1. Department of Medical Biochemistry and Biophysics, Karolinska Institutet, S-171 77 Stockholm, Sweden, Department of Medical Microbial Ecology, Karolinska Institutet, S-171 77 Stockholm, Sweden, and Department of Medical Nutrition, Karolinska Institutet, Huddinge University Hospital F60, NOVUM, S-141 86 Huddinge, Sweden