Resistant starch

About Resistant starch

Starch that escapes digestion in the small intestine and is fermented in the colon. Supplements are usually high-amylose maize starch (type 2) or retrograded starch produced by cooking and cooling (type 3).

Resistant starch is the fibre that ferments furthest down the colon and produces the most butyrate, which is why it has attracted so much interest — butyrate is the preferred fuel of colonocytes and the mechanism behind many colonic health hypotheses. The human outcome evidence has not matched the enthusiasm. Trials of insulin sensitivity give mixed results, with some clear positives in men and little in women; the large CAPP2 trial of resistant starch in Lynch syndrome found no reduction in colorectal cancer during the trial period, though a long-term follow-up reported a reduction in non-colorectal cancers that was not the pre-specified outcome.

Sold as

High-amylose maize starch powder, Green banana flour, Potato starch (uncooked), Capsule

Standardised to

Grams of resistant starch, which is a fraction of total powder weight — raw potato starch is roughly 70% resistant starch — a product without this marker may not resemble what was studied.

Also known as

RS2, High-amylose maize starch, Retrograded starch, Green banana flour

Regulation: The FDA has authorised a qualified health claim for high-amylose maize resistant starch and reduced type 2 diabetes risk, with wording noting that the evidence is limited and inconclusive. Sold otherwise as a food ingredient or supplement with no pre-market efficacy review.

What the research used

The amounts, forms and durations published trials of Resistant starch actually administered.

When it was taken

Each window says whether a trial compared it against an alternative, or whether it is convention and pharmacology. Most timing advice is the second kind.

In the food catalogue

The whole-food form, where one exists. The evidence for a concentrated extract rarely transfers to the food, or the other way round — these are cross-links, not equivalents.