1. The use of a nutritional composition containing dietary fiber, a peptide having 7 or more amino acid units, as well as a source of tryptophan, which may be the indicated peptide or different from it, for the prevention or treatment of a disorder selected from the group consisting of negative emotions and introvert behavior. 2. The use of a combination of dietary fiber, a peptide having 7 or more amino acid units, as well as a source of tryptophan, which may be or differ from the indicated peptide, and optionally one or more other components, for the prevention or treatment of a disorder selected from the group consisting of negative emotions and introverted behavior. 3. The use of claim 1 or 2, wherein the fiber, when used in a subject, is a stimulator of the GPR43 receptor. The use according to claim 1 or 2, wherein the dietary fiber comprises a fiber selected from the group of unmodified or modified cereal fibers. The use of claim 4, wherein the cereal is unmodified or modified rice fiber. The use according to claim 1 or 2, wherein the dietary fiber comprises at least 15 wt.% Non-acetogenic saccharide units, preferably at least 60 wt.% Consists of non-acetogenic saccharide units, in particular at least 90 wt. .% consists of non-acetogenic saccharide units. 7. The use of claim 1 or 2, wherein, under conditions existing in the colon of the subject in which the fiber is used (in combination, in a nutritional composition or in another form), at least a portion of the fiber is fermented, thereby obtaining propionate, butyrate or acetate where the ratio of molar amounts of the amount of propionate formed plus1. Применение питательной композиции, содержащей пищевое волокно, пептид, имеющий 7 или больше аминокислотных единиц, а также источник триптофана, который может быть указанным пептидом или отличаться от него, для профилактики или лечения расстройства, выбранного из группы, состоящей из отрицательных эмоций и интровертного поведения.2. Применение комбинации пищево