Eating Fish Oil With Mercury While Pregnant Can Lead to Infant Deafness, Blindness or Mental Retardation

When a pregnant woman eats a fish-rich diet, the mercury content can reduce the beneficial effects fish oil has on her child's brain development. Babies exposed in the womb to higher methyl mercury levels scored lower on skills tests.

Of five nutrients tested, only the benefits of the fish oil DHA were affected by the mercury. The extent to which methyl mercury interferes with fish oil's brain benefits is uncertain.

Environmental Health News reports:

"The beneficial effects of eating fish during pregnancy on a baby's brain development are relatively well accepted. However, some fish can contain high levels of mercury ... Government agency advisories suggest women of childbearing years eat fish with low mercury levels as well as limit consumption of fish that contain high levels."

Dr. Mercola's Comments:

There is no doubt that omega-3 fats are important for the healthy development and growth of a developing baby.

In fact, omega-3 fat, especially DHA (docosahexaenoic acid), is so essential to a child's development that if you -- and therefore your child -- are deficient in it, your child's nervous system and immune system may never fully develop, and it can cause a lifetime of unexplained emotional, learning and immune system disorders.

In the past, the ideal way to receive these fats was from seafood. However in the last 50 years industrial pollution with chemicals and heavy metals has changed all that.

In fact, babies exposed in the womb to higher levels of mercury, due to their mom's fish-rich diet, scored lower on skills tests when they became infants and toddlers. To put it simply, the beneficial effects of the omega-3s were cancelled out by the mercury.

Fish is Not a Safe Source of Omega-3 Fats Anymore

I rarely eat fish anymore, unless I'm able to verify that it is not contaminated, and based on tests conducted during the past several years, it's clear that finding uncontaminated fish is getting more and more difficult. For example, a study from the U.S. Geological Survey detected mercury in every single fish sample from streams across the United States.

"The Madison Declaration on Mercury Pollution" also declared a general world-wide warning to the public a few years ago to be careful about how much and which fish you eat, stating that increasing mercury concentrations are now being found in a number of fish-eating wildlife species in remote areas of the planet.

It's important to realize that mercury is a neurotoxin that is easily transferred to your child while in the womb. Studies have shown that the level of mercury in the umbilical cord blood of newborns is 1.7 times higher than the mercury level in their mother's blood.

Eating fish just two or more times a week has been found to raise mercury levels seven times beyond those in women who had not eaten any fish for a month, according to the CDC.

If you have high levels of mercury in your system from eating a lot of fish (or from other sources like dental fillings or vaccinations) you could be putting your baby at risk for far more than just canceling out the benefits of omega-3.

If infants or fetuses are exposed to mercury, it can cause:

  • Mental retardation
  • Cerebral palsy
  • Deafness
  • Blindness

There is even a study published in Environmental Health Perspectives showing mercury exposure from fish consumption is positively associated with premature delivery.

This is why, if you are pregnant or planning to become pregnant, it's important to avoid eating fish unless you can verify, via lab testing, that it does not contain mercury. Smaller fish are far less likely to be contaminated, so sardines and other tiny fish would likely be relatively toxin free, while large fish, like tuna, tend to be highly contaminated.

Other fish that tend to contain potentially hazardous levels of mercury include:

If you eat fish caught from local waters, you should view these state-by-state fish advisories from the U.S. EPA before continuing to do so, as many fish caught in U.S. waters are heavily contaminated.

Avoid Fish But Don't Skimp on Your Omega-3s

Again, it is my strong recommendation to avoid eating most fish other than very small fish or those grown in minimally polluted areas like the Arctic, Antarctic or Alaskan waters.

But that doesn't mean you don't need to get your omega-3 fats.

Omega-3s contain a powerhouse of nutrients to ensure that your baby will develop properly and reach its highest potential. These nutrients help to maximize the intelligence of your child, and protect your baby from brain injuries such as autism, pervasive developmental delay, and ADHD.

Studies have shown that sufficient levels of omega-3 fats optimize brain growth in children, especially during the third trimester. DHA makes up 15 percent to 20 percent of the cerebral cortex and 30 percent to 60 percent of the retina so it is absolutely necessary for normal development of the fetus and baby.

Because the fetus depends on the mother's DHA sources, the constant drain on a mother's DHA reserves can easily lead to a deficiency and some researchers believe that preeclampsia (pregnancy-related high blood pressure) and postpartum depression could be linked to a DHA deficiency -- just one more reason why it's so important to maintain your levels during pregnancy.

So what's the best option, if fish are mostly contaminated and eating mercury-contaminated fish will cancel out the benefits of the omega-3 fat anyway?

Choose a safe alternative to fish, and remember it must be an animal-based form of omega-3!

Many insist that omega-3 from plant-based sources (ALA) are interchangeable with animal-based omega-3 (EPA and DHA), but this is simply not the case.

Plant-based omega-3 fats are highly beneficial and should also be consumed, but the evidence is very clear that they are not an acceptable substitute for animal-based omega-3 fats. (This is primarily related to the fact that your body does not easily convert the ALA in plant-based fats to the longer fats of EPA and DHA needed for brain and heart health.)

This leaves marine oils, mainly purified fish oil or krill oil, as alternatives. Personally, I take krill oil every day, and I'm convinced that it's the best option for most people, for several reasons.

  • Omega-3 in krill oil is bound in a phospholipid matrix, making it far more bioavailable than fish oil. In fact, nearly 100 percent of the DHA and EPA in krill oil are immediately available to your body.

    The omega-3 in fish oil, on the other hand, are in a triglyceride molecule that has to be broken down in your gut into its base fatty acids EPA and DHA. Once the fatty acids are absorbed into your bloodstream, your liver then has to attach it to phoshphatidyl choline molecule for it to be used by your body.

    Because of this, your body can only absorb about 15 to 20 percent of it, while the rest is eliminated in your intestine. (This is also what causes so many people to "burp up" the fish oil taste, and not tolerate the fish oil very well.)

  • Krill oil naturally contains the powerful antioxidant astaxanthin, which prevents the perishable DHA and EPA from going rancid. The vast majority of fish oil being sold is actually rancid before you even open the bottle, as it doesn't contain this protective antioxidant, which prevents the DHA and EPA from oxidizing.
  • Krill oil works at a lower dose. For the reasons mentioned above, krill oil is effective at far lower dosages, so you may only need one 500 mg capsule per day.
  • Krill is far more sustainable source of omega-3 fats. Krill are harvested under very strict environmental standards and at the current harvesting rate should easily last hundreds of years while many fish are being farmed out of existence in our generation.

For more in-depth information about the inherent benefits of krill oil over fish oil, please see my recent interview with industry expert Dr. Rudi Moerck, and for more tips on how to make your pregnancy as healthy as possible, read my No-Nonsense Guide to a Naturally Healthy Pregnancy and Baby.