Olive oil, eggs improves vision

By Sade Oguntola

Bottles of Olive OilRegular intake of eggs and olive oil in your diet may be protective against macular degeneration associated with age or the damaging effects of chemicals in tobacco smoke, experts have suggested.

This potential benefit of olive oil to the eyes was proven in the laboratory using cells from the human retina, with mitochondria - the cell’s power stations. Its protective use was traced to a polyphenol in it, reported researchers in the Journal of Neurochemistry.

The researchers from the Chinese Academy of Sciences, DSM Nutritional Products, and the University of California, Irvine, said the protective effects of olive oil was as potent as other antioxidants that work on the cells of the retina in the same way.They said the findings in the laboratory showed that the polyphenol content of olive oil is indicative that dietary administration of olive oil may be an effective measure in reducing and or preventing cigarette smoke-induced or age-related deterioration of the retinal pigment, such as age-associated macular degeneration (AMD).

Age-related macular degeneration (AMD) is the leading cause of legal blindness for people over 55 years of age in the Western world, according to AMD Alliance International. Though the problem was initially thought not to be in Nigeria, however cases of AMD have started to be discovered according to Dr. Adeyinka Ashaye, a consultant, ophthalmologist from the University College Hospital(UCH), Ibadan.

AMD is a degenerative retinal disease that causes central vision loss and leaves only peripheral vision. Early detection is said to be a means of prevention so that treatment or rehabilitation can be undertaken early enough. However, links to diet have been emphasized. The many health benefits of olive oil is attributed to hydroxytyrosol, an antioxidant compound believed to play a significant role in the many health benefits attributed to olive oil. Previous research by a team from the University of Barcelona found that LDL or ‘bad’ cholesterol levels might be reduced substantially after consuming just 25 millilitres of virgin olive oil daily for one week. Other studies have suggested that it could also protect against cancer.

A number of diet-based compounds concentrated in the retina may have the capacity to alter exogenous and endogenous defense and repair systems in response to oxidative stress and inflammation. The nutrients include lutein and zeaxanthin, omega-3 fatty acids, provitamin A carotenoids, vitamin A, retinol, alpha-tocopherol and vitamin C.

Supplementing with carotenoids such as lutein and zeaxanthin was associated with a lower risk for age-related macular degeneration, according to another report. Lutein and zeaxanthin are found in leafy green vegetables, corn, egg yolks, squash, broccoli and peas. The carotenoids are believed to reduce the risk of AMD by absorbing blue light that could damage the macula,(................................) by preventing free radicals from damaging eye cells and by strengthening eye cell membranes.

Published in the September issue of Archives of Ophthalmology, the research was undertaken as part of the Age-Related Eye Disease Study (AREDS) - a major clinical trial sponsored by the National Eye Institute under the umbrella of the National Institutes of Health. The AREDS Research Group assessed 4,519 participants between the ages of 60 to 80 years when they enrolled in 1992 through 1998.

Just as the consumption of omega-3 fatty acids and omega-3 rich fish could reduce the risk of developing AMD by 40 per cent according to a study published in the Archives of Ophthalmology, so also increasing egg consumption to six eggs per week could be similarly effective. Eggs were effectively increasing the macular pigment optical density (MOPD) being a rich source of lutein and zeaxanthing, suggested two studies from the University of Massachusetts.

The studies that were both published in the October issue of the Journal of Nutrition., suggested that an egg a day could boost blood levels of the carotenoids lutein and zeaxanthin and reduce the risk of AMD. In the first study, Elizabeth Goodrow and co-workers investigated the effects on eating one egg every day on blood concentrations of lutein and zeaxanthin in 33 men and women over the age of 60 in a randomized cross-over design.

The volunteers were fed one egg or an egg substitute for five weeks before crossing over to the other intervention. After five weeks of the one egg per day intervention, lutein and zeaxanthin blood content had increased by 26 and 38 per cent, respectively, compared to no-egg run-in without it affecting the blood levels of total cholesterol, LDL cholesterol, HDL cholesterol, and fats.

In the second study, Adam Wenzel and co-workers looked at the effect of a 12-week egg intervention on serum lutein and zeaxanthin levels, and the so-called macular pigment optical density (MOPD) in 24 women aged between 24 and 59. The women were randomly assigned to eat six eggs every week.

Unlike the other study, only zeaxanthin level, but not lutein, increased in those that had eggs, while MPOD increased in both egg intervention groups, a result that suggested that the egg diet offers an alternative method of protecting against potential AMD.

They said that though the aggregate concentration of carotenoid in one egg yolk may be modest relative to other sources, such as spinach, their bioavailability to the retina appears to be high. Even though researchers said the prevalence of the condition is likely to increase as the population ages but there is currently no known way of preventing the condition.

However, more and more research is focusing on potentially modifiable risk factors and nutrient-based approaches, most notably on the carotenoids lutein and zeaxanthin.