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Low contribution of rice and vegetables to the daily intake of selenium in JapanRizky Abdulah a; Kaori Miyazaki a; Minato Nakazawa a; Hiroshi Koyama aa Department of Public Health, Gunma University Graduate School of Medicine, Japan

Online Publication Date: 01 November 2005

To cite this Article Abdulah, Rizky, Miyazaki, Kaori, Nakazawa, Minato and Koyama, Hiroshi(2005)'Low contribution of rice andvegetables to the daily intake of selenium in Japan',International Journal of Food Sciences and Nutrition,56:7,463 471

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Low contribution of rice and vegetables to the daily

intake of selenium in Japan

RIZKY ABDULAH, KAORI MIYAZAKI, MINATO NAKAZAWA, &

HIROSHI KOYAMA

Department of Public Health, Gunma University Graduate School of Medicine, Japan

AbstractThe growing interest in the prevention role of selenium in certain degenerative diseases such as

cancer and cardiovascular disease has fostered research on natural sources of selenium. In this

research, total selenium concentrations in over 120 items of selected Japanese foods weredetermined. The selenium concentration was measured fluorometrically by measurement of the

fluorescence of piazselenol resulting from the reaction of selenite with 2, 3-diaminonaphtalene.

The selenium level in rice, which is the staple food consumed in Japan, is lower than the other

countries. But the mean levels of selenium in meat and fish products are among the highest

values reported in other countries. Although the numbers of samples of selected foods analyzed

are small, the results describe the picture of the selenium level of Japanese foods.

Keywords: Selenium, foods, Japan, spectrofluorometry

Introduction

Selenium is an important part of antioxidant enzymes (National Research Council1989) that protect cells against the effects of free radicals produced during normal

oxygen metabolism (Arteel et al. 1998, 2000). The body has developed defenses such

as antioxidants to control levels of free radicals because they can damage cells and

contribute to the development of some chronic diseases (Combs and Gray 1988; Neve

1996; Heliovaara et al. 1994; Look et al. 1997; Combs et al. 1997). The selenium

content of plants varies tremendously according to its concentration in soil, which

varies regionally. Around the world, there are many selenium-poor regions in which

overt deficiency syndromes are endemic: these regions include arid regions in

Australia, China, northern North Korea, Nepal and Tibet. People living in a low-

selenium area usually have very low selenium dietary intake; for instance, people inNepal have 23 mg selenium intake per day (Moser et al. 1988), and the Chinese

Nutrition Association reported people in China to have only 26 mg/day, and in some

regions below 10 mg/day. Meanwhile, the recommended dietary allowance*/the

average daily dietary intake level that is sufficient to meet the nutrient requirements of

nearly all (97 /98%) individuals in each life-stage and gender group */of selenium is

55 mg/day.

Correspondence: Hiroshi Koyama, MD, PhD, Professor, Department of Public Health, Gunma University,

Graduate School of Medicine, 3-39-22, Showa-machi, Maebashi City, Gunma 371-8511 Japan. Tel: 81 27

220 8010. Fax: 81 27 220 8016. E-mail: [email protected]

ISSN 0963-7486 print/ISSN 1465-3478 online # 2005 Taylor & Francis

DOI: 10.1080/09637480500490640

International Journal of Food Sciences and Nutrition,

November 2005; 56(7): 463 /471


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The daily intake of selenium depends on its concentration in food, the amount of

food consumed, the chemical form of the element, and its bioavailability. It is different

between each country and, for that reason, it is important to determine the selenium

content in different commonly consumed foods in order to estimate the daily intake of

selenium in each region.

Beside the low selenium status in some parts of the world, the change of selenium

intake status in some countries may also give cause for concern. For example, in 1978dietary selenium intakes in the United Kingdom were 60 mg/day on average (Thorn et

al. 1978), but the 1994 survey by Barclay et al. (1995) found that the selenium intake

had dropped to 34 mg/day. The same phenomena also happened in Japan. Suzuki et al.

