Abstract: The invention relates particularly but not exclusively to the basic food products consumed by human beings.The method of improving and retaining the nutritional qualities of basic foods and drinks consists in incorporating in these products, after the final stage of normal usefulness of the yeasts contained therein, an anti-mycotic product such as selenium sulphide or any selenium salt or heavy-metal salt.The method is applied by adding very small quantities of selenium sulphide to bread, wines, beer and other foods and beverages requiring the addition of yeasts for preparing them for consumption.The method of the invention may also be applied in the treatment of products other than food products, for example tooth-pastes, bottles, under-garments and medical equipment made of plastics materials.