TL;DR – Quick Summary ⚡

  • Thiamine (vitamin B1) deficiency is often overlooked but common.
  • Symptoms: fatigue, brain fog, mood changes, insomnia, loss of appetite.
  • At-risk groups: people with obesity, diabetes, pregnancy, psychiatric conditions, elderly, and those on certain medications.
  • Studies show deficiency rates from 10% up to 90% in some groups.
  • Thiamine testing is rare, so deficiency is often missed.

Many people are told that thiamine deficiency is very rare, only affecting alcoholics or people with severe malnutrition. But research shows this isn’t true. Subclinical vitamin deficiencies—especially thiamine—are more common than most realize.

Early Signs of Thiamine Deficiency

Thiamine deficiency can be tricky to spot. Early symptoms are often mistaken for other problems, such as:

  • Fatigue and low energy
  • Mood changes, irritability, or anxiety
  • Brain fog and memory issues
  • Insomnia
  • Loss of appetite

Because the RDA for thiamine is low (1.1–1.2 mg/day) and fortified foods are common, deficiency is often dismissed and rarely tested.

How Common Is Thiamine Deficiency?

Research shows thiamine deficiency is widespread and under-recognized:

  • Some studies report deficiency in 10%–90% of people tested.
  • Rates depend on the group studied and the testing methods used.

Thiamine Deficiency in Different Groups

Thiamin Deficiency, Obesity and Bariatric Surgery

Over 40% of U.S. adults are obese. Among patients waiting for bariatric surgery, 15%–29% were deficient in thiamine, and deficiency often worsens after surgery.

Diabetes and Thiamin Deficiency

One study found thiamine levels were 76% lower in diabetics compared to healthy people. Another showed 96% deficiency rates in diabetics.

Pregnancy and Thiamin Deficiency

  • 27%–36% of pregnant women don’t get enough thiamine.
  • Prenatal vitamins often lack sufficient thiamine.
  • Women with severe vomiting (hyperemesis) are at especially high risk, with deficiency appearing after just a few weeks.

Psychiatric Conditions and Thiamin Deficiency

Brain energy depends on thiamine. A study found 30% of psychiatric patients were deficient. Supplementation may improve depression and anxiety.

Elderly Adults and Thiamin Deficiency

In one study, 50% of elderly participants were deficient despite eating enough thiamine. Hospitalized elderly often show deficiency rates of 20%–40%.

Medications and Alcohol and Thiamin Deficiency

  • Alcohol use depletes thiamine.
  • Drugs like diuretics (furosemide), cardiac glycosides, and anticonvulsants lower thiamine.
  • One study found 98% of patients on high-dose furosemide had thiamine deficiency.

Benfotiamine, or S-benzoylthiamine O-monophosphate, is a fat-soluble form of vitamin B1, thiamin. It is absorbed and utilized by the body quicker and more efficiently than regular water-soluble thiamin1,2. The bioavailability of Benfotiamine is approximately 5-fold that of thiamin and 3.7-fold higher than thiamin hydrochloride according to one study3.

Why Thiamin Deficiency Matters

Thiamine plays a vital role in energy production, brain function, heart health, and immunity. Without enough, people may face fatigue, nerve issues, mental health struggles, and long-term complications.

Benfotiamine (S-benzoylthiamine O-monophosphate) is a special fat-soluble form of vitamin B1 (thiamine). Because it is absorbed and used by the body more efficiently than regular water-soluble thiamine, it offers stronger benefits for nerve and brain health. Research shows benfotiamine is about five times more bioavailable than standard thiamine and nearly four times higher than thiamine hydrochloride.1,2,3

Scientific Studies That Support Our Need for Thiamin

  1. Bioavailability assessment of the lipophilic benfotiamine as compared to a water-soluble thiamin derivative. Ann. Nutr. Metab. 1991;35(5):292–296.
  2. Pharmacokinetic study of benfotiamine and the bioavailability assessment compared to thiamine hydrochloride. J. Clin. Pharmacol. 2014;54(6):688–695.
  3. Int J Clin Pharmacol Ther. 1996 Feb;34(2):47-50. Pharmacokinetics of thiamine derivatives especially of benfotiamine
  4. Observations on induced thiamine (vitamin B1) deficiency in man. Arch. Intern. Med. 1940, 66, 785–799.
  5. Preoperative thiamine deficiency in obese population undergoing laparoscopic bariatric surgery. Surg. Obes. Relat. Dis. 2005, 1, 517–522.
  6. Preoperative nutritional status of patients undergoing Roux-en-Y gastric bypass for morbid obesity. J. Gastrointest. Surg. 2006, 10, 1033–1037.
  7. Thiamin deficiency in people with obesity. Adv. Nutr. 2015, 6, 147–153.
  8. Cells 2021, 10(10), 2595 Hiding in Plain Sight: Modern Thiamine Deficiency
  9. Preventing Wernicke encephalopathy after bariatric surgery. Obes. Surg. 2018, 28, 2060–2068.
  10. Wernicke Encephalopathy After Bariatric Surgery. Ann. Surg. 2008, 248, 714–720.
  11. High prevalence of low plasma thiamine concentration in diabetes linked to a marker of vascular disease. Diabetologia 2007, 50, 2164–2170.
  12. Vitamin B status in patients with type 2 diabetes mellitus with and without incipient nephropathy. Diabetes Res. Clin. Pract. 2015, 107, 57–165.
  13. Vitamin profile of 563 gravidas during trimesters of pregnancy. J. Am. Coll. Nutr. 2002, 21, 33–37
  14. Wernicke’s encephalopathy in hyperemesis gravidarum: A systematic review. Eur. J. Obstet. Gynecol. Reprod. Biol. 2019, 236, 84–9
  15. Thiamine, riboflavin and pyridoxine deficiency in psychiatric in-patients. Br. J. Psychiatry 1982, 141, 271–272.
  16. Adjuvant thiamine improved standard treatment in patients with major depressive disorder: Results from a randomized, double-blind, and placebo-controlled clinical trial. Eur. Arch. Psychiatry Clin. Neurosci. 2016, 266, 695–702.
  17. The impact of thiamine treatment on generalized anxiety disorder. Int. J. Clin. Med. 2011, 2, 439.
  18. Thiamin status of the elderly: Dietary intake and thiamin pyrophosphate response. J. Am. Coll. Nutr. 1994, 13, 57–61.
  19. Clinical relevance of thiamine status amongst hospitalized elderly patients. Gerontology 1999, 45, 96–101.
  20. Is thiamine deficiency in elderly people related to age or co-morbidity? Age Ageing 2000, 29, 111–116.
  21. Can J Clin Pharmacol. 2003 Winter;10(4):184-8. Diuretic use: a risk for subclinical thiamine deficiency in elderly patients