70 bananas a day...that's clinically insane. Meaning, if you keep eating that way, your brain will deteriorate to the point where you become clinically insane.
Your brain needs more fat than that. Believe me, I tried the low-fat fruitarian diet, and it was slowly killing my brain. Panic attacks and crippling social anxiety suddenly became a daily problem when I ate that way.
The interesting this is that the more heavy/dry fruits (like banana, durian, mamey sapote) are much slower to cause these problems. Wetter and more cleansing fruits (like apples/citrus) will bring it on much faster. That's a broad brush, but it's generally true.
Yeah, it took me years to recover from low-fat fruitarianism. Now I can actually eat nothing but fruit on a given day, if I want, without a panic attack. I never do it, but it's nice to know that I can.