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B17.5
Thiamine Research
Probably helps
182 peer-reviewed studies
What the evidence says
Probably helps
Thiamine helped in about half (7/12) of the studies that measured an effect — promising, but not unanimous.
Most evidence is from high-quality meta-analyses and randomised trials published 1971–2026 with a typical study size of 163 participants.
Based on 182 studies · 19 meta-analyses · 128 RCTs · 21,040 total participants
Confidence
High confidence
What the studies found
7helped2unclear3didn't help· 170 more without graded effect data
By outcome
Therapeutic & clinical
Probably helps156 studies
Beriberi & Wernicke-Korsakoff
Mostly mechanism / observational16 studies
Glucose & metabolic
Mostly mechanism / observational15 studies
Heart & blood pressure
Mostly mechanism / observational12 studies
Safety profile
Mostly mechanism / observational10 studies
Cognitive function
Mostly mechanism / observational8 studies
Energy & fatigueImproved energy from carbohydrate metabolism · 2-4 weeks
Mostly mechanism / observational4 studies
Women's healthMay help reduce menstrual discomfort and PMS symptoms · 1-3 cycles · Provides essential nutrients for healthy pregnancy · Ongoing
67 studies in the last 5 years · Latest meta-analysis: 2026
197119982026
1Systematic Reviewn=3,254 · very large study2025
In plain English: There is some evidence to support the use of nutritional interventions for improving psychological symptoms of PMS.
Robinson J et al. · Nutrition reviews (2025)
There is some evidence to support the use of nutritional interventions for improving psychological symptoms of PMS.
However, more research using consistent protocols, procedures to minimize risk of bias, intention-to-treat analysis, and clearer reporting is required to provide conclusive nutritional recommendations for improving PMS-related psychological outcomes.
3Vitamin B1 deficiency prevalenceMeta-Analysisn=1,494 · large study2022
Bahardoust M et al. · Obesity surgery (2022)
Large benefit
← WorseNo effectBetter →
Twenty-seven percent of patients who underwent bariatric surgeries experience vitamin B1 deficiency.
A total of 11 studies examining 1494 patients were included in this meta-analysis.
Thiamine supplements should be prescribed for the patients for the rest of their lives, and also standard post-surgery follow-ups are necessary in terms of monitoring dietary factors.
4Dysmenorrhoea pain reductionMeta-Analysisn=3,101 · very large study2016
In plain English: There is no high quality evidence to support the effectiveness of any dietary supplement for dysmenorrhoea, and evidence of safety is lacking.
Pattanittum P et al. · The Cochrane database of systematic reviews (2016)
Noticeable benefit
← WorseNo effectBetter →
Supplements versus other supplementsThere was no evidence of a difference in effectiveness between ginger and zinc sulphate (MD 0.02 points, 95% CI -0.58 to 0.62; one RCT, 101 women).
Vitamin B1 may be more effective than fish oil (MD -1.59 points, 95% CI -2.25 to -0.93; one RCT, 120 women).
There is no high quality evidence to support the effectiveness of any dietary supplement for dysmenorrhoea, and evidence of safety is lacking.
In plain English: Diabetes is associated with lower levels of various thiamine markers, suggesting that individuals with diabetes may have higher thiamine requirements than those without diabetes, but well-designed studies are required to confirm these findings.
Ziegler D et al. · Metabolism: clinical and experimental (2023)
Huge benefit
← WorseNo effectBetter →
Compared to controls, individuals with diabetes showed lower concentrations of thiamine (pooled estimate SMD [95 % CI]: -0.97 [-1.89, -0.06]), thiamine monophosphate (-1.16 [-1.82, -0.50]), and total thiamine compounds (-1.01 [-1.48, -0.54]).
Diabetes is associated with lower levels of various thiamine markers, suggesting that individuals with diabetes may have higher thiamine requirements than those without diabetes, but well-designed studies are required to confirm these findings.
19Neuropathy symptom improvementMeta-Analysisn=46 · small study2021
In plain English: PN is associated with lowered plasma vitamin B12 and elevated methylmalonic acid and homocysteine.
Stein J et al. · European journal of neurology (2021)
Huge harm
← WorseNo effectBetter →
Borderline
B12 treatment (vs. the comparators) showed a non-significant association with symptom improvement (1.36 (0.66-2.79), n = 4, I2 = 28.9%).
Treatment with B1 was associated with a significant improvement in symptoms (5.34 [1.87-15.19], n = 3, I2 = 64.6%, p = 0.059).
Analysis of seven trials combined showed a non-significant higher odds ratio for improvement under treatment with the B-vitamins (2.58 [0.98-6.79], I2 = 80.0%, p < 0.001).