Concentrations of Thiocyanate and Goitrin in Human Plasma, Their Precursor Concentrations in Brassica Vegetables, and Associated Potential Risk for Hypothyroidism

Nutr Rev. 2016 Apr;74(4):248-58. doi: 10.1093/nutrit/nuv110. Epub 2016 Mar 5.

Abstract

Brassica vegetables are common components of the diet and have beneficial as well as potentially adverse health effects. Following enzymatic breakdown, some glucosinolates in brassica vegetables produce sulforaphane, phenethyl, and indolylic isothiocyanates that possess anticarcinogenic activity. In contrast, progoitrin and indolylic glucosinolates degrade to goitrin and thiocyanate, respectively, and may decrease thyroid hormone production. Radioiodine uptake to the thyroid is inhibited by 194 μmol of goitrin, but not by 77 μmol of goitrin. Collards, Brussels sprouts, and some Russian kale (Brassica napus) contain sufficient goitrin to potentially decrease iodine uptake by the thyroid. However, turnip tops, commercial broccoli, broccoli rabe, and kale belonging to Brassica oleracae contain less than 10 μmol of goitrin per 100-g serving and can be considered of minimal risk. Using sulforaphane plasma levels following glucoraphanin ingestion as a surrogate for thiocyanate plasma concentrations after indole glucosinolate ingestion, the maximum thiocyanate contribution from indole glucosinolate degradation is estimated to be 10 μM, which is significantly lower than background plasma thiocyanate concentrations (40-69 μM). Thiocyanate generated from consumption of indole glucosinolate can be assumed to have minimal adverse risks for thyroid health.

Keywords: Chinese cabbage; broccoli; glucoraphanin; glucosinolate; indole; kale; phase II enzymes.

Publication types

  • Research Support, N.I.H., Extramural
  • Review

MeSH terms

  • Brassica / adverse effects
  • Brassica / chemistry*
  • Diet
  • Glucosinolates / adverse effects
  • Glucosinolates / blood
  • Glucosinolates / pharmacology*
  • Humans
  • Hypothyroidism / blood
  • Hypothyroidism / chemically induced*
  • Imidoesters / adverse effects
  • Imidoesters / pharmacology
  • Indoles / adverse effects
  • Indoles / blood
  • Indoles / pharmacology*
  • Iodine / metabolism
  • Isothiocyanates / adverse effects
  • Isothiocyanates / blood
  • Isothiocyanates / pharmacology*
  • Oxazolidinones / blood*
  • Plant Extracts / adverse effects
  • Plant Extracts / blood
  • Plant Extracts / pharmacology
  • Thiocyanates / blood*
  • Thyroid Gland / drug effects
  • Thyroid Gland / metabolism
  • Thyroid Hormones / metabolism
  • Vegetables / chemistry

Substances

  • Glucosinolates
  • Imidoesters
  • Indoles
  • Isothiocyanates
  • Oxazolidinones
  • Plant Extracts
  • Thiocyanates
  • Thyroid Hormones
  • isothiocyanic acid
  • progoitrin
  • goitrin
  • Iodine
  • sulforafan
  • thiocyanate
  • glucoraphanin