The paper provides data on the use of nanostructured cobalt sulfate in the production of marmalade as functional food for prophylactic purposes. The particle trajectory analysis method (NTA method) was used to determine the sizes of nanostructured cobalt sulfate. In this case, the smallest size (25.7 nm) is formed only in gellan gum with a “core : shell” ratio of 1:1. When the “core : shell” ratio in gellan gum is 1:3, the average size of nanocapsules is 49.9 nm. This result can be explained by the tighter packing of cobalt sulfate in the capsule. In sodium alginate, the average nanocapsule size is already 191 nm. The polydispersity coefficient in all studied shells and at different “core : shell” ratios are practically equal and amounts to 0.84–1.09, which corresponds to a spherical shape.