Calcium, Copper, Iron, Magnesium and Zinc Utilization of Humans as Affected by Consumption of Black, Decaffeinated Black and Green Teas

Abstract

LEARNING OUTCOME: The black, decaffeinated black and green teas had little, if any, influence on the subjects’ utilization of calcium, copper, iron, magnesium and zinc. Controversy exists as to the nutritional effects of tea. Both beneficial and detrimental nutritional effects have been demonstrated in animal and human studies. The objectives of the study were to compare effects of black, decaffeinated black and green teas on the utilization of calcium, copper, iron, magnesium and zinc in young adults. All minerals were quantitated using atomic absorption techniques. A 56-day metabolic balance study was divided into four experimental treatments arranged in a randomized crossover order during which no, black, decaffeinated black or green teas were consumed. International students (five females and four males) consumed a laboratory controlled diet low in the above minerals. The subjects received the same diet, except for the teas, during all treatments. Initial hematologic measurements indicated that subjects had normal iron status. For calcium, copper, magnesium and zinc, no significant differences were found in intake, fecal, urinary and balance values by gender, treatment or gender-by-treatment interactions. For urinary iron values, significant (P<0.05) or near significant (P=0.07) differences by gender were observed in all treatments. Iron balance values of both genders were significantly higher (P<0.05) in the green tea than in other treatments. No significant differences were observed in intake and fecal iron values by gender, treatment or gender-by-treatment interactions or in urinary and balance iron values by sex. Overall, with few exceptions, these teas did not affect the calcium, copper, iron, magnesium and zinc balances of young adults fed diets low in these minerals.