(1988) found that the daily intake of selenium in Japan was 104 mg/day on average,

while the next survey in 1993 (Moriyama et al. 1993) found that the daily intake of

selenium in Japan had dropped to 69 mg/day. Based on these data, to prevent

selenium-related diseases it is important to monitor the average of selenium intake in

each region.

The aim of this study was to determine selenium in foods commonly consumed in

Japan. This study provides the mean and standard deviation of selenium in Japanesefoods and imported foods commonly consumed in Japan. This information is

important for the assessment of the new daily intake of selenium by Japanese and

can be added to the development of a database on the selenium content of foods,

which can be useful to the treatment of selenium-related diseases.

Materials and methods

Food selection and preparation

Food samples were obtained from 18 families in Iwate prefecture Japan, using the

duplicate meals method, meaning that for each food eaten an identical serving is

placed in a container for analysis (Willet 1998). Vegetables and fruits were first rinsed

with tap water several times to ensure that all contaminants were removed. All food

samples were kept in a plastic bag and immediately transferred to the laboratory. All

samples were frozen at (/808C until analysis.

Selenium analysis

The selenium concentration was measured fluorometrically by measurement of the

fluorescence of piazselenol resulting from the reaction of selenite with 2,3-diamino-

naphtalene (DAN) (Watkinson 1966). The food samples were wet-digested by heating

with a mixture of HNO3 and HClO4 (2:1), gradually increased to 1908C, and then

cooled to room temperature. Then 0.5 ml of 10 N HCl was added and reheated to

1508C for 15 min in order to facilitate the reduction of Se(IV) to Se(VI).

The pH of the digested samples was adjusted to 1 /2 with 25% ammonia solution

and 20% HCl, using thymol blue as an indicator of standard color to the required pH.

To obtain piazselenol, the solution was complexed with 0.1% DAN, and was manually

extracted with cyclohexane. The cyclohexane phase containing the selenium /DAN

complex was then measured spectrofluorometrically at an excitation wavelength of

378 nm and an emission wavelength of 525 nm (Twinkle LB970; Berthold

Technologies, Bad Wildbad, Germany).

464 R. Abdulah et al.


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The accuracy of the selenium analysis can be considered satisfactory, by measure-

ment of the reference material (bovine liver, SRM 1577b; National Institute of

Standards and Technology, Gaithensburg, Maryland, USA), which gave the value

0.739/0.03 mg/g, compared with the certified value of 0.739/0.06 mg/g.

Results and discussionThe selenium content in various Japanese foods is presented in Table I. Low selenium

content was present in the cereal product, especially in the traditional foods consumed

in Japan, such as rice, udon and Japanese rice cake (1 /5 mg/100 g). The high-

selenium source of cereal products was found in bread and macaroni (17.4 and

44.9 mg/100 g).

Fish product, except hanpen and Satsuma-age, are considered as the rich selenium

source for Japanese people. The highest selenium concentration was obtained

from dried bonito fish (273.5 mg/100 g). The overall means of the fish product was

61.38 mg/100 g.

A moderate level of selenium concentration found in meat products and egg (13.6 /

95.4 mg/100 g). Meanwhile, dairy products except for processed cheese have a low

level of selenium content (1 /3.3 mg/100 g). A similar result also obtained from

vegetables and fruits. Selenium content of vegetables and fruits were low and in a

very wide range from 0.2 mg/100 g in Japanese ginger to 8.5 mg/100 g in water

dropwort.

The selenium content of animal species is relatively higher than that of plant

species. The low selenium status in vegetables and fruits is because plant species do

not require selenium for growth. This is very different to animal species, where

selenium is an essential element and the animal cannot survive if the tissue levels of

selenium are too low (Barclay et al. 1995). Moreover, the low protein fraction in plant

products may decrease the selenium level in the plant, since food selenium is mainly

present in the form of selenoamino acids (Navarro-Alarcon and Lopez-Martinez

2000). In cruciferous vegetables (such as onion and garlic) the selenium level is higher

than in other vegetables, because these plants have a greater fraction of sulfur-

containing amino acids and their derivatives, and also sulfur-containing compounds

such as glucosinolates or sulfoxides (Klapec et al. 2004). Adequate analogs of these

can be formed by substitution of sulfur with selenium, resulting in a higher selenium

level (Ip and Ghanter 1994).

