Fish Oils Help Maintain Brain Power

Omega-3 Fatty Acids for Cognitive Livewires

Fish Oils Help Maintain Brain Power
Omega-3s reduce the risk for cognitive impairment,
as well as protecting against heart disease
By Aaron W. Jensen, Ph.D.

A fishing rod is a stick with a hook at
one end and a fool at the other.

— Samuel Johnson


h, but if the fool does catch a fish and eat it, he’s not such a fool after all. He nourishes not only his body, but also his mind. It’s not for nothing that we call fish “brain food,” and it’s clear that we should be eating more of our finny friends than we do. Despite (or could it be because of?) our phenomenal abundance of good, wholesome, inexpensive food, we are not exactly known for our smart dietary choices. Our favorite vegetables are low-nutrient iceberg lettuce and high-fat French fries; we’re drawn irresistibly to the drive-thru at the local fast-food joint; coffee and doughnuts are a typical answer to the breakfast dilemma; and we’ve elevated the “more-is-better” approach to an art form at the ubiquitous all-you-can-eat buffet.

Surely you’re not surprised, then, that most of us don’t eat the two servings of fish per week recommended by healthcare professionals. There are so many healthful things we should eat, but don’t, it’s enough to drive a person to . . . supplements. Not that supplements are a viable substitute for food (after all, they’re not called substitutes, are they?), but they do help make up for shortcomings in our diet. It’s important to realize, however, that supplements are valuable even with a good diet. Much can be done, especially as we age, to augment the benefits of a good diet with supplemental infusions of nutrients that even good diets provide in suboptimal amounts, or perhaps not at all.

We’re Not Getting Enough Omega-3 Fatty Acids

Let’s get back to fish. Our diet has definitely been improving in this department. For example, the U.S. consumption of salmon increased by 23% annually between 1987 and 1999—an 1100% increase in 12 years.1 That’s good news, because fish—especially coldwater fish, such as salmon, tuna, mackerel, and herring—are rich in certain polyunsaturated fatty acids (PUFAs) that are known to be both heart-healthy and brain-healthy. The most important of these PUFAs are omega-3 fatty acids, and salmon is one of the best dietary sources of “omega-3s,” as well as being loved for its wonderful flavor.

The trouble is, though, we’re still not eating nearly enough coldwater fish, and it’s not likely that we will anytime soon, especially with the recent news of toxin contamination in farmed salmon (see the sidebar “How Safe Is Salmon?”). Thus we’re not likely to get optimal amounts of omega-3 fatty acids unless we supplement with them. Current estimates suggest that Americans consume only 100–200 mg/day of omega-3s from fish.2 That’s far below the 650 mg/day recommended for maintaining good general health, and very far below the 1000–4000 mg/day believed to be required for maintaining healthy blood lipid levels and a healthy cardiovascular system.3

How Safe Is Salmon?

The earth’s oceans are becoming increasingly polluted, and many contaminants and poisons have entered the marine food chain. Apex predators—swordfish and shark, e.g.—tend to “bioaccumulate” certain toxins, such as methylmercury and organochlorine compounds (e.g., DDT, dieldrin, dioxins, and PCBs). We should limit our intake of these unfortunate fish. But what about fish that are somewhat lower in the food chain, such as salmon—how safe are they to eat?

Because salmon feed on algae that are rich sources of omega-3 fatty acids, they are one of the best dietary sources of these beneficial compounds. Depending on where the salmon came from, however, omega-3s may not be the only thing they’re contributing to our diet. A recent paper in Science assessed the contaminants in about 2 metric tons of farmed salmon and wild salmon collected from around the world, and revealed some alarming facts regarding the farmed fish.1 Although there was no difference in methylmercury levels between farmed and wild salmon, the levels of 14 toxic organochlorine compounds were significantly higher in the farmed fish. Moreover, the concentrations of the contaminants in salmon farmed in Europe were much higher than those found in salmon farmed in North or South America.

So the next time you’re in the grocery store shopping for salmon fillets, try to find fish harvested from the wild. That may not be easy, though, as the vast majority of commercial salmon nowadays is farm-raised. Of course, a fish-oil supplement, although not quite as tasty as salmon, is a safe and convenient way to bolster your diet with a daily supply of those heart- and brain-healthy omega-3 fatty acids.

