ZEAXANTHIN, a key nutrient and a strong antioxidant member of the carotenoid family may be far more important in preventing or stabilising macular degeneration than previously realised.

This was deduced from a recent study conducted by the Medical Research Council Environmental Epidemiology Unit of the University of Southampton, the United Kingdom.

Macular pigment, which is primarily composed of lutein and zeaxanthin, is thought to protect the retina from damage due to light exposure and oxidative stress.

It has been shown that a high macular pigment density helps to retain visual sensitivity as we age and evidence indicates that raising the intake of dietary zeaxanthin can increase macular pigment.

The macular pigment acts like 'sunglasses' by protecting the critically important central sight from damaging light waves, UVB.

The distribution of lutein and zeaxanthin in the eye may indicate they have different functions.

Zeaxanthin is the dominant component in the centre of the macula, while lutein dominates at the outer edges.

The eye preferentially places dietary zeaxanthin in the very centre of the macula, the most critical area for central vision, with the greatest need for protection.

This selective uptake of zeaxanthin occurs even though lutein is more available in the diet by a 20:1 ratio.

Previous investigations may have obscured evidence of zeaxanthin's greater protective role by looking at the two carotenoids together, rather than separately.

Although both of these carotenoids protect the retina, zeaxanthin has been shown to be a better photoprotector. A recent animal study supports the photoprotective activity of zeaxanthin.

Food sources of lutein and zeaxanthin include corn, egg yolks and green vegetables and fruits. Broccoli, green beans, peas, brussel sprouts, cabbage, kale, collard greens, spinach, lettuce, kiwifruit and honeydew are some examples.

Lutein and zeaxanthin are also found in the petals of many yellow flowers such as the marigold, and in lycium (the Chinese kei chi).

Chicken egg yolks are a rich food source of lutein and zeaxanthin. The average amount of lutein in chicken egg yolk is about 290 microgrammes per yolk, and the average amount of zeaxanthin, about 210 microgrammes per yolk.

However, the downside of obtaining lutein and zeaxanthin via consuming egg yolks is a possible elevation of LDL-cholesterol.

Another good alternative would be a supplement containing a combination of both lutein (at least 6mg of lutein per capsule) and zeaxanthin.

This story was first published in The New Straits Times on Feb 25, 2008.