The selenium level in mushrooms is also above the average selenium level in other

vegetables. However, mushrooms mainly accumulate inorganic forms of selenium

(Klapec et al. 2004).

The mean level of selenium in cereal products (except bread and macaroni) in Japan

is lower than other countries (Table II); especially in rice, the staple food consumed in

Japan. The low level of selenium in Japanese rice might be related to the selenium

concentration in the soil in Japan; it is generally below 1 mg/kg (Mizutani et al. 2001).

In contrast, the mean levels of selenium in meat and fish products are among the

highest values reported in other countries. Fish and meat products provide a

significant part of the Japanese peoples dietary selenium, but the bioavailability of

selenium in fish must also considered, because the interaction of selenium with

mercury and other heavy metals present in fish and marine animals may form

Daily intake of selenium in Japan 465


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Table I. Selenium concentration in selected Japanese foods.

Selenium content (mg/100 g)

Food item n Present study

Previous report (Suzuki

and Tanusi 1993)

Cereal products

Mochi (rice cake) 1 2.2 2.0White bread 2 44.99/1.3 6.0

Udon , boiled (Japanese traditional noodle) 4 4.39/1.0 /

Chinese noodle, boiled 1 5.7 8.0 (raw)

Macaroni, boiled 1 17.4 21.0 (raw)

Rice, cooked 4 1.39/0.5 4.0 (raw)

Potato products

Konnyaku, block type (alimentary yam paste) 5 1.69/0.7 2.0

Shirataki, noodle type (alimentary yam paste,

in noodle form)

3 1.59/0.2 2.0

Potatoes, boiled 1 0.5 1.0 (raw)

Sweet potatoes 7 3.19/0.7 4.0 (raw)

Taro, boiled 2 1.49/0.5 1.0 (raw)

Seeds

Sesame seeds, roasted 1 24.4 42.0 (dried)

Chestnuts, boiled 1 0.8 3.0 (raw)

Soybean products

Nama-age (drained tofu) 1 7.5 5.0

Abura-age (fried tofu) 3 6.19/1.3 7.0

Itohiki-natto (fermented soybeans) 8 15.99/5.1 2.0

Kinzanji-miso (fermented soybeans paste) 1 4.5 /

Okara (bean card refuse) 1 2.9 3.0

Momen-tofu (cotton tofu) 1 2.9 3.0

Fish productsKatsuo-bushi, dried strip (dried bonito fish) 4 273.59/0.6 250.0

Red Bream, cooked 4 85.09/13.9 160.0 (raw)

Salted chum Salmon, grilled 3 45.19/6.0 67.0 (raw)

Yellow fin Tuna, raw 1 59.1 81.0

Salted Pink Salmon, grilled 1 31.1 36.0 (raw)

Pond smelt, grilled 1 80.6 100.0 (raw)

Short-necked Clam, canned 2 78.29/8.6 380.0

Salted Jellyfish 1 12.7 /

Mushi-kamaboko (steamed fish paste) 2 18.69/4.4 84.0

Yaki-chikuwa , boiled (fish sausage) 8 21.39/4.4 68.0

Hanpen , boiled (minced fish and steamed) 1 8.3 45.0

Satsuma-age, fried (minced fish and steamedwith vegetable paste)

4 9.39/1.2 55.0

Salted Pollack roe 3 97.79/29 170.0

Scallop, cooked 1 45.5 93.0 (raw)

Squid and Cuttlefish, grilled 5 63.69/15 38.0 (raw)

Tiger Prawn, boiled 1 89.2 58.0 (raw)

Octopus, boiled 2 48.39/2.8 34.0 (raw)

