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There's no doubt that fish should be a part of your diet. Fatty fish are great for a keto diet. Fish contain many essential nutrients, such as omega-3 fatty acids. As I've talked about before, omega-3 has some incredible health benefits. However, the question that many of you have asked me is, "what fish should I eat to avoid mercury?"
When it comes to fish consumption, you really have to watch out for types that are high in mercury. All fish have at least trace amounts of mercury. However, some have very low levels, and others have very high levels. If you eat fish with high levels of mercury often enough, you can accumulate way too much mercury, which can contribute to many health issues.
In This Article:
- What is Mercury?
- Why do fish contain mercury?
- Fish ranked by mercury levels
- How to detoxify mercury in the body
What is mercury?
Mercury, also known as quicksilver, is a heavy metal. It is the only metallic element that is liquid at room temperature (though several are liquid just above room temperature). Mercury naturally occurs in the environment, and it's also released into the air by industrial pollution.
Once mercury is in the air, it falls to the surface of the earth where it can accumulate in oceans, rivers, and lakes. The form of mercury that is in water is called methylmercury. Methylmercury is the type of mercury that is potentially dangerous in high amounts—especially for young children, pregnant women, and women of childbearing age.
Mercury is known as a nervous system toxin. Nervous system toxins can cause some serious health effects, including loss of coordination, muscle weakness, impaired speech and hearing, and stinging or needle-like sensations. For this reason, the U.S. Food and Drug Administration recommends that you limit eating fish that have high mercury levels.
Often times, a mild amount of mercury in the body can go unnoticed and cause chronic fatigue, weakness, and insomnia. Though the body can get rid of small amounts of mercury on its own, it can take months or even years to get rid of large amounts of mercury built up in your system.
Why do Fish Contain Mercury?
As I mentioned before, essentially all fish contain at least trace amounts of mercury. Since mercury falls from air into water, it can build up in the fish that swim and feed in the water. Some fish contain far more mercury than others. There are several reasons for this.
First, different bodies of water and different areas within a body of water can significantly impact how much mercury the fish or shellfish contains. Some areas will be less polluted than others due to both environmental and industrial factors. Fish that live closer to the surface of the ocean are at more risk of being polluted by mercury. Since preindustrial times, the amount of mercury in waters shallower than 100 meters has tripled.
Another factor is the size of the fish. Larger predator fish eat smaller fish. Those smaller fish eat even smaller fish—and so on. The larger fish that ingest, the smaller fish will be exposed to an extra dose of methylmercury. This continues on through the food chain until the largest fish are exposed to significantly more mercury. This phenomenon is known as biomagnification.
The lifespan of a type of fish is yet another factor. The longer a type of fish lives, the longer it is exposed to mercury through the environment and the consumption of other fish. In general, long-lived fish, like king mackerel, are going to be much higher in mercury—so stay away from these. Small fish and shellfish are often the least contaminated by methylmercury.
Fish ranked by mercury levels
Take a look at which types of fish to avoid, which to have occasionally, and which you can have regularly.
Avoid - very high mercury levels:
- Mackerel and King Mackerel
- Orange Roughy
- Tuna (Ahi or Bigeye)
Once a month - high mercury levels:
- Sea bass
- Tuna (Albacore or Yellow)
Once a week - moderate mercury levels:
- Tuna (Canned Light Tuna and Skipjack)
Frequent - low mercury levels:
Before you consume fish, check this list so you know how often you can have it. Keep in mind that I'm basing these mercury levels on an average-sized meal. So you want to avoid having excessive amounts of a high-mercury fish in each meal to prevent mercury poisoning.
Pregnant women, nursing mothers, and young children should avoid all fish with high mercury levels. Instead, stick to low-mercury fish like light tuna (not albacore), tilapia, trout, sardines, flounder, and catfish. If you can't find a fish on this list, check the U.S. Food and Drug Administration or the U.S. Environmental Protection Agency's website for more. You can also check local advisories about the safety of local-caught fish.
If you already have mercury poisoning from eating fish exposed to high methylmercury levels, I've got some remedies for you that should really help.
How to Detoxify Mercury in the Body
If you have high levels of mercury in your system, the first thing you want to do if figure out what caused this mercury exposure. Most often, it's one of two things—you're consuming fish with high mercury content, or you have an amalgam. Amalgams are metal fillings for your teeth. These contain 50% mercury. Pregnant women should especially avoid these types of fillings.
Frequently having high-mercury fish or shellfish is a major cause of high mercury levels. Take a look at my list of high-mercury fish above.
Once you know what is causing high mercury, you should do whatever you can to avoid further exposure. Then, you can work on detoxifying. Here are the best things you should have to detoxify:
- Lipoic acid
These are natural chelators. Chelators are things that go in and bind to the mercury and pull it out of the body. Give these detoxifiers a try and see how they work for you.
I also made a nice downloadable printout with all of these fish categorized by levels of mercury. You can take this with you on your next shopping trip, so you know exactly which types of fish to buy. You can find the printout here.