Two studies suggest that thiamin (vitamin B-1) may reduce stuttering. One study was of children; the other study investigated adults who stutter.

The Hale Study

A 1951 study 1 investigated thiamin with an unspecified number of children.

Each child received either 30 mg of thiamin (vitamin B-1) or a placebo for one month, and then the opposite for a second month. In four cases in which a child started on thiamin, and then stuttering returned when the child went on the placebo, thiamin was given in a third month, with the results that all four of these children’s speech improved.

The study was double-blind. “In most cases follow-up observations continued beyond the two-month control period.”

Stuttering wasn’t measured. The previous article in the same issue of the journal was about ways to measure stuttering. In other words, in 1951 measuring stuttering was just beginning.

The results of the Hale study were:

  1. 80% of the two- and three-year olds had “observably improved” speech.
  2. 50% of the four-year-olds “were definitely improved.”
  3. Little improvement was seen in the five-year-olds.
  4. No improvement was seen in the seven- and eight-year-olds.
  5. As noted above, four children did an ABA design study, with thiamin switching off their stuttering, stuttering returning on the placebo, and then thiamin switching off the stuttering again.
  6. Except for one child, all of the children who responded to thiamine did so within two weeks.

The first four results are similar to what we now know is the spontaneous recover rate for children, that is, 80% of pre-schoolers recovery from stuttering without therapy, and after a child is about five years old spontaneous recovery becomes unlikely. I.e., the number of children who responded to thiamin was unimpressive.

The interesting results of the Hale study are in the last two: the effects were seen within two weeks of starting thiamine, and in four children thiamin appeared to switch stuttering on and off. Without treatment, most spontaneous recovery occurs 31 to 36 months (two-and-a-half to three years) after onset. The 80% spontaneous recovery rate is over five years. 2 In other words, the Hale study found that thiamin was effective for about the same number of children who would have spontaneously recovered without treatment; but thiamin speeded up recovery time from two-and-a-half to five years to two weeks. It would be interesting to investigate if the children who don’t respond to thiamin are the same children who don’t spontaneously recover from stuttering; perhaps these children have some neurological abnormality, or perhaps they don’t absorb B vitamins well?

The diminishing effect with older children could be because two- and three-year-olds typically weigh about 30 pounds; when seven- and eight-year-olds typically weigh about 60 pounds, so the older children were getting about half the dosage. I.e., the young children received about one milligram of thiamine per pound of body weight, when the older children received half a milligram per pound.

How does this study measure up to modern studies? The biggest problem is the lack of measurement of stuttering, not disclosing the number of subjects, and the lack of statistics. This doesn’t invalidate the study; rather, it limits the results to either dramatic or nothing. In contrast, a modern study of a medication can measure subtle effects.

The article also referred to an unpublished study 3 of 17 adults in which “the greatest speech improvement was observed during the periods of thiamin consumption as compared to those periods during which a placebo was administered.”

Vitamin B-1 foods

The Schwartz Study

In a recent double-blind study 4 of 38 adult male stutterers, half received 300 milligrams of vitamin B-1 (three 100 mg pills, one with each meal, plus a daily B-complex pill). The others received a placebo. Of the 19 men who received the vitamin, stuttering was “largely eliminated” in six of the men. For the other 13 men no effect was seen. The six men were then followed for seven months and “their speech has remained essentially free of stuttering.”

Adult men typically weigh about 190 pounds so these men received more than one milligram per pound of body weight, or a little more than was effective for the young children in the Hale study.

The study was rejected by Nature because it didn’t follow formal procedures for registering human subjects and because a news release with the results had been released. The study wasn’t rejected for scientific reasons. The author hasn’t submitted the study to any other journals because he is continuing the study with the men whose speech wasn’t affected, with a combination of 1000 mg thiamin, B-complex, and magnesium orotate.

Magnesium supplements were added because a study 5 that tested minerals in the blood of 53 stuttering children aged 5-12, and a control group of 22 non-stuttering children aged 6-16. Sodium, potassium, calcium and magnesium were tested. The only significant difference was found in magnesium. 47% of the stuttering children were low in magnesium. One of the functions of magnesium is in metabolizing B vitamins.

How Important Is Evidence Quality?

Evidence standards can be lower for treatments that have no side effects, are inexpensive, require no time, etc. If all you have to do is pick up a $5 bottle of vitamins at the drug store, the evidence we have is good enough to recommend trying thiamine.

In contrast, medications with harmful side effects, brain surgery (yes, this has been suggested!), or lengthy, expensive therapy programs should be proven in large, high-quality studies before they are recommended.

The StutterSense Poll

An informal poll on the StutterSense blog found that of 22 stutterers who had tried thiamine, 36% said that it didn’t help, 36% said that it helped somewhat, and 27% said that they experienced a dramatic improvement in their speech.

