Preparation process for dietary supplements, comprising at least two steps, the first step of which is to obtain a basic composition comprising liquid vegetable extracts (that contain alcohol), essential oils, water and optionally powdered vegetable extracts, mineral elements, vitamins, vegetable oils, marine plasma, organic silica, etc., and the second step of which is used to solidify the mixture by adding a solidifying premix comprising alginates, a vegetable gum and optionally solidification retarders such as dry hydrophilic plants, water chelators or other substances, even chemicals. The advantage of the process is that it enables dietary supplements to be obtained in a dry solid state that can be stored at ambient temperature or in a refrigerator, and is stable over time, without losing the nutritional and therapeutic value of the vegetable or natural substances contained therein.