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Food, Health, and Eco-news
Fish Fats Boost Brain Resilience; Fast Food Diet Deepens Brain Damage
Omega-3s and exercise boost rat brains' growth and plasticity; "fast-food" diet exacerbates brain injuries
by Craig Weatherby

Omega-3 fish fats play key roles in brain function, as seen in cell, animal, and human studies. For more on this, see the related links at the end of this article.

And of the two omega-3s essential to human health and survival—DHA and EPA—only DHA is deemed critical to brain development, overall brain functions, learning, memory, and mood.

The omega-3s in brain cell (neuron) membranes are critical to brain “plasticity”: the term brain researchers use to describe the capacity for healthy brains to grow new tissue and neuron-to-neuron connections.

Key Points
  • Omega-3s and exercise independently enhanced brain resilience and learning in rats.
  • Omega-3 DHA boosted brain levels of beneficial, pro-plasticity agents in part by reducing oxidation damage.
  • Simulated fast-food diets rendered rats more susceptible to brain injury.
  • Vitamin E reduced the ill effects of simulated fast-food diets.
This continuous process of growing new neurons and making connections among them is essential to learning, movement, orientation, memory, and recall.

Fish and algae are the only food sources of these long-chain omega-3s, which the body can also produce—very inefficiently—from the plant-source omega-3 called ALA.

For several years, scientists from the University of California at Los Angeles (UCLA) have been probing the effects of various dietary fats in the brains of rats, to see what happens to the organ's “plasticity” under varying conditions.

A summary report of their first study, published four years ago, begins by stating the known benefits of omega-3 DHA in brain cell membranes:

Omega-3 fatty acids (i.e., docosahexaenoic acid; DHA) regulate signal transduction and gene expression, and protect neurons from death” (Wu A et al. 2004).

This initial study examined the ability of omega-3 DHA to help rats' brains cope with the effects of traumatic injury.

Evidence shows that repeated concussions, particularly in athletes, can lead to early-onset dementia and similar disorders. With at least three concussions, the risk of early-onset Alzheimer's disease increases fivefold (Cantu RC 2007).

Significantly, the brain changes induced by concussions overlap key changes seen in people suffering from Alzheimer's and other forms of dementia.

And if the results of recent rat studies can be replicated in humans, then omega-3s and dietary antioxidants like vitamin E may prove useful in helping to prevent or substantially reduce the brain-damaging effects of concussions … and possibly the similar chemical changes seen in dementia patients' brains.

First study finds omega-3 DHA protects against concussive injury
For their initial study, the UCLA team divided lab rats into two groups (Wu A et al. 2004):

  • Standard “rat chow” diet.
  • Standard “rat chow” diet plus added omega-3 DHA.
Each group was fed their diet for four weeks before receiving a “fluid percussion injury” (FPI) to the brain, which produces damage like that seen in concussion and dementia patients alike.

The FPI increased oxidative stress in the rats' brains, impaired their learning ability (in a maze), and reduced levels of the key chemicals required to enhance and maintain brain plasticity.

But the UCLA team found that DHA protected the rodents' brains from the ill effects of mild concussion-like injury (Wu A et al. 2004):
  • “Supplementation of omega-3 fatty acids in the diet counteracted all of the studied effects of FPI, that is, normalized levels of … [pro-plasticity agents] …, reduced oxidative damage, and counteracted learning disability.
  • “These results imply that omega-3 enriched dietary supplements can provide protection against reduced plasticity and impaired learning ability after traumatic brain injury.”
Omega-3s and exercise show independent brain benefits
Extensive research shows that exercise brings substantial benefits for the brain as well the rest of the body.

Exercise not only improves cognitive function in normal individuals, but it has been associated with a lower risk for AD and other types of dementia. And in Alzheimer's patients, one of the most important effects of exercise is improved cognition.

Studies in animal models also suggest that exercise might attenuate some of the cognitive symptoms and brain changes characteristic of dementia.

Recent research has sought to identify molecular and cellular changes in the central nervous system elicited by exercise.

Animal studies have identified several key responses to exercise, including “up-regulation” of growth factors, increased renewal of neuronal (brain) tissue, and improved learning and memory (Dishman RK et al. 2006; Cotman CW et al. 2002).

In their latest study, the UCLA team fed rats a standard lab-rodent chow, but added enough omega-3 DHA to equal 1.25 percent of their daily calorie intake (Wu A et al. 2008).

The rats were then divided into two groups:
  • Exercise Group—Allowed to exercise vigorously (e.g., a wheel in the cage)
  • Non-Exercise Group—No easy way to exercise (e.g., no wheel in the cage)
The researchers tested the rats after 12 days and found that, compared to rats fed regular chow, all of the DHA-supplemented rats showed significantly increased spatial learning ability, with even greater enhancements seen in the exercising group.

On a cellular level, the DHA-enriched diet increased levels of six beneficial chemicals:
  • BDNF (Brain-derived neurotrophic factor)
  • Mature BDNF
  • CREB (cAMP responsive element-binding protein)
  • Synapsin I
  • Hippocampal Akt
  • Hippocampal CaMKII
Importantly, exercise increased levels of these beneficial factors even higher.

