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Starting Solid Foods: Where the "Four-Month" and "Six-Month" Guidelines Actually Agree

By Leon MoriguchiPublished May 13, 2026Updated May 18, 20265 min read日本語版あり
Audience
Parents of children four to six months old

TL;DR

  • ·The WHO "six months" and ESPGHAN: the European Society for Paediatric Gastroenterology, Hepatology and Nutrition — a body that publishes pediatric nutrition and digestive-health guidelines for European clinicians/AAP "four to six months" are not contradictory — one is a population-level public health threshold for settings with poor sanitation, the other is a clinically calibrated window for individual children; both point to the same practical zone
  • ·No major guideline recommends starting before four months; the lower bound is the one point of universal agreement, grounded in renal and digestive immaturity and aspiration risk
  • ·Developmental readiness signs — head control, fading tongue-thrust reflex, and interest in food — are more informative than calendar age alone, and a delay of one to two weeks in a typically developing child has no meaningful effect on nutritional outcomes

Contents

  1. Lead
  2. The "six-month rule" and the "four-to-six-month window" are not in conflict
  3. Readiness signs: the child's timeline, not the calendar's
  4. Japan's guidelines: the 2019 revision
  5. A practical decision sequence
  6. Summary
  7. References

Lead

"When should I introduce solid foods?" Ask the internet and the answers scatter across a surprisingly wide range: "around five to six months," "exclusive breastfeeding until six months," "introduce from four months to build tolerance." Side by side, these sound like they contradict each other.

They don't — but understanding why requires knowing that different organizations are answering slightly different versions of the question, from different starting points, for different audiences.

This article does not try to identify the single correct age. Instead, it maps why the guidelines differ in their wording, where they converge on the same core, and what to actually look at when deciding whether your specific child is ready now.

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In the memori app

The memori app keeps the accumulation of feeds and meals in a form you can read back later.

  • Nursing, pumping and bottles run on a timer, with side and volume recorded alongside.
  • Solids build up into a list of what's been eaten, so a first-time food is easy to spot.
  • Height, weight and head circumference are drawn over national reference curves.
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