|LE Magazine January 1998 |
Lutein May Halt Macular Degeneration
New studies show how you can protect yourself against a major cause of blindness with nutrients from green, leafy vegetables.
The car in front of you is going 30 in a 45-mph zone, crossing over the line and refusing to move over. If this sounds familiar, chances are you've encountered the road hazard known as "Watch out, grandpa's at the wheel." Grandpa's not inebriated; he just can't see. He has an eye condition called macular degeneration. It can lead to blindness, and there is no cure. Like cataracts and glaucoma, macular degeneration robs a person's autonomy by stealing his or her sight. It is the second leading cause of blindness in the elderly after cataracts.
Usually grandpa or grandma won't admit they can't see very well. Grandpa figures if he drives slowly and stays in one lane, nothing will happen. Because it's such a gradual process, people frequently don't realize how bad their sight has become. Eventually grandpa will back into somebody at a gas station, or inadvertently run off the road, and his insurance company will permanently sideline him. Losing one's driving privileges can be very traumatic - especially for someone who has been behind the wheel a long time. Elderly people can become withdrawn and severely depressed over losing their driving privileges.
Fortunately, research shows that a simple dietary supplement, lutein, may prevent age-related macular degeneration. This is one condition where prevention should be a high priority; once the macula is gone, it's gone.
Macula means "spot." Macular degeneration is, literally, degeneration of the spot. In the case of the human eye, we're talking about a spot on the retina about the size of a pencil eraser. The retina is the part of the eye where all the action is. A layer of cells on the inside of the eyeball, the retina is actually an extension of the brain. It is composed of nerve cells that connect to the brain. Rods, which perceive light intensity, and cones which perceive color, are two types of nerve cells found in the retina. Much of the rest of the eye functions solely to direct light to this important part of the eye. The retina is multi-layered-like an onion-with a layer of pigment cells under the rods and cones. Retinal detachment occurs when the rod-and-cone layer separates from the pigment layer.
Since the retina is made up of lots of nerve cells, there is plenty of fat that is susceptible to oxidation. Free radicals are generated in the eye partly by ultraviolet (UV) light. While most of the UV spectrum is absorbed by the cornea, "energetic" blue light sails through and hits the retina. Mitochondria are another source of free radicals in the eye. Rods and cones are jammed with mitochondria, which generate the energy necessary to transform light into vision. If not enough antioxidants are present to grab the radicals, the retina can be damaged. The macula is located on the part of the retina that creates the sharpest vision. When the macula goes, vision goes as well. The macula is yellow. Its color comes from substances found in vegetables known as carotenoids. One of the things carotenoids do is scavenge free radicals. The idea that carrots are good for your eyes is close to being scientifically correct, because carrots do contain the types of carotenoids the macula needs. However, other vegetables are better sources. Corn and spinach contain more macula-friendly carotenoids than carrots. Humans can't manufacture carotenoids; they must come from the diet.
John T. Landrum and Richard A. Bone of Florida International University, in Miami, have been demystifying the macula since the early '80s. In 1993, they published some important findings. The retina contains two carotenoids, zeaxanthin and lutein. The closer you get to the macula part of the retina, the more zeaxanthin shows up. (More rods show up as well). According to Landrum and Bone, the macula itself is composed of zeaxanthin. The zeaxanthin is actually a mixture of two stereoisomers, one of which is converted from lutein. As one moves away from the macula towards the outer parts of the retina, lutein predominates.
In 1993, the blood of 421 people from the Eye Disease Case-Control Study Group who had age-related macular degeneration was assayed for vitamins C, E and carotenoids. Researchers found a strong relationship between carotenoids and macular degeneration, but little if any relationship with vitamins C and E. Nonetheless, vitamin E may have a role. A study published in the American Journal of Clinical Nutrition reports that in monkeys, areas of the retina where vitamin E and carotenoids are the lowest coincide with the areas where age-related macular degeneration begins. Vitamin E may recycle the carotenoids.
In 1994, a retrospective study was done at the Massachusetts Eye and Ear Infirmary in Boston. Three hundred fifty-six people with advanced age-related macular degeneration and 520 control subjects were grilled about what they ate. People who ate green leafy vegetables such as collard greens were less likely to have macular problems. This was the first hint that macular degeneration might be controlled by dietary means.
In eyes taken from autopsies, the ones with age-related maculardegeneration have about 30 percent less carotenoids than healthy eyes. This strengthens the link between dietary carotenoids and the health of the macula.
In 1995, Bone and Landrum set up a two-person study to find out if lutein supplements would increase macular pigment. Within 10 to 20 days of taking 30 mg a day, lutein levels rose tenfold in the two men. (The supplement was provided in canola oil since lutein is fat-soluble.) Measurements confirmed that the supplement was reaching their eyes; their maculae were getting denser, and gaining pigment. (The macula is naturally about as thick as tissue paper.) After 140 days, macula pigment increased about 20 percent in one person, and 40 percent in the other. Even after lutein was discontinued, their maculae continued to improve for about six weeks. Researchers believe that both the increase and loss of carotenoids from the macula is a slow process. Although this study was miniscule, it is the first proof that taking supplements can restore lost pigment.