These key brain chemicals help create new connections between brain cells, grow new brain cells, and enhance overall the brain plasticity needed for memory and learning.

The DHA diet also lowered levels of oxidized (damaged) proteins in the brain's memory center, called the hippocampus.

And the combination of supplemental omega-3 DHA and exercise resulted in greater reductions in oxidized (damaged) hippocampal proteins.

As the UCLA group wrote, “These results indicate that the [omega-3] DHA diet enhanced the effects of exercise on cognition and … synaptic plasticity, a capacity that may be used to promote mental health and reduce risk of neurological disorders”. (Wu A et al. 2008)

Fast-food diets blunts rats' brains; vitamin E reduces ill effects
In 2004 and 2005, the same UCLA team published the results of studies in which they fed lab rats either a simulated fast-food diet high in sugars and saturated fat, or a simulated fast-food diet supplemented with vitamin E.

The simulated fast-food diet lacked fruits, nuts, seeds, and vegetables… and the food factors essential to brain function and maintenance, such as antioxidants and essential fats (omega-3s and omega-6s).

This unbalanced fast-food diet was designed to mimic typical fast-food meals, and the effects were as negative as one might expect.

Rats were fed a simulated fast-food diet for four weeks before being subjected to a mild “fluid percussion injury” (FPI) or sham brain surgery.

The researchers reported that fluid percussion brain injury impaired the rats' spatial learning capacity during a maze-navigation test, and that these deleterious impacts were aggravated in rats given the fast-food diet.

In addition, the combination of mild brain insults and a fast-food diet reduced brain levels of two key chemicals involved in brain plasticity: synapsin I and CREB.

As the UCLA scientists wrote, “The results suggest that [brain injury] and [fast food] diet[s] impose a risk factor to the molecular machinery in charge of maintaining neuronal [brain] function ...”

Unsurprisingly, given the nutrient's antioxidant capacities, the addition of vitamin E to the rats' simulated fast-food diet reduced brain oxidation levels, which protected brain plasticity and functions by blocking oxidation-related reductions in the pro-plasticity agents listed above (e.g., BDNF, CREB, Synapsin 1).

The brain changes produced in the lab rats by mild, artificially induced brain injury are similar to those seen in the aging human brain, so it seems reasonable to suggest that exercise and diets high in omega-3s would help maintain brain plasticity.

What is the equivalent omega-3 DHA dose for people?
How much fish oil would you need to take to equal, proportionately, the amount of DHA fed to the rats in these studies?

In fact, the daily dose of DHA taken over a short term is probably irrelevant. What matters is reaching an optimal level of DHA in brain cell membranes, by taking an adequate amount of fish oil—say, 3,000 mg per day—consistently.

But the answer is 15 to 40 capsules (1,000mg), calculated as follows:
  • The rats ate an amount of DHA equal to 1.25 percent of their daily calorie intake.
  • The average American consumes about 2,000 calories per day.
  • Three 1000 mg fish oil capsules contain about 30 calories, which is 1.5 percent of 2,000 calories.
  • Since fish oil ranges from seven to 20 percent DHA, you'd need to take 15 to 40 average fish oil capsules a day to approximate the 1.25 percent of daily calories that DHA constituted in the lab rats' temporary diets.
Instead, we advise you to stick to a normal, recommended daily dose of fish oil (about 3,000 mg), which should be just as effective at raising DHA levels in your brain cells after a few weeks or months.

  • Cantu RC. Chronic traumatic encephalopathy in the National Football League. Neurosurgery. 2007 Aug;61(2):223-5. Review.
  • Cotman CW, Engesser-Cesar C. Exercise enhances and protects brain function. Exerc Sport Sci Rev. 2002 Apr;30(2):75-9. Review.
  • Dishman RK, Berthoud HR, Booth FW, Cotman CW, Edgerton VR, Fleshner MR, Gandevia SC, Gomez-Pinilla F, Greenwood BN, Hillman CH, Kramer AF, Levin BE, Moran TH, Russo-Neustadt AA, Salamone JD, Van Hoomissen JD, Wade CE, York DA, Zigmond MJ. Neurobiology of exercise. Obesity (Silver Spring). 2006 Mar;14(3):345-56. Review.
  • Wu A, Ying Z, Gomez-Pinilla F. Docosahexaenoic acid dietary supplementation enhances the effects of exercise on synaptic plasticity and cognition. Neuroscience. 2008 Aug 26;155(3):751-9. Epub 2008 Jun 17.
  • Wu A, Ying Z, Gomez-Pinilla F. Dietary omega-3 fatty acids normalize BDNF levels, reduce oxidative damage, and counteract learning disability after traumatic brain injury in rats. J Neurotrauma. 2004 Oct;21(10):1457-67.
  • Wu A, Ying Z, Gomez-Pinilla F. The interplay between oxidative stress and brain-derived neurotrophic factor modulates the outcome of a saturated fat diet on synaptic plasticity and cognition. Eur J Neurosci. 2004 Apr;19(7):1699-707.
  • Wu A, Molteni R, Ying Z, Gomez-Pinilla F. A saturated-fat diet aggravates the outcome of traumatic brain injury on hippocampal plasticity and cognitive function by reducing brain-derived neurotrophic factor. Neuroscience. 2003;119(2):365-75.