How Early Should You Avoid High-Mercury Fish Before Pregnancy?

This post was written by Hanro – A guest blogger.

It’s common knowledge that the consumption of high-mercury fish should be minimised during pregnancy. The reason is because of the toxic mercury called methylmercury that bioaccumulates in fish.

Mercury is a natural element found in small quantities throughout nature. But, due to pollution, mercury levels are abnormally high. Also, it seems that the mercury levels are getting worse. The main source being from the outlets of manufacturing plants.

These factories release mercury into the air and it eventually winds up in the ocean. Through bioaccumulation, mercury builds up in the bodies of fish. The higher you go up in the food chain the higher the mercury levels become. Hence why the big fishes like swordfish, marlin, tuna and shark contain the most mercury.

What Are The Risks Of Mercury Poisoning?

Methylmercury is a neurotoxicant, meaning it causes damage in the nervous system. Infants and newborns are more at risk than adults due to their bodies being more vulnerable.


Excess mercury has been associated with the following risks in babies and fetuses:

  • Microcephaly in newborns, which in plain English means brain shrinkage (1)
  • Increased risk of children being born with epilepsy (2)
  • Decreased attention span (3)
  • Development of motor dysfunction, memory loss, learning disabilities as well as depression-like behaviour (4)

How Long Does It Take To Detox From Excess Mercury?

Research studies have found that it can take up to one year to detox 99% of the mercury in our bodies (6). So if you consume fish with high mercury levels, try to avoid consumption one year before pregnancy. This way your body can remove most of the mercury.

If you’re unsure about your mercury levels and you consume a lot of fish, you can do a mercury hair test before considering pregnancy. Talk to your doctor about this as they can assist. It’s a simple test that only requires a hair sample. Hair is used as mercury contaminates the whole body.

Safest Source Of Omega-3

If you’re extremely cautious you may want to consider taking a no-risk approach to consuming your omega-3. Fish is a rich source of omega-3, but studies have found that fish with high mercury levels can negate the benefits of the omega-3.

Not only do they cancel out the benefits, but they seem to exceed it. The effect was a drop of IQ points in young children exposed to high mercury levels. As expected the largest fish had the most damaging effects with an average drop of eleven IQ points (7).

Rich sources of omega-3 are found in some seeds including flax seeds, chia seeds and hemp seeds. One tablespoon of flax or chia and two tablespoons of hemp will give you your daily omega-3 requirements.

Flax seeds

Make sure the flaxseed is ground otherwise it will just go through your body without being absorbed. I like flax as it has a phytonutrient called lignan. This powerful nutrient has been shown to suppress breast cancer cell growth. Additionally, a big handful of walnuts should also supply adequate omega-3.

Be sure you don’t consume too much omega-6 fatty acids. The reason is that they steal the enzymes that your body uses to turn the omega-3 into DHA and EPA. Rich sources of omega-6 to avoid are corn oil, peanut oil, soybean oil, safflower oil, cottonseed oil, sesame, and sunflower oil.


There you have it, ladies. In summary, maximise your intake of omega-3 whilst minimising the intake of mercury. It’s sad to see how we are polluting our environment, especially the ocean.

What we’re not aware of is that in harming the environment we could also be indirectly harming ourselves and potentially our future generation.

What are your thoughts on organic produce, is it too expensive? Let us know in the comments below.


Hanro is one of the top nutritionists in South Africa. He helps women who struggle to lose weight transform their bodies into  the stunning figures they’ve always wanted. This way they have fewer worries and can focus on the things that matter. Be it spending time with family, reading, advancing their career or pursue passionate hobbies like crafts. To learn more you can head to his website: Opposed Nutrition. You can also follow him on Facebook or Twitter.

Facebook Comments

Hi, I’m Shan. I’m an entrepreneur and a sucker for good adventures. I was listed in Forbes Africa 30 under 30 2019 and just recently launched my start-up – MomSays.

Find me on: Web | Twitter | Instagram | Facebook

Leave a Reply

Your email address will not be published. Required fields are marked *