By Jennifer Rae Vliet
Today on The Plain Truth, we will be exploring the topic of mercury and its impact on our health. This is especially important for those who regularly consume fish, as mercury exposure can pose serious health risks. In fact, some scientists even claim they have found ways to reduce the amount of mercury in canned tuna, making this a subject worth examining more closely.
We believe we are called to follow the food laws of Scripture that God established long before the time of Moses. The plain truth is that God’s instructions are always for our good, and He does not change. As we learn more about the levels of mercury found in fish, we are reminded of the wisdom in His guidance. In this discussion, we will share helpful information and practical tips to assist everyone in making informed choices when consuming canned tuna and other Biblically permissible seafood.
Are There Fish Without Mercury? List With the Lowest Levels
There are no fish without mercury, as all marine life contains trace amounts of this toxic heavy metal due to environmental pollution.
However, some species contain much lower levels than others, making them safer for regular consumption without the risk of mercury toxicity and associated health issues.
Here’s a comprehensive guide to mercury levels in fish and how to choose the safest options to minimize mercury exposure.
What is mercury?
Mercury is a heavy metal that’s naturally present in the environment and the only type of metal that’s liquid at room temperature. It has a silvery appearance and is commonly used in thermometers, barometers, and fluorescent light bulbs.
Processes such as volcanic activity and the weathering of rocks, as well as coal burning, mining, and improper disposal of mercury-containing products, can release elemental mercury into the atmosphere.
Airborne mercury particles typically enter bodies of water through precipitation, where microbes convert them into methylmercury, a highly toxic compound that can contaminate aquatic organisms.
Mercury easily accumulates in fish, particularly larger predatory species, as they ingest smaller contaminated organisms, leading to higher concentrations of methylmercury in their tissues.
Watch the video below to learn which types of fish contain the highest levels of mercury.
Why is mercury bad for you?
Mercury is highly toxic and can have serious health consequences. Mercury poisoning, also known as mercury toxicity, occurs when excessive amounts of mercury accumulate in the body, which can cause significant tissue and organ damage over time.
Excessive intake of contaminated fish is the most common source of methylmercury exposure for humans.
Methylmercury is a particularly dangerous form of mercury as it can easily enter the bloodstream and cross the blood-brain barrier, impacting the central nervous system.
Because mercury is highly reactive, it can bind to proteins and enzymes, disrupting their function and causing oxidative stress that damages cellular components such as lipids, proteins, and DNA.
Furthermore, mercury isn’t easily broken down or eliminated from cells, and mercury builds up in tissues over time, particularly in organs such as the kidneys, liver, and brain.
Pregnant women and young children are particularly vulnerable to the effects of mercury. Mercury exposure during pregnancy can interfere with fetal brain development, increasing the risk of developmental delays, learning disabilities, and behavioral problems.
Research published in Toxics summarizes the detrimental effects of mercury as follows, “Developmental exposure to methylmercury has been linked to cognitive and behavioral dysfunction in children, while cumulative exposure over an adult’s lifetime has been linked to the development of neurodegenerative diseases, such as Parkinson’s disease.”
This highlights why pregnant women and young children shouldn’t eat fish in excess, particularly large predatory species, to minimize the health risk of consuming too much mercury.
Are there fish without mercury?
Due to environmental pollution, mercury is present in almost all marine life.
However, tiny fish and those lower in the food chain tend to accumulate less mercury as they feed on plankton and algae, which generally contain only small amounts of this neurotoxic metal.
Examples of low-mercury fish include sardines, anchovies, and herring, which are smaller fish with a shorter lifespan, greatly reducing their mercury exposure.
In contrast, larger predatory fish, such as swordfish and tuna, accumulate higher levels of mercury. As they consume other fish, the mercury content of their prey builds up in their bodies, which is a process known as biomagnification.
Here’s a guide to fish and seafood with high, moderate, and low mercury levels.
Fish with high mercury levels
It’s generally advised to avoid fish with high mercury levels or to limit consumption to no more than once a month.
Fish with high mercury levels include:
- Bluefish
- Grouper
- King mackerel
- Orange roughy
- Shark
- Swordfish
- Big eye tuna
- Albacore tuna
- Yellowfin tuna
- Ahi tuna
- Halibut
- Perch
- Sea Bass
Fish and seafood with moderate mercury levels
Intake of fish species with moderate mercury levels should be limited to once weekly.
This helps minimize the risk of mercury accumulation while benefiting from the nutritional value of fish, such as heart-healthy omega-3 fatty acids, high-quality protein, and essential vitamins.
Fish and crustaceans with moderate mercury levels include:
- Bass
- Cod
- Snapper
- Monkfish
- Canned tuna
- Skipjack tuna
- Lobster
Fish and seafood with low mercury levels
Low-mercury fish and seafood options can be enjoyed regularly and are an excellent addition to a nutritious diet, offering omega-3 fats, iodine, vitamin B12, and selenium.
These nutrients play a critical role in supporting heart health, brain function, strong immune defenses, and balanced thyroid hormone levels, making them essential for overall well-being.
Scientists Found a Surprisingly Simple Way to Cut Mercury Content in Canned Tuna by 35%
Using a water-based solution with this amino acid draws mercury out of fish and requires no additional production steps.
An estimated 10% of Americans eat canned tuna at least once a week, according to a 2022 Consumer Reports survey. Consumer Reports also found that certain types of canned tuna can have unhealthy levels of mercury, which is particularly harmful for pregnant women. However, researchers from Chalmers University of Technology in Sweden say they’ve developed a new method of packaging that helps reduce mercury levels in each can.
“Our study shows that there are alternative approaches to addressing mercury contamination in tuna, rather than just limiting consumption. Our goal is to improve food safety and contribute to enhanced human health, as well as to better utilize food that is currently under certain restrictions,” Mehdi Abdollahi, an associate professor at the Department of Life Sciences at Chalmers, shared with SciTechDaily about their new work now published in the journal Global Challenges.
15 Ways to Use Canned Seafood, According to Chefs
According to the team, they created a new method of packaging that puts the tuna in a water-based solution that contains 1.2% cysteine, an amino acid that draws mercury out of the fish. It tested whole pieces of fresh and canned tuna, minced canned tuna, and steamed tuna, and found the highest value of mercury reduction at 35% when testing canned minced tuna, which it purchased from a standard grocery store. The team added that this was because the minced tuna had greater surface area contact with the solution. “This method has the potential to enable the application of effective active packaging strategies, thereby increasing the safety of fish products for consumption,” the researchers noted in their research.
They further explained that the method involves treating them in the solution first, then absorbing the mercury onto “powdered, thiolated silica and thiolated polymers,” which could be replicated by using “adsorbent-filled sachets placed within the container.” This would also mean the system is self-contained and does not require any extra steps in the processing of the tuna, and users can simply discard the water solution after opening the package as they typically do.
“The beauty of this type of packaging is that it is active while the product is on the shelf. No additional production steps would be needed if a method like this were used industrially. Przemysław Strachowski, the first author of the study, stated.
In their conclusion, the researchers added, “There is an undeniable need to develop safe and effective tools for reducing mercury levels in fish meat. These tools can complement the industry’s efforts to minimize mercury release into the environment and offer new insights and ideas to enhance the safety of fish consumption.”