  1. Hites RA, Foran JA, Carpenter DO, Hamilton MC, Knuth BA, Schwager SJ. Global assessment of organic contaminants in farmed salmon. Science 2004;303:226-9.

Omega-3s Are Good for the Heart . . .

One group of people with no such problem are the Inuit—at least those who still live more or less in the traditional way, on a diet rich in coldwater fish (their other traditional staple being seal meat and blubber). It was in the mid-1970s, when researchers observed that native Greenlanders consumed large amounts of fat but had a low risk for heart disease, that the health benefits of omega-3 fatty acids for the heart came to be appreciated (see the sidebar “Omega-3 Fatty Acids and Heart Health”). We now know that those benefits derive primarily from two of the omega-3s, called DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid).

Omega-3 Fatty Acids and Heart Health

Many scientific studies have examined the beneficial effects of omega-3 fatty acids, notably DHA and EPA, on the cardiovascular system. The results reveal that the omega-3s act through a variety of mechanisms. For example, they help to:

  • Regulate heart rhythm
  • Reduce platelet aggregation (which leads to blood clotting)
  • Reduce levels of CRP (C-reactive protein), a marker for inflammation that’s strongly associated with the risk for heart disease
  • Reduce inflammation in blood vessels
  • Improve endothelial (blood-vessel-lining) cell function
  • Reduce the risk for atherosclerosis
  • Increase nitric oxide synthesis (which increases vasodilation)
  • Reduce blood pressure
  • Reduce triglyceride (fat) levels
The combined improvements in these factors may correspond to specific health benefits that decrease the risk for heart disease.1 Fish oils are thus considered highly beneficial in the fight against heart disease, and the American Heart Association makes these recommendations:2
  • Patients with no sign or documentation of coronary heart disease should eat two servings of fish (preferably oily) each week.
  • Patients with documented coronary heart disease are encouraged to consume a minimum of 1 gram of DHA/EPA daily, preferably from oily fish, although supplements may be considered in consultation with a doctor.
  • Patients with documented high triglyceride levels should consume 2–4 grams of DHA/EPA supplements per day under a physician’s care.
  1. Din JN, Newby DE, Flapan AD. Omega-3 fatty acids and cardiovascular disease—fishing for a natural treatment. Br Med J 2004;328:30-5.
  2. Kris-Etherton PM, Harris WS, Appel LJ, for the Nutrition Committee of the American Heart Association. Fish consumption, fish oil, omega-3 fatty acids, and cardiovascular disease. Circulation 2002;106:2747-57.

. . . And for the Brain

Pioneering research in the Netherlands has shown that DHA and EPA are also good for the brain. In the late 1990s, Dutch researchers reported that the amounts and types of lipids (fats and other fatty substances) in our diet have a significant impact on the risk for dementia later in life.4 High intakes of total fat, saturated fat, and cholesterol all increase that risk, with total fat intake being the strongest predictor. The researchers also observed, however, that consuming fatty fish significantly decreases the risk for dementia—Alzheimer’s disease in particular—in older individuals.

The Dutch group recently extended their previous findings by assessing the cognitive abilities of a younger group of individuals.5 The results paralleled their earlier observations and provide compelling evidence that, in middle-aged people, saturated fat and cholesterol are associated with an increased risk for cognitive impairment, while omega-3 fatty acids are associated with a reduced risk.

The study focused on a population aged 45–70 (average age 56). Using standard neuropsychological tests that measure cognitive domains such as memory, cognitive speed, and cognitive flexibility, the researchers evaluated 1613 subjects at the beginning of the study and again about 5 years and 10 years later, to monitor cognitive decline. They assessed each cognitive domain, as well as overall cognitive performance, with respect to each of nine categories of dietary lipids (including “fatty fish” as a category).

Omega-3s Reduce Risk for Cognitive Decline

Overall, two of the nine categories of lipids (saturated fatty acids and cholesterol) apparently increased the risk for cognitive decline; two other categories (fatty fish and combined DHA/EPA) decreased the risk; and the remaining five categories (monounsaturated fatty acids, polyunsaturated fatty acids, alpha-linolenic acid, linoleic acid, and total fat) had no significant effect on cognitive function.* Although the specific results of this study were somewhat erratic and inconsistent, the general conclusions they suggest are in substantial agreement with those of other studies in the same area. The authors summed it up by saying:

The most consistent findings from epidemiologic and clinical studies so far seem to be that cholesterol and (saturated) fat are positively, and fish and marine omega-3 PUFAs inversely, associated with dementia and cognitive impairment.

