Man cannot live on bread alone – not least because man would develop scurvy about a month or so into that little experiment.

The best diets have plenty of variety in them, making sure you get everything from vitamin C to iron to linoleic acid without even having to think. Even fad diets that focus on just a few foods or on eliminating certain things are usually varied enough to be reasonably nutritious. Still, in the extremely unlikely scenario that you had to live on just one food, are some nutritionally more complete than others? Could you get what you need from, say, just potatoes, or just bananas, or just avocados?

One thing is for sure, the candidates would not include meat or most fruits and vegetables. Meat doesn't have fibre, nor does it have key vitamins and nutrients. Fruits and vegetables may have vitamins, but they don't have anywhere close to enough fat or protein, even eaten in quantity. The body does not need as much as you might think to stay alive, but you omit them at your peril.