Heavy metals in Sushi – scientists reveal which fishes are safer to consume

Sushi is being increasingly consumed around the world for its nutritional value, but scientists warn that too much sushi could expose you to dangers of heavy metal that is now being found in a variety of fish.

To analyze which fish is ideal for consumption as Sushi, researchers looked at the concentration of various toxic elements in these foods and evaluated the risk of consuming them in infant, adolescent and adult population. They say that eight pieces of salmon-based maki, nigiri or sashimi or maki unagi (eel) is the safest combination of sushi for adult and adolescent populations.

The study by TecnATox (Centre for Environmental, Food and Toxicological Technology) has analysed the presence of arsenic and various heavy metals in sushi. Likewise, rice is a food that provides many nutrients and fibre and is low in fat, but it too can be source of pollutants such as arsenic.

Scientists looked at concentrations of various toxic elements (cadmium, nickel, lead, mercury, inorganic arsenic and methylmercury) and iodine in a hundred pieces of sushi, specifically those known as sashimi (raw fish), maki (a seaweed roll stuffed with rice, raw fish or other ingredients) an nigiri (balls of rice with fish or seafood on top). The researchers also calculated dietary exposure to all of these contaminants in various population groups (infants, adolescents and adults) and evaluated the risks to health.

The main results show a significantly higher concentration of inorganic arsenic in maki and nigiri, compared to sashimi, a finding associated with the presence of rice. They also show higher levels of mercury and methylmercury in sushi that contains tuna due to the bioaccumulation and biomagnification of this metal.

The research group also wanted to determine how consumption of this foodstuff varied in different groups of the population. They examined an average intake of 8 pieces of sushi in adults and adolescents and an average intake of 3 pieces in infants and found an increase in exposure to nickel and lead, although this remained within safe established levels.

Finally, the results were analysed as a whole to determine which combinations of sushi do not represent a risk.

The researchers stressed that the amounts of sushi analysed constitute only one of the five recommended meals a day. This means that the consumption of other foods throughout the day may also lead to exposure to certain toxic elements, such as arsenic (present in rice and rice-based foods), mercury (present in tuna and swordfish) or nickel (present in vegetables, pulses and cereals).

Due to its nutritional benefits, the researchers still recommend the consumption of sushi, but they also stress the need to do so in moderation in order to minimise the intake of certain food toxins.

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