1 banana = 358mg potassium. The RDA is 4700mg. You'd need 13 bananas to hit RDA from bananas alone. Lethal hyperkalemia requires acute intake of ~18,000mg+ potassium (50+ bananas in a short period) — and your kidneys would excrete the excess. Banana hyperkalemia is a meme, not a real risk for healthy people. Exception: kidney failure patients CANNOT excrete potassium — for them, even 2-3 bananas could be dangerous.
1 banana = 12g sugar. 5 bananas = 60g sugar (15 teaspoons). While it's natural sugar with fiber, 5 bananas/day is a lot. The fiber slows absorption (GI 51 — moderate, not low), but 60g of any sugar daily should be considered. For diabetics or those watching carbs: 1-2 bananas max.
Underripe bananas (green): high resistant starch + pectin → can cause constipation. Overripe bananas (brown spots): low resistant starch, high sugar → can loosen stools. The banana paradox: green = constipating, brown = laxative. 2-3 medium-ripe bananas = neutral.
📋 Verdict
2-3 bananas/day: fine for almost everyone. 5-7/day: pushing it on sugar, still safe for healthy people. 10+: excessive sugar, would displace other foods, potential digestive issues. The "bananas cause potassium overdose" fear is overblown for healthy people — you'd have to eat 50+ in a short time, and you'd vomit first.