Record ID: MS-N085 · Family: Nutrition and dietary intervention / hereditary cancer prevention · Clinical question: Does resistant starch reduce cancer incidence in people with Lynch syndrome?

Evidence label: Randomized long-term evidence found no colorectal-cancer reduction; a prespecified follow-up found fewer non-colorectal Lynch-associated cancers, which needs confirmation.

Evidence at a glance

• Benefit: No colorectal benefit; fewer non-colorectal Lynch-associated cancers were observed after long follow-up.
• Certainty: Moderate for no colorectal effect of the tested regimen; low-to-moderate for the extracolonic signal because it was not the main anticipated finding.
• Risk: Mostly gastrointestinal intolerance; supplements do not replace Lynch surveillance or risk-reducing care.
• Cancer control: Possible prevention signal for some extracolonic cancers, not treatment of existing cancer.

What was studied

CAPP2 randomized people with Lynch syndrome, double-blind, to 30 g/day resistant starch or placebo for up to four years; average exposure was about two years. The resistant-starch and aspirin assignments used a factorial design.

The updated analysis followed participants for up to 20 years through registry and clinical data.

What the results show

Colorectal cancer occurred in 52 participants assigned resistant starch and 53 assigned placebo—no meaningful difference. Earlier follow-up was also null: 27 of 463 versus 26 of 455 participants developed colorectal cancer.

Non-colorectal Lynch-associated cancers occurred in 27 resistant-starch participants versus 48 placebo participants: intention-to-treat HR 0.54 (95% CI 0.33–0.86). The signal was especially influenced by upper gastrointestinal cancers and should not be generalized to all cancers or ordinary dietary fiber.

Important limits

• The extracolonic result emerged despite no colorectal benefit and spans several uncommon cancer sites.
• Duration of supplementation varied; adherence beyond the intervention period is not the exposure being tested.
• Long follow-up improves relevance but introduces incomplete and heterogeneous ascertainment across countries.
• This tested a specific 30-g supplement, not bananas, cooked-and-cooled starches or a generic high-fiber diet.
• The result needs replication before it becomes a stand-alone prevention strategy.

Safety and practical context

Resistant starch can cause gas, bloating and altered bowel habits. Most importantly, it must not replace colonoscopy, gynecologic risk management, aspirin discussions or other gene-specific Lynch surveillance.

Questions for the care team

• Which Lynch gene do I carry and what surveillance is recommended?
• Does the 30-g research product resemble any supplement I can obtain?
• Could gastrointestinal symptoms or prior surgery make this unsuitable?
• How should this uncertain extracolonic signal be weighed against proven surveillance?

Sources checked

• CAPP2 planned long-term follow-up, Cancer Prevention Research 2022 (PMID 35878732)
• Earlier CAPP2 resistant-starch analysis, Lancet Oncology 2012 (PMID 23140761)

Funding and conflicts: CAPP2 had public and charitable support; industry supplied study materials in the original program. Full sponsor roles and author disclosures are reported in the papers.

Last literature search: October 20, 2026 · Record appraisal: October 20, 2026

Educational information only. This record is not a prescription and does not replace advice from the oncology team, registered dietitian or oncology pharmacist.