LED-based lighting unit

The present disclosure relates to light emitting diode based methods, systems and lighting units, particularly for facilitating vitamin D production, reducing microbial stress, and optionally providing working light within a building such as an animal farm production facility, hospital, office, venue, storage facility, manufacturing facility, grocery store, school/classroom, and the like. A lighting unit is provided to reduce microbial stress in a building, in particular from zoonotic, aerosol, bacterial and viral microbial stress on animal and/or human surfaces and on building interior surfaces, preferably in combination with a sensor, while being configured for promoting the formation of natural vitamin D3 in animals and/or humans, and preferably also providing visible working light. One embodiment relates to a lighting unit for 1) reducing microbial stress and 2) stimulating the production of natural vitamin D3, the lighting unit comprising: at least a first UV-ble configured for emitting monochromatic UV-B light having a maximum intensity between 292-302nm, preferably between 295-299nm, more preferably between 296-298nm, most preferably at 297 nm; and/or at least a first UV-C LED configured to emit monochromatic UV-B light having a maximum intensity between 278-288nm, preferably between 281-285nm, more preferably between 282-284nm, most preferably at 283 nm; and/or at least a first UV-C LED configured to emit monochromatic UV-C light having a maximum intensity between 228-238nm, preferably between 231-235nm, more preferably between 232-234nm, most preferably at 233 nm.