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Folate RDA May Be Insufficient

By Robert Bock

A study of Irish women indicates that current dietary standards for the nutrient folate -- known to prevent a devastating class of birth defects and possibly cardiovascular disease -- do not take into account the increased folate requirements of a large minority of people genetically at risk for folate deficiency.

The study, published in the May 31 issue of the Lancet and funded in part by NICHD, shows that a much greater number of women than was previously believed are genetically at risk for an enzyme defect that causes a vitamin deficiency that predisposes them to having children with a neural tube defect -- a debilitating class of birth defects affecting the brain and spinal cord.

"This challenges the assumption underlying the recommended daily allowance -- that virtually everyone can take the same amount of a vitamin and do fine," said Dr. James L. Mills, chief of NICHD's pediatric epidemiology section.

He added that the study he and his colleagues conducted focused solely on women, but the same genetic defect, present in men, might also increase the risk for heart disease, stroke and cancer of the colon.

Neural tube defects (NTDs) are a class of birth defects affecting the brain or spinal cord. They occur in about one per thousand pregnancies in the U.S. each year. Among the most common NTDs are spina bifida, in which a piece of the spinal cord protrudes from the spinal column, causing paralysis below the protrusion, and anencephaly, a fatal condition in which the brain fails to develop normally.

Currently, the National Academy of Sciences' recommended daily allowance (RDA) for folate is 400 micrograms per day for pregnant women and 180 micrograms for other adult women and 200 micrograms for male adults. The results of the current paper suggest that people having two copies of the abnormal gene may need more folate than these guidelines specify to compensate for their genetic deficiency. Additional studies will be needed, however, to determine exactly how much more folate they would require.

Hearing Test Identifies Problems in Children
With Language Impairment

By Jo Bagley

A hearing test has uncovered auditory processing problems that may be at the root of a childhood language disorder that often affects school performance, according to a study reported in a recent issue of Nature.

The same hearing test has the potential to improve the ability to identify these children, many of whom become discouraged with school because of frequent failures tied to their language difficulties.

The language disorder, known as specific language impairment (SLI), affects approximately 3 to 6 percent of children who are normal with the exception of varying degrees of difficulty understanding and expressing spoken language. Many but not all children who have reading problems fall into this category.

"SLI has sometimes been viewed as being specific to language," said Dr. Beverly Wright of Northwestern University, primary investigator of the study. She used a different approach. "I decided to use my background in psychoacoustics to test the ability of these children to process nonspeech sounds or sounds unrelated to language," she explained. "Our team was astounded by what we observed."

What they found were clear and distinct differences between the ability of all children in their study with SLI to process brief tones in special sound contexts as compared to normal children. The differences depended on where the tones were placed in time in relation to other sounds as well as on the frequencies (pitches) of the tones in relation to the frequencies of other sounds.

A child who has problems perceiving rapid sounds or sounds in certain contexts will have problems learning, understanding and expressing spoken language.

Wright and her colleagues are continuing research to train children to overcome their auditory processing difficulties and thus improve their language ability and subsequent school performance.

"This research offers a fresh approach to a perplexing problem that often leads to continual failure in school," commented Dr. James B. Snow, Jr., director of the National Institute on Deafness and Other Communication Disorders, which provided partial support for this study.

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