Nearly a decade ago, scientists at the U.S. National Eye Institute (NEI) cited “consistent evidence” that diets rich in omega-3s from fish protect the eyes.
One of the two omega-3s in fish fat – called DHA – is an essential component of the eye’s critical retinal cells, and exerts beneficial anti-inflammatory/anti-oxidant influences on their genes.
Unsurprisingly, it’s been proven that a shortage of retinal DHA – which can result from a diet low in omega-3s – reduces visual acuity.
The NEI researchers based their judgment on DHA’s known role in the retina’s structure and functions, and on evidence from lab and epidemiological (non-clinical) population studies.
A blinding threat on the rise: Can omega-3s help?
Age-related macular degeneration (AMD), which impairs vision in the center of the visual field, is the main cause of blindness in people over 50.
Rates of AMD are projected to increase 50 percent by the year 2020 … so we urgently need new ways to prevent and treat the blinding disease.
In the nine years since NEI scientists noted the role of omega-3s in retinal health, evidence detailing these fats’ effects – and linking fishy diets to lower risk of AMD – has continued to accumulate.
For example, see “New Eye Benefit Seen in Omega-3s”, “Omega-3s’ Eye-Protection Powers Affirmed”, “Women's Eye Health Linked to Omega-3 Intake”, and other reports in the Omega-3s & Eye Health section of our news archive.
However, it takes more than statistical links between a diets rich in a given nutrient and lower rates of a disease to prove that the nutrient exerts a substantial preventive or curative effect.
And we still lack evidence from large, lengthy, well-controlled clinical trials … the kind needed to prove that seafood-source omega-3s can really prevent or treat AMD.
Both of the major omega-3s in fish fat (EPA and DHA) appear to protect the retina – and may help prevent AMD – by suppressing three harmful processes:
- Inflammation Leaking from blood vessels
- Overgrowth of blood vessels
- Buildup of a substance called lipofuscin
Now, a mouse study takes another big step toward understanding exactly how seafood-source omega-3s … and lends more weight to the idea that fish fats protect against AMD.
Importantly, the new findings may enable development of omega-3-derived drugs for AMD treatment or prevention … agents much more potent than the fish fats themselves.
Harvard study sees potential for potent omega-3-based drugs
Earlier this month, Boston-based researchers reported that substances mice made internally from dietary omega-3s reduced blood vessel overgrowth and blood vessel leakage in powerful ways.
The new study was conducted by scientists from the Massachusetts Eye and Ear Institute, Harvard Medical School, and other institutions.
And the researchers are confident that the results will apply to people as well, thanks to relevant similarities between the eyes and metabolisms of mice and men.
As lead author Kip Connor, Ph.D., said, their findings “not only show promising therapeutic potential for resolution of AMD, but also for other conditions or diseases that involve pathologic angiogenesis [blood vessel overgrowth] and inflammation.” (MEE 2014)
To test the effect of fatty acids on blood vessel overgrowth, researchers fed mice one of three diets beginning two weeks before they induced the condition using lasers:
- Omega-3 enriched
- Omega-6 enriched
- No omega fatty acids (control diet)
Encouragingly, retinal lesions and vascular leakage were significantly reduced in the animals on the omega-3 enriched diet.
Further, the laser-damaged retinas of mice on the omega-3 diet didn’t draw the kind of harmful immune-system overreaction normally seen in AMD, “thereby suppressing inflammation that is thought to exacerbate this disease”. (MEE 2014)
To understand why omega-3s brought these benefits, and to identify possible drug candidates, the researchers looked for helpful “metabolites” (metabolic breakdown products) produced by the animals from the dietary omega-3s.
The Boston team hit pay dirt when they found the metabolites directly responsible for the retina-protecting effects of dietary omega-3s.
Specifically, the protective effects of omega-3s were actually exerted by immune-system “messenger” chemicals called eicosanoids.
These powerfully eye-protective eicosanoids are made from dietary omega-3s, via a major metabolic pathway called cytochrome P450.
As the researchers’ press release noted, their findings “show promising therapeutic potential [for omega-3 metabolites] in AMD disease resolution.” (MEE 2014)
In fact, as Dr. Connor said, “Given the prevalence of neovascular eye disease, the potential impact of this study is highly significant. It is our hope that future studies will allow us to develop specific therapeutics that harness this knowledge resulting in a greater visual outcome and quality of life for patients suffering from these sight threatening diseases.” (MEE 2014)
Keep your fingers (not your eyes) crossed for new omega-3-based drugs for AMD.
In the meantime, it seems very wise to keep your eyes well-supplied with fish and/or omega-3 fish oil.
- [Age-Related Eye Disease Study Research Group]. The Relationship of Dietary Lipid Intake and Age-Related Macular Degeneration in a Case-Control Study: AREDS Report No. 20. Arch Ophthalmol 2007 May;125(5):671-9.
- Children's Hospital Boston (CHB). Can blindness be prevented through diet? Increasing omega-3 intake in mice reduces damaging vessel growth in the eye. June 24, 2007. Accessed at http://www.childrenshospital.org/newsroom /Site1339/mainpageS1339P1sublevel309.html
- Children's Hospital Boston (CHB). Omega 3's – more evidence for their benefit. Feb. 9, 2011. Accessed at http://www.eurekalert.org/pub_ releases /2011-02/chb-o3020411.php
- Chong EW, Kreis AJ, Wong TY, Simpson JA, Guymer RH. Dietary omega-3 fatty acid and fish intake in the primary prevention of age-related macular degeneration: a systematic review and meta-analysis. Arch Ophthalmol. 2008 Jun;126(6):826-33.
- Massachusetts Eye and Ear (MEE). Omega-3 Inhibits Blood Vessel Growth in a Model of Age-Related Macular Degeneration in Vivo. June 16, 2014. Accessed at http://www.masseyeandear.org /news/press_releases/recent/2014_Omega3_PNA/
- SanGiovanni JP, Chew EY, Clemons TE, Davis MD, Ferris FL 3rd, Gensler GR, Kurinij N, Lindblad AS, Milton RC, Seddon JM, Sperduto RD; Age-Related Eye Disease Study Research Group. The relationship of dietary lipid intake and age-related macular degeneration in a case-control study: AREDS Report No. 20. Arch Ophthalmol. 2007 May;125(5):671-9.
- Sapieha P et al. 5-Lipoxygenase Metabolite 4-HDHA Is a Mediator of the Antiangiogenic Effect of ω-3 Polyunsaturated Fatty Acids. Sci Transl Med 9 February 2011: Vol. 3, Issue 69, p. 69ra12. DOI: 10.1126/scitranslmed.3001571
- Seddon JM, Cote J, Rosner B. Progression of age-related macular degeneration: association with dietary fat, transunsaturated fat, nuts, and fish intake. Arch Ophthalmol. 2003 Dec;121(12):1728-37. Erratum in: Arch Ophthalmol. 2004 Mar;122(3):426.
- Seddon JM, George S, Rosner B. Cigarette smoking, fish consumption, omega-3 fatty acid intake, and associations with age-related macular degeneration: the US Twin Study of Age-Related Macular Degeneration. Arch Ophthalmol. 2006 Jul;124(7):995-1001.
- Seddon JM, Rosner B, Sperduto RD, Yannuzzi L, Haller JA, Blair NP, Willett W. Dietary fat and risk for advanced age-related macular degeneration. Arch Ophthalmol. 2001 Aug;119(8):1191-9.