Y=0.0014X (r=0.9999, n=27) Fig. 1. Standard curve of oxalic acid (ox) Table 1. Recovery of Oxalic Acid Added to Green Tea (Maccha) *1 Number o

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1 Oxalic Acid and Calcium Contents in Tea Chieko KAMIYA*1, Mieko OGAWA*1 and Hironori OHKAWA*2 (*1Laboratory of Food Science, Mizuho Junior College: 2-13, Shunko-cho, Mizuho-ku, Nagoya, Japan; *2Laboratory of Food Science, Faculty of Education, Mie University: 1515, Kamihama-cho, Tsu, Mie, Japan) Daily intake of tea was examined by means of a questionnaire survey of Sadou teachers in Aichi and Kyoto prefectures from the viewpoint of preventing urinary stones by calcium oxalate. The oxalic acid and calcium contents in tea (Maccha, Gyokuro, Sencha, Bancha and Black tea) were determined and their balance was calculated. Average calcium shortages calculated from the intake of oxalic acid per cup of tea were 10.23mg in Maccha, 5.26mg in Black tea, 2.21mg in Gyokuro, 1.87mg in Sencha, and 0.81mg in Bancha, and consequently daily intake of a cup of milk is recommended to counterbalance the deficit of calcium arising from tea drinking. (Received November 2, 1990)

2 Y=0.0014X (r=0.9999, n=27) Fig. 1. Standard curve of oxalic acid (ox) Table 1. Recovery of Oxalic Acid Added to Green Tea (Maccha) *1 Number of determination *2 Coefficient of variation, % *3 Water: water-soluble; 2NHCl: total

3 Y=0.0055X (r=0.9998, n=27) Fig. 2. Standard curve of calcium Table 2. Recovery of Oxalic Acid Added to Black Tea *1 Number of determination *2 Coefficient of variation, % Table 3. Recovery of Calcium Added to Green Tea (Maccha) *1 Number of determination *2 Coefficient of variation, %

4 Table 4. Determination of Oxalic Acid and Calcium in Green Tea (Maccha) *1 2g maccha was used for a cup. *2 T: Total *3 S: Water-soluble

5 Table 5. Determination of Oxalic Acid and Calcium in Green Tea (Gyokuro) (mg)

6 Table 6. Determination of Oxalic Acid and Calcium in Green Tea (Sencha) (mg) Table 7. Determination of Oxalic Acid and Calcium in Green Tea (Bancha) (mg)

7 Table 8. Determination of Oxalic Acid and Calcium in Black Tea (mg) *1 Tea bag Table 9. Contents of Oxalic Acid and Calcium in One Cup of Tea and the Shortage of Calcium (mg) *1 Ca shortage (mg/cup)=(ox (mg)/cup)/2.25-(ca (mg)/cup); (Ca [40]: C2H2O4 [90]=1:2.25) *2 Maccha (n=45), Gyokuro (n=36), Sencha (n=45) and Bancha (n=27), Blach tea (n=12) *3 Refer to Table 4 *4 Refer to Table 5 *5 Refer to Table 6 *6 Refer to Table 7 *7 Refer to Table 8

8 Table 10. Summary of the Replies of the Questionnaire and the Calculated Amounts of Oxalic Acid and Calcium *1 Calcium shortage (mg/day)=(oxalic acid (mg)/day)/2.25-(ca (mg)/day); (Ca (40): C2H2O4 (90)=1:2.25) *2 Average *3 M: Maccha; G: Gyokuro; S: Sencha; B: Bancha; Bl: Black tea *4 M: Male; F: Female

1) Hodgkinson, A.: "Scientific Foundations of Urology" Vol. I p. 289-296 (1976), William Heinemann Medical Books Ltd., London. 5) Ohkawa, H.: J. Assoc. Off. Anal. Chem. 68, 108-111 (1985).

10 1) Hodgkinson, A.: "Scientific Foundations of Urology" Vol. I p (1976), William Heinemann Medical Books Ltd., London. 5) Ohkawa, H.: J. Assoc. Off. Anal. Chem. 68, (1985). 6) Ohkawa, H., Ogawa, M., Kamiya, C.: Bull. Fac. Educ. Mie Univ. 39, Nat. Sci., (1988). 7) Osborne, D. R., Voogt, P.: "The Analysis of Nutrients in Foods" p and New York. (1978), Academic Press, London 16) Zarembski, P. M., Hodgkinson, A.: Brit. J. Nutr. 16, (1962). 17) Itoh, R., Oka, J.: J. Nutr. Sci. Vitaminol. 31, S7-S10 (1985).

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