The CNP-building-blocks database is composed of four distinct datasets. First, the food nutrient database indicates the content of macronutrients (i.e. carbohydrates, lipids and proteins) and simple molecules constituting them (i.e. oligosaccharides, fatty acids and amino acids) for 954 food items (both raw and processed food). Second, the elemental composition database informs about the concentration of carbon, nitrogen (calculated using chemical formulas and amino acid concentrations, but also starting from protein contents through the use of conversion factors) and phosphorus in the 954 food items. Third, the carbon, nitrogen and phosphorus content of 13 food categories (e.g. vegetables, fruits, grains, seeds, meat and fish/seafood) is provided by the third set of data belonging to the CNP-building-blocks database. Fourth, the data quality file summarizes the type of changes made in the phases of data processing and food nutrient database construction.