It's no big surprise-lutein and zeaxanthin will probably turn out to be important radical scavengers in other parts of the body as well. Of particular interest is a potential role in heart disease. In this regard, researchers recently have demonstrated that zeaxanthin inhibits LDL oxidation in cell culture. Interestingly, when a combination of lutein, zeaxanthin, alpha-carotene and beta-carotene is given by mouth, more lutein and zeaxanthin than beta-carotene show up in fat and cholesterol droplets called chylomicrons. This may suggest a preference for these types of carotenoids by cells that contain fat and cholesterol. The extent of the body's utilization of lutein and zeaxanthin in areas outside of the retina will become clear after further research.
It is likely that macular degeneration is an indication of an overall deficiency in antioxidants. Research shows that people with age-related macular degeneration have lower levels of glutathione enzymes in general. Chronic exposure to chemicals (such as living in air- or water-polluted areas), increased exposure to UV-induced radiation (such as residing in Florida or Palm Springs), or inadequate intake of vegetables and fruits could, over time, lower glutathione and other antioxidants to the point where oxidant-sensitive tissue like the macula is completely destroyed.
Macular degeneration is neither mysterious nor inevitable, and preventing this age-related condition is as much about saving self-reliance as it is about saving sight. Research clearly shows that the health of the macula depends on the carotenoids lutein and zeaxanthin. It's a simple prescription, but it could mean the difference between being able to see and not being able to see.
Make sure you get enough lutein and zeaxanthin every day. While large-scale studies haven't absolutely proven that lutein and zeaxanthin supplements will prevent macular degeneration, it's a safe bet, considering the evidence.
America's obsession with dietary fat and cholesterol may be misguided. A study in the Journal of Nutrition implicates meat protein- not fat-as a major cause of high cholesterol. Although it is too early to tell whether this finding will hold up in humans, animals on a cholesterol-free diet can end up with high cholesterol if they consume a high casein (milk protein) diet. Researchers in Japan discovered that cholesterol levels skyrocketed when animals were fed casein protein versus soy protein. The difference? Casein is an animal-based protein high in the amino acid methionine. Soy is a plant-based protein deficient in methionine. According to this research and studies done in rabbits, methionine raises cholesterol.
In contrast, when rats are fed a soy diet, their cholesterol falls. Adding methionine to the soy diet sends their cholesterol soaring again. But although the beneficial effect of soy on cholesterol is reduced by methionine, it is not completely reversed. Soy has an additional protective effect that keeps cholesterol somewhat lower than when the animals consume casein only.
Several theories about how soy reduces cholesterol have been suggested. Japanese researchers believe that the high glycine in soy may lower cholesterol. Glycine has been shown to have cholesterol-lowering effects in rodents. If this scenario is correct, soy packs a one-two punch: its lack of methionine keeps cholesterol low, and its glycine content helps lower cholesterol.
Effect Of Estrogen
Estrogen enhances the cholesterol-lowering effect of soy. When female monkeys who had had their ovaries removed were given beta-estradiol with a soy-based diet, their aortic cholesterol fell significantly. Soy has many benefits beyond just lowering cholesterol. In the monkey study, soy improved lipid profiles, insulin sensitivity and glucose effectiveness. It also decreased lipid peroxidation in the arteries. Animals given estradiol showed a reduction in abdominal fat, fasting insulin and body weight, smaller LDL particles, and less aortic cholesterol. Combining soy and estrogen was the most beneficial of all, giving all the benefits of each.
In other studies, high cholesterol was produced in rabbits on a low-fat, zero-cholesterol diet within five weeks if the protein fed the rabbits was casein. Adding butter had no effect. The same rabbits fed a soy-based diet had lower cholesterol than those fed either meat protein or regular chow. According to one research group, cholesterol turns over faster on a soy protein diet, but is absorbed more on a meat diet.
Meat protein has now been associated with two of the major risk factors for heart attack
NAC Prevents Flu Symptoms
A new study indicates that N-acetylcysteine (NAC) is effective in blocking flu symptoms in elderly and chronically ill people. More than 200 people participated in a multi-center trial of NAC during the cold season. Not only did NAC keep people from getting sick in the first place, it greatly reduced symptoms and duration of illness. The percentage of people on NAC who got flu symptoms was 29 percent, versus 51 percent for those not taking it. The severity of symptoms also was reduced. Of those taking NAC, only 26 percent reported their symptoms as moderate, versus 47 percent for those on placebo. Seventy-two percent of those getting the flu while taking NAC reported their symptoms as mild. Sore throat occurred about 20 percent of the time in those taking NAC, versus 60 percent of the time in those not taking it. There also were significant reductions in coughing, body aches, headache, bronchitis and running nose.
In addition to clinical symptoms, researchers measured changes in immunity in the two groups. Although the group taking NAC was just as likely to contract the influenza virus, they were far less likely to become sick from it. NAC appears to have a remarkable ability to protect immunity. Researchers found that a number of participants started out with sub-normal immunity, and ended up with normal or near-normal immunity. After six months, the number of people with little or no immune response had plummeted in the group taking NAC, while the number with normal immunity had increased significantly. In the placebo group, the number of people with little or no immunity remained virtually the same throughout the six-month trial.
Participants in the trial were given 1,200 mg of NAC per day without adverse sideeffects. They took NAC in two divided doses-with breakfast, and at bedtime.
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