Sardines, cooked 2 34.99/11 52.0 (raw)

Flatfish, cooked 1 66.3 31.0 (raw)

Mackerel, grilled 2 62.79/19.1 19.0 (raw)

Pacific saury, grilled 3 55.99/14.8 47.0 (raw)

Pacific saury, canned 1 63.4 310.0



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Table I (Continued)




and Tanusi 1993)

Meats

Pork liver, grilled 1 95.4 29.0 (raw)Pork ham, grilled 3 38.29/9.1 20.0 (raw)

Beef round, grilled 1 25.7 25.0 (raw)

Chicken breast, grilled 2 13.69/0.8 22.0 (raw)

Milk and dairy products

Milk 6 2.09/0.8 4.0

Milk, skimmed 1 3.3 3.0

Processed Cheese 1 24.7 17.0

Yoghurt 3 1.79/0.6 3.0

Lactic acid bacteria beverage 2 1.09/0.0 1.0

Egg, boiled 4 37.39/3.4 57.0 (raw)

Dashimaki-tamago (Japanese Eggrolls) 12 25.7 34.0

VegetablesPerilla leaves 1 7.0 2.0

Perilla seeds 2 1.6 8.0

Japanese Radish, sprouts 1 6.5 /

Takana-zuke (green mustard rinse with pepper) 2 0.79/0.1 3.0

Bamboo shoots, canned 1 5.0 1.0

Lettuce 1 0.7 1.0

Tomato 4 0.39/0.2 1.0

Garlic bulb 1 2.3 /

Onion leaves 1 2.1 2.0

Myoga bract and flower (Japanese ginger) 2 0.29/0.1 1.0

Chinese cabbage, raw 1 1.3 3.0

Chinese cabbage, boiled 2 0.89/0.2

/

Chinese cabbage, salted 3 2.39/0.7 /

Sweet pepper, grilled 7 1.69/0.8 /

Broccoli, boiled 1 0.8 /

Spinach, boiled 5 1.39/0.6 /

Soybean sprouts, boiled 2 1.59/0.1 /

Okra pods immature 1 0.6 2.0

Turnip root, salted 1 0.2 4.0

Red turnip, root 2 0.4 /

Squash, cooked 5 2.89/1.4 2.0 (raw)

Cauliflower, boiled 1 1.0 1.0 (raw)

Chrysanthemum flower, boiled 3 0.39/0.1 3.0 (raw)

Cabbage, raw 3 1.39/0.1 1.0

Cucumber 6 0.79/0.3 1.0

Edible burdock, cooked 2 1.69/0.4 1.0 (raw)

Komatsuna leaves, boiled 1 1.2 2.0

Garland chrysanthemum leaves 1 1.7 /

Ginger 1 6.9 1.0

Oriental pickling melon, salted 1 1.1 3.0

Water dropwort 1 8.5 6.0

Japanese radish leaves, boiled 2 3.09/0.1 5.0 (raw)

Japanese radish root 5 0.3 1.0

Japanese radish root, boiled 3 0.7 /

Takuen-zuke radish, salted 3 0.39/0.1 1.0

Snap beans pods immature (boiled) 3 1.49/0.4 2.0 (raw)

Onion 2 2.29/1.2 /



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insoluble inorganic complexes and reduce the bioavailability of selenium it self

(Robinson and Thomson 1983; Johnston and Savage 1991).

The daily intake of selenium in Japan is higher than the recommended value: 104

mg/day (Suzuki et al. 1988) and 69 mg/day (Moriyama et al. (1993). But the daily

intake of selenium from rice or other staple food in Japan is low; however, the Japanesestill consume high selenium from fish, meat and other imported food. In addition,

many fish products and meat products in Japan are taken from the sea outside Japan or

are even imported from the USA, which is one of the high-selenium regions in the

world.

