What is the natural diet for humans? This is a common question but — we evolve based on behaviour and our behaviour may have a number of consequences, some beneficial and others not so much.
Evolution is based on changes that enable us to pass on genes for future generations. If a genetic change affects cholesterol metabolism and causes an increase in heart disease this may not be relevant in evolutionary terms because heart disease usually affects people later in life.
It still may have an impact on human society because of the important influence of grandparents involved in child-minding and their importance as a repository of knowledge.