New Xanthophyll Science
Friday, July 25, 2008
A study published in the August 2008 Journal of Lipid Research found that the xanthophyll carotenoids, lutein (LUT) and zeaxanthin (ZEA) are preferentially taken up by the retinal cells compared to beta carotene.
Researchers have also discovered the manner in which lutein and zeaxanthin are transported from the bloodstream to the eye, shedding further light on how these two carotenoids promote eye health.
Evidence has been steadily accumulating to support the role of dietary lutein and zeaxanthin in protecting against the development of age-related macular degeneration (AMD), the leading cause of vision loss in people over 55 years of age in the Western world.
Because past studies have shown that a protein called SR-B1 (scavenger receptor class B, type 1) is involved in intestinal absorption of lutein and zeaxanthin, the authors of the current study investigated whether the same protein is also involved in transporting these nutrients to the eye.
During the in vitro study, the researchers examined the uptake of lutein, zeaxanthin and beta carotene by human retinal pigment epithelial (RPE) cells. They found that the cells were more efficient at absorbing lutein and zeaxanthin compared to beta carotene and that when the protein SR-BI was active, the RPE cells absorbed the carotenoids. But when they added compounds to inhibit SR-BI, the uptake of zeaxanthin and beta-carotene were significantly decreased by between 40 and 60 percent. Inhibition of another transport protein, CD36, had no effect. This indicated that not only does SR-B1 help the intestines absorb lutein and zeaxanthin, it also helps the eyes absorb these two critical nutrients.
This study supports the potential of lutein and zeaxanthin to inhibit the development of age-related macular degeneration by providing a valid mechanism explaining how xanthophylls can be transported from the blood into the eyes.
Another study published in the June 2008 issue of Free Radical Biology Medicine suggests that lutein can decrease intracellular H(2)0(2) accumulation by scavenging superoxide and H(2)0(2) and the nuclear factor-kappaB (NF-kB) regulated inflammatory genes in lipopolysaccharide-stimulated macrophages. This suggests that lutein supplementation could be important for those at increased risk of both macular degeneration and Alzheimer's, since these diseases share many of the same genes and both diseases are suggested to have an inflammatory component.
It's important to note that excess body fat has also been suggested to interfere with lutein and zeaxanthin transport to the eye.
Ellen Troyer, MT MA
Biosyntrx Chief Research Officer