Hmmm..., the bread and water diet wouldn't be the best one. Not only would you run into nutrional problems, but you'd also get really tired of it! I suspect that would be true of other things in a person's lifestyle.
How to survive on a bread and water diet
>>But even sourdough might not be enough to survive. Eventually, just like the potato scenario, you would probably run into nutritional deficiencies. Even sourdough bread made with wild yeast, bacteria, and whole grains likely will not provide enough nutrients like vitamin C, B12, and D, as well as calcium. Without these key players, humans would run into some serious problems. With no vitamin C source, a person could develop scurvy, which results in weakness of the muscles and fatigue. Calcium is necessary to prevent osteoporosis, which results in weakened bone mass. Plus, humans need fat to survive as well, which sourdough bread doesn’t have.
If you did attempt to eat one food for an extended period of time, you would probably get sick of eating the item far before you gave yourself any severe nutritional deficiencies. That’s due to a psychological phenomenon called sensory specific satiety. Scientists have found that the more you eat something, there’s a corresponding decline in pleasantness. But some foods are more prone to this than others (like high protein foods), and some researchers have found that bread might be in fact fairly resistant to this phenomenon.<<