Janelle MonÃ¡e claims she developed mercury poisoning after becoming a pescatarian.
The Hidden Figures actress told The Cut she â€œstarted feeling her mortalityâ€ after swapping meat for fish.
MonÃ¡e did not discuss her health scare further but admitted she is waiting to have a child until she has made a full recovery.
What is mercury poisoning?
Mercury is a naturally-occurring element found in air, water and soil, according to the World Health Organization (WHO).
A toxic form called methylmercury can accumulate in fish, seafood and the animals that eat them.
Mercury builds up the more it is digested, with animals at the top of the food chain – like swordfish or shark – containing the highest amounts.
Dental fillings can also release mercury.
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Symptoms of mercury poisoning include tremors, insomnia, memory loss, headaches, and cognitive and motor dysfunction.
Excessive exposure can damage the nervous, digestive and immune systems, as well as the lungs, kidneys, skin and eyes.
Unborn babies can come into contact with mercury if their mother eats fish rich in the metal.
This can affect the foetusâ€™ growing brain and nervous system, resulting in impaired thinking, memory, language and motor skills as a child.
Among â€œfishing populationsâ€, between 1.5 and 17 in every 1,000 children have cognitive impairment, the WHO reports.
It considers mercury â€œone of the top 10 chemicals or groups of chemicals of major public health concernâ€.
Mercury levels can be tested via a hair, blood or urine sample, Medicine Net reported.
Treatment involves removing the â€œsourceâ€.
Chelation therapy can also help. This involves administering chelating agents, chemical compounds that react with metal ions to form a stable, water-soluble complex, to remove heavy metals from the body.
Mercury exposure can also come about via inhaling its vapour or absorption through the skin.
People can reduce their risk by not burning coal, a â€œmajor source of mercuryâ€.
They can also phase out non-essential products that contain the metal, like batteries, thermometers, some light bulbs, skin-lightening products and certain cosmetics.
A form of mercury called ethylmercury has been used in â€œvery small amountsâ€ as a preservative in vaccines for more than 10 years, with â€œno evidence it poses a riskâ€, according to the WHO.
How much fish is safe to eat?
A â€œhealthy, balanced diet should include at least two portions of fish a week, including one of oily fishâ€, according to the NHS.
Oily fish includes salmon, mackerel and sardines.
The NHS warns these types of fish can contain â€œlow levels of pollutants that can build up in the bodyâ€.
â€œGirlsâ€, pregnant or breastfeeding women, and those hoping to become pregnant – even if in the future, should therefore have no more than two portions of oily fish a week.
Everyone can â€œsafely eat as many portions of white fish per week as they likeâ€, these include cod, pollack and hake.
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There are exceptions, however.
Sea bream, rock salmon, sea bass, turbot and halibut can contain â€œsimilar levels of certain pollutants as oily fishâ€, and should be limited.
Children, pregnant women and those trying to conceive should not eat shark, swordfish or marlin, due to their high mercury levels.
Others adults should consume these no more than once a week.
Shellfish does not need to be limited, aside from brown crab meat.
Find out more about a healthy fish intake on the NHSâ€™ website.