A Double-Blind Study on Myself

In late 2011 I tried 300 mg thiamine. My speech greatly improved within a few days. Then two months later my speech deteriorated. It wasn’t as bad as before using thiamine, but it wasn’t much better. I was disappointed that the effect had “worn off” over time. Then I remembered that I’d finished the first bottle of sixty tablets and gone to the drugstore to buy a new bottle. I looked and saw that the new bottle was 100 mg tablets. I went back to 300 mg and my fluency immediately returned. I’d done a double-blind study on myself!

In 2013 I increased my dosage to 1200 mg and my speech improved, almost to complete fluency.

I’ve since backed down the dosage to where my speech is pretty good. I can control my speech and speak fluently, or just talk with mild stuttering. I take 300mg of thiamin twice a day (600mg total), plus I take 300mg and 400mg of magnesium daily (700mg total).

You’ll see in the comments that there are different forms of thiamin. Some thiamin is fat-soluble and other thiamin is water soluble; some stutterers say that one works for them but the other doesn’t. I’ve tried both and I don’t notice a difference. I just take thiamin hydrochloride (HCl), the “regular” inexpensive vitamin B-1.

Magnesium also comes in a variety of forms. I’ve tried several and noticed no difference. I found two brands that each mix five forms of magnesium (citrate, taurinate, succinate, etc.). I have no idea whether any of these is better than the others, so I take one of each daily, to cover all bases.


Safety of Thiamine

The Recommended Daily Allowance (RDA) of vitamin B-1 is 1.4 mg, i.e., the minimum amount needed for health. The maximum safe dosage is 7000 milligrams per day.

What Thiamine Does in the Brain

Thiamine’s role in the brain is beyond my area of expertise, but I’ll quote Paul Brocklehurst. Dr. Brocklehurst studied medicine for two years but had to drop out due to severe stuttering. Twenty-five years later he returned to university, earned a degree in speech therapy, and then in 2011 earned his Ph.D. with a dissertation on stuttering. He writes:

Of particular interest is the role that thiamine plays in maintaining cerebellar function and structure. Thiamine deficiency contributes to a reduction in the number and size of Purkinje cells in parts of the cerebellar vermis (Philips et al. 1987). Thus, thiamine deficiency can lead to clinical and subclinical manifestations of ataxia (poor spatial and temporal muscle co-ordination). The most common example of this (in adults) is related to excess alcohol consumption (alcohol can lead to thiamine deficiency). Also of interest, is the fact that thiamine plays a role in the production of and enzyme pyruvate dehydrogenase (PDH), which is needed for the production of myelin. Imaging studies have shown that some PWS have myelin deficiencies and/or impaired cerebellar function, so both myelin deficiency and cerebellar impairment could play a role in predisposing to stuttering. 6

The following is from a paper about thiamine deficiency in alcoholics:

Thiamine is a helper molecule (i.e., a cofactor) required by three enzymes involved in two pathways of carbohydrate metabolism. Because intermediate products of these pathways are needed for the generation of other essential molecules in the cells (e.g., building blocks of proteins and DNA as well as brain chemicals), a reduction in thiamine can interfere with numerous cellular functions, leading to serious brain disorders. 7

And there’s always Wikipedia:

the nervous system is particularly sensitive to thiamine deficiency, because of its dependence on oxidative metabolism…The brain requires a much greater amount of thiamine than in other cells of the body. Much of ingested thiamine never reaches the brain because of passive diffusion and the blood brain barrier.



  1. Hale, L. (1951). A consideration of thiamin supplement in prevention of stuttering in preschool children. Journal of Speech and Hearing Disorders, 16:4; 327-333.
  2. Yairi, E., & Ambrose, N.G. Early Childhood Stuttering for Clinicians by Clinicians. (2005, ISBN 89079-985-7), page 167.
  3. Penson, E.M. An exploratory study of the effect of thiamin hydrochloride on adults who stutter. M.A. thesis, Ohio Univ., 1951.
  4. Schwartz, M. Thiamin and Stuttering; a preliminary study. (accessed 2013 April 24)
  5. Schleier E, Schelhorn P, Groh F. (1991) Biochemical studies in stuttering in children. Otolaryngol Pol. 1991;45(2):141-4.
  6. Brocklehurst, Paul. 2013. RE:Vitamin B1 and stammering. [ASHA SIG 4]: SIG 04, Fluency and Fluency Disorders Digest for Friday May 10, 2013
  7. Peter R. Martin, M.D., Charles K. Singleton, Ph.D., and Susanne Hiller–Sturmhöfel, Ph.D. 2004 The Role of Thiamine Deficiency in Alcoholic Brain Disease.