Why do resistant starches qualify as part of dietary fiber in the context of gut microbiome nutrition?

Because they are fully digested into glucose in the stomach and therefore serve as the primary caloric source for colonic cells directly.

Because resistant starches are water-soluble vitamins produced by plants and do not undergo fermentation by microbes.

Because they are always absorbed in the duodenum and then secreted into the colon via bile, which classifies them as fiber by definition.

Because they resist digestion in the small intestine and reach the colon where microbes ferment them, qualifying them functionally as fiber.