What it does in the body
- Butyrate production (preferential SCFA from RS fermentation)
- Colonocyte nourishment and colorectal cancer prevention
- Blood glucose regulation (reduces glycemic response of starchy meals)
- Insulin sensitivity improvement
- Prebiotic effect (promotes beneficial Bifidobacteria and Faecalibacterium)
How much you need (Daily Value)
| Group | Recommended | Source |
|---|---|---|
| Adult male | 15-20g/day recommended by some researchers; typical Western intake only 3-8g/day | CSIRO/research consensus |
| Adult female | 15-20g/day recommended | CSIRO/research consensus |
| Pregnancy | Same as adults; may help with gestational diabetes glucose control | Research-based |
| Children | No specific guideline; part of overall fiber recommendation | N/A |
| Older adults | 15-20g/day; particularly beneficial for insulin sensitivity and colon health | Research-based |
Richest food sources
| Food | Amount | Where |
|---|---|---|
| Green (unripe) banana | 8-12g per 100g | global |
| Raw potato starch | 60-70g per 100g | global |
| Cooked and cooled rice (day-old) | 3-5g per 100g | east-asia |
| Cooked and cooled potato | 3-4g per 100g | global |
| Green banana flour | 40-50g per 100g | south-america |
| Cooked and cooled lentils | 3g per 100g | south-asia |
| Hi-maize resistant starch (RS2) | 60g per 100g | global |
| Plantain (unripe, cooked) | 5-8g per 100g | caribbean |
If you don't get enough
Mild: Suboptimal butyrate production, reduced microbial diversity
Moderate: Impaired colonic health, increased colorectal cancer risk, suboptimal glycemic control
Severe: No isolated RS deficiency syndrome; long-term low intake contributes to chronic disease risk
Time to onset: Gut microbiome changes within 2-4 weeks; cancer risk develops over decades
Too much
Upper limit: No UL; up to 40-50g/day tolerated by most people when introduced gradually
Flatulence and bloating if introduced too rapidly (colonic fermentation). Rarely, exacerbation of SIBO symptoms
How well you absorb it
Not absorbed in small intestine (by definition). Fermented to SCFAs in colon; butyrate and other SCFAs are absorbed colonically (~2 kcal/g for RS)
Helped by: Cooling cooked starch (promotes retrogradation → RS3 formation), Diverse gut microbiome (better fermentation capacity), Gradual introduction
Hindered by: Reheating (partially reverses retrogradation but not completely), Antibiotics (disrupts fermenting bacteria), Small intestinal bacterial overgrowth (premature fermentation)
Cooking & storage
Cooking destroys RS (gelatinization). Cooling after cooking creates RS3 (retrogradation). Each cook-cool cycle increases RS. Reheating partially reduces RS but retains more than freshly cooked. Green banana becomes regular starch when ripe and cooked.
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