November 28, 2006
Two new studies indicate that important nutrients, contained in, among other things, egg, play a part in the prevention of the most common type of age related blindness.
Macular degeneration, otherwise known as retinal calcification, is the degeneration of retinal cells in the eye’s macula (a yellow spot in the middle of the eye which is the centre of the visual field and has a high concentration of cells responsible for colour vision). Because the macula is in the centre of the eye, if one looses cells in the macula, one also looses sight in the centre of the eye. This means that peripheral vision is retained. With macular degeneration, it is possible to become oriented in, for example, a room, but it is difficult to see what lies directly ahead, including faces, the TV, or a newspaper. One retains ones sense of space, but is functionally blind. It is very irritating for sufferers because they cannot recognize their children or close friends it they meet them on the street. They cannot see their faces, only a black dot.
The first sign of macular degeneration is that straight lines aren’t seen as being straight, but bend so that text and the blinds in front of the window “bulge.” The next sign is the loss of colour vision, because the macula has the highest concentration of colour discerning cells (cones) in the eye.
Earlier studies have shown that it is possible to reduce the risk of macular degeneration with certain antioxidants. Recent studies are interesting because thy have shown that natural measures can be used to in increase the retina’s contents of important chemicals, thereby decreasing the risk of macular degeneration.
At the University of Wisconsin in Madison, USA, an analysis of 1,700 older women from the huge Women’s Health Initiative (a study over what it now a period of 15 years including 161,000 women of the ages 50 – 79) showed that their density of macula pigment was positively correlated with the amount of carotenoids such as lutein and zeaxanthin in the diet and negatively correlated with diabetes and obesity.
A coinciding intervention study was undertaken at the University of New Hampshire, USA, where a group of 24 women, aged 24-59, ate 6 eggs weekly over a period of 12 weeks.
Both lutein and zeaxanthin is found in eggs yolks from which they are readily absorbed into the blood and thereafter concentrated in the retina.
One group received eggs with 331 micrograms lutein and zeaxanthin per yolk. Another received eggs with 964 micrograms lutein and zeaxanthin per yolk and a third group received a daily sugar pill, which they were told contained lutein and zeaxanthin.
I both of the groups which ate the daily egg their levels of lutein and zeaxanthin increased. The same was not true of the group which received the sugar pill. This effect was known from earlier studies with eggs, but this study went one step further and measured the participants density of macula pigment as well as serum – cholesterol and triglycerides at the start of the study and after 4, 8, and 12 weeks.
Serum – cholesterol was not increased in either of the groups which received eggs, but both cholesterol and triglyceride levels increased significantly in the participants who received sugar pills.
Conversely, serum zeaxanthin (not lutein) as well as, importantly, the retina’s content of sight pigment increased in the eggs groups, but not in the sugar group.
Even though there are significantly more carotenoids in vegetables, such as spinach, the authors of the study prefer eggs because of their high bioavailability of lutein and zeaxanthin.
It is nice to, one more time, establish that eggs are good. And they don’t taste too bad either!
By: Vitality Council
• Mares JA, Larowe TL, et al. Predictors of optical density of lutein and zeaxanthin in retinas of older women in the Carotenoids in Age-Related Eye Disease Study, an ancillary study of the Women’s Health Initiative. Am J Clin Nutr., 2006, 84(5): 1107-1122.
• Wenzel AJ, Gerweck C, et al. A 12-wk egg intervention increases serum zeaxanthin and macular pigment optical density in women. J Nutr., 2006; 136(10): 2568-2573.