Supplementation during fetal development, natural childbirth, as well as the method of breastfeeding and the lack of recognition of metabolic diseases (e.g., obesity, hybrid diabetes, various endocrinopathies, MTHFR polymphrism) with a balanced nutritional regimen in adolescence predestines the proper functioning of the microbiome and the child’s immune system [73]. Here, MTHFR is linked to metabolic disease.