FODMAP Stacking Calculator
FODMAP stacking occurs when multiple food items containing small, individually low-FODMAP portions of the same fermentable carbohydrate group (such as fructans, sorbitol, or GOS) are consumed in a single meal or within a 3 to 4-hour window. While each food item falls beneath clinical trigger thresholds in isolation, their combined cumulative mass saturates intestinal transporters and exceeds colonic bacterial fermentation capacity, provoking gas, visceral distension, abdominal cramping, and rapid motility shifts.
Use the interactive plate builder below to test combinations of foods. The calculator evaluates your cumulative category totals and flags when you risk exceeding safe physiological limits.
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You have combined multiple foods containing the same fermentable carbohydrate group in one meal. Even if each portion is individually low FODMAP, their cumulative load will saturate enterocyte transporters and trigger rapid bacterial gas fermentation within 3 to 12 hours.
The 3-to-4 Hour Gastrointestinal Clearance Rule
The gastrointestinal tract clears typical meal volumes from the stomach and duodenum in approximately 3 to 4 hours. To prevent FODMAP stacking, space meals containing the same carbohydrate family (such as Fructans or Sorbitol) by at least 3.5 to 4 hours.
Track multi-ingredient stacking across 2 to 36-hour lag windows
GutLog on iOS automatically evaluates multi-ingredient meals against your subsequent bowel movements using a Poisson arrival baseline model. Identify whether your pain is driven by fructans, sorbitol, or delayed motility without manual calculations.
The biological mechanism of carbohydrate stacking
When Monash University laboratory researchers assign a green low-FODMAP rating to a food portion, that rating applies solely to that single ingredient eaten in isolation. The digestive tract does not process foods individually:
Transporter saturation
Enterocyte brush-border transporters have finite rate limits. For example, GLUT5 transporters can absorb limited amounts of free fructose per hour. When you eat two different fruits that each contain safe amounts of fructose within 2 hours, the transporters saturate, leaving the remaining fructose in the bowel lumen to cause osmotic water shifts.
Colonic fermentation threshold
Oligosaccharides (fructans and GOS) cannot be broken down by human enzymes and always reach the colon. A small amount (e.g. 1 slice of wheat bread) produces a manageable gas volume that healthy colonic walls absorb or expel easily. Adding a second fructan source (such as broccoli stalks) doubles gas production, triggering visceral hypersensitivity pain fibers.
How to prevent stacking in everyday meals
- Diversify FODMAP categories: If your meal contains a fructan grain (like sourdough), choose vegetables from the sorbitol or mannitol-free categories (such as carrots, cucumbers, or spinach).
- Observe the 3.5 to 4-hour window: Wait at least 3.5 to 4 hours before consuming another snack or meal containing the same FODMAP group to allow gastric and upper small bowel clearance.
- Track with longitudinal lag windows: Use GutLog on your iPhone to correlate meals against symptoms across 2, 4, 8, 12, 24, and 36-hour windows.