Arline Geronimus argues that African Americans age faster than white people in America due to racism and stress. This has many important consequences - one of which is that waiting until their 20s to have children may not actually be healthier for black women and children, as is normally true for the American population as a whole.
Geronimus blames the faster "weathering" of African Americans on stress. She blames racism as the main source of differential stress. I think this is a plausible way of accounting for the fact that African Americans as a group are much less healthy than other Americans at the same age.
I would add, though, that there is another source of stress that is distinctively high for African Americans: the stress of single parenthood. Black Americans are especially likely to engage in the most stressful kind of single parenthood, the kind that results from never having married in the first place.
Geronimus has taken much heat for her views on racial weathering from stress. If we are looking at sources of stress, though, some are more self-inflicted than others - and thus can be addressed more directly by those enduring the stress.