Bioavailability of Nickel in Man: Effects of Foods and Chemically-Defined Dietary Constituents on the Absorption of Inorganic Nickel

Abstract

By serial determination of the change in plasma nickel concentration following a standard dose of 22.4 mg of nickel sulfate hexahydrate condtaining 5 mg of elemental nickel, the bioavailability of nickel was estimated in human subjects. Plasma nickel concentration was stable in the fasting state and after an unlabeled test meal, but after the standard dose of nickel in water was elevated 48.8, 73.0, 80.0, and 53.3 μg/l, respectively, at hours 1, 2, 3, and 4. Plasma nickel did not rise above fasting levels when 5 mg of nickel was added to two standard meals: a typical Guatemalan meal and a North American breakfast. When 5 mg of nickel was added to five beverages—whole cowmilk, coffee, tea, orange juice, and Coca Cola®—the rise in plasma nickel was significantly suppressed with all but Coca Cola®. Response to nickel also was suppressed in the presence of 1 g of ascorbic acid. Phytic acid in a 2:1 molar ratio with nickel, however, did not affect the rise in plasma nickel. The chelate of iron and ethylenediaminetetraacetate, NaFeEDTA, an iron-fortifying agent suggested for application in Central America, slightly but significantly depressed plasma nickel rise at 2 hours, whereas disodium EDTA depressed plasma nickel levels significantly below the fasting nickel curve at 3 and 4 hours postdose. These studies suggest that the differential responses of inorganic nickel to distinct foods, beverages, and chemically-defined dietary constitutents could be important to human nutrition.nickel ascorbic acid phytic acid EDTA