Nutrient abundant in Sockeye Salmon adds to omega-3s' preventive impact on age-related macular degeneration (AMD)
by Craig Weatherby
Omega-3s were confirmed as potent eye protectors in a study we summarize elsewhere in today's edition of "Vital Choices" (see “Omega-3s from Fish Affirmed as Potent Eye-Protectors”).
And in a happy coincidence for lovers of fatty fish—especially wild salmon—the same journal published research that positions vitamin D as a comparably powerful preventive aid against age-related macular degeneration (AMD).
These findings follow a string of studies linking vitamin D to reduced risks of Alzheimer's, depression, bone fractures, multiple sclerosis, lupus, fibromyalgia, diabetes, heart disease… and several major cancers (Visit our archive and search for “vitamin D”).
As it happens, wild salmon—especially wild Sockeye salmon—are the richest food sources of the “sunshine and seafood” vitamin.
People obtain vitamin D primarily from exposure to UV sunrays. The only whole foods in which it occurs in abundance are fatty ocean-going fish, especially wild salmon. (Farmed salmon contain considerably less vitamin D, according to a recent study; see “Wild Salmon Affirmed as Top Vitamin D Source”.)
Compared with wild salmon (360 to 687 IUs per 3.5 oz serving), fortified milk (100 IU per 8 oz serving) is a significant but much poorer source. In fact, cod liver oil is the only “food” higher in vitamin D.
Vitamin D makes the perfect eye-health fit for omega-3s
The authors of the new study analyzed existing data from the US government's huge National Health and Nutrition Examination Survey.
Their results indicate that Americans whose blood levels of vitamin D ranked in the top one-fifth were 36 percent less likely to develop “dry” (early stage) AMD, compared with those who ingested the least vitamin D (Parekh N et al 2007).
And they found that fish-lovers enjoyed an even more dramatic 59 percent drop in the risk of “wet” (later stages) AMD: the form that causes eight out of 10 cases of blindness related to either form of the disease.
The researchers—led by Niyati Parekh, Ph.D. of the University of Wisconsin-Madison—dug deeper to determine any different correlations between AMD risk rates and intake of the leading food sources of vitamin D:
- Fish-rich diets reduced risk of wet (advanced) AMD by 59 percent: a result consistent with the ability of marine omega-3s to reduce wet AMD risk, reported in today's accompanying article.
- Vitamin D supplements reduced risk of early, dry AMD in people who did not consume milk daily, which confirms that vitamin D is indeed the eye-health factor common to milk and fish.
- Milk-heavy diets reduced risk of dry (early) AMD by 25 percent.
Dr. Parekh and her colleagues speculated that the beneficial effects of vitamin D might stem from an anti-inflammatory effect and/or by its preventing overgrowth of new blood vessels in the retina, which causes the wet form of AMD.
Omega-3s reduce the risk of both forms of AMD—dry and wet—but excel at stopping the wet form. In complementary fashion, vitamin D seems to specialize at deterring the early, dry form.
Thus, the two make a powerful preventive pair that comes in one delicious package: wild Alaska salmon.
- Parekh N, Chappell RJ, Millen AE, Albert DM, Mares JA. Association Between Vitamin D and Age-Related Macular Degeneration in the Third National Health and Nutrition Examination Survey, 1988 Through 1994. Arch Ophthalmol. 2007 May;125(5):661-669.
- [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.