Tonight, we present the third of her reports, focused on the role of dietary omega-3 fats in brain health. This report covers the role of omega-3s in brain function and performance.
We'll publish the second part of her brain research bulletin, focused on mental health, in our next issue.
What’s going on in your head? Fish fat is part of the answer...
First of two reports on brain research presented at the ISSFAL 2010 conference
By Joyce A. Nettleton, D.Sc.
From their influences over the “talk” between neurons (brain cells) to the mental and behavioral conditions they affect, two key kinds of essential polyunsaturated fats—omega-3 and omega-6—are key players in brain function.
We’re talking about omega-6 ARA and omega-3 DHA… both of which are essential for brain structure and function.
But while the body can retain or create enough ARA more easily, omega-3 DHA levels drop fast in the brains of people who do not often consume fish or fish oil (Brenna JT et al., 2007; Chang CY et al. 2009).
A few plant foods such as flax, leafy greens, beans, and walnuts provide small amounts of an omega-3 fat called ALA, but the body can’t use this “short-chain” omega-3... except as fuel.
The body can only convert about two to five percent of dietary ALA into the two long-chain omega-3s it actually needs to survive: the EPA and DHA found in fish fat.
Before we review some of the key findings presented or debated at ISSFAL, we should note that DHA is the dominant fatty acid in the brain by far, and is essential to the structure of brain cells (neurons) and their key functions.
For example, DHA promotes the growth of neurites—branches that extend from neurons to allow communication with other neurons—and the formation of synapses, the points of communication between neurons (Kim HY et al., 2010; Cao D et al. 2009).
Omega-3 DHA also gives rise to cell-stabilizing compounds such as neuroprotectin D1, which reduces the inflammation seen in stroke and neurodegenerative diseases, inhibits cell death, prolongs the survival of brain cells and appears to help deter Alzheimer’s and retinal degeneration (Zhang C et al., 2010).
Fish fat aids brain’s sugary food supply
The brain’s primary fuel is glucose (blood sugar), whose ability to reach the brain is impaired in animals deficient in omega-3s.
Glucose transport can be restored by supplementing animals’ diets with omega-3 EPA or DHA, but not omega-6 ARA (Pifferi F et al., 2007).
Affirming the findings of prior research reported here in Vital Choices, presentation at ISSFAL reported that omega-3 deficient animals had a lower rate of glucose uptake and a slower rate of glucose utilization compared with omega-3-fed animals (Harbeby E et al., 2010).
Accordingly, the authors suggested that impaired glucose metabolism might contribute to cognitive decline in aging.
Long-chain “marine” omega-3s affect mood and cognition
Although omega-3 fatty acids affect brain structure and function, it is a big leap to link omega-3 fatty acid status and mental or cognitive performance.
That said, animal studies have shown that low levels of DHA are associated with neuro-developmental problems such as attention deficit hyperactivity disorder (Levant B et al., 2010a).
Working with rats fed either adequate or deficient levels of omega-3s for two generations, investigators at the University of Kansas Medical Center, Kansas, USA, reported that the omega-3 deficient diet resulted in a 44 percent reduction in brain DHA in the first set of offspring and a 62 percent reduction in the second generation animals (Levant B et al., 2010b).
Compared with the animals fed sufficient omega-3s, the second generation animals had higher levels of activity that persisted into the adolescent period. There was no difference between the groups when each was presented with a novel situation.
The investigators attributed these findings to the reduced accumulation of DHA in brain during development rather than the amount of omega-3 in the diet.
Recent studies in children support some of these observations, but not all behavioral measures have been related to the fatty acids in the participants’ tissues (Gow R et al., 2010; Kirby A et al., 2010).
Seafood-borne omega-3s and brain performance
Hopes have been raised that boosting our consumption of fish or the omega-3s they contain may prevent the decline in cognitive function that often accompanies aging.
Fish fats may not be magic bullets, but there are encouraging indications that demand follow up.
Results to date suggest that selected individuals with mild Alzheimer’s disease may benefit from omega-3s, but firm conclusions remain elusive (Cederholm T and Palmblad J, 2010).
One ISSFAL report observed no link between fatty fish or EPA plus DHA with cognitive performance or wellbeing after 13 to 26 weeks of consuming EPA plus DHA (van de Rest O et al., 2010).
However, EPA plus DHA intake was linked to having an optimistic disposition.
Australian study links omega-3s to better brain performance
Natalie Sinn and her colleagues at the University of South Australia found links between the blood levels of omega-3 and omega-6 fats in older people with mildly impaired cognition (Sinn N et al. 2010).
People 65 years of age or older with mildly impaired cognition had less omega-3 EPA but more omega-6 DPA... a fatty acid usually seen only in people seriously lacking in omega-3s.
