres+2.
- Typical mercury levels:
- Canned sardines: around 0.015 ppm (parts per million) Leigh Torres+1Dr. Berg+1
- Fresh/frozen salmon: about 0.034 ppm, and canned salmon even lower at ~0.021 ppm Wikipedia
Nutritional Benefits
- Sardines are powerhouse sources of omega-3 fatty acids: approximately 2 g of DHA + EPA per 3 oz serving, along with calcium and vitamin D foodstruct.com+10health.clevelandclinic.org+10sweetishhill.com+10.
- Salmon also provides high-quality omega-3s, good protein, and vitamin D, though per serving omega-3 content is typically lower than sardines—roughly 400–700 mg per 56 g serving versus sardines’ 1,600–1,800 mg per 85 g serving consumerlab.com.
Summary Table
| Fish | Mercury (ppm) | Omega‑3s (DHA+EPA) | Additional Nutrients |
|---|---|---|---|
| Sardines | ~0.015 ppm | ~1,600–1,800 mg | Calcium, Vitamin D, B vitamins |
| Salmon | ~0.021–0.034 ppm | ~400–700 mg | High‑quality protein; Vitamin D, B’s |
Health Considerations
- Both are excellent low-mercury seafood choices recommended even for pregnant or nursing individuals—the FDA and other authorities consistently list them among the safest fish Wikipedia+8Wikipedia+8Leigh Torres+8Livestrong.comconsumerlab.com.
- ConsumerLab testing found that while most canned salmon and sardines are low in mercury, some canned sardine products had elevated arsenic levels; so it’s worth checking brand-specific info if available consumerlab.com.
✅ Bottom Line
- Neither salmon nor sardines carry high mercury risk.
- Sardines generally have lower mercury and higher omega-3 content per serving compared to salmon.
- Salmon, however, remains a nutritious, low-mercury option with its own benefits.
🐟 Why Big Fish = More Mercury
Mercury builds up in fish through a process called bioaccumulation. Here’s what happens:
- Tiny organisms absorb mercury from polluted water.
- Small fish eat those organisms and accumulate mercury.
- Big fish eat lots of small fish—so they absorb even more mercury.
💀 The longer a fish lives and the bigger it is, the more mercury it likely has.
🚫 High-Mercury Fish to Avoid
These fish are near the top of the food chain and tend to have the highest mercury levels:
| Fish | Avg. Mercury (ppm) | Why Avoid? |
|---|---|---|
| Shark | 0.979 ppm | Apex predator—very high mercury |
| Swordfish | 0.995 ppm | Among the highest mercury levels |
| King mackerel | 0.730 ppm | Large species, unsafe for pregnant women |
| Tilefish (Gulf of Mexico) | 1.123 ppm | Extremely high mercury |
| Bigeye Tuna (Ahi) | 0.689 ppm | Not to be confused with skipjack or light |
| Marlin | 0.485 ppm | Large predatory fish |
| Orange Roughy | 0.571 ppm | Long-living deep-sea fish |
🧠 These are especially dangerous for children, pregnant women, and nursing mothers, due to risk of neurological harm from methylmercury.
✅ Best Low-Mercury Fish (Eat Often)
These are small, fast-growing, and naturally low in mercury:
| Fish | Avg. Mercury (ppm) | Bonus Nutrients |
|---|---|---|
| Sardines | 0.015 ppm | Omega-3s, calcium, vitamin D |
| Salmon | 0.021–0.034 ppm | Protein, omega-3s, vitamin D |
| Anchovies | 0.017 ppm | Omega-3s, iron |
| Herring | 0.084 ppm | Vitamin B12, selenium |
| Tilapia | 0.013 ppm | Low-fat protein, selenium |
| Trout | 0.071 ppm | Omega-3s, vitamin B6 |
| Mussels/Clams/Oysters | <0.025 ppm | Iron, B12, zinc, and copper |
🧠 Pro Tip: Wild-Caught vs. Farmed
- Wild-caught salmon usually has slightly more mercury than farmed but often more omega-3s and fewer contaminants like PCBs.
- Farmed fish may be lower in mercury but risk exposure to other toxins depending on farming practices.
🔁 Rule of Thumb
“The smaller the fish, the safer the dish.”
Big fish live longer and eat lots of small fish, giving them more time to accumulate mercury and other toxins. Small fish like sardines, anchovies, and herring are safer, healthier, and more sustainable choices.