It depends on the case; there is no single guideline.
Soy milk, especially fermented, improved the gut environment in a small study (n=10): more bifidobacteria and lactobacilli, fewer clostridia, and less fecal sulfide (putrefaction). A preliminary prebiotic/probiotic signal.
See the study (small trial (n=10)) →Lifestyle · Highest evidence: Low · 1 finding
Information, not medical advice. Prescription drugs require a doctor.
Information, not medical advice. Scientific evidence reflects the quality of the studies.