How fish, nuts, olive oil meals reduce blindness risk

Thursday, June 04, 2009

How fish, nuts, olive oil meals reduce blindness risk

Besides carrots and green leafy vegetables, researchers have enlisted more foods that can reduce the risk of blindness especially in the elderly. CHUKWUMA MUANYA writes.

TWO new studies published in the May issue of Archives of Ophthalmology offer hope of reducing risk of blindness due to Age-related Macular Degeneration (AMD) and cataract.

Three leading causes of blindness are age-related macular degeneration, diabetic retinopathy, and retinopathy related to premature birth. All three conditions involve retinopathy, which is the abnormal development of blood vessels in the eye.

Researchers have found that regular consumption of fish, nuts, olive oil and other foods containing omega-three fatty acids and avoiding trans-fats may significantly lower the risk for AMD.

Food sources of omega-3s include leafy green vegetables, walnuts, flaxseeds and fatty fish such as salmon, herring and sardines. Omega-6s are found in meat and vegetable oils such as safflower oil, sunflower oil, corn oil, and soy oils.

Earlier studies have shown that omega-3 fatty acids may help prevent blindness by thwarting the growth of abnormal blood vessels in the eye.

According to the study, which involved tests on mice, which appeared in the advance online edition of the journal Nature Medicine, omega-3s may reduce retinopathy.

Research reveals and recommends that including certain important foods in daily diets can help block the causes of macular degeneration and prevent the progression of initial stages of other eye-disorders connected with dietary lack.

These foods are those rich in antioxidants, like Vitamin C and E containing items, carrots and olive oil, besides beta carotene, foods with lutein and zeaxanthin and those rich in zinc and omega-3 fats.

Earlier studies have linked mayonnaise, creamy salad dressings, cheese, beef, pork and lamb, as well as certain vegetable oils, to an elevated risk of age-related cataracts. One of those studies; however, also suggests that oily fish, the type with dark flesh, hold cataracts at bay.

However, eating dark flesh oily fish such as salmon and cod, which are rich in omega-3 fatty acids, has been shown to improve brain function and reduce the risk of developing heart diseases and arthritis.

Age-related cataracts are the leading cause of blindness. Indeed, cataract surgery is the most frequent eye-related surgical procedure performed in Nigeria.

In one of the new studies, Australian scientist Dr. Jennifer S.L. Tan, of the University of Sydney's Westmead Hospital and her research team studied 2,454 participants in the Blue Mountains Eye Study, which began in 1992 to 1994.

Over the years, study participants filled out a food frequency questionnaire in order to document their intake of various fatty acids. Then, after five and 10 years passed, digital photographs of the research subjects' eyes were taken to study their retinas and check for the development of AMD.

The researchers found that eating just one serving of fish each week was associated with a 31 per cent lower risk of developing early AMD. What's more, eating just one to two servings of nuts per week was associated with a 35 per cent lower risk of early AMD.

"In conclusion, our findings support the hypothesis that increased intake of omega-three polyunsaturated fatty acids and regular consumption of fish and/or nuts in the diet may protect against the development of early AMD," the authors wrote in the study.

They theorise that these healthy fatty acids may protect the eye by preventing the build-up of plaque in the arteries and by reducing inflammation, blood vessel formation and oxygen-related cell damage in the retina.

In another study reported in the same issue of Archives of Ophthalmology, Dr. Elaine Chong, of the Centre for Eye Research Australia and colleagues analysed data from 6,734 people between the ages of 58 and 69. Between 1990 and 1994, the research subjects' intake of nutrients was calculated from a food frequency questionnaire.

Then the study participants were studied between 2003 and 2006 to see if they developed AMD. During this follow-up period, 2,872 cases of early AMD were diagnosed and 88 cases of late AMD were also found. Who were most likely to have late-stage AMD? The people who ate the most trans-fats (usually the result of eating baked goods and processed foods). On the other hand, those who consumed the most omega-three fatty acids were far less likely to have even early AMD.

In this study, fish didn't seem to be the big protector against in AMD- instead olive oil was the clear "star" of this research. "Olive oil intake (100 millilitres or more per week vs. less than one millilitre per week) was associated with decreased prevalence of late AMD," the authors wrote. "Our findings suggest that people who follow a diet low in processed foods high in trans-unsaturated fatty acids and rich in omega-three fatty acids and olive oil might enjoy some protection from developing AMD."

These studies aren't the first to show that nutrients may protect your sight as you age. Previously, the National Eye Institute's (NEI) Age-Related Eye Disease Study (AREDS) found that taking high-doses of antioxidants and zinc significantly reduced the risk of advanced AMD and its associated vision loss.

According to the NEI web site, this is highly significant because slowing down AMD's progression from the intermediate stage to the advanced stage can save the vision of many people. Specifically, the AREDS study involved the daily intake of 500 milligrams of Vitamin C, 400 International Units of Vitamin E, 15 milligrams of beta-carotene, 80 milligrams of zinc as zinc oxide and two milligrams of copper as cupric oxide.

If the findings apply to people, "simple supplementation (with omega-3 fatty acids) could be a cost-effective intervention benefiting millions of people," said Dr. Lois Smith, in a news release from Children's Hospital, Boston, United States.

Smith works in the Ophthalmology Department of Harvard Medical School and Children's Hospital, Boston. Smith and colleagues studied omega-3 and omega-6 fatty acids in newborn mice.

The body needs omega-3s and omega-6s and must get those fatty acids through diet or supplements. Western diets tend to be heavy on omega-6s and skimpy on omega-3s.

