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The National Center For Stuttering 

Thiamin and Stuttering; a preliminary study

Martin F. Schwartz, Ph.D.

In the December, 1951 issue of the Journal of Speech and Hearing Disorders there appeared a brief report on the effects of Thiamin (vitamin B1) on the stuttering of children.1 Specifically, 30 mg of the vitamin was given to unspecified numbers of stuttering children between the ages of two and eight. A double blind, supplement/placebo-reversal format was employed. According to the investigator: “Observable speech improvement occurred in 55% of all cases” and “of the two- and three-year olds, 80% were observably improved” while “only 50% of the four-year-olds were observably improved.” There seemed to be no positive effect for the Thiamine above that age. The author’s conclusion was that 30 mg of Thiamin was useful in reducing stuttering in children, providing they were under the age of 5.

Decades later, as Executive Director of The National Center For Stuttering, I remembered that report, and when parents called requesting guidance for young children who had recently begun to stutter, along with the usual recommendations,2 I suggested giving the child 30 mg of Thiamin daily - provided the child was between 2 and 4 and the parents had first obtained permission from their pediatrician.

Over the years, as a result of this recommendation, I accumulated a body of anecdotal information regarding early childhood stuttering and Thiamin. Here were the relevant observations: If Thiamin proved to be effective, the result occurred within a week or two and was dramatic. It was as if a ‘switch’ had been thrown, and the stuttering, as reported in the 1951 study, was markedly reduced. Almost 60 percent of the children showed the ‘switch’ effect. For those children, the possibility of a placebo seemed unlikely. On the other hand, if a week or two passed with no improvement, none would likely occur, regardless of the length of time the supplement was taken.

In no instance, was more than 30 mg of the vitamin recommended.

In 2002, I began an informal exploration using larger amounts of Thiamin with adults who stuttered. It was from this exploration that the idea for the present study emerged.

The Study

In this study I examined the percent syllables stuttered from two groups of presumed equivalent stutterers, one taking 300 milligrams of Thiamin (vitamin B1) daily and the other, a placebo.

In all, 38 males between the ages of 21 and 37, participated. All had stuttered since early childhood. Apart from the stuttering, their speech was perceptually normal, they were native speakers of American English, and all had at least a high school education. None was receiving speech therapy at the time of the study.

Excluded was anyone with a medical condition that would interfere with Thiamin absorption or any medication or dietary habits that could negate the effects of ingesting the vitamin.3

The experiment lasted for 2 weeks. This time period was selected because prior clinical experience and the 1951 report had both indicated that positive speech effects of Thiamin, if they were to occur, would take place within the first two weeks. In addition, a study prior to this one (unpublished) had shown that 300 mg daily of the vitamin was the upper limit at which positive speech effects might be expected to occur within the two week time period for adults.

Accordingly, all subjects were instructed to take one pill with each meal for a total of three pills daily. Each pill contained either 100 mg of Thiamin or a placebo. Subjects were assigned randomly to each of the two groups and received either the vitamin or the placebo in a classic randomized, double blind presentation format.

Prior to starting the protocol, all subjects were administered a modified version of the percent syllables stuttered portion of the SSI (Stuttering Severity Instrument) #4 test4, the most commonly used instrument for quantifying stuttered speech. Samples were obtained from three speaking situations: reading, face-to-face conversation and telephone calls. The percent syllables stuttered constituted an average derived from the three speaking situations. This average, obtained before and after the experimental intervention, constituted the data used for the statistical analysis.

In all instances, judgments of stutter events were made from simultaneous audio/video recordings by two clinicians with a total of 47 years working with individuals who stutter. The video component was considered essential since, for some individuals, a significant number of stuttering blocks were silent.

The Mann-Whitney U test was used for the data analysis.


Inter- and intra-judge reliability correlation coefficients for the judgments were greater than 94%.

The average percent stuttered syllables for the two groups prior to the start of the study were not significantly different. For the control group (the one receiving the placebo) the difference in percent syllables stuttered between the pre and post trial was also not significantly different. On the other hand, the difference in percent syllables stuttered between the pre and post trial for the supplement group was significant (p<.01).

A closer examination of the data from the supplement group revealed that the ‘switch effect’ was present for 6 of the 19 subjects. For these, the average percent syllables stuttered, post supplement, was substantially less than 1%, with some of the subjects clearly demonstrating no stuttering whatsoever. Pre supplement, the average percent syllables stuttered for this subgroup had been 9.1%. Deleting the data for the ‘switch’ group, and comparing the pre and post supplement results for the remaining 13 subjects yielded no significant difference.


Within the limits of this study, one may conclude that for slightly more than 30% of adult males who stutter between the ages of 21 and 37, 300 mg of Thiamin, taken daily, in the absence of precluding medical conditions, may be of significant value in either substantially reducing or eliminating their stuttering.

The implications for further research are obvious and considerable, provided these findings are valid. At this point, a replication is planned using a lipid-based form of the vitamin that has been shown to yield higher plasma levels.


1 A Consideration Of Thiamin Supplement in Prevention Of Stuttering In Preschool Children. Lester L. Hale, JSHD, Vol. 16: 327-333, 1951.

2 Useful suggestions can be found at: http://www.mnsu.edu/comdis/kuster/Parents/starkweather.html

3 Thiamine deficiency can be caused by malnutrition, antacids, barbiturates, diuretics, a diet high in thiaminase-rich foods (raw freshwater fish, raw shellfish, ferns) and/or foods high in anti-thiamine factors (tea, coffee and carbonated beverages) tobacco and by grossly impaired nutritional status associated with chronic diseases, such as alcoholism, gastrointestinal diseases, HIV-AIDS, and persistent vomiting.

4 Stuttering Severity Instrument, 4th Edition, Glyndon D. Riley, © pro-ed, 2009, Austin, Texas

Martin F. Schwartz, Ph.D. is Executive Director of The National Center For Stuttering and Research Professor of Speech Pathology (retired), Department of Surgery, IRPS, New York University Medical School.

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