Methodology for Adding Heme Iron and Non-Heme Iron to a Food and Nutrient Database and Dietary Analysis Software.

BACKGROUND: Including both heme and non-heme forms of iron in food and nutrient databases is important because they differ in bioavailability and potentially have differential health impacts. OBJECTIVE: The study describes the methodology used for assigning heme and non-heme iron values to foods in the University of Minnesota Nutrition Coordinating Center (NCC) Food and Nutrient Database. DESIGN: /Methods: The NCC Database includes about 19,500 foods, and heme and non-heme iron values (mg/100g) were assigned to foods using a multi-step process: (1) Reviewed scientific literature and international food composition databases to gather analytical data; (2) Assigned values to the core foods based on the above sources and imputation rules; (3) For non-core foods, values were assigned using the NCC Food Calculation program; and (4) As a quality assurance measure, all assigned values were systematically reviewed for consistency across NCC food groups. RESULTS: In the 2025 version of the NCC Database, heme and non-heme iron values were assigned to all foods, with no missing values. Core foods with zero total iron were assigned 0 mg for both forms of iron (14% of core foods). For eggs, dairy, and plant foods with iron content, 100% of the iron was assigned as non-heme (68% of core foods). For meats and seafoods, heme iron was calculated based on literature heme-to-total iron ratios, and non-heme iron was determined by subtraction of heme iron from total iron (18% of core foods). Imputation was required for 24% of the meat and seafood core foods. CONCLUSIONS: The methodology used to add heme and non-heme iron to the NCC Database resulted in complete data, though imputation was required for some meats and seafoods.