1. Dietetic, nutrient or pharmaceutical composition, characterized in that it comprises alkaline sphingomyelinase in an amount that is sufficient to exert a dietetic, nutritional or therapeutic effect of disorders connected with intestinal development, cancerous processes, disorders of the immune response, inflammatory and apoptosic processes of the intestine and its associated structures, disorders connected with cholesterol synthesis, disorders due to the hydrophobic nature of the surfaces of the gastrointestinal tract, allergic disorders of the gastro-intestinal tract, disorders relating to digestive processes, inflammatory intestinal diseases, polyposis, in particular familial polyposis, hypercholesterolaemia, infections with Helicobacter pylori, disorders connected with intestinal homeostasis and diseases of the central and peripheral nervous systems, provided that the pharmaceutical composition is not a dermatological composition. 2. Composition according to Claim 1, suitable for use in pediatric diets. 3. Composition according to Claim 1, suitable for use in enteral alimentation. 4. Composition according to any one of Claim 1-3, characterized in that the alkaline sphingomyelinase is of bacterial origin, and the bacteria containing the alkaline sphingomyelinase are chosen from amongst Grampositive bacteria, Gramnegative bacteria and lactic acid bacteria, or from mixtures thereof. 5. Composition according to Claim 4, characterized in that the lactic acid bacteria are chosen from the group comprising Lactobacillus acidophilus, Lactobacillus brevis, Lactobacillus buchneri, Lactobacillus casei, Lactobacilluscatenaforme, Lactobacillus cellobiosus, Lactobacillus crispatus, Lactobacillus curvatus, Lactobacillus delbrueckii, Lactobacillusfermentum, Lactobacillus jensenii, Lactobacillus leichmannii, Lactobacillusminutus, Lactobacillus plantarum, Lactobacillus rogosae, Lactobacillus salivarius, Bifidobacterium adolescentis, Bifidobacterium angulatum, Bifidobacterium bifidum, Bifidobacteriumbreve, Bifidobacterium catenulatum, Bifidobacterium dentium, Bifidobacterium eriksonii, Bifidobacterium infantis, Bifidobacterium longum, Bifidobacterium plantarum, Bifidobacterium pseudocatenulatum, Bifidobacterium pseudolongum, Streptococcus lactis, Streptococcus raffinolactis and Streptococcus thermophilus. 6. Composition according to Claim 5, characterized in that bacteria are the Lactobacillus brevis CD2 strain, DSM 11,988. 7. Composition according to any one of the preceding claims, characterized in that it also contains bile acids, in particular ursodeoxycholic acid, pectin, sphingomyelin or its compounds, drugs or foods containing sphingomyelin, arginine deiminase, fatty acids, polyunsaturated fatty acids, non fermented sugars, in particular lactulose, cholesterol inhibitors, ceramidase inhibitors, protease inhibitors, immunomodulators, anti-carcinogenic agents, vitamins, growth factors, surfactants, cereals, fibre, emulsifiers, stabilizers, lipids, antioxidants, preservatives, free-radical neutralizers and/or vasoprotectors. 8. Composition according to any one of the preceding claims, which can be administered orally or parenterally. 9. Use according to Claim 2, characterized in that the composition is administered, in combination with artificial milk, condensed milk, soybean milk, powdered milk, partially gumanized milk and baby foods in general. 10. Use of alkaline sphingomyelinase for the preparation of a dietetic, nutrient or pharmaceutical composition suitable for the prevention and/or treatment of disorders connected with intestinal development, cancerous processes, disorders of the immune response, inflammatory and apoptosic processes of the intestine and its associated structures, disorders connected with cholesterol synthesis, disorders due to the hydrophobic nature of the surfaces of the gastrointestinal tract, allergic disorders of the gastro-intestinal tract, disorders relating to digestive processes, inflammatory intestinal diseases, polyposis, in particular familial polyposis, hypercholesterolaemia, infections with Helicobacter pylori, disorders connected with intestinal homeostasis and diseases of the central and peripheral nervous systems, provided that the pharmaceutical composition is not a dermatological composition. 11. Composition according to any one of the preceding claims, characterized in that it contains from 1 x 10<2> to 1x 10<13> CFUs of lactic acid bacteria per gram of composition. 12. Composition according to any one of Claims 7 to 9, characterized in that it contains 200 x10<9> Streptococcusthermophilus, 150 x10<9> Bifidobacteria and 4 x10<9> Lactobacillus acidophilus per gram of composition. 13. Composition according to any one of Claims 10-12, characterized in that it also contains bile acids, in particular ursodeoxycholic acid, pectin, sphingomyelin or its compounds, drugs or foods containing sphingomyelin, arginine deiminase, fatty acids, polyunsaturated fatty acids, non fermented sugars, in particular lactulose, cholesterol inhibitors, ceramidase inhibitors, protease inhibitors, immunomodulators, anti-carcinogenic agents, vitamins, growth factors, surfactants, cereals, fibre, emulsifiers, stabilizers, lipids, antioxidants, preservatives, free-radical neutralizers and/or vasoprotectors. 14. Composition according to any one of Claims 10-13, which can be administered orally or parenterally. 15. Use of alkaline sphingomyelinase for the preparation of a dietetic, nutrient or pharmaceutical composition suitable for the prevention and/or treatment of disorders connected with intestinal development, cancerous processes, disorders of the immune response, inflammatory and apoptosic processes of the intestine and its associated structures, disorders connected with cholesterol synthesis, disorders due to the hydrophobic nature of the surfaces of the gastrointestinal tract, allergic disorders of the gastro-intestinal tract, disorders relating to digestive processes, inflammatory intestinal diseases, polyposis, in particular familial polyposis, hypercholesterolaemia, infections with Helicobacter pylori, disorders connected with intestinal homeostasis and diseases of the central and peripheral nervous systems, provided that the pharmaceutical composition is not a dermatological composition. 16. Use according to Claim 15 in pediatric diets. 17. Use according to Claim 15, in enteral alimentation. 18. Composition according to any one of Claims 15-17, characterized in that the alkaline sphingomyelinase is of bacterial origin, and the bacteria containing the alkaline sphingomyelinase are chosen from amongst Gram-positive bacteria, Gramnegative bacteria and lactic acid bacteria, or from mixtures thereof. 19. Use according to Claim 18, characterized in that the lactic acid bacteria are chosen from the group comprising Lactobacillus acidophilus, Lactobacillus brevis, Lactobacillus buchneri, Lactobacillus casei, Lactobacillus catenaforme, Lactobacillus cellobiosus, Lactobacillus crispatus, Lactobacillus curvatus, Lactobacillus delbrueckii, Lactobacillus fermentum, Lactobacillus jensenii, Lactobacillus leichmannii, Lactobacillus minutus, Lactobacillus plantarum, Lactobacillus rogosae, Lactobacillus salivarius, Bifidobacterium adolescentis, Bifidobacteriumangulatum, Bifidobacterium bifidum, Bifidobacterium breve, Bifidobacterium catenulatum, Bifidobacterium dentium, Bifidobacterium eriksonii, Bifidobacterium infants, Bifidobacterium longum, Bifidobacterium plantarum, Bifidobacterium pseudocatenulatum, Bifidobacterium pseudolongum, Streptococcus lactis, Streptococcus raffinolactis and Streptococcusthermophilus. 20. Composition according to Claim 19, characterized in that bacteria are the Lactobacillus brevis CD2 strain, DSM 11,988. 21. Composition according to any one of Claims 15-20, characterized in that the lactic acid bacteria are used in the composition as live, lyophilized or sonicated bacteria as sphingomyelinase.