Mercury is known to be highly toxic and has been linked to diseases of the brain, heart, kidneys, lungs, and immune system. It is contained in almost all the fish that we eat, so should we be worried?
Matt Reed gave us some ‘fish for thought’ last week on BBC Radio Gloucestershire in an interview with Faye Hatcher regarding heavy metals in fish. Matt’s main message is that it all depends on the type and quantity of fish we eat.
Whilst all fish has naturally occurring mercury, it is mostly found in trace amounts. Matt told Faye Hatcher and BBC listeners that it is the bigger fish that contain larger amounts of mercury, such as shark, marlin, swordfish, Spanish mackerel and large tuna, that we need to wary of, though not completely avoid. These bigger predatory fish eat the smaller fish, which results in an accumulation of mercury in a process called biomagnification. In other words, mercury concentrations in fishes depend on diet and lifespan: those that consume other fish and live longest have the highest mercury concentrations.
The current advice of the Food Standard Agency (FSA) is that we limit consumption of these large fish to one or two portions a week (depending on the fish). The FSA also advises that we eat at least two portions of fish per week, including one oily fish, to maintain good health. This quota can therefore safely include one portion of a larger fish variety.
It seems therefore that we can continue to enjoy all the fish of our seas and rivers, so long as we are mindful to the type and amount we consume.
One word of warning though. Whilst the amount of mercury we get from food isn’t harmful for most people, fish with higher levels of mercury should be avoided by small children, pregnant women, or women wanting to become pregnant, as mercury could affect the baby’s developing nervous system.
Matt’s interview can still be listened to until 7 June at this link. (Matt’s interview starts at 17.12 mins)
More information can be found on the FSA website.