Few consequences of aging seem scarier than a shrinking brain.
But brain shrinkage happens to most people … and greater shrinkage is linked to higher risk for Alzheimer's and other forms of dementia.
Earlier, we reported on several studies linking higher blood levels of omega-3s – or regular use fish oil supplements – to better cognitive health and less age-related brain shrinkage.
The long-chain omega-3s also found in seafood – specifically DHA – account for about 40 percent of the fatty acids in the brain, where they play essential structural and functional roles.
(The body can make DHA from plant-source omega-3s, but only very inefficiently. This conversion provides just enough DHA to maintain normal – not necessarily optimal – brain, eye, and immune function.)
DHA is concentrated near the synapses, where critical communications between brain cells (neurons) occurs.
A new study in older women adds more hard evidence that diets rich in seafood-source omega-3s help preserve brain volume and function.
These findings strongly suggest that diets rich in seafood-source omega-3s should help deter or delay dementia.
Fish oil may slow brain shrinkage linked to dementia
The new study involved 1,111 women in the Women's Health Initiative Memory Study, and comes from University of South Dakota scientists.
Each volunteer's omega-3 (EPA and DHA) levels was measured at the outset of the memory study.
Eight years later – when the women's ages averaged 78 – they underwent MRI scans to measure their brain volume.
The women with higher levels of omega-3s had slightly larger brain volumes.
Specifically, the brains of the women whose omega-3 levels measured double the average were 0.7 percent larger than their peers'.
Even more importantly, the brain advantage seen in the women with higher omega-3 levels was greatest in the hippocampus region, which plays key roles in memory formation and recall.
Among the women with higher omega-3 levels, the hippocampus/memory region was 2.7 percent larger than the same brain area in women with lower omega-3 levels. (In Alzheimer's disease, the hippocampus begins to atrophy even before symptoms appear.)
According to lead author James V. Pottala, PhD, "… the results suggest that the effect on brain volume is the equivalent of delaying the normal loss of brain cells that comes with aging by one to two years.” (AAN 2014)
Omega-3s and brain decline: The picture is mostly positive but mixed
The record of research on omega-3s and dementia is mixed, with some positive findings and other studies showing no benefit.
For example, the same University of South Dakota team recently published the results of a six-year study among 2,157 women (Ammann EM et al. 2013).
The women had normal cognitive capacities at the outset, and received annual cognitive tests for a median of 5.9 years.
Their omega-3 (DHA + EPA) blood levels and cognitive capacities were measured at the start of the trial, and annually thereafter for about six years.
After adjusting the results to account for the known effects of various personal characteristics, no significant differences were found between women in the high and low DHA + EPA levels … either at the time of the first annual cognitive tests or over time.
As the authors wrote, "We did not find an association between RBC [red blood cell] DHA + EPA [omega-3] levels and age-associated cognitive decline ...”. (Ammann EM et al. 2013)
But as the authors of a recent evidence review concluded, the overall picture is encouraging (Cederholm T et al. 2013):
Animal studies have been consistently positive, with rodents getting omega-3s over long periods showing three big advantages: 1) less buildup of the amyloid proteins linked to Alzheimer's disease; 2) less brain shrinkage in the hippocampus/memory region; 3) better cognitive performance over time.
Most epidemiological studies have linked higher fish intakes or omega-3 DHA blood levels to reduced rates of age-related cognitive decline.
The results of clinical trials in healthy old people have been mixed. Some small, short-term trials have detected positive effects in older adults who were cognitively healthy or had only mild cognitive impairment at the outset. In others, no advantages seen among the participants taking fish oil vs. placebo capsules.
Omega-3 supplements have not produced significant benefits in people already diagnosed with Alzheimer's disease … though the leading drugs don't help much either.
The negative outcomes of most of the clinical trials published to date may be misleading, because, as the authors pointed out, "the treatment periods may have been too short.” (Cederholm T et al. 2013)
And, given the positive evidence to date, the authors suggest following "the general CDC dietary recommendations of 2-3 fish meals per week or the equivalent intake of long chain omega-3 fatty acids, particularly DHA.” (Cederholm T et al. 2013)
Unsurprisingly, it may well be that omega-3s just can't do it all alone ... as we'll explain.
Omega-3s need help from plant-rich, whole food diets
The apparent anti-dementia effect of omega-3s varies greatly, based the presence or absence of a gene variation called ApoE4, which is linked strongly to increased risk for Alzheimer's and heart disease.
Omega-3s seem to bring more benefit in people who don't carry the ApoE4 gene variation (Huang TL et al. 2005; Whalley LJ et al. 2008).
But diets rich in omega-3 DHA may bring serious brain benefits to ApoE4 carriers who also cut back on sugars, starches, and omega-6 fatty acids (from cheap vegetable oils) and get plenty of antioxidant-rich vegetables and fruits (Henderson ST et al. 2004; Florent-Béchard S et al. 2007; Johnson EJ et al. 2008).
The standard American diet suffers from a pro-inflammatory excess of omega-6 fats from cheap vegtable oils (corn, soy, cottonseed, sunfloer, safflower).
In combination with sugars, refined starches, and sedentary lifestyles, this omega-6 overload raises the risk of obesity, diabetes and heart disease, which are major risk factors for cognitive decline and Alzheimer's disease … particularly in people carrying the ApoE4 variation.
Thus, to get maxiumum brain benefits from seafood-source omega-3s, everyone – especially ApoE4 carriers – must cut back on refined carbs and omega-6 fats, eat ample amounts of whole, antioxidant-rich plant foods, and get active!
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