Content uploaded by Michael Kob
Author content
All content in this area was uploaded by Michael Kob on Apr 16, 2018
Content may be subject to copyright.
CRUCIFEROUS VEGETABLES
AND THE THYROID GLAND: FRIENDS OR FOES?
Michael Kob, MD, Division of Clinical Nutrition, Bolzano Central Hospital, Bolzano, Italy
Cruciferous (brassica) vegetables are very common
foods, especially in plant-based diets. They contain
many healthy nutrients, including phytochemicals
with anticarcinogenic, antioxidative and
antiinflammatory activity[1]. However, they also
contain goitrogens[2] such as progoitrin (fig. 1) and
thiocyanate-producing indole glucosinolates (fig.
2), which may interfere with thyroid hormone
production or utilization (fig. 3). The aim of this
evidence-based literature review is to provide
information regarding the influence of cruciferous
vegetables on thyroid function in humans.
A review of articles relating cruciferous vegetables
with thyroid function in humans was performed.
Four observational studies[3,4,5,6],one case report[7],
one article investing the goitrogens content of
brassica vegetables[8] and three experimental
studies were found[9,10,11].
Most of the brassica vegetables have low goitrin
contents, with the exception of collards, Brussel
sprouts and some Russian kale species (fig. 4). The
consumption of 150 gof cooked Brussel sprouts/die
for four weeks did not show any negative effect on
thyroid parameters[11].
The only studies with negative outcomes were
1) acase report where 1-1.5 kg of raw Bok Choy was
consumed daily over several months[7] and
2) observational studies from the seventies,where
children consumed large amounts of milk by cows fed
with high glucosinolate-containing food crops.
CONCLUSIONS: There is little reliable evidence that the consumption of normal dietary levels of
cruciferous vegetables affects thyroid function. Furthermore, the goitrogen-concentration can be
decreased by cooking by boiling, which causes leaching of glucosinolates into water and inactivation
of the enzyme myrosinase [12].
REFERENCES: [1]Wagner AE et al., Oxid Med Cell Longev 2013; [2]Jahangir M et al., Compr Rev Food Saf 2009; [3]Clements FW, Med J Aust
1957; [4]Chandra AK, Indian J Med Res 2008; [5]Fernando R et al., Int J Int Med 2012; [6]Gaitan E, Annu Rev Nutr 1990; [7]Chu M et al., N Engl J
Med 2010; [8]Felker P et al., Nutr Rev 2016; [9]Langer P et al., Endokrinologie 1971; [10]McMillan M et al., Hum Toxicol 1986; [11]Shapiro TA, Nutr
Cancer 2006; [12]Rungapamestry V et al., J Agric Food Chem 2006;
Fig. 1: Conversion of progoitrin to goitrin by the enzyme myrosinase [2]
BACKGROUND
METHODS
RESULTS
Fig. 2: Glucosinate degradation [2]. Indole glucosinates produce
thiocyanates
THIOCYANATES
GOITRIN
GOITRIN
THIOCYANATES
⊖
⊖
Fig. 3: Inhibitition of the Sodium Iodide Symporter (NIS) and the
Thyroperoxidase (TPO) by goitrin and thiocyanates
Fig. 4: Thiocyanate-producing glucosinolate and progoitrin concentrations
in different cruciferous vegetable[8]
0
100
200
300
400
500
600
700
800
900
Kale (B.
oleracea
leaves)
Kale (B. napus
leaves)
Brussel sprouts B. oleracea
acephala
group
(collards)
Broccoli rabe Cima di rapa
variants
Chinese
cabbage
Turnip tops Pak Choi
THIOCYANATE-PRODUCING GLUCOSINOLATE CONCENTRATIONS [umol/100g]
PROGOITRIN CONCENTRATION [umol/100g]
Contact: michael.kob@sabes.it
