What to watch with MY FOODBOOK and Müdigkeit?

When using MY FOODBOOK (a food diary) to address fatigue, watch for patterns in nutrient intake (vitamin D, B12, iron), alcohol consumption, and meal timing. The evidence linking these to fatigue is mixed: vitamin D deficiency is strongly supported, while microbiome or 'leaky gut' claims lack clinical validation (see Leaky Gut panel context). Genetic chronotype tests (CLOCK/PER) explain <5% of variance and are often marketing. Alcohol, even moderate, can worsen fatigue (source: PMC12787200). Objective circadian phase assessment via melatonin onset or cortisol acrophase (PMID:41776245) is more reliable than consumer DNA tests. MY FOODBOOK is a useful self-tracking tool, but do not overinterpret genetic or microbiome results. Persistent fatigue warrants medical evaluation for anemia, thyroid, sleep disorders, and depression. Evidence: mixed – some links are strong (vitamin D, alcohol), others weak or unproven (leaky gut, chronotype genetics).