Fish is a mixed bag. It contains high concentrations of protein and other essential nutrients, is low in saturated fat and provides the valuable omega 3 fatty acids, EPA and DHA. There is overwhelming evidence that EPA and DHA contribute to brain and heart health and children’s proper growth and development. That is why fish has been recommended as part of a well balanced diet. Choosing fish over other animal products can be a sensible choice.

Unfortunately, nearly all fish and shellfish contain traces of methylmercury. Mercury accumulates in fish when polluted water is filtered through their gills. The longer a fish lives, the more the mercury accumulates. Large fish eat small fish and accumulate all of the mercury that was in the small fish. This mounts up exponentially. Our tissues also accumulate the mercury of all the fish we eat throughout our lifetimes.

It has been demonstrated that fish contain enough mercury to harm an unborn baby or harm a young child’s developing nervous system. As the recognition that mercury damages the brains of our children has increased over the last two decades, the Environmental Protection Agency has had to lower the “acceptable” level more than once. I have been telling patients for years that if something can damage a fetus and result in childhood learning abnormalities, it can’t be a practice that promotes long-term health and wellness in adults. The developing fetus may be seen as a sensitive indicator of the potential of toxins to cause cellular damage in adults as well.

No fish is completely free of mercury and other pollutants. If you eat fish regularly, your body is undoubtedly high in mercury. I’ve observed that a person’s mercury level correlates exceptionally well with the amount of fish consumed. Individuals eating fish a few times a week have been found to have blood mercury levels exceeding the maximum level recommended by the National Academy of Sciences, which is 5 micrograms. (1,2) Mercury is poisonous to the brain. Every year, more than 300,000 newborns are thought to develop adverse neurodevelopmental effects because of mercury exposure in utero. For women of childbearing age, it is not sufficient to avoid eating fish after becoming pregnant. Fish must be avoided for a few years before conception to guarantee the baby is not harmed by mercury. In later life, high body stores of mercury cause brain damage and memory impairment, leading to dementia. Even the FDA, which normally ignores reports on our dangerous food practices, acknowledges that large fish such as shark, swordfish, and yellowfin and bluefin tuna are potentially dangerous.

Like mercury, other pollutants, including PCBs, accumulate in fish and in the body tissues of people who eat fish regularly. These pollutants can remain in your body for decades, creating a higher risk of serious diseases such as cancer. Fish is one of the most polluted foods we eat. People who would be disgusted at the thought of drinking polluted water don’t think twice about eating polluted fish with 1000 times more pollution in it. In some cases, such as with the PCB’s in Great Lakes trout and salmon, it can be shown that a person would have to drink the lake water for 100 years to accumulate the same quantity of PCB present in a single half pound portion of these fish. (3)

The EPA and DHA fat in fish can have some blood-thinning effects that can counter the pro-inflammatory diet rich in animal products and saturated fat that most people eat. But while fish oil has an anti-clotting effect like aspirin and a beneficial anti-arrhythmic effect that may reduce the risk of heart attack, mercury in fish has the opposite effect- it increases heart attack risk. Eating fish has not shown a consistent ability to decrease heart attack deaths. In fact, scientific studies have shown that those who eat lots of fish have an increased heart attack death rate. The potential benefit from fish’s blood-thinning effects to counter the clot-promoting effects of a diet rich in animal products was offset by the higher exposure to mercury. (3) Another problem with fish is that because fish oils inhibit blood clotting, they increase the likelihood that the delicate vessels in the brain can bleed, causing a hemorrhagic stroke.

Regular consumption of fish or fish oils should be avoided if a person has a family history or is at risk of hemorrhagic stroke or other bleeding disorders. It is important to remember that the best way to prevent a heart attack or stroke is to follow a high nutrient diet with little or no animal products, thereby ensuring that such blockages don’t develop in the first place.

Consumption of all types of fish is also linked to higher breast cancer rates. It may be the pollution in the fish or the cancer-promoting effect from the high level of animal protein.
When 23.963 women were followed as part of the Diet, Cancer, and Health Study, what stood out most was the link between fish consumption and breast cancer. The conclusion of the researchers was “This study showed that higher intakes of fish were significantly associated with higher incidence rates of breast cancer. (4) Women consuming little or no fish were found to have approximately half the incidence of breast cancer compared with high consumers of fish.

The bottom line regarding fish is . . . eat it infrequently or not at all. If you do have fish on occasion, only choose the lowest mercury types such as shrimp, tilapia, haddock, scallops, squid, trout, hake and ocean perch. Never eat the high mercury content fish- swordfish, shark, tuna, snapper, lobster, grouper and sea bass. Be aware of the place where the fish was caught; don’t accept recreational fish from questionable waters.

It is probably safer to avoid fish completely and instead rely on a clean, low dose DHA supplement, such as my DHA Purity or a clean fish-oil supplement taken a few times a week. Since my DHA Purity supplement is not fish-derived, it is entirely vegan and you can be assured of achieving adequate DHA levels without mercury and other pollutants. A small amount of fish oils via supplements is an option, but they should be purchased from a reliably clean source (well-documented), close to the date of manufacturing, and be refrigerated upon receipt.

Keep in mind that DHA fat is not considered an essential fat because the body can manufacture DHA from short chain omega-3 found in greens, flax seeds, hemp seeds, chia seeds and walnuts. The question remains if you do not eat any fish or take any DHA fat can the body can make the ideal amounts of DHA to assure optimal nerve and brain health in later life? Maybe some people can, but there is a percentage of individuals who do not, so I advise my patients not to take chances and take some DHA on a regular basis.

1. Highhtower JM, Moore D. Mercury levels in high-end consumers of fish. Environmental Health Perspectives 2003;111(4):604-608.
2. Mahaffey KR, Clickner RP, Bodurow CC. Blood organic mercury and dietary mercury intake. National Health and Nutrition Examination Survey 1999 and 2000. Environmental Health Perspectives 112(5):562-570.
3. Some fish found to contain high levels of contaminants. 1989. Family Practice News, June 15-30:46.
4. Gellar E, Sans-Gallardo I, Van’s Veer P, et al. Mercury, fish oils, and the risk of myocardial infarction. N Eng J Med 2002; 347:1747-1754.
5. Strip C, Overhand K, Christensen J, et al. Fish intake is positively associated with breast cancer incidence rate. J Nut 2003; 133(11):3664-3669. J Ural 2004 Apr; 171(4):1402-7.
6. Attar-Bash NM; Freeman AG; Sinclair AJ. Alpha-lanoline acid and the risk of prostate cancer. What is the evidence? J Ural 2004;171(4):1402-7.