Having higher blood levels of omega-6 DPA levels was associated with poorer performance on two verbal tests and auditory learning, while higher blood levels omega-6 ARA were linked to poorer scores on a test of backwards digits.
These observations support the idea that long-chain fatty acids of the omega-3 family may deter age-related loss of cognitive abilities.
Swedish trial finds omega-3s boost vision and decision powers
As reported at ISSFAL, investigators in Sweden conducted a small trial of 28 healthy individuals aged 70 to 82 years to see whether the consumption of long-chain omega-3s affected their cognitive ability (Lindmark L et al., 2010).
The participants consumed 3.2 grams of long-chain omega-3s for four months, after which they showed significant improvement in two tests of cognitive function, one for visual ability and one for executive function. The scores correlated with the participants’ increased in blood omega-3s, but because the supplement contained several other substances besides the omega-3 fatty acids, the findings cannot be attributed only to the omega-3s.
Fishy spread boosts kids' brains
Cognitive improvement in 7- to 9-year-old South African children who consumed a spread containing fish flour was reported last year (see “Fishy Bread-Spread Boosts Kids’ Brains”; Dalton A et al., 2009).
Further analysis of data from the fish-spread study, reported at ISSFAL, showed that cognitive development improved significantly more in children with lower baseline cognitive and spelling scores compared with children whose scores were higher at baseline (Smuts CM et al., 2010).
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Cederholm T, Palmblad J. Are omega-3 fatty acids options for prevention and treatment of cognitive decline and dementia? Curr Opin Clin Nutr Metab Care 2010;13:150-155.
Chang CY, Ke DS, Chen JY. Essential fatty acids and human brain. Acta Neurol Taiwan 2009:18:231-241.
Dalton A, Wolmarans P, Witthuhn RC et al. A randomised control trial in schoolchildren showed improvement in cognitive function after consuming a bread spread, containing fish flour from a marine source. Prostaglandins Leukot Essent Fatty Acids 2009;80:143-149.
Gow RV, Sumich A, Rubia K et al. The relationship between measures of depression, anxiety and anger/disruptive behavior and omega-3/6 fatty acids in adolescents with and without ADHD. Abstract. ISSFAL 2010, Maastricht, Netherlands. P 115.
Harbeby E, Tremblay S, Mercier-Tremblay J et al. Omega-3 fatty acids and brain glucose utilization: an 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) study in the rat. Poster. ISSFAL 2010, Maastricht, Netherlands. P 161.
Hibbeln JR, Lewis M, Johnson J et al. Low omega-3 fatty acid status and increased risk of suicide death among active duty U.S. military: a case control comparison. Poster. ISSFAL 2010, Maastricht, Netherlands. P 192.
Kim HY, Lee J, Cao D, Xiong ZM. Metabolism of docosahexaenoic acid in hippocampal development. Abstract. ISSFAL 2010, Maastricht, Netherlands. P 52.
Kirby A, Woodward A, Jackson S et al. Childrens’ learning and behaviour and the association with cheek cell polyunsaturated fatty acid levels. Res Dev Disabil 2010;31:731-742.
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Levant B, Zarcone TJ, Fowler SC (b). Effects of dietary n-3 fatty acids and brain DHA content on activity and response to novelty in the developing rat. Abstract. ISSFAL 2010, Maastricht, Netherlands. P 114.
Lindmark L, Popova D, Ilieva I et al. Intake of omega-3 correlates with changes in cognitive funcion and levels of eicosapentaenoic acid and omega index in elderly subjects. Poster. ISSFAL 2010, Maastricht, Netherlands. P 185.
Pifferi F, Alessandri JM, Haedke U et al. n-3 Fatty acids modulate brain glucose transport in endothelial cells of the blood-brain barrier.Prostaglandins Leukot Essent Fatty Acids 2007;77:279286.
Sinn N, Milte CM, Coates AM et al. Erythrocyte polyunsaturated fatty acid status and memory, mood and cognition in older adults with mild cognitive impairment and healthy controls. Poster. ISSFAL 2010, Maastricht, Netherlands. P 136.
Smuts CM, Dalton A, Wolmarans PW et al. The effect of omega-3 fatty acid intervention in children with higher compared to lower baseline cognitive scores: a secondary analysis. Poster. ISSFAL 2010, Maastricht, Netherlands. P 216.
Van de Rest O, Geleijnse JM, Kok FJ et al. Fish fatty acids and mental health in older people. Abstract. ISSFAL 2010, Maastricht, Netherlands. P 117.
Zhang C, Bazan NG. Lipid-mediated cell signaling protects against injury and neurodegeneration. J Nutr 2010;140:858-863.