Evidence for a clinically important adverse effect of fiber-enriched diet on the bioavailability of levothyroxine in adult hypothyroid patients

Yair Liel, Ilana Harman-Boehm, Shraga Shany

Research output: Contribution to journalArticlepeer-review

109 Scopus citations

Abstract

To evaluate the effect of dietary fiber supplements on levothyroxine (T4) bioavailability in hypothyroid patients, dietary fiber-containing supplementation was withheld from patients requiring disproportionately high doses of T4, in whom a dietary history revealed ingestion of a dietary fiber supplement. The dose of T4 was maintained at a constant level. Serum thyrotropin (TSH) was assessed before and after removal of the dietary fiber supplements. T4 requirements, reflected by either decreased serum TSH or by decreased T4 dose, was observed in conjunction with decreased dietary fiber intake compared with T4 requirement during increased dietary fiber intake. In vitro experiments carried out to determine the mechanism of interaction between dietary fiber and T4 revealed dose dependent, nonspecific adsorption of levothyroxine by wheat bran. These results indicate a decrease in T4 bioavailability by dietary fiber through a mechanism involving nonspecific adsorption of T4 to dietary fibers. Increased intake of dietary fiber may account for the need for larger than expected doses of T4 in some hypothyroid patients.

Original languageEnglish
Pages (from-to)857-859
Number of pages3
JournalJournal of Clinical Endocrinology and Metabolism
Volume81
Issue number2
DOIs
StatePublished - 20 Feb 1996

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Biochemistry
  • Endocrinology
  • Clinical Biochemistry
  • Biochemistry, medical

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