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Correspondence
Recommended dietary selenium intake and selenium concentration in nuts
To the Editor: We read with interest the detailed and up to date review
article of Kaprara and Krassas, published in the last issue of Hell J Nucl Med [1]. We think that some interesting points of this article should be
discussed. The authors report the recommended dietary selenium (Se)
intake from the World Health Organization (WHO): 40 Ìg/day for men
and 30 Ìg/day for women. This intake is based on Se intake needed to
achieve two-thirds of maximum activity of erythrocyte glutathione peroxidase (GPx), with lower limits of safe population intake calculated
from basal metabolic rate [2]. Nevertheless the main criterion for estimating recommended intake, including the estimated average requirement and recommended dietary allowance of the recent US and Canadian Dietary Reference Intake (DRI) for Se and other countries, was the
maximization of plasma GPx [2]. Table 1 shows the recommended intake of Se for adults worldwide [2].
The authors presenting the mean Se concentrations in various European food sources (Table 1 of the review article) illustrate the Brazil
nuts as Cashews. This illustration is wrong considering that Brazil nut is
the fruit of an enormous tropical tree (can exceed 30m in height), the
Lecythidaceae family (Bertholletia excelsa) (Fig. 1), and Cashew nut is
the fruit of a small tropical tree (10-12m in height) of the Anacardiaceae
family (Anacardium occidentale) (Fig. 2) [3]. Brazil nuts are not produced in Europe, but exported to Europe from Amazonian states of
Brazil, Peru, Colombia, Venezuela and Ecuador where the tree grows [3].
Brazil nuts natively contain very high concentrations of Se. Nevertheless,
Cashew nuts do have a rather moderate amount of Se. The results of an
elemental analysis of various nuts showed a Se concentration far higher in Brazil nut (11 ppm or 1100 Ìg/100g) than in the other nut samples
(e.g. Cashew: 0.2 ppm or 20 Ìg/100g, English walnut (Juglans regia):
0.04 ppm or 4 Ìg/100g) [4].
a)
b)
Men
Women
USA and Canada (RDA)
55
55
Australia (RDI)
85
70
United Kingdom (RNI)
75
60
World Health Organization (NR)
40
30
Europe (PRI)
Germany, Austria, Switzerland (RNI)
55
55
30-70
30-70
RDA: recommended dietary allowance; RDI: recommended dietary intake;
RNI: reference nutrient intake; NR: normative requirement estimate;
PRI: population reference intake
Bibliography
1. Kaprara A, Krassas GE. Selenium and thyroidal function; the role of radioimmunoassays. Hell J Nucl Med 2006; 9: 195-203.
2. Thomson CD. Assessment of requirements for selenium and adequacy
of selenium status: a review. Eur J Clin Nutr 2004; 58: 391-402.
3. Bärtels A. Guide des plantes tropicales. Les Éditions Eugen Ulmer, Paris
2001, p. 287, 312.
4. Furr AK, MacDaniels LH, St John LE Jr, et al. Elemental composition of
tree nuts. Bull Environ Contam Toxicol 1979; 21: 392-396.
Elias E. Mazokopakis, MD, PhD1 Eftichios E, Protopapadakis, PhD2
1. Department of Internal Medicine, Naval Hospital of Crete, Chania,
Greece
2. Institute of Subtropical Plants and Olive Trees, Chania, Greece
Authors’ reply
Figure 1. a) Brazil nut tree, b) Brazil nuts, c) Shelled Brazil nuts
b)
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c)
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Country
Elias Mazokopakis, MD, PhD
Iroon Polytechniu 38A, Chania 73 132, Crete, Greece,
Tel.: +302821 0 82754, Fax: +302821 0 89307
E-mail: [email protected]
c)
a)
Table 1. Recommended selenium intake for adults (Ìg/day) in various
countries [2]
We would like to thank Dr EE. Mazokopakis and Dr EE. Protopapadakis
for their interesting and valuable comments. Regarding selenium (Se) intake for adults we concentrated our interest only in WHO recommended doses and not those recommended in various countries. Concerning
the mean Se concentrations in various European food sources, we have
to admit that being Endocrinologists we didn’t know the great difference,
which exists between Brazil nut and Cashew nuts. After their valuable
information we now know the difference and it will be used in communications in the future. Their letter was very much appreciated.
Athina Kaprara, Gerasimos Krassas
Department of Endocrinology, Diabetes and Metabolism,
Panagia General Hospital, Thessaloniki, Greece
Professor Gerasimos Krassas, MD, PhD, Chairman,
Department of Endocrinology, Diabetes and Metabolism,
Panagia General Hospital, ¡. Plastira 22, 55132, N. Krini,
Thessaloniki, Greece. Tel: +302310479633,
Fax: +302310282476, e-mail: [email protected]
Figure 2. a) Anacardium occidentale tree, b) Cashew nuts, roasted and
salted, c) Cashews ready for harvest
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Hellenic Journal of Nuclear Medicine ñ January - April 2007
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www.nuclmed.gr
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