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Why Alcoholics with Vitamin B1 (Thiamine) Deficiency Need Parenteral Thiamine vs Oral Thiamine

Summary:

  • Our bodies get thiamine from two different sources with the majority coming from our diet and then normal flora found in our large intestines.
  • In the small intestine, alcohol is in part known to inhibit the absorption of thiamine across the brush boarder membrane due to its ability to inhibit the gene expression of thiamine transporter-1 (THTR-1), but not thiamine transporter-2 (THTR-2).
  • Within the large intestine, it was noted in the same animal studies that absorption was also inhibited.  This was in part due to a reduction in the gene expression of both THTR-1 and THTR-2.
  • Due to this effect of alcohol on the intestinal absorption of thiamine, replacement of thiamine should be done intravenously.

Editor-in-Chief: Anthony J. Busti, MD, PharmD, FNLA, FAHA
Reviewers:
Jon D. Herrington, PharmD, BCPS, BCOP
Last Reviewed: October 2015

Explanation

  • In order for the human body to have vitamins present to aid in various biological processes they must be ingested through our diet or administered directly into the body parenterally.  The ingestion or administration of vitamins is important since our bodies do not synthesize their own vitamins.  Anything that impairs these sources of vitamin delivery can put the patient at risk for medical complications, as seen in chronic alcoholics who become deficient in vitamin B1 (thiamine).1,2   

    Our bodies get thiamine from two different sources with the majority coming from our diet and then normal flora found in our large intestines.  The problem with thiamine is in our ability to become deficient fairly quickly compared to some other vitamins.  This is in part why thiamine is added to some foods and reported on many food labels.   Natural sources of thiamine include whole-grain cereals and breads, legumes, and meats such as pork and liver, whereas milk, fruits, seafood and vegetables are not good sources.3  As previously mentioned, alcoholics are commonly known to be deficient in thiamine.  The main mechanism behind this appears to be alcohol's ability to inhibit the gastrointestinal absorption of ingested thiamine from our diet.1,2

    How does alcohol reduce the absorption of thiamine in the gastrointestinal tract?
    As it relates to absorption in the small intestine, it appears that alcohol has the ability to impair the entry of thiamine into the enterocytes lining the brush boarder membrane that line the luminal side of the jejunum.4  In addition, alcohol can impair the movement of thiamine from within the enterocyte of the small intestine through the basolateral side where it would normally enter into the portal circulation for delivery into the body.  Animal studies suggest, that the impairment across the brush boarder membrane within the lumen appears to be due to alcohol's ability to reduce the gene expression for thiamine transporter-1 (THTR-1) but not thiamine transporter-2 (THTR-2).  This means the number of thiamine transporters to bring thiamine into the enterocyte was decreased.  As such, even though thiamine was present in the intestinal tract, it was not being absorbed in the presence of alcohol. 

    Within the large intestine, it was noted in the same animal studies that absorption was also inhibited.  This was in part due to a reduction in the gene expression of both THTR-1 and THTR-2.  Furthermore, this suggests that alcohol may have tissue specific effects on thiamine transport and distribution.   While this data comes from animal models, it appears to be consistent with what is seen clinically in patients suffering from chronic alcoholism.  If left untreated, these patients are at increased risk for Wernicke-Korsakoff Syndrome. 

    When treating or preventing patients from developing worsening Wernicke-Korsakoff Syndrome, the recommended route of thiamine delivery is intravenously.  This is done in part to prevent them from aspirating since many alcoholics will present with altered mental status and/or episodes of emesis.  In addition, if thiamine were to be administered by mouth it would not be as efficiently absorbed due to the mechanisms above.  Therefore, intravenous thiamine is the recommended route of thiamine replacement, especially in the acute setting.

    References:

    1. Gastaldi G, Casirola D, Ferrari G et al. Effect of chronic ethanol administration on thiamine transport in microvillous vesicles of rat small intestine.  Alcohol Alcohol 1989;24:83-89.  
    2. Hoyumpa AM, Jr. Mechanisms of thiamin deficiency in chronic alcoholism.  Am J Clin Nutr  1980;33:2750-2761.  
    3. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. National Academy Press, Washington, DC, 1998.
    4. Subramanya SB, Subramanian VS, Said HM.  Chronic alcohol consumption and intestinal thiamin absorption: effects on physiological and molecular parameters of the uptake process.  Am J Physiol Gastrointest Liver Physiol 2010;299:G23-31.

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MESH Terms & Keywords

  • Thiamine, Thiamin, Vitamin B1, IV Thiamine, Oral Thiamine, Chronic Alcoholism