A supplement essential for good eyesight
The Irish Times
Health Supplement, p. 13
21 April 2009
DOES IT WORK? Lutein and your vision
LUTEIN is a very popular dietary supplement, especially among older people worried about their eyesight. It was first isolated from egg yolks, and is present in corn and dark green vegetables like broccoli, spinach, Brussels sprouts, romaine lettuce and peas.
Much of the interest in lutein as a dietary supplement has developed because lutein from the diet accumulates in a small region of the eye. Light passes through the pupil and hits the retina at the back of the eye. The centre of the retina is called the macula and this is where lutein accumulates. The macula is very important for what we see directly in front of us, for seeing the fine details when reading and writing and for colour. As we age, the macula can become damaged leading to a condition called age-related macular degeneration (AMD). With AMD, vision in the centre of the eye becomes blurry and colours fade. Peripheral vision usually remains adequate. However, AMD is the leading cause of blindness in older people and treatments are not available.
Research has noted that European and American diets are providing less lutein, probably due to reduced vegetable intake. The recommended daily intake of lutein is 6mg, while the average intake among Europeans is 2.2mg. This has led to much interest in lutein being added to foods and beverages and to the use of lutein dietary supplements.
Evidence from studies
Extensive research has been carried out on lutein in the laboratory. Lutein is one of a large family of compounds called carotenoids. The best known of these is beta-carotene, which is converted into vitamin A in the body. In general, carotenoids are effective antioxidants. People with reduced levels of antioxidants tend to be at higher risk of a number of diseases like cancer and heart disease. The risk of age-related macular degeneration (AMD) is higher in people whose diet is low in antioxidants and particularly when lutein intake is low.
One study in people over 55 years found that those with the most lutein in their diet (more than 6mg per day) had almost half the risk of AMD as those with the lowest amount (less than 0.5mg per day).
Little research has been conducted on lutein dietary supplements. Although lutein is particularly important in the eye, it exists throughout the body. Taking supplements raises the blood lutein levels within a few weeks, while eye levels take longer to increase. One randomised, controlled trial gave men 10mg lutein or 10mg lutein plus other antioxidants or placebo. After one year those taking lutein had greater improvement on four different vision tests than those taking the placebo. Those taking lutein plus other antioxidants had the largest improvements.
No adverse effects have been reported for lutein. Smoking and alcohol lead to reduced blood levels of lutein. Cigarette smoking is known to increase the risk of AMD. When smokers took supplements of beta-carotene, their risk of cancer increased further. This has not been examined with lutein, but since it is also a carotenoid, this provides another reason to stop smoking.
All of the evidence points to lutein being essential for good eyesight, especially as we age. Most studies have examined the benefits of dietary sources of lutein such as green leafy vegetables, with few examining lutein supplements. In those, people taking a range of antioxidants had more improvements than those taking lutein only. Although more research is needed, additional lutein in the diet would seem to keep our eyes healthy. About 6-10mg lutein per day appears to be optimal. A cup of cooked spinach contains about 26mg, while a cup of broccoli contains about 3mg lutein.