The limitation of this study was the very small sample size (n0/1) in some of the

foods. We tried to analyze daily foods consumed in a regular Japanese family; since

they consumed a variety of foods, we were only able to collect a very small sample size

in some of the food items. A follow-up study is needed in order to monitoring the daily

intake of selenium with more variety of foods and bigger sample size.

Table I (Continued)




and Tanusi 1993)

Eggplant, raw 6 2.79/1.0 1.0

Eggplant, salted 1 2.9/

Carrot 13 1.79/1.0 /

Nozawana leaves 2 1.09/0.7 /

Fruits

Umezuke (salted apricot) 1 0.9 6.0

Umeboshi (salted and dried apricot) 3 1.09/0.5 5.0

Banana 4 1.19/0.5 1.0

Grape 1 0.1 1.0

Apple 15 0.39/0.3 /

Orange 3 0.2 1.0

Japanese persimmons 3 0.29/0.1 1.0

Japanese pear 2 0.59/0.1 /

MushroomBunasimeji 2 9.59/0.0 /

Champignon, canned 1 11.5 /

Nameko, raw 1 4.8 /

Maitake , cooked 1 9.1 /

Enokitake , cooked 2 2.19/0.1 /

Jews ear black, reconstituted 1 6.4 8.0 (dried)

Shiitake , cooked 2 1.99/0.6 /

Shiitake , raw and reconstituted 1 6.2 11.0 (dried)

Houkitake 1 22.8 /

Amitake 1 6 /

Seaweed products

Kelp, dried 2 2.39/1.1 /

Konbu-tsukudani (dried kelp boiled in soy sauce) 1 5.49/0.6 8.0

Hijiki, reconstituted (seaweed species) 2 3.99/0.0 3.0 (dried)

Hitoguesa (seaweed species) 1 7.7 11.0

Wakame, blanched and salted (seaweed species) 1 1.2 4.0



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Table II. Comparison of selenium data of selected foods in various countr

Source of data and selenium content (mg/100 g)

Food

Croatia (Klapec

et al. 2004)

United Kingdom

(Barclay et al. 1995)

New Zealand (Thomson

and Robinson 1990)

Slovakia (Kadrabova

et al. 1996)

Irelan

Cas

Rice 4.05 13 2.6 3.4

Bread 4.77 4.4 1 1.76

Potato 0.95 1.6 0.29 0.35

Beef 13.1 7.6 / 2.34

Pork 18.35 14 3.1 6.87

Chicken 16.28 / 12 12.32

Tuna 85.92 / / /

Sardines 57.1/

32/

Milk 4.09 1.5 0.6 0.71

Processed cheese 5.34 6.7 3.4 2.25

Yoghurts 2.99 1.45 0.68 /

Eggs (whole) 17.73 / 18 21.52

Cabbage 6.61 / 0.09 1.66

Cauliflower 2.44 / 0.17 0.22

Lettuce 1.45 / 0.27 0.09

Onion 1.53 / 0.16 0.58

Tomato 0.79 / 0.2 0.05

Apple 0.88 / 0.09 0.14

Banana 2.03 / 0.91 0.58

Orange 0.76 / 0.12 0.13


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Suzuki T, Imai H, Kobayashi K, Hongo T, Kashiwazaki H, Ohtsuka R, Suzuki H, Ishida H. 1988. Dietary

intake of selenium in Japan-An estimation from analytical and reported values of selenium in foodstuffs

and cooked dishes. Nihon Eiyo Shokuryo Gakkai Shi 41:91 /102.

Thomson CD, Robinson MF. 1990. Selenium content of foods consumed in Otago, New Zealand. NZ Med

J 103:130 /135.

Thorn J, Robertson J, Buss DH, Bunton NG. 1978. Trace nutrients: selenium in British food. Br J Nutr

39:391 /396.

Watkinson JH. 1966. Fluorometric determination of selenium in biological material with 2,3-Diamino-naphthalene. Anal Chem 38(1):92 /97.

Willet W. 1988. Nutritional epidemiology. 2nd ed. New York: Oxford University Press. p 24.


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