Korean Nickel-Restricted Diet Based on Analysis of Nickel Content in Food Products

Abstract

Background: Nickel is a leading cause of allergic contact dermatitis. Patients with nickel allergy may suffer from persistent dermatitis not only through contact with nickel-plated items but also through ingestion of nickel-containing food. Objective: This study aimed to evaluate the current nickel content in Korean food products and provide more up-to-date Korean nickel-restricted diets that would increase patient compliance. Methods: The most frequently consumed food items were selected with replicates. Food samples were prepared according to the practices of normal consumers. The solid specimens were finely ground, and the liquid specimens were homogenized using a sterilized mixer. Tea bags were brewed in 100 mL of distilled water at 100 ℃ for 5 minutes. Solid (0.5 g) and liquid (2 g) specimens were subjected to microwave-assisted nitric acid digestion using inductively coupled plasma-mass spectrometry. Results: In total, 147 samples were collected from different food categories, including plant-based products, animal-based products, packaged foods, and drinks. Cocoa powder had the highest concentration of nickel (1.56 mg/kg), which is consistent with the results of previous studies. Soy products such as fermented soybean paste (Doenjang) (L16 mg/kg), fermented soybean with red chili paste (Ssamjang) (0.67 mg/kg), and tofu (0.37 mg/kg) had elevated concentration of nickel. Moreover, nut-derived products such as chocolate (1.10 mg/kg), ground coffee (0.86 mg/kg), almond (0.84 mg/kg), and peanuts (0.64 mg/kg) contained elevated nickel concentration. Conclusion: The nickel content in food constantly changes depending on the food processing procedures and place of origin. Therefore, revising the nickel-restricted diet is necessary to enhance patients' understanding of it and help reduce dietary nickel intake. © 2024 Korean Dermatological Association. All rights reserved.