*There was some overlap in these categories. The PUFA (polyunsaturated fatty acid) category, e.g., encompasses numerous compounds, including four of the ones considered in this study: DHA and EPA, as well as alpha-linolenic acid (which is also an omega-3 fatty acid), and linoleic acid (which is an omega-6 fatty acid). The -3 and -6 designations, by the way, denote an important aspect of the molecular structures of these compounds.


The Dutch study is important because it’s the first of its kind dealing primarily with middle-aged subjects. Middle age is when mild cognitive impairment (MCI) often begins to develop, and because MCI usually (but not always) leads eventually to Alzheimer’s disease later in life . . . well, surely you see the point. Signs of cognitive decline in middle age tend to foretell much more debilitating impairment years or decades down the line. That’s why early intervention, before any obvious signs of cognitive loss appear, may be vital to protect our brain health for the indefinite future.

Omega-3s Are Vital for Healthy Brain Function

That omega-3 fatty acids play an essential role in brain function is not surprising, given the biochemical versatility of these compounds. For example, omega-3s are thought to suppress inflammation in many tissues. This could be particularly important in the brain, as neurons (brain cells) are very delicate and may be susceptible to damage caused by inflammation. Indeed, current neuropathological and epidemiological evidence suggests that inflammatory processes may be a factor in cognitive decline, just as they are in a variety of other serious diseases (see the article on page 21 of this issue).

Omega-3 fatty acids may play other roles in maintaining optimal brain function as well. For example, they may help neurons maintain membrane fluidity and synaptic plasticity, properties that enhance the transmission of signals between adjacent neurons and facilitate cognitive processes. Further evidence that omega-3s are important to long-term brain health is the fact that DHA levels in the brains of Alzheimer’s patients are typically lower than those in age-matched controls of cognitively normal adults.

Exert Control—and Consider Supplements

Besides diet, other factors are involved in the risk for cognitive decline. These include age, gender (being male increases your risk), smoking (which adds the equivalent of 4 years to your cognitive age), education (better education reduces your risk, presumably because you’re smart enough to follow a healthy lifestyle), mental exercise (“use it or lose it”), physical exercise (a fit body increases the likelihood of a fit mind), and cardiovascular fitness (a strong heart helps keep the brain humming). Some of these factors we can control, others we can’t. The important thing is to exert control wherever you can—diet, smoking, mental exercise, physical exercise, and cardiovascular fitness—so as to maximize your chances of remaining a cognitive livewire for the rest of your life.

To help you along the path to optimal brain function, consider the safety, convenience, and reliability of fish-oil supplements. It’s an economical approach to stacking the cognitive odds in your favor and carries with it a wealth of other benefits, especially for your heart. A fool might fail to see the wisdom of this—but you’re no fool!

References

  1. Hites RA, Foran JA, Carpenter DO, Hamilton MC, Knuth BA, Schwager SJ. Global assessment of organic contaminants in farmed salmon. Science 2004;303:226-9.
  2. Kris-Etherton PM, Taylor DS, Yu-Poh S, et al. Polyunsaturated fatty acids in the food chain in the United States. Am J Clin Nutr 2000;71(Suppl):S179-88.
  3. Kris-Etherton PM, Harris WS, Appel LJ, for the Nutrition Committee of the American Heart Association. Fish consumption, fish oil, omega-3 fatty acids, and cardiovascular disease. Circulation 2002;106:2747-57.
  4. Kalmijn S, Launer LJ, Ott A, Witteman JC, Hofman A, Breteler MM. Dietary fat intake and the risk of incident dementia in the Rotterdam Study. Ann Neurol 1997;42(5):776-82.
  5. Kalmijn S, van Boxtel MPJ, Ocké M, Verschuren WMM, Kromhout D, Launer LJ. Dietary intake of fatty acids and fish in relation to cognitive performance at middle age. Neurology 2004;62:275-80.


Dr. Jensen is a cell biologist who has conducted research in England, Germany, and the United States. He has taught college courses in biology and nutrition and has written extensively on medical and scientific topics.

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