Austin Frakt reviews the literature supporting the idea that health care has a large impact on health.
Robin Hanson gives the other side:
So I want to say loudly and clearly what has yet to be said loudly and clearly enough: In the aggregate, variations in medical spending usually show no statistically significant medical effect on health. (At least they do not in studies with enough good controls.) It has long been nearly a consensus among those who have reviewed the relevant studies that differences in aggregate medical spending show little relation to differences in health, compared to other factors like exercise or diet. I not only want to make this point clearly; I want to date other health policy experts to either publicly agree or disagree with this claim and its apparent policy implications.