Does fish sauce have a lot of mercury?

November 3, 2025 •

3 min read

According to a 2020 study, mercury concentrations found in commercially available fish sauces are well below the maximum permitted levels for fish products. This reassuring fact provides a direct and science-backed answer to the question: Does fish sauce have a lot of mercury?

Quick Summary

Mercury levels in fish sauce are very low and pose no significant health risk, primarily because it is made from small, short-lived fish species like anchovies, which accumulate minimal mercury.

Key Points

Small fish, low mercury: Fish sauce is typically made from small fish like anchovies, which are low on the food chain and contain very little mercury.
Scientific evidence confirms safety: Studies have found that commercially available fish sauces contain mercury levels far below international safety limits, posing no significant health risk.
Mercury cannot be removed by fermentation: The mercury stored in the fish muscle tissue is stable and does not get eliminated during the fish sauce fermentation process.
Not a significant dietary source: Compared to large predatory fish like shark or swordfish, fish sauce is not a notable contributor of mercury to the average person's diet.
Biomagnification is the key factor: Mercury levels are highest in larger, longer-living fish at the top of the food chain, which is why fish sauce remains low in mercury.

The Science Behind Mercury in Seafood

Mercury is a naturally occurring element that is also released into the environment through industrial pollution. In aquatic ecosystems, microorganisms convert this mercury into a highly toxic form called methylmercury, which is then absorbed by fish and other marine life. The level of mercury in a fish is directly related to its position in the food chain and its lifespan, a process known as biomagnification.

Why Large Predatory Fish Pose the Biggest Risk

Larger, longer-living predatory fish are at the top of the aquatic food chain and eat many smaller fish throughout their lives. This means they accumulate and store higher concentrations of mercury in their muscle tissue.

Common examples of high-mercury fish include:

Shark
Swordfish
King Mackerel
Bigeye Tuna
Tilefish (Gulf of Mexico)

The Role of Small Fish in Fish Sauce Production

Most high-quality fish sauce is made from fermented small fish, predominantly anchovies, and sea salt. The use of these smaller species is the key reason for the low mercury levels in the finished product. These fish are low on the food chain and have shorter lifespans, which means they have less time to accumulate significant amounts of mercury. Fermentation does not change the mercury content; mercury is stored in the fish's muscle tissue and is not released or broken down during the fermentation process.

Scientific Studies Confirm Low Levels

Several scientific studies have analyzed the mercury content in commercial fish sauces and consistently reported very low concentrations. A study validated a sensitive method for measuring mercury in fish sauces and tested ten different commercial brands from Vietnam and Thailand. The results showed a mercury content range from 0.8 to 42.8 µg·kg⁻¹, with all samples falling well below the regulatory limits for fish products. This is an important finding, as it means that for the average consumer, fish sauce contributes a negligible amount of mercury to their diet.

Fish Sauce vs. High-Mercury Fish: A Comparative Analysis

To put the mercury levels in fish sauce into perspective, consider the comparison below. Mercury is measured in parts per million (ppm) or micrograms per gram (µg/g), which are equivalent. One ppm equals 1000 µg/kg. The data illustrates how the fish source directly impacts the final product's mercury load.


Seafood Product	Typical Mercury Level (ppm or µg/g)	FDA/EPA Category	Mercury Risk
Fish Sauce (using anchovies)	< 0.043	Not applicable	Very Low
Canned Light Tuna (Skipjack)	0.13	Best Choice	Low
Canned Albacore Tuna	0.35	Good Choice	Moderate
Swordfish	1.0	Avoid	High
Shark	0.98	Avoid	High

Is There a Health Concern for Frequent Consumers?

For most people, the consumption of fish sauce does not pose a significant health risk related to mercury exposure. Even with higher estimated consumption in regions like the Asia-Pacific (approx. 4 kg per year per person), studies conclude that the mercury intake from fish sauce is negligible compared to the provisional tolerable weekly intake (PTWI) set by the Joint FAO/WHO Expert Committee on Food Additives. While sensitive populations, such as pregnant women and children, are advised to monitor their seafood intake, fish sauce remains a very low-risk component of a healthy diet.

What About Mercury-Contaminated Fish Sauce?

Mercury is a stable element and, once absorbed by the fish, it remains present in the fermented liquid. Unlike some other contaminants like PCBs that can be reduced through cooking, mercury cannot be eliminated by processing or fermentation. The key to safety lies in the type of fish used. Reputable manufacturers sourcing smaller, wild-caught fish from relatively clean waters ensure a safer product. Adhering to established food safety regulations, like those observed in the aforementioned studies, further mitigates risk.

Conclusion

In conclusion, fish sauce does not have a lot of mercury. Its low mercury content is a direct result of being produced from small, short-lived fish species like anchovies, which are naturally low in the contaminant. Scientific studies have confirmed that commercial fish sauces contain mercury levels far below safety thresholds, making them a safe condiment for general consumption. While larger predatory fish and certain types of tuna carry higher mercury loads due to biomagnification, the average use of fish sauce does not contribute a significant amount of mercury to the diet. Consumers can enjoy this umami-rich ingredient with confidence, knowing the risk of mercury exposure is minimal.

Determination of Mercury in Fish Sauces by Thermal Decomposition Gold Amalgamation Atomic Absorption Spectroscopy after Preconcentration by Diffusive Gradients in Thin Films Technique

Frequently Asked Questions

Yes, fish sauce is generally considered safe for pregnant women in normal culinary amounts because it is made from small fish with very low mercury levels. Larger, high-mercury fish like shark and swordfish should be limited during pregnancy, but this does not apply to fish sauce.

While most fish sauce is made from low-mercury fish like anchovies, products made from larger, predatory fish may have slightly higher levels. However, studies on commercial fish sauces, including those using varying fish compositions, still show levels well below safety thresholds.

No, mercury is stored in the muscle tissue of the fish and is not removed or destroyed during the fermentation process. The low mercury content in fish sauce is due to the low initial concentration in the small fish used to make it.

Fish sauce has significantly lower mercury levels than most tuna products. For example, canned light tuna has a much higher concentration of mercury than the typical fish sauce, while high-mercury albacore and bigeye tuna are even riskier.

The primary factor is biomagnification, where mercury accumulates at increasing concentrations as it moves up the food chain. Larger, older predatory fish have the highest levels, while small fish at the bottom have the lowest.

The maximum permitted mercury content is generally regulated for fish products, and studies show that commercial fish sauces easily comply with these standards, meaning manufacturers must ensure their products meet safety regulations.

No, cooking methods do not reduce the mercury content in fish. Mercury is stored in the muscle, not the fat, so it cannot be cooked out. This means fish sauce, made from cooked and fermented fish, retains the low levels of mercury present in the original small fish.