Janelle Monáe claims she developed mercury poisoning after becoming a pescatarian.
The Hidden Figures actress told The Cut she “started feeling her mortality” after swapping meat for fish.
Monáe 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 foetus’ growing brain and nervous system, resulting in impaired thinking, memory, language and motor skills as a child.
Among “fishing populations”, between 1.5 and 17 in every 1,000 children have cognitive impairment, the WHO reports.
It considers mercury “one of the top 10 chemicals or groups of chemicals of major public health concern”.
Mercury levels can be tested via a hair, blood or urine sample, Medicine Net reported.
Treatment involves removing the “source”.
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 “major source of mercury”.
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 “very small amounts” as a preservative in vaccines for more than 10 years, with “no evidence it poses a risk”, according to the WHO.
How much fish is safe to eat?
A “healthy, balanced diet should include at least two portions of fish a week, including one of oily fish”, according to the NHS.
Oily fish includes salmon, mackerel and sardines.
The NHS warns these types of fish can contain “low levels of pollutants that can build up in the body”.
“Girls”, 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 “safely eat as many portions of white fish per week as they like”, 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 “similar levels of certain pollutants as oily fish”, 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 NHS’ website.