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[SCIENTIFIC AMERICAN 2007-4] 自闭症的饮食--禁食面包和牛奶能缓解症状吗？
简译一篇2007年4月号“SCIENTIFIC AMERICAN”的报道。
自闭症的饮食--禁食面包和牛奶能缓解症状吗？
网上有许多易令人轻信的说法，其一就是自闭症患者禁食谷蛋白和酪蛋白具有神奇的疗效，有些家长会热心地描述他们禁食面奶后立刻见效的奇妙进步。据调查，40%的自闭儿曾经做过禁食。这种狂热，与其说基于科学，不如说基于希望，因为目前尚没有充分的研究证据证明禁食可以改善自闭症的症状。禁食法的几种假说猜测，自闭症孩子的肠胃代谢紊乱，产生的代谢副产物伤害脑细胞或者诱发不当的免疫反应，从而致病。虽然6个研究小组的研究支持禁食，可不幸的是那些研究都存在着严重的缺陷，如，都缺乏有效的对照组。禁食孩子的进步，也许源于同期其他的训练成就呢，甚至源自孩子自身成长的因素，这都难以说清。最近，美国加州大学的科学家主持了一项关于禁食的极为严格的测验，结果将在1年内出来。这项研究采用了双盲对照组的方法，父母和研究者都不会知道某个孩子禁食与否，如此减少自以为是的干扰，仅从行为效果上作评测。但是原来期望的60个志愿者，如今只30个参加，样本数量少了一半。
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原文如下
SCIENTIFIC AMERICAN
APRIL 2007
The Autism Diet
CAN AVOIDING BREAD AND MILK EASE THE DISORDER?
BY MARK ALPERT
If you can believe the many testimonials posted on the Web, a diet free of gluten and casein is a miracle treatment for autism. Parents of children suffering from the disorder, which is characterized by impaired social and communication skills, fervently describe astounding improvements that occurred as soon as they removed gluten (a mixture of plant proteins found in wheat, rye and barley) and casein (the main protein in dairy products) from their kids’ meals. Surveys indicate that as many as 40 percent of children with autism have been placed on special diets at one time or another. This enthusiasm is grounded more in hope than in science; so far researchers have no good evidence that dietary interventions can alleviate the symptoms of autism. Recently, however, investigators have launched the fi rst rigorous tests of the diets, and the results may be available within a year.
The assumption behind the diets is that people with autism often have gastrointestinal abnormalities that allow unusual amounts of digestive by-products into the body (the so-called leaky gut syndrome). The by-products of gluten and casein, according to one hypothesis, disrupt brain function by altering opioid activity, which is involved in pain regulation and social bonding. Another theory posits that the gut leakage triggers a harmful immune response. These hypotheses are far from rock-solid; in fact, scientists have not even confi rmed that people with autism have a higher-than-normal incidence of gastrointestinal problems. But the causes of autism are so poorly understood and the disorder is so variable that some investigators are willing to consider the possibility that gluten and casein may somehow exacerbate symptoms in some children, perhaps just by producing intestinal discomfort.
Unfortunately, the initial studies of diets that eliminate gluten and casein were badly flawed. Although half a dozen research groups reported improvements in behavior and cognition in autistic children after several months on the elimination diets, nearly all the studies lacked control subjects, individuals who continued to digest the suspect proteins. Because the researchers did not compare the restricted-diet children with a control group, they could not specify whether the behavioral and cognitive gains actually resulted from the diets, from the children’s maturation or from other therapies conducted at the same time.
The new studies, in contrast, involve control subjects and have a double-blind design: neither the researchers nor the parents will know whether the autistic children are consuming gluten or casein, so the evaluations of the children’s behavior will not be tainted by wishful thinking. In a study led by Robin Hansen of the University of California, Davis, all participants go on a gluten-free diet for two months; then, for the next two months, half the subjects eat daily snacks containing gluten while the other half get indistinguishable gluten-free snacks. Susan Hyman of the University of Rochester is running a similar study testing the behavioral effects of both gluten and casein. An investigation at the University of Pittsburgh Medical Center will monitor the effects of combining the gluten-free, casein-free diet with supplements of omega-3 fatty acids, another popular but unproved therapy for autism.
The researchers have run into some trouble recruiting autistic subjects. Many parents who are committed to the gluten-free, casein-free diet do not want to participate because their children may be included in a control group and receive the offending substances. Hansen says she originally hoped for 60 subjects but now expects 30. Her results should be available in about six months. “It’s a hard study to do, but it’s worth doing,” says Susan E. Levy, director of the Regional Autism Center at Children’s Hospital of Philadelphia. “I’m hopeful that we’ll know a lot more in a year.”
REVERSING THE DAMAGE
Although research on diet and autism is still in its infancy, scientists are making great strides in understanding the genetic roots of the disorder, which strikes about one in 150 U.S. children. Mutations of a gene called MECP2 cause Rett syndrome, the most physically disabling of the conditions in the autism spectrum.
A team led by Adrian Bird of the University of Edinburgh in Scotland recently showed that reactivating MECP2 in mice reversed their neurological damage, eradicating tremors and restoring normal breathing in animals that were, in some cases, only days from death. Many genes are involved in causing the more common forms of autism, but the new research holds out the hope that scientists may someday develop therapies that could repair the brains of children suffering from the disorder.
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发表于 2006-8-19 08:54:44