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Large doses of vitamin B1 counteract chronic fatigue in inflammatory bowel diseases and possibly also in other conditions

Large doses of vitamin B1 counteract chronic fatigue in inflammatory bowel diseases and possibly also in other conditionsA team of scientists from Århus University Hospital has discovered that high-doses supplementation with vitamin B1 can help against chronic fatigue that is seen with chronic inflammatory bowel diseases like Crohn’s disease and ulcerative colitis. High doses of vitamin B1 may even help against chronic fatigue in fibromyalgia and other neurological disorders. The scientists have not yet mapped out how the large vitamin doses affect the brain and energy levels and several theories are on the table.

Chronic inflammatory diseases like Crohn’s disease and ulcerative colitis are not limited to causing local symptoms in the digestive tract but can also cause chronic fatigue, a widespread problem. In the dormant phase, 15-54 percent of patients experience devastating physical and mental fatigue that cannot be compared with regular tiredness. It affects their quality of life, mood, and ability to work and perform. The Danish study from Århus University Hospital included 40 patients (35 women and 5 men) with inflammatory bowel disease in its dormant phase. All the included patients had suffered severe and prolonged fatigue for over six months. Half the patients had Crohn’s disease, while the other half had ulcerative colitis. There was no immediate explanation to the participants’ fatigue.
The aim of the study was to reduce the participants’ self-reported fatigue with four weeks of high-dosage vitamin B1 supplementation. Their fatigue was measured using the IBD-F (Inflammatory Bowel Disease Fatigue Questionnaire) scale where higher scores mean worse fatigue.
The participants were split in two groups and none of them knew who got what.
Group 1 started by getting vitamin B1 for four weeks, while group 2 got placebo during the same period. The groups switched interventions after four weeks
Tablets containing 300 mg of vitamin B1 as thiamin hydrochloride were used. This is a very high dose, considering that the reference intake (RI) level is only 1.1 mg. The 300-mg tablets were given in varying doses, depending on the following:


  • Under 60 kg/2 tablets (600 mg)
  • 60-70 kg/3 tablets (900 mg)
  • 71-80 kg/4 tablets (1,200 mg)
  • Over 80 kg/5 tablets (1,500 mg)


  • Under 60 kg: 3 tablets (900 mg)
  • 60-70 kg: 4 tablets (1,200 mg)
  • 71- 80 kg: 5 tablets (1,500 mg)
  • Over 80 kg: 6 tablets (1,800 mg)

It is not stated clearly if the participants took all tablets at once or divided them into portions (which is bound to give better utilization). However, the volunteers were advised against taking the tablets at night because of the risk of transient insomnia.

Vitamin B1 helps against chronic fatigue in inflammatory bowel disease

The study showed that high-dose vitamin B1 supplementation was statistically and clinically significant compared with placebo. In different terms, the participants felt substantially better during the period where they took supplements of vitamin B1 with an average 4.5-point fatigue reduction on the IBD-F scale. Forty-five percent of the volunteers had normal fatigue levels after four weeks of treatment with vitamin B1. According to the scientists, this therapy may be of huge importance to these vulnerable patients and their quality of life. It is inexpensive, simple, and without side effects.
The Danish study is published in Alimentary Pharmacology and Therapeutics.

Can high-dosed vitamin B1 also help against chronic fatigue in other diseases?

During the period 2013-2018, the Italian doctor Antonio Costantini and his team of scientists conducted a number of small-scale studies that showed that large doses of vitamin B1 (600 – 1,800 mg) could reduce chronic fatigue in inflammatory bowel disease and neurological disorders such as sclerosis, Parkinson’s disease, and cluster headache (Horton’s disease). However, the studies were rather small and without placebo groups. Nonetheless, the new Danish study helps shed light on vitamin B1’s potential in treating chronic fatigue.

How can vitamin B1 help against fatigue?

Vitamin B1 is a water-soluble vitamin that is important for our energy metabolism and especially our carbohydrate metabolism. Carbohydrates constitute the primary source of fuel for the brain and nervous system. Vitamin B1 is also important for normal nerve and brain function and for maintaining a normal mental balance.
High-dosed vitamin B1 supplementation is not believed to work simply by addressing the lack of the nutrient, yet scientists don’t know the exact mechanism. However, is it possible that the large doses of the vitamin are able to compensate for some of flawed enzyme functions such as the transport of vitamin B1 from the blood to the cells’ mitochondria, which is where our energy is produced.
There are different theories about high-dosed vitamin B1 supplementation and how it affects the brain and nervous system by:

  • Improving the energy turnover
  • Improving cerebral blood flow
  • Reducing the cerebral blood pressure
  • Reducing local brain inflammation
  • Increasing the synthesis and release of dopamine (important for people with Parkinson’s disease)

It is even possible that high-dosed vitamin B1 supplementation helps you wake up faster in the morning if this is a problem.

Supplementation with vitamin B1

Vitamin B1 should be taken in combination with the other B vitamins and not together with antacids. Vitamin B1 is water-soluble and therefore non-toxic, as excess amounts of the vitamin are excreted in the urine. It is safe to take high quantities of the vitamin, and there are no known side effects. If you take a very high quantity you may want to split it into several smaller doses and take the over the course of the day. Beware that vitamin B1 taken at night may give you excessive energy and disrupt your sleep.


Palle Bager et al. Randomized clinical trial: High-dose oral thiamine versus placebo for chronic fatigue in patients with quiescent inflammatory bowel disease. Alimentary Pharmacology and Therapeutics. 18 November 2020

Sasja Jul Håkonson. Højdosis B1-vitamin kan modvirke kronisk træthed hos patienter med inflammatorisk tarmsygdom. Sygeplejersken. 2021

Jeffry Lubell. Why does High-Dose Thiamine Relieve Fatigue in Individuals with Diverse Conditions? Hypotheses grounded in Thiamine´s Role as a Carbonic Anhydrase Inhibitor. EDS Perspectives 2021

Jeffery Lubell. Nearly 2/3rds of Survey Respondents report large Benefits from High-Dose Thiamine (B-1) HealthRising 2021

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