Eating the right food is crucial for healthy eyes, so that they can keep us seeing well, both now and in the future.
In particular, lutein (pronounced LOO-teen) and zeaxanthin (pronounced zee-ah-ZAN-thin) are very important. These eye nutrients have been found to reduce the risk of both macular degeneration and cataracts, both common causes of sight loss as we age.
Lutein and zeaxanthin are classed as xanthophylls (pronounced ZAN-thuh-fills), which are yellow pigments found naturally in many plants and vegetables. Xanthophylls belong to a group of natural red and orange coloured nutrients called carotenoids. Though lutein is considered a yellow pigment, in high amounts it appears orange-red.
In nature, lutein and zeaxanthin absorb excess high-energy blue light rays to avoid damage to plants from excess sunlight.
Recent research has discovered a third xanthophyll in the macula. Called meso-zeaxanthin, this carotenoid is not found in food and appears to be made in the retina from the lutein we eat. Also, another xanthophyll called astaxanthin which gives salmon its red colour has been found to have anti-oxidant properties too when added to supplements.
As well as being found in green or yellow leafy plants, fruits and vegetables, lutein and zeaxanthin are found concentrated in the macula of the human eye, giving it a yellowish appearance.
Did you know....?
In a 2011 survey of Americans aged 45-65, more than half the respondents said they take vitamins to protect their joints, bones or heart health. But less than a fifth said they take eye health supplements.
In addition, two-thirds were unaware of the key role that lutein plays in eye health.
How do Lutein and Zeaxanthin help the eye?
Lutein and zeaxanthin seem to act as antioxidants at the back of the eye. Similar to other natural antioxidants, including vitamin C, beta carotene and vitamin E, these xanthophylls protect cells from free radical damage. These are unstable molecules that can damage and destroy cells causing many illnessses.
It is thought that they block blue light from reaching the back of the eye known as the retina, reducing the risk of damage to the delicate cells and blood vessels that could lead to macular degeneration (AMD).
A number of studies have found that lutein and zeaxanthin either help prevent AMD or may slow progression of the disease:
Studies published in American Journal of Epidemiology, Ophthalmology and Archives of Ophthalmology found higher levels of lutein and zeaxanthin in the diet are associated with a lower incidence of AMD.
Two studies published in Investigative Ophthalmology and Visual Science found that eyes with greater levels of macular pigments were less likely to have or develop macular degeneration.
Despite the findings of these studies, some experts note that other research fails to show a relationship between the dietary intake or blood levels of lutein and zeaxanthin and a person's risk of developing AMD over time.
In addition to protecting the retina, lutein and zeaxanthin also may reduce the risk of cataracts. Recent studies published in Archives of Ophthalmology have found that healthy diets with high levels of lutein, zeaxanthin and other carotenoids were associated with a lower risk and prevalence of cataracts in women.
Foods Containing Lutein and Zeaxanthin
The highest amounts of lutein and zeaxanthin are found in green leafy vegetables and other green or yellow vegetables (see list below). Out of all of these, cooked spinach and kale are the best vegetables to eat to gain the most lutein and zeaxanthin.
Non-vegetarian lutein and zeaxanthin is found in egg yolks. However, if you have high cholesterol, it is advisable to eat these yellow nutrients from fruits and vegetables. The top ten foods containing lutein and zeaxanthin are:
Remember that taking vitamin supplements does not replace a healthy diet but improves it. Eating a diet high in fruits and vegetables also gives extra benefits to health. It is thought that nutrients eaten from food can be more powerful than those from supplements. However, it can be hard to achieve the high doses required from food alone.
There currently is no Recommended Dietary Allowance (RDA) or Recommended Daily Intake (RDI) for lutein or zeaxanthin, but some nutritionists recommend at least 6 milligrams (mg) of lutein per day for eye health.
There are no known side effects of taking too much lutein or zeaxanthin. Rarely, if too many foods or supplements containing carotenoids are taken, the skin can develop a harmless yellow colour that disappears on reducing the amount taken or eaten.