Spinach has yet to receive its due when it comes to health food. A study now shows that spinach plays a vital role in caring for our eyes. Maybe it’s wise for us to take a cue from Popeye.
WITH the help of a new eye instrument, a study has been launched to determine whether spinach, the vegetable that had bestowed Popeye with super-human strength was also the reason for the 77-year-old sailor having a very good eyesight.
Spinach and other vegetables like sweetcorn, kale and broccoli are rich in a chemical called lutein and together with another carotenoid, zeaxanthin they form an oily, yellow substance at a central point of the retina known as the macula.
This yellow oil, called macular pigment, is thought to protect the macula from age-related macular degeneration or AMD, a disease that studies in the United Kingdom have shown to affect up to 12% of men and 29% of women over the age of 75.
“The macula is a small area of the retina responsible for seeing detail and colour in our central field of vision,” said Dr Ian Murray, who is leading the research in Manchester’s Faculty of Life Sciences at Manchester University.
He was reported in the New Scientist magazine as saying that since macular pigment is wholly derived from a person’s diet one would expect that eating foods containing high levels of these compounds increases macular pigment which in turn helps slow down the degenerative process. This latest study on volunteers with early-stage AMD would test that idea.
Scientists however, do not yet understand why some people are susceptible to age-related macular degeneration but warn the incidence is likely to rise as the population ages.
In collaboration with Tinsley Ophthalmic Instruments, Dr Murray’s laboratory has developed a lightweight instrument that can measure the levels of lutein and zeaxanthin and provide an indication as to whether low levels of macular pigment may be linked with premature visual impairment.
He was quoted by New Scientist as saying: “If the instrument demonstrates that the patient has low levels of macular pigment then they can be advised to take a lutein or zeaxanthin supplement and encouraged to eat vegetables high in these carotenoids.
“AMD is a devastating disease where those affected slowly lose central vision making reading and most day-to-day activities virtually impossible. The main risk factors for the disease are age and heritance but it is also linked to controllable factors such as poor diet, smoking and obesity. Having their macular pigment measured and learning about the health of their eyes might be the first step to a change in lifestyle for many people.”
Hope to improve sight of blind people
The AMD instrument has been taken up by an American company which is currently using it to test patients’ levels of macular pigment and advise on the use of food supplements.
A team of scientists hopes to improve the sight of blind people by implanting proteins from spinach leaves into their eyes. When light falls on the proteins, it creates an electrical voltage which could stimulate healthy regions of the retina and produce meaningful images, they say.
“The idea is to insert these proteins into cells in the retina,” says Elias Greenbaum of Oak Ridge National Laboratory in Tennessee, US.
“If we can do that, we know light can make them produce voltages high enough to stimulate the optic nerve.”
Greenbaum, who is working on the project with Mark Humayun of the University of Southern California’s Doheny Eye Institute, Los Angeles, says the spinach proteins, known as photo-reaction centres, perform a similar task to photoreceptor cells in the retina. These cells, which lie at the base of the retina, send electrical pulses to the optic nerve when illuminated. These impulses are then interpreted as images by the brain. Humayun has already shown that artificially stimulating retinal cells with electrical voltages can produce very elementary vision.
“He found that if you lay an electrode array over retinal tissue and stimulate it, you can produce basic images that the person can recognise,” says Greenbaum.
The two now hope to use the photo-reaction centres to replace damaged or diseased photoreceptor cells in blind or partially-sighted people.
“In two of the major diseases that cause blindness, you lose the photoreceptor cells,” says Greenbaum.
To do it, they plan to embed the photo-reaction centres into tiny fatty spheres called liposomes and inject these into the membranes of retinal cells.
When light falls on them, Greenbaum hopes they will produce voltages strong enough to trigger electrical impulses down the optic nerve.
“What we need to do is find out whether these voltages can trigger neural events and allow the brain to interpret the images,” says Greenbaum.
Greenbaum and Humayun are currently experimenting with implanting the proteins into retinal cells in the laboratory and stress it will be some time before they try the technique in animals or humans.
“The spinach proteins known as photo-reaction centres, perform a similar task to photoreceptor cells in the retina. These cells, which lie at the base of the retina send electrical pulses to the optic nerve when illuminated.” Elias Greenbaum
Challenges Magazine Vol1 Issue4, 2008 (Challenges Magazine is a journalism skills training project for persons with disabilities started in 2007)