The phrase "bioavailable form" refers to a substance or compound that can be easily used by the body. It means that the form of the substance is easily absorbed and utilized by the body's cells for various functions. Full definition
Vitamin D3 or cholecalciferol is the most bioavailable form of Vitamin D. Vitamin D is a fat soluble vitamin so dietary fat intakes must be sufficient to allow absorption. (nourishedrootspdx.com)
Modern mothers are wising up and feeding their children nuts, seeds, and greens, for highly bioavailable forms of calcium, and letting their children out in the sun. (greensmoothiegirl.com)
Offal is particularly concentrated in bioavailable forms of vital nutrients including zinc, iron and B vitamins, alongside specialty nutrients that are difficult to obtain from other foods: (wellnessmama.com)