956.7 Configuraciones básicas de redes sociales

There are other approaches to the prevention and treatment of diabetic retinopathy. We have already discussed the importance of good control of the blood sugar in the prevention of diabetic complications. There is no question that diabetics who are conscientious in maintaining tight control have a sig- nificantly lower risk of developing diabetic retinopathy. Certain nutritional factors appear to be important as well. One

group of researchers looked at differences in dietary patterns between those diabetics who had retinopathy and those who did not.5

They found that diabetics without retinopathy had higher intakes of carbo- hydrates (starch) and fiber and lower intakes of protein than those who did have retinopathy.

The beneficial effect of a lower protein intake may be surprising to some people, but it should not be. Most of us consume much too much protein (up to double the recommended dietary allowance), and excess protein is harmful, especially to diabetics. The American Diabetes Association has recommended for some time that diabetics consume no more than the recommended dietary allowance of protein,6_{because excess protein can accelerate loss of kidney func-}

tion. Since deterioration of the eyes in diabetics often parallels deterioration in the kidneys, it is interesting to note that too much protein is a risk factor for both problems. The excess protein that people in Western countries consume comes from an animal product–based diet. A plant-based diet, rich in whole grains, vegetables, and fruits, contains a more moderate amount of protein, which is ideal. Fiber, of course, comes only from plant products.

I mentioned earlier that the buildup of hard exudates, the fat-rich leakages in the macula of the eye, is of concern and must be watched closely. The more hard exudates develop in the retina, the greater the likelihood of vision loss. These hard exudates are directly related to cholesterol levels in the blood. People who have higher cholesterol levels tend to have more hard exudates and poorer vision than people with lower cholesterol levels.7_{The question we}

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Consuming less protein may help prevent complications.

must ask, then, is whether lowering of cholesterol levels can reduce hard exu- dates and help stabilize eyesight. If so, we would have an effective nonsurgical alternative to laser treatments. This question has already been answered. More than a half dozen studies published over the past forty years have shown that lowering blood cholesterol levels aggressively, by either dietary or medical means, can make hard exudates go away.

Dr. Walter Kempner, an internal medicine specialist at Duke University in the 1940s, studied the effect of what he called the “rice diet,” which consisted of rice, fruit, and fruit juice, on people with uncontrollable high blood pres- sure. The diet not only helped the blood pressures but also caused large declines in blood cholesterol levels. As an incidental finding, Dr. Kempner noted significant improvement in the retinopathy of two diabetics who par- ticipated in his study.

Dr. William Van Eck followed up on these findings in 1959 by placing dia- betic patients on a high-carbohydrate, ultralow-fat diet.8_{Not only did all of}

these patients experience a fall in their blood cholesterol levels, but in eight of ten patients with retinopathy, the hard exudates, some of them quite large, either regressed or disap- peared completely. The results strongly sug- gested that dietary lowering of cholesterol

levels can make hard exudates disappear, and Dr. Van Eck suggested that a diet such as this be considered for diabetics who have high cholesterol levels and retinopathy with hard exudates.

A Swedish study in 1965 employed a similar diet, with fewer than 10 per- cent of calories derived from fat.9_{In most cases, the hard exudates in these dia-}

betic patients disappeared almost completely. In a number of patients, the number of red dots seen in the retina, indicative of microaneurysms, also diminished. In this, as in all of the other cholesterol-lowering studies, no effect on neovascularization (proliferative retinopathy) was seen. The researchers in this study also noted that improvement in vision may occur as the hard exu- dates resolve, although this does not happen in most cases.

Not everyone is willing to follow a healthy low-fat diet, so other approaches have been considered. Since substituting vegetable oils like corn oil for fats of animal origin can lower cholesterol levels, another study evaluated diabetics with retinopathy who were placed on a corn oil diet. Here again, not only did

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Lowering cholesterol levels can clear up leakages

and avert the need for laser treatment.

cholesterol levels fall somewhat, but there was also a marked reduction in the amount of hard exudate.

Cholesterol-lowering drugs have also been used effectively to improve dia- betic retinopathy, proving that it is the cholesterol-lowering effect of the treat- ments rather than some other dietary factor that is responsible for the beneficial effect on the leakages. Clofibrate and Atromid (a combination of clofibrate and another drug), two of the early medications used to lower blood cholesterol levels, were shown in the late 1960s to bring about a significant reduction in hard exudates just as the dietary approaches had.

Most recently, in 1991, a group of researchers treated six patients suffering from diabetic retinopathy with pravastatin, a potent drug of the “statin” class that lowers cholesterol levels by inhibiting its production by body cells.10

Another drug, cholestyramine, was added if necessary, the goal being to lower blood cholesterol levels to 150 milligrams per deciliter or less. The average cho- lesterol level of these patients was 231 before drug therapy and 165 during ther- apy. All six patients showed an improvement in hard exudates. In four of them, there was an improvement in the number of microaneurysms as well. During the one-year study period, one patient showed an improvement in vision, and five showed no change. Of course, no change is an excellent result, because the whole point of diabetic retinopathy treatment is to prevent loss of vision. Laser treatments do not usually result in any improvement in vision, either.

What is amazing about all of these stud- ies is that although they deal with small num- bers of patients, they are absolutely consistent in their results. There is no question that dietary (preferably) or medical treatment to bring

blood cholesterol levels down can reduce or eliminate hard exudates and, in some cases, microaneurysms. Lowering cholesterol levels, especially by dietary means, obviously confers other health benefits as well.Although neovascularization (pro- liferative retinopathy) often requires laser treatment on an urgent basis, the treat- ment of nonproliferative (background) diabetic retinopathy, the type marked by hard exudates and other leakage in the macula, is rarely an emergency. Therefore, the prudent course in most of these cases is to lower blood cholesterol levels, care- fully monitoring the retinopathy at regular intervals to make sure no worsening is taking place. If successful, there may be no need for laser treatments, which are expensive and can have adverse side effects. In my own medical practice, I was able

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It is an approach that is ignored in most medical

to save many people from having to undergo laser treatments in just this way. Sadly, it is an approach that is ignored in most medical practices today.