The Food Standards Agency says some people in the United Kingdom are eating fish that are not the right size and shape for their health, the BBC reported.
The agency said some people believe that eating fish can help reduce cholesterol.
However, the fish in question are usually not as fatty as fish from other countries, and they do not have the same nutritional value, the agency said.
The group also advises people not to eat “fish products that have been contaminated by faeces.”
The Food Standards Authority has asked customers to return fish and seafood products to the shops that sold them and to stop using them in the coming weeks.
The FSA has also asked fish processors to make their products free of faecal matter, the AP reported.
A report by the British government earlier this year found that more than 3,300 people in England and Wales reported being diagnosed with heart problems related to the consumption of fish and shellfish.
It said there was no evidence of health risks to human health from eating fish.