Chapter 154
Antioxidant Supplementation?
If cataracts arise through oxidation, then you can just eat more antioxidants, right? In the eye’s lens, the vitamin C concentration is 50 times higher than in the blood, because the body uses it to fend off these oxidative attacks. Experiments with eye fluid removed and examined during cataract surgery after vitamin C supplementation confirm that what you eat changes what makes it to the eye, but can it also reduce risk?
People who consume more antioxidants in their diet have a lower risk of age-related cataract. This also applies to individual antioxidants—vitamin C, beta-carotene, lutein, and zeaxanthin—but not to others, such as vitamin A, vitamin E, and alpha-carotene. With vitamin C, both higher intake and higher blood levels correlated with a lower cataract risk. Those who consume the amount of vitamin C found in about two oranges a day have a 40 percent lower risk. The researchers concluded that vitamin C intake from the diet “should be recommended for primary prevention against cataracts,” which corresponds to a recommendation from a meta-analysis on lutein and zeaxanthin in connection with cataract risk: “Ophthalmologists should advise patients to consume more lutein-rich foods, such as dark green leafy vegetables.” Why not recommend antioxidants as dietary supplements instead?
Antioxidant supplementation?
Details on this at see.nf/antioxmulti, but supplements with vitamin C, vitamin E, and beta-carotene with or without zinc had no effect whatsoever on cataract formation. Perhaps there is a threshold effect such that supplementation only shows an effect when there is a dietary deficiency. Take lutein and zeaxanthin, for example: In the human eye lens, they are the only carotenoids, so beta-carotene predictably showed no effect. Supplementation with lutein and zeaxanthin also failed, but only in participants who got enough of them from their diet. In the participants with the lowest intake at baseline, supplementation did show an effect. It probably would have helped them to eat more green leafy vegetables as well.
Multivitamin supplementation?
With multivitamins, you often hear that they are taken “just in case,” but as I note in see.nf/antioxmulti, the results for cataract prevention with such supplements are inconsistent. For example, one study found that participants randomized to take Centrum for about ten years had a 34 percent lower risk for one form of cataract, but a 100 percent higher (that is, double) risk that another form would develop or worsen. Because of these opposing effects, “we cannot make a recommendation,” the scientists concluded.
Clear vision
In addition to foods rich in antioxidants, consuming anti-inflammatory foods is also associated with a lower cataract risk. The aging toxin AGE could also accelerate cataract formation by cross-linking proteins in the eye’s lens. That could explain why meat consumption (including poultry) is associated with an increased cataract risk. In contrast, people who eat at least 30 grams of legumes a day have only half the risk of developing a posterior chamber lens cataract; however, the scientists did not adjust the data for meat consumption, so it is hard to say whether the effect was not merely an indirect consequence of lower meat intake.
The “European Prospective Investigation into Cancer and Nutrition” study is large enough to go into detail. It compared the development of cataracts in people with “high” versus “low” meat consumption and pescatarians on the one hand, and vegetarians and vegans on the other. The scientists deliberately selected health-conscious participants in order to rule out confounders such as smoking, exercise, and other variables unrelated to diet; therefore, “high” meat consumption was defined as one serving (100 g) a day or more. Yet even compared with health-conscious people who ate relatively little meat, those who ate even less (less than 100 g per day) had 15 percent fewer cataracts.
Compared with those who ate at least one serving of meat a day, those who cut it out entirely but ate fish (pescatarians) had a 21 percent lower risk; people who ate no meat at all (vegetarians) reduced their risk by 30 percent; and those who went a step further and also cut out eggs and dairy products (vegans) had a 40 percent lower risk of getting a cataract. A similar stepwise risk reduction is also seen in other diseases as the proportion of plants in the diet increases—namely diabetes, high blood pressure, and obesity. A follow-up study from Taiwan confirmed that people who do not eat meat are significantly less likely to develop cataracts than people who average about half a serving of meat a day.
Why are the figures higher among vegetarians than among vegans? Maybe it is the dairy products. Since 1935, from studies with titles like “Yogurt Causes Cataracts in Rats,” it has been known that galactose, the breakdown product of the milk sugar lactose, can cause cataracts. When galactose accumulates in the eye, the lens can swell dangerously. Thank goodness the human liver can break down more galactose than a rat liver can. Some children are born with a genetic defect, and in them this does not work as well (as a result they get cataracts), but could lifelong consumption of dairy products also increase cataract risk in people with normally active detoxification enzymes? After all, from an evolutionary perspective, milk consumption in adulthood is something new.
In the general population, milk consumption does not appear to increase cataract risk, but some people may be more susceptible to it. People vary from birth in how well they can break down galactose. In those with normal but lower levels of the galactose-breaking enzyme galactokinase, high lactose intake from milk and dairy products can quadruple the risk of developing a cataract at some point in life. This has been used as an explanation for why women develop cataracts more often than men, because women generally have lower galactokinase activity.
Preserving dignity
I am placing this section at the end, contrary to alphabetical order.
A good death
There are all kinds of data about dying, but not about the subjective experience. For the minority who receive palliative care, death might be described as good, but for the majority of people who die in hospitals or nursing homes, unfortunately one has to assume it is less good. Unfortunately, most die there.
Although almost everyone would prefer to die at home, people mostly die in some kind of institution. Nearly 80 percent of Americans say they would like to die at home, but fewer than 30 percent are granted that. A death in an institution with intensive medical involvement has consequences not only for patients but also for caregiving family members. At the end of life, cancer patients who die in a hospital not only experience more physical and emotional stress and a poorer quality of life in their final days; their relatives are also five times more likely to suffer post-traumatic stress disorder and almost nine times more likely to sink into severe, prolonged, exhausting grief. These data come from an observational study. Of course, the patients were not randomized to different places of death, so the data do not show cause and effect, but they are cause for concern.