Did the tortoise only reach age 40? What type of tortoise? "I" personally would not offer bread nor milk to a tortoise....however, in "the day" folks use to feed all kinds of stuff ....not that it is good but did it anyways....
I had one of the little redfoot tortoise here out on the porch one day--he was catching some rays and I was also tossing out bread crumbs for the peacock and one got caught in the wind and landed about a foot away from him and he darted (yes, darted--tortoise crazy speed ) for the bread and chomped it down crazy fast then he scampered all over acting as though he was on the hunt for more.....
Yes, I'm afraid bread was high on the list of foods to feed box turtles and tortoises in the olden days. If you look at the ingredients in bread, its not all that harmful, but not as a steady diet.
Milk is actually pretty weird stuff- sugars, fats, and proteins. No animal besides man drinks milk as an adult and no animal besides man drinks it as an adult. (And yes, I know a lot of people give it to cats, etc., but since cats, like most other animals and many people, are lactose intolerant, it is not a good idea!)
No reptile (or bird, fish, etc.) can properly digest milk, so it was mostly a fatty sugar water that probably gave it intestinal issues on a regular basis.
Bread is not as much of an issue. There is debate about the value of processed grains, but the bigger concern is that most supermarket bread is pretty salty and has other chemicals in it. There are many people who use water-dampened bread to help fight protozoan infections, and I have heard of people offering dampened bread to help with hydration issues, etc.
Neither of these is what we would offer as a real diet- but this is also a great example of how you can do some things really, really wrong and have the animal live a really long time. It does not mean that it was healthy and happy the whole time, but it lived.