Looking at the RDA you need probably 100 uG of vit A per banana to eliminate all chance of illness. Less would be OK, or better than nothing. More would proba

Looking at the RDA you need probably 100 uG of vit A per banana to eliminate all chance of illness. Less would be OK, or better than nothing. More would probably be highly unwise to prevent vit A toxicity. For the sake of argument I will make the ridiculous claim that vit A synthesis is 10000x less efficient than carbohydrate synthesis. This is absolutely laughable but I want to error on the extreme side of caution. So you trade the photosynthesis energy that could have been 1 g of banana mass for some micrograms of vit A. A typical banana (whatever that means) weighs about a tenth of a kilo, or rephrased a bunch of ten weigh about a kilo. So a banana will weigh about 1 percent less. Bananas aren't all that calorie dense so figure a bit less than a calorie per gram. So enough Vit A to prevent significant disease will cost much less than one calorie per banana. The numbers I chose were intentionally ridiculous worst case, so it should be far less than one gram per banana. Some folks who have not done the research or math seem under the impression that a Vit A enhanced banana must somehow be 1/10 the size of a normal banana or something equally unlikely.