It depends on the case; there is no single guideline.
Effect by goal · level of evidence
Blood sugar control (personalized diet)
associationModeratestudy (AA)
Study of 800 people with continuous glucose monitoring (47,000 meals): the blood sugar rise after the SAME meal varies greatly from one person to another, so universal dietary recommendations have a limit. An algorithm using microbiota, habits and lab tests predicted the individual response. It pushes toward personalized nutrition.
Blood sugar control (personalized diet) — association (Moderate, study). A study of 800 people with continuous glucose monitoring (47,000 meals): the blood sugar rise after the SAME meal varies widely from one person to another, so universal dietary recommendations have a limit. An algorithm using gut microbiota, habits, and lab tests predicted the individual response. It points toward personalized nutrition. 26590418
Information, not medical advice. Prescription drugs require a doctor.
Information, not medical advice. Scientific evidence reflects the quality of the studies.