Smith's team added omega-3s or omega-6s to the diets of female mice that had just given birth. The mother mice passed the omega-3s or omega-6s to their new-borns through their breast milk.

The omega-3 supplements were given at a dose similar to that of the traditional Japanese diet. The omega-6 supplements were given at a dose like that of a typical Western diet.

The baby mice were exposed to high levels of oxygen for five days, starting when they were one week old. Those conditions put the eye at risk of losing healthy blood vessels, which sets the stage for abnormal blood vessels to develop.

The newborn mice kept more of the healthy blood vessels in their eyes if their mothers' diets were supplemented with omega-3s instead of omega-6s. With more of their healthy blood vessels intact, the newborn mice in the omega-3 group were less likely to have abnormal blood vessels develop in their eyes.

In short, omega-3s reduced retinopathy before it started. The study shows that the results may be related to omega-3s' anti-inflammatory effects. Children's Hospital, Boston plans to study omega-3s in premature babies, who are at risk for vision loss.

The study would include premature babies who can't feed on their own. Omega-3s would be added to their IV solution. "We want to give omega-3 right from the beginning to mimic what the infants would be getting from their mothers in utero, had they not been born prematurely," Smith notes in the news release. That study is designed to test whether omega-3 fatty acids will help the babies develop healthy eyes, including the blood vessels in their eyes.

Secretary, International Society for the Study of Fatty Acids and Lipids, Dr. Ray Rice, told The Guardian: " The bottom-line is that if you do not eat fish at least twice a week, you are not getting enough omega-3 and your body will be likely to suffer from age-related cataracts, heart disease, arthritis, depression, poor mental development and mental disorders. The white coloured flesh oily fish does not have much omega-3, but the dark coloured flesh fish has high omega-3 content. If you ate that twice a week, then you will be quite fine.

"But if you eat walnut, flaxseed, linseed and white coloured flesh fish, that means you will not be getting enough omega-3 and the chances is that you will be getting too much of omega-6. Having part of these two, omega-3 and omega-6, in the body will not be ideal and may predispose the body to some health risks that may not make themselves apparent till about 30 to 40 years latter. Down the line you will be more likely to developing age-related cataracts, irregular rhythm heart beats, more risk of heart disease, the joints will be susceptible to wear and tear. In any way, if you have enough omega-3 intake, that will not be the case."

Rice argued it is better to go for cod liver oil supplements because the form present in walnuts, flaxseed or linseed oil and small amounts in green vegetables is not enough, and is not particularly useful to the body; it has to be converted into a different form.

He insisted that dark coloured flesh oily fish is the best source of omega-3. "We should get it from fish than from supplements. But there are many people who do not have access to fish, maybe fresh fish, some people do not like fish, some people are allergic to it, they do not know how to cook it, they do not like the smell, all sort of reasons. So it is important that we have a good reliable source of omega 3 available in the form of cod liver oil," Rice said.

Rice continued: "Traditionally, cod liver oil has been valued because of the Vitamin A and Vitamin D content which is barely unique, because it has such high concentration of these nutrients, and it is especially valued in Africa where their deficiency is a major problem. But in the past 30 to 40 years, we have found out more about the composition of the oil. Particularly, one of the components the oil is made from, the omega-3 polyunsaturates is unique because there are no other components of our diet that contains such large amounts than fish. The human body must have a certain amount of these polyunsaturates to remain healthy.

"There are two families of what we call essential fatty acids and omega-3 family is one of them and omega-6 is the other. If humans do not have small amounts of these nutrients in their diets on regular basis, then their health deteriorates and that is really the basic message. There is a wide range of positive effects when the omega-3 intake is increased by taking cod liver oil or fish, or some other means. Each and every area of the body uses the omega-3 to enable it function the way that God intended."

A team of researchers from Boston, United States, in their first study of women participating in a nearly-30-year-old diet-and-health study, published in the American Journal of Clinical Nutrition link the primary fat in corn oil, linoleic acid, to incipient cataracts called opacities, in the lenses of the women's eyes. In this study, this single fat accounted, on average, for roughly five per cent of calories consumed each day, and more than 85 per cent of polyunsaturated-fat intake.

Paul F. Jacques, director of Nutritional Epidemiology for the Agriculture Department's Jean Mayer Human Nutrition Research Centre on Ageing at Tufts University, United States, notes that lens opacities are "a sensitive marker for the development of cataracts" but does not initially cause vision loss.

The second study, also by Jacques' team, included women who had undergone surgery for removal of cataracts. Compared with women their age who never had such a procedure, these women were much less likely to have eaten omega-3 fatty acids, the type found in many fish oils. In this study, eating vegetable oils did not appear to be linked with cataracts, but eating mayonnaise and salad dressings did.

The studies appear slightly contradictory, acknowledges Jacques. However, he adds, it might be that one type of fat is more likely to affect early stages of cataract susceptibility and the other has its most notable impact in the latter stages of cataract development. In any case, the findings are consistent with earlier work suggesting that fat consumption can affect a person's vulnerability to cataracts.

Reacting to the study, a biologist at the University of Lagos, Akoka, Professor Peter Odeigah said: "That makes sense because fatty substances affect the flexibility and permeability of cell membranes throughout the body. Cataracts are associated with changes in lens-membrane structure and function and, thus, could be affected by dietary fats."

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Bottesini said:

Pinky, that's amazing and I am glad you posted it.

The problem with my retina and macula are due to ocular histoplasmosis, but it seems it does a lot of the same thing as macular degeneration.

I am certainly going to try working to get my diet in line with what is in this article to see if I can keep the vision I have left.

Or at least slow the progression.

Thanks, Pinky.

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