You may have heard about mercury in fish and seafood and that some have higher levels of mercury than others. But are you confused about what is safe to eat and how much mercury is OK to ingest? What about the fish which is high in mercury vs. those with safer levels? Is it OK to eat fish at all? If you've been worried about the health effects of mercury in your diet but still want to enjoy fish and seafood regularly, here are some important facts to review before diving into that tilapia filet or shrimp scampi.
The Lowdown on Mercury
According to WebMD, "Mercury is a metal found naturally in the environment. Human activities, such as farming, burning coal, and using mercury in manufacturing, increase the mercury cycling through the air, water, and soil. In water, mercury changes its form and becomes methylmercury. Fish absorb this mercury. When you eat fish containing mercury, you absorb the mercury, and at high levels it can be harmful. Mercury will leave the body over time in the urine, feces, and breast milk."
If you eat fish, you will undoubtedly take mercury in some amount into your body. According to Precision Nutrition, "We absorb and disseminate methylmercury well when we eat it — it easily passes through the gastrointestinal wall and is distributed throughout the body within 30 hours. Mercury can affect nearly all organs and is able to cross the blood-brain and placental barriers."
How Much is OK?
As per Precision Nutrition, methylmercury guidelines are as follows:
The FAO/WHO "provisional tolerable weekly intake" is 1.6 mcg/kg
The U.S. EPA safe level for daily intake is 0.1 mcg/kg
U.S. Pharmacopeia recommends less than 15 mcg/day.
Variations must be taken into account during pregnancy, so any woman who is planning to become pregnant or is pregnant should consult her OB/GYN for information regarding safety.
Which Fish are Highest and Lowest in Mercury?
As per the National Resources Defense Council (NRDC), "King mackerel, marlin, orange roughy, shark, swordfish, tilefish, ahi tuna, and bigeye tuna all contain high levels of mercury."
Since canned tuna is one of the more commonly consumed fish items in the U.S., the NRDC says, "Stick to light or skipjack tuna, and limit it to less than two servings a week."
And if you're a sushi lover, "You can reduce mercury exposure from sushi by holding back on all types of tuna, mackerel, sea bass, and yellowtail. Eel, salmon, crab, and clam are lower in mercury. Anchovies, sardines, and scallops, are lower in mercury as well."
What are the Health Risks?
According to Precision Nutrition, "Chronic mercury exposure causes serious health problems, especially for the nervous system and kidneys. Mercury might also harm cardiovascular health, DNA transcription, calcium balance, and protein synthesis. Mercury's also been linked to multiple sclerosis and autism and may promote oxidative stress and inflammation."
Toxicity can create instance of the following symptoms:
- Hearing difficulties
- Loss of taste and other oral problems
- Memory loss
- Changes in mood and emotional stability
- Tremors, balance problems
- Pain to the extremities
What to Do?
Moderation is the key to any diet. Limit fish intake, particularly those with greater amounts of mercury. Discuss with your doctor if you are ill, pregnant, or concerned with any symptoms. As per NRDC, "When in doubt, smaller is better. Forgo the big predators (like shark and tuna) and pick the little guys, like anchovies, sardines, and scallops, which are lower in mercury.