Prebiotic Powerhouses

Beyond the alliums you already met, the standout prebiotic is resistant starch. Slightly green bananas are loaded with it — the starch slips through your small intestine undigested and feeds bacteria in your colon. Cooked-then-cooled potatoes and rice develop resistant starch too, which makes yesterday's leftover rice better for your gut than a freshly cooked batch.

Asparagus is another inulin-rich pick, alongside garlic, onions, and leeks. Oats deserve a mention as well: their beta-glucan fiber helps Bifidobacteria flourish, among other beneficial species linked to immune function and lower inflammation.