There’s considerable evidence that the long-chain omega-3s in fish and fish oils can help forestall memory loss in the elderly and even enhance mental acuity in healthy adults as young as 22. (For more on this, visit our Newsletter Archive and use the search term “brain” to capture all of our past articles on this topic.)
But the mechanisms underlying these improvements have not been entirely clear. We know that one of the two major omega-3s in fish oil, called DHA, is essential to optimal brain cell performance, and that fact alone makes fish and fish oil smart things to consume frequently.
- Animal study helps explain how omega-3s protect aging people from memory loss.
- Findings provide important “mechanistic” support for benefits seen in animal, population and clinical studies.
When it comes to potential nutritional interventions for health problems, it is important to know why a dietary factor works, so that we can be sure that it really is responsible for any benefits seen in population or clinical studies.
Earlier this year, a British team published their discovery of a previously unknown way in which omega-3s promote optimal brain function (Dyall SC et al 2006).
Plastic brains: a good thing
To understand the Brit’s brain findings, we need to define a key term. “Neuro-plasticity” refers to the brain’s ability to form new connections (synapses) among its cells (neurons), and thereby adapt to external environments and form new memories.
Human aging is usually accompanied by decreased neuro-plasticity, and this deficit is largely responsible for age-related losses of memory and mental flexibility.
Consequently, our interest was piqued when we stumbled across an obscure study in which researchers at several London-based institutes discovered how omega-3s help preserve neuro-plasticity in the brains of rats.
The UK team knew that brain-cell receptors for a neurotransmitter called glutamate play a significant role in neuro-plasticity. Glutamate is the most common neurotransmitter in the brain, and it is critical to learning and memory formation, in part through its role in regulating neuro-plasticity.
Given the importance of glutamate-receptor function to age-related losses in memory and cognitive capacities, the research team set out to see whether a preparation containing the two key omega-3s (EPA and DHA) would enhance performance of glutamate receptors in three areas of the brains of aged rats: the prefrontal cortex (decisions and impulse control), the hippocampus (memory and spatial navigation) and the striatum (movement and executive functions).
Specifically, they set out to see what effect omega-3s would have on key glutamate-receptor “subunits” called GluR2 and NR2B.
The researchers started by comparing the efficiency of these key glutamate-receptor subunits in young (three to four week-old) adult rats with their performance in elderly (24 to 26 month-old) rats.
As expected, the elderly rats showed age-related deficits in the glutamate-receptor subunits in all three brain structures.
The omega-3 challenge
To test the effects of dietary omega-3s on these key glutamate-receptor subunits, the elderly animals were then divided into two groups:
- Group A received a standard rat diet
- Group B received a diet supplemented for 12 weeks with omega-3s (EPA and DHA, in the ratio found in most fish oils).
As they’d hypothesized, the age-related deficits in the glutamate-receptor subunits were reversed fully in the group fed the omega-3-supplemented chow. In addition, the omega-3 group (B) showed improvements in the phospholipid content of their brains, as well as increases in the DHA content of their brain-cell membranes.
In contrast, the Group A rats showed no improvements.
As the London team said, “This study supports the neuro-protective effect of omega-3 fatty acids in brain aging, and illustrates specific mechanisms underlying this effect.”
This arcane bit of science seems to validate strongly the assumption that omega-3s are indeed responsible for the brain-function improvements seen in animal and human studies.
- Dyall SC, Michael GJ, Whelpton R, Scott AG, Michael-Titus AT. Dietary enrichment with omega-3 polyunsaturated fatty acids reverses age-related decreases in the GluR2 and NR2B glutamate receptor subunits in rat forebrain. Neurobiol Aging. 2006 Feb 23; [Epub ahead of print]
- Bourre JM. Roles of unsaturated fatty acids (especially omega-3 fatty acids) in the brain at various ages and during ageing. J Nutr Health Aging. 2004;8(3):163-74. Review.