I think if we're healthy we have a good chance at withstanding anything out there - but that it's not a sure-fire means of success. There are plenty of nasty diseases out there that even a healthy person cannot ward off.
It's an interesting thought to follow a Biblical diet, but on the other hand people in times before us had very short lives, in part because they weren't getting enough important nutrients in their food. So if we were to return to eating the way they did, we'd get diseases like scurvy and such killing us off. So I think some sort of modern balance is required, to eat the various foods we now know are important. In the olden days, it was often only the rich who could eat those foods. The poor would eat just wheat gruel or whatever and live a short, unhealthy life.
