by Craig Weatherby
Annually, some 750,000 Americans suffer a stroke and about 160,000 die from it.
Stroke is the third leading cause of death in the U.S. and the leading cause of adult disability, whose estimated societal price tag is a staggering $74 billion per year.
The most common kind by far are ischemic (iss-keem-ik) strokes, which doctors sometimes call “brain attacks” … because, like heart attacks, they result when inflamed plaque in an artery ruptures and constricts blood flow.
Population studies suggest that the risk of ischemic stroke is reduced by one-quarter or more among people who eat fish frequently (Bouzan C et al. 2005; Mozaffarian D et al. 2005; Psota TL et al. 2006).
And fish may help protect people from “silent” strokes, which damage minuscule areas of brain tissue (Virtanen JK et al. 2008). While they produce no immediate symptoms, the cumulative damage from serial silent strokes can degrade brain function.
(For more on this topic, see “Stroke: An Update on Fish and other Factors” and “Fish May Reduce Rates of ‘Silent’ Stroke”.)
Population studies cannot prove a cause-effect relationship between higher intake of a food and a reduced risk of a disease, and clinical trials are needed.
Until we have evidence from clinical trials, we must rely on animal studies to see whether any immediate post-stroke treatments can blunt the brain damage caused so quickly by ischemic strokes.
Before examining the exciting new findings from LSU, let’s review the currently approved therapeutic options for ischemic stroke.
Treatment options are limited… and the window is narrow
Much of the damage caused by an ischemic stroke occurs in the first few hours.
Injection of a clot-busting (thrombolytic) drug into the veins may increase the chances of a full recovery compared with other treatment methods. The leading choices are anti-platelet drugs, anticoagulant drugs, and tissue plasminogen activator (TPA).
Therapy with clot-busting drugs must begin within three hours of the stroke’s occurrence. After that, the risks of bleeding or other complications begin to outweigh potential benefits.
So-called “neuroprotective” drugs are the newest research frontier in rapid stroke treatments designed to minimize brain damage …and omega-3 DHA falls into this category.
During and after an ischemic stroke, a series of chemical and electrical processes leads to the death of nerve cells …and the search for agents that can interrupt this damaging cascade is an urgent one.
Like thrombolytic drugs, neuroprotective agents must be administered within a few hours after a stroke.
LSU team documents even greater brain-guarding benefits of DHA
Omega-3 DHA is essential to brain cell structure and functions, and constitutes some 60 percent of the fat in human brains …and it’s needed to end runaway inflammation, which produces some of the damage initiated by ischemic strokes.
Starting in 2005, a team led by Professor Nicolas Bazan, M.D., Ph.D., of Louisiana State University published two experiments in which rats suffered much less stroke-related brain damage when given small doses of DHA within three hours (Belayev L et al. 2005; Belayev L et al. 2009).
Now, in an encouraging development, rats given omega-3 DHA within five hours after undergoing an induced stroke suffered much less brain damage, compared with rats that did not get DHA beforehand.
The LSU research team administered either DHA or saline intravenously to rats at three, four, five, or six hours after the onset of stroke.
Their findings confirm DHA’s protective potential, show that it persists when treatment is delayed by five hours, and demonstrate that DHA may reverse some stroke-induced brain damage (Belayev L et al. 2010).
They also subjected the rats to MRI scans, which showed substantially less stroke-induced neurological deficits in the group given DHA, which also enjoyed reduced brain swelling and faster, fuller recoveries.
Further, DHA reduced the volume of destroyed tissue. Oddly, the reduction in damage was actually greater when the DHA was given five hours after the stroke, versus only three hours afterwards.
The damaged area was reduced by an average of 40 percent when DHA was administered at three hours, by 66 percent when DHA was given at the four hour point, and by 59 percent when rats received DHA five hours after their stroke.
And the LSU team found at least one reason for DHA’s apparent post-stroke benefits, which is that this brainy omega-3 fat triggered production of Neuroprotectin D1 (NPD1) …a naturally occurring neuroprotective molecule derived from DHA.
Not only did treatment with it save brain tissue that would have died, DHA treatment rendered some areas indistinguishable from normal tissue within seven days.
As Dr. Bazan said in a press release, “We are just now beginning to understand the significant impact of omega-3 essential fatty acids on stroke. There is no simple solution just yet, but each new discovery brings us closer to defeating stroke and other debilitating neurodegenerative diseases” (LSU 2010).
Belayev L et al. Docosahexaenoic acid therapy of experimental ischemic stroke. Transl Stroke Res. 2010; DOI: 10.1007/s12975-010-0046-0
Belayev L, Khoutorova L, Atkins KD, Bazan NG. Robust docosahexaenoic acid-mediated neuroprotection in a rat model of transient, focal cerebral ischemia. Stroke. 2009 Sep;40(9):3121-6. Epub 2009 Jun 18.
Belayev L, Marcheselli VL, Khoutorova L, Rodriguez de Turco EB, Busto R, Ginsberg MD, Bazan NG. Docosahexaenoic acid complexed to albumin elicits high-grade ischemic neuroprotection. Stroke. 2005 Jan;36(1):118-23. Epub 2004 Nov 29.
Bouzan C, Cohen JT, Connor WE, Kris-Etherton PM, Gray GM, König A, Lawrence RS, Savitz DA, Teutsch SM. A quantitative analysis of fish consumption and stroke risk. Am J Prev Med. 2005 Nov;29(4):347-52.
Louisiana State University (LSU). Research shows fish oil component given up to 5 hours after stroke limits brain damage. November 8, 2010. Accessed at http://www.eurekalert.org/pub_releases/2010-11/lsuh-lrs110810.php
Mozaffarian D, Longstreth WT Jr, Lemaitre RN, Manolio TA, Kuller LH, Burke GL, Siscovick DS. Fish consumption and stroke risk in elderly individuals: the cardiovascular health study. Arch Intern Med. 2005 Jan 24;165(2):200-6. Erratum in: Arch Intern Med. 2005 Mar 28;165(6):683.
Psota TL, Gebauer SK, Kris-Etherton P. Dietary omega-3 fatty acid intake and cardiovascular risk. Am J Cardiol. 2006 Aug 21;98(4A):3i-18i. Epub 2006 May 30. Review.
Virtanen JK, Siscovick DS, Longstreth WT Jr, Kuller LH, Mozaffarian D. Fish consumption and risk of subclinical brain abnormalities on MRI in older adults. Neurology. 2008 Aug 5;71(6):439-46.