Holden J M, Wolf W R, Mertz W
J Am Diet Assoc. 1979 Jul;75(1):23-8.
Levels of zinc and copper in the self-selected diets of twenty-two men and women were determined by atomic absorption spectrophotometry. Sixty-eight per cent of the subjects consumed less than two-thirds of the recommended allowance for zinc (15 mg). Eighty-one per cent consumed less than two-thirds of the suggested level of copper (2.0 mg). Average daily intake of protein exceeded the recommended allowance. However, the mean zinc:calorie ratio for those subjects was only 4.19 mg. per 1,000 kcal. Using the recommended allowances for zinc and for energy, the zinc:calorie ratio would be 6.5 mg. per 1,000 kcal. For copper, the suggested nutrient density is 0.85 mg. per 1,000 kcal vs. the 0.50 mg. per 1,000 kcal observed in this study. These metallo:calorie ratios indicate that the nutrient density of these two trace elements in the diet is low and that diets supplying adequate amounts of energy and protein do not guarantee adequate levels of zinc and copper.
通过原子吸收分光光度法测定了22名男性和女性自行选择饮食中的锌和铜含量。68%的受试者锌摄入量低于推荐摄入量（15毫克）的三分之二。81%的受试者铜摄入量低于建议水平（2.0毫克）的三分之二。蛋白质的平均每日摄入量超过了推荐摄入量。然而，这些受试者的锌与热量的平均比值仅为每1000千卡4.19毫克。按照锌和能量的推荐摄入量，锌与热量的比值应为每1000千卡6.5毫克。对于铜，建议的营养素密度为每1000千卡0.85毫克，而本研究中观察到的是每1000千卡0.50毫克。这些金属元素与热量的比值表明，饮食中这两种微量元素的营养素密度较低，提供足够能量和蛋白质的饮食并不能保证锌和铜的充足水平。
