That language is from the Declaration of Independence, not the United States Constitution. The Declaration was written in 1776, before there was a United States. As beautiful and important as it is, the Declaration is not the founding law of these United States. The Constitution is, and it was written 11 years after the Declaration.
And what does the 8th amendment mean, if not the preservation of innocent life, including the right not be killed by starvation by order of a court?