Fish and Mercury

What is Mercury in Fish?

Mercury is a toxic metal that pollutes the environment, mainly from burning fossil fuels. It settles in water and soil, becoming part of the food chain. Small fish eat microorganisms contaminated with mercury, then bigger fish eat these fish – resulting in a build up of mercury. The bigger, older and more predatory the fish, the more mercury it contains. The form of mercury in fish is called methylmercury, and it can accumulate over time.

Why is Mercury in Fish a Concern for Babies?

Methylmercury is harmful, especially for babies and young children.

Methylmercury has toxic properties and can severely affect unborn babies and infants.^1,2,3 This is because their brain, nervous system, and organs are still developing. Long-term exposure can lead to neurological issues like delayed motor skills, memory problems, and learning difficulties.

But don’t worry—by choosing low-mercury fish, you can protect your baby while still providing essential nutrients like omega-3 fatty acids, protein, and iodine from fish.

Which Fish is Safe for Babies?

All low mercury fish are safe for babies. We recommend prioritising low mercury fish that are also rich in omega-3 fats. These include:

• Salmon
• Atlantic mackerel (the type commonly used in canned mackerel)
• Sardines
• Trout
• Herring

Other low-mercury fish include:

• Snapper
• Cod (hake, hoki, or blue grenadier)
• Whiting
• Prawns
• Tinned tuna (small species, like skipjack)

Fish to Avoid for Babies

Large predatory fish tend to have high mercury levels. Avoid giving these to babies or limit intake:

• Shark (flake)
• Swordfish
• Barramundi
• Bigeye tuna (commonly found in sushi)

If your baby eats one of these high-mercury fish occasionally, avoid giving them any more fish for the next two weeks. This is the advice from the Food Standards Australia New Zealand (FSANZ).⁴

How Much Fish Should Babies Eat?

There is no specific recommendation for babies, however FSANZ recommends that all population groups consume 2-3 portions of low mercury fish a week.⁵ For adults, a portion is 150 g, and for children a portion is 75 g (children < 6 years). We recommend offering a 50 g portion of low mercury fish 2-3 times/week to a child < 2 years old.

Is Canned Tuna Safe for Babies?

Yes! Canned tuna has lower levels of mercury than other tuna because the tuna used for canning are smaller species that are generally caught when the fish are young. This advice varies internationally due to the different species of tuna used in canning. Tuna sold in Australian supermarkets is well regulated.⁶ According to FSANZ, “It is safe for everyone (including pregnant women and children) to consume canned tuna as part of their fish intake.”⁷

Offer tuna in 50g servings, however prioritise other low-mercury fish like salmon or sardines, which have more omega-3s.

Mercury in Fish and Breastfeeding

Though methylmercury can pass into breast milk, the small amount is not harmful. The benefits of breastfeeding far outweigh the risks. Stick to the recommendation of 2-3 servings of low-mercury fish per week, just like during pregnancy.

For more guidance on what to eat during pregnancy and postpartum, check out our book Nurture the Seed.

Does Cooking Fish Reduce Mercury?

No, unfortunately cooking, freezing, or canning fish won’t reduce its mercury content.

Nutritious Fish Recipes for Babies

Looking for delicious ways to prepare fish for your baby? Try these easy recipes:

• Fish & Rice Cakes
• Sardine Fritters
• Mackerel Pate

References:

1. Mergler D, Anderson HA, Chan LH, Mahaffey KR, Murray M, Sakamoto M, Stern AH; Panel on Health Risks and Toxicological Effects of Methylmercury. Methylmercury exposure and health effects in humans: a worldwide concern. Ambio. 2007 Feb;36(1):3-11. doi: 10.1579/0044-7447(2007)36[3:meahei]2.0.co;2. PMID: 17408186.

2. Bose-O’Reilly S, McCarty KM, Steckling N, Lettmeier B. Mercury exposure and children’s health. Curr Probl Pediatr Adolesc Health Care. 2010 Sep;40(8):186-215. doi: 10.1016/j.cppeds.2010.07.002. PMID: 20816346; PMCID: PMC3096006.

3. Grandjean P. Methylmercury toxicity and functional programming. Reprod Toxicol. 2007 Apr-May;23(3):414-20. doi: 10.1016/j.reprotox.2007.03.002. Epub 2007 Mar 12. PMID: 17408921.

4. Food Standards Australia New Zealand, Mercury in fish, foodstandards.gov.au, 2020, accessed on 9th July 2023.

5. Food Standards Australia New Zealand, Mercury in fish, foodstandards.gov.au, 2020, accessed on 9th July 2023.

6. John Sumner and Cath McLeod, Seafood Consumption in Australia: Risks and Benefits, June 2015, Australian Government: Fisheries Research and Development Corporation.

7. Food Standards Australia New Zealand, Mercury in fish, foodstandards.gov.au, 2020, accessed on 9th July 2023.