The Purported Benefits of Eating Fish


From the landmark Global Burden of Disease study, researchers compiled the top 20 causes of disability and death. Number 1 on the list was high blood pressure, two and 3 had been smoke, and the fourth leading cause of loss of life and wellbeing was not eating enough fruit. Deficiency of exercise was number 10, followed by an excessive amount of sodium, not enough nuts and seeds, not enough whole grains, and then not enough vegetables. Number 18 on the top 20 list was not getting enough long-chain omega-3 fatty acids like DHA and EPA found in fish, because of their supposed protective effect against heart disease. As I talk in my movie Is Fish”Brain Food” for Older Adults? , even years ago when the study was published, researchers were questioning the advantages of those fish fats, as more and more randomized controlled trials put them to the evaluation and they failed, culminating in the meta-analysis I found in my video Is Fish Oil Only Snake Oil? That seemed to put the issue to rest.

Consumption of fish and fish oil wasn’t only hyped for cardiovascular protection, though. Omega-3s have also been touted to cure depression. But after taking into consideration all of the negative effects that went unpublished, there seems to be no advantage for major depression or for preventing suicide, even as I researched in my video Fish Consumption and Suicide.

What about omega-3s for the prevention of cognitive decline or dementia? The accessible randomized controlled trials show no benefit for cognitive function using omega-3 supplementation in studies lasting from 6 to 40 months among healthy elderly adults.

It may sometimes even make matters worse. “Greater current fish consumption predicted worse performance on many cognitive rate constructs. Greater fish ingestion in youth predicted lower perceptual speed and simple/choice reaction time.” This may be due to neurotoxic contaminants, such as mercury, in fish. We’ve known that the developing brain is particularly sensitive to the harmful effects of mercury, but the aging brain is also.

This would explain results which have demonstrated higher omega-3 amounts to be associated with elevated levels of cognitive impairment and dementia. More EPA (eicosapentanoic acid) was found in the cognitively impaired, and also more DHA (docosahexanoic acid) was discovered in the demented, presumably because of pollutants such as mercury and polychlorinated biphenyls (PCBs) in fish which have been related to cognitive impairment and Alzheimer’s disease.

The exact same cognitive”acts interrupted in adults, namely attention, fine-motor function and verbal memory, are very similar to a number of those previously reported in children with prenatal exposures,” which is, exposed in the uterus. And, the adults vulnerable to mercury through fish ingestion didn’t have just delicate EEG brain wave changes, but”visible shortages in neurobehavioral performance steps,” for example poorer performance on tests of fine motor speed and dexterity, as well as concentration, for example. “Some aspects of verbal learning and memory were also disrupted by mercury exposure,” and also the greater the mercury levels, the worse they did.

That study, however, was done downstream of a gold mining operation, which uses a process that uses a great deal of mercury. Other such studies were done on individuals eating fish beside chemical plants or toxic spills, or eating whale meat. What about a more mainstream people? An”elite group of well-educated participants”–many were corporate executives like CEOs and CFOs—-all residing in Florida and rich enough to afford so much fish that 43 percent exceeded the U.S. Environmental Protection Agency’s safety limit for mercury were analyzed. Researchers found that excess seafood intake, which they identified more than three to four servings per month of large-mouth fish like tuna, snapper, and bass, elevates germ amounts and causes cognitive dysfunction, leading to roughly a 5 percent drop in cognitive functionality. This might not seem like much, but it is”a decrement that no one, let alone a health-conscious and achievement-oriented person, is likely to welcome”

“It might be well worth noting the irony in the situation; this is, the very fact that corporate executives who chose to overconsume seafood for health reasons sustained a drop in their executive acts. Yet, in case a 4.8% drop in executive role because of excessive fish ingestion happens in highly functioning, healthy adults having considerable cognitive book, the major concern for additional study is whether similar [mercury] level elevations in individuals already suffering from cognitive reduction may result in substantially greater reductions,” especially with cognitive decline, dementia, and fish consumption on the upswing.

Fruit deficiency is the number-one dietary risk element? For more, see Inhibiting Platelet Aggregation with Berries.

But what about th Inuit? Watch Omega-3s as well as the Eskimo Fish Tale.

For much more on the shift of the evidence on fish and heart disease, visit my Is Fish Oil Just Snake Oil? video.

The greatest threat of mercury exposure may be for children, as I discuss in Mercury vs. Omega-3s for Brain Development and How Long to Detox from Fish Before Pregnancy? .

Other videos on the effect of fish contaminants and wellness among adults include Fish and Diabetes and Fish Presence and Suicide.

Mercury isn’t the sole neurotoxic contaminant of seafood, however.

Michael Greger, M.D.

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