Fishing around for mercury

Article by: Cynthia Xu, Accredited Practising Dietitian

A few individuals I know have a fear around eating fish due to the mercury content in seafood. While that fear is valid, it does not mean there needs to be a complete avoidance of fish. A bit of understanding of mercury accumulation in food helps to go a long way.

Where does the mercury come from?

Mercury occurs naturally in the environment and accumulates in the aquatic food chain, including all fish. So it is true that fish is the main source of mercury in the diet for most people. However, this doesn’t mean it’s time to worry. The level of mercury in most fish is very low and as we only consume moderate amounts of fish, the benefits of eating fish (hooray for heart healthy omega-3 fatty acids) far outweigh the risk posed by the small amount of mercury present.

The mercury food chain

The natural aquatic hierarchy determined the mercury content of the fish. That means the longer living predatorial head honchos such as the shark, marlin and swordfish tend to accumulate higher levels of mercury (through eating those lower down the chain).  The mercury content is also affected by the environment in which they fish thrive, so in some countries the mercury content in fish can be higher.

Who needs to be careful?

High levels of mercury can affect the young developing brain. Therefore the unborn baby (pregnant women and those planning pregnancy) and young children are those who need to be the most aware of mercury consumption as they are most vulnerable to its harmful effects.

How much to eat?

Pregnant women and women planning pregnancy:           1 serve = 150 grams

Children (up to 6 years of age):                                            1 serve = 75 grams

• 2 – 3 serves per week of any fish and seafood not listed below

…or…

• 1 serve/week of Orange Roughy (Deep Sea Perch) or Catfish & no other fish that week

…or…

• 1 serve / fortnight of shark, swordfish or marlin and no other fish that fortnight

Rest of the population:                                                          1 serve = 150 grams

• 2 – 3 serves per week of any fish and seafood not listed below

…or…

• 1 serve per week of shark, swordfish or marlin and no other fish that week

What do the serves look like?

150g serve = E.g. 2 frozen crumbed fish portions, 1 fillet of fish

75g serve = E.g. 3 fish fingers, 1 frozen crumbed fish portion, ½ filler of fish, 1 tuna snack can

Tags: fish, mercury poisoning, Omega 3