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Do Some Fish Oil Supplements Contain Mercury?

fish oil, supplements, mercury, fishFish oil supplements are increasingly popular, but it has sometimes been suggested that they could also expose you to the harmful pollutants found in some species of fish.

However, studies have found that most of the widely available supplements contain little or no mercury, dioxins or PCBs.

Most companies use species of fish that are lower on the food chain, like cod and sardines, that accumulate less mercury. Many companies also distill their oils to help remove contaminants.

A report by, which conducts independent tests of supplements, examined 41 common fish oil products and found none contaminated with mercury or PCBs. Another report, by researchers at Harvard Medical School and at Massachusetts General Hospital, studied five popular brands of fish oil and found that the brands had “negligible amounts of mercury.”

Dr. Mercola's Comments:

Animal-based omega-3 fats, which come mainly from fish and fish oils, are not regularly consumed in sufficient amounts in the U.S. Omega-6 fats, however, which come from vegetable oils like corn, soy, and canola are severely over-consumed, mainly due to the massive consumption of processed foods.

When omega-6 fats predominate in your diet – as it does for most people – it encourages the production of inflammation in your body.

Since so many diseases have now been linked to chronic inflammation, optimizing your omega 3 to omega 6 ratios is really one of your most important nutrition concerns to get right. 

I used to recommend fish oil for this purpose, but based on the available research, I now believe krill oil is an even better option for most people, which I will expound upon at the end of this article. But first… 

Why Do You Need Plenty of Omega-3 Fats?

Many scientists believe that one major cause behind today's high incidence of heart disease, hypertension, diabetes, obesity, premature aging, and some forms of cancer is the profound imbalance between your intake of omega-6 and omega-3 fats.

Here is just a sampling of omega-3's benefits:

  • Antiarrhythmic: counteracting or preventing cardiac arrhythmia
  • Antithrombotic: tending to prevent thrombosis (a blood clot within a blood vessel)
  • Antiatherosclerotic: preventing fatty deposits and fibrosis of the inner layer of your arteries from forming
  • Anti-inflammatory: counteracting inflammation (heat, pain, swelling, etc.)
  • Improves endothelial function: a major factor in promoting the growth of new blood vessels
  • Lowers blood pressure
  • Lowers triglyceride concentrations

One of the easiest ways to improve your overall health is to shift your ratio by consuming more omega-3 fats -- which actually promote the production of substances that fight inflammation -- while also cutting down on omega-6 fats in vegetable oils.

By far, the best type of omega-3 fats are animal-based omega-3s found in fish. That's because the omega-3 in fish is high in two fatty acids crucial to your health: DHA and EPA. These two fatty acids are pivotal in preventing heart disease, cancer, and many other diseases.

For example, one study called the Diet and Reinfarction Trial, showed a 29 percent reduction in overall mortality rates in survivors of a first acute myocardial infarction who consumed fish rich in omega-3 fats at least twice weekly for two years.

Your brain is also highly dependent on DHA, as low DHA levels have been linked to depression, schizophrenia, memory loss, and a higher risk of developing Alzheimer's. Researchers are now also linking inadequate intake of these omega-3 fats in pregnant women to premature birth and low birth weight, and to hyperactivity in children.

As you likely know, however, eating fish is generally no longer recommended, leaving you with little choice but to take a high quality supplement to ensure you’re getting enough omega-3s in your diet.  

But is Fish Oil Really Your Best Source of Healthy Omega-3 Fats?

Since most all fish is severely contaminated with heavy metals, PCBs and other toxins these days, it stood to reason that fish oil may carry the risk of contamination as well. However, based on the two recent studies above, that does not appear to be a major problem. tested 52 fish oil products and found no evidence of mercury, PCBs or other contaminants typically found in fish. The study published in Archives of Pathology and Laboratory Medicine, however, did find mercury in two of the five brands tested. 

But although mercury contamination turns out to be an insignificant concern when it comes to fish oil, I still believe krill oil is an even better source of omega-3 fats for most people, for a number of reasons. 

Fish oil, although a good source of omega-3 in general, does have certain drawbacks.  

First it’s weak in antioxidant content. This is a concern because as you increase your intake of omega-3 fats by consuming fish oil, you actually increase your need for even more antioxidant protection.

Fish oil is also highly perishable, so antioxidants are necessary to ensure that the fish oil doesn't oxidize and become rancid inside your body (oxidation leads to the formation of unhealthy free radicals).  

Is Fish Oil Sustainable? 

Yes that is the big question mark.  Last month the Canadian Medical Journal published an article which pointed out the obvious.  

The authors stated that if we continue with our current course of fish oil supplementation the world will be depleted of fish in the next 40 years.  In  other words, our current practice is simply not sustainable  The scientists used this as an argument to refrain from using fish oil.  This makes about as much sense as asking people to not drink water as we are running low. 

The key issue is that there are OTHER, more sustainable sources of animal based omega-3 fats, and as a culture we need to recognize that if we fail to make a shift to more sustainable forms of animal based omega-3 fats future generations will have major health dilemmas.  

Healthy Alternatives for Animal Based Omega-3 Fats

Krill oil, on the other hand, is chock-full of natural antioxidants. In fact, research has shown it to be as much as 48 times higher in antioxidants than fish oil. So with krill oil, you can be sure you’re getting these incredibly healthy fats without having to worry about oxidation issues.

Additionally, whereas the DHA and EPA in fish oil are found in the triglyceride form, krill oil supplies them in a double chain phospholipid structure.

What makes this so beneficial is that the fats in your cell walls are in the phospholipid form, so the structure of the EPA and DHA in krill oil makes them much more absorbable. This is particularly beneficial for healthy brain function as your brain is highly dependent on DHA for optimal performance.

I personally take krill oil every day, and it’s one of the very few supplements I recommend to just about everyone.