Carotenoids

Carotenoids are the blue-light absorbing plant pigments are found in red and yellow plants, powered by photosynthesis as well as some kinds of fungus and bacteria. They are valuable antioxidants that help protect the eye from many eye diseases. These antioxidants are used throughout the body, but are found in the highest quantities in the retina or macula of the eye.

All of the carotenoids are important for maintaining macular health.

Read about food sources for carotenoids.

Carotenoid types

The carotenoids can be grouped into two types.1

  • Xanthophylls - (these include an oxygen atom in their makeup) - astaxanthin, lutein, zeaxanthin and meso-zeaxanthin. Lutin and zeaxanthin accumulate in the retina naturally; meso-zeaxanthin is created from lutein in the retina.
  • Carotenes - alpha and beta carotene and lycopene

Researchers believe that there are specific proteins in the retina which bind to the xanthophylls, accounting for their prevalence in the retina and their importance in protecting macular health.1

Macular Protection

Repeated research has determined that the carotenoids are helpful in combating age-related macular degeneration. Lutein has been associated with a lowered risk of AMD.2. Lutein in combination with zeaxanthin is found to be even more helpful.3 Other research has found that levels of mesozanthin, produced from lutein in the retina, are low in patients with retinal conditions.4 The other major carotenoid, astaxanthin has been found to be effective in protecting the retina from the damaging effects of light, a significant cause of retinal diseases.5 Lycopene, of the carotene type of carotenoid, also is helpful in preventing macular degeneration and supporting macular health.3, 9

Lens Protection

Similarly, researchers have found evidence that these carotenoids help protect the lens of the eye from developing cataracts. Lutein,6 Lutein combined with Zeaxanthin,7 and the antioxidants generally, have been found to reduce cataract risk.8 Research has also indicated that lycopene is helpful in reducing the risk of cortical catract.8

Optic Nerve Protection

The mechanics are still unclear, but one of the carotenoids, crocin (from saffron) appears to inhibit "microglial activation" (inflammatory response to damage to neurons) and therefore shows promise for glaucoma and the optic nerve conditions.10, 11 In addition, scientists are now recognizing that damage to the optic nerve is at least partly due to oxidative stress. The carotenoids, such as zeaxanthin, reduce oxidative stress and inflammation and thus may support optic nerve health.12. Finally, researchers have also pointed out that thinner and less dense macular pigment in the eye contributes to some forms of glaucoma and the carotenoids are known to increase macular pigment thickness and density.13

Footnotes

1. J. Widomska, Can Xanthophyll-Membrane Interactions Explain Their Selective Presence in the Retina and Brain?, Foods, January, 2016.
2. lUTEIN (1990s, 2002, 2004) and Macular Degeneration
3. Lutein & Zeaxanthin ('90s, '00-'08, 2016): Macular Degeneration
4. Meso-Zeaxanthin (1990s, 2003, 2007) & Macular Degeneration
5. Astaxanthin (2012, 2013) & Macular Degeneration
6. Lutein (2003, 2015) Helps Age-Related Cataracts
7. Lutein (1995, 1999, 2012) and Zeaxanthin Help Cataracts
8. Antioxidants (1998, 2001-2, '05, 2013) and Cataract Prevention
9. Low Lycopene Levels related to ARMD
10. B. Lv, F. Huo, et al, Crocin Upregulates CX3CR1 Expression by Suppressing NF-κB/YY1 Signaling and Inhibiting Lipopolysaccharide-Induced Microglial Activation, Neurochemical Research, August, 2016.
11. B. Lv, T. Chen, et al, Crocin protects retinal ganglion cells against H2O2-induced damage through the mitochondrial pathway and activation of NF-κB, International Journal of Molecular Medicine, January, 2016
12. R. Manikandan, et al, Zeaxanthin and ocular health, from bench to bedside, Fitoterapia, March, 2015.
13. W. F. Siah, J. Loughman, Lower Macular Pigment Optical Density in Foveal-Involved Glaucoma, Ophthalmology, October, 2015.