Jean-Francois Demonet and colleagues’ extensive Seminar on developmental dyslexia (May 1, p 1451)
omits any reference to the nutrients essential for normal brain development and function. In 1989, we reported that dyslexic children were severely zinc-deficient in their sweat and had higher concentrations of toxic metals in their sweat and hair. The difference between the zinc concentrations in passive sweat of dyslexic children and their matched controls was highly significant (p<0·0001).
Animal studies show that zinc deficiency in offspring causes impaired learning which can be corrected by zinc supplementation. However, maternal zinc deficiency during early fetal development causes permanent impaired learning and impairs the offspring’s stress-coping mechanisms, which can increase urinary loss of zinc throughout life in response to stress.
Good nutritional care involves correction of common deficiencies in both parents before conception, and maintenance of an adequate zinc status during pregnancy, lactation, and growth. This strategy seems to prevent troublesome dyslexia, even in families with a genetic susceptibility to the disorder. The deleterious effects of numerous genetic disorders could possibly be remedied by feeding high-dose B vitamins and by ensuring adequate levels of zinc, folic acid, and other essential nutrients.
Zinc deficiency, which can also be diagnosed from measurements of concentrations of zinc in white cells, impairs the function of B vitamins and blocks essential phospholipid pathways. In dyslexia there is evidence for reduced incorporation of docosahexaenoic acid and arachidonic acid into cell membranes, by contrast with schizophrenia in which there is an increased rate of loss of these omega-3 essential fatty acids.
The fact that children and adults with developmental dyslexia are likely to continue to have important nutritional deficiencies throughout their lives, which further impair their already permanently impaired brain function, is too important to be ignored by dyslexia experts. Doctors who practise nutritional medicine, which includes monitored nutritional supplementation for individuals, find that the younger a child is repleted, the more rapid is the improvement in learning and behaviour. It is particularly important for children with developmental dyslexia that any treatable nutritional deficiencies should be diagnosed. Controlled trials find that vitamin and mineral supplements improve intelligence scores and brain-function tests, and reduce brain-wave abnormalities.
