Nature ensures health
Study a jungle or a natural overgrowth. Where are the pest attacks? The jungles are often healthy even in this age of chemical pollution because the natural ecological laws operate.
Nothing in nature is superfluous. Each action and cycle complements and cooperates with the whole. The end product of one organism becomes the input for another. There are no pests or diseases (except to complete the decomposition cycle). Wild animals too remain healthy as they serve their purpose in the overall cycle and also benefit from it.
In case of conscious agriculture the natural cycles are disturbed leading to soil health issues and pest attacks. This is why Masanobu Fukuoka recommended the no intervention agriculture that was closest to nature.
Similarly study indigenous populations living in dense forests. They too are free from chronic diseases. Recent studies show how children sent to live in forests and asked to live without much washing and cleaning develop a richer microbiome. The other factors are the indigenous populations have their own indigenous knowledge based upon natural laws and wisdom.