Ayurveda’s laboratory was the entire universe, its ingredients simply the basic building blocks of this universe itself: the great 5 elements (panch maha bhutas) - Space (Akasha), Air (Vayu), Fire (Tejas), Water (Aap) and Earth (Prithvi). Shake up the 5 elements and you have the recipe for creating this universe in all its entirety and variety.
Man is a part and parcel of this universe and can hardly be considered in isolation. The pancha maha bhautik Sharira (body) along with manas (mind) and atman (soul) constitutes you and me, the Purusha (the living, breathing, feeling self) in constant interaction with the outer universe (loka).
The self of the person (Purusha) is a continuum of the universal self while the physical body composed of pancha maha bhutas (five great elements) originates from the pancha maha bhautik seed and derives nourishment from food and drinks of similar composition. Hence equilibrium and non antagonism between the internal and external milieu of man is essential for the maintenance of the living body. Since the individual human being is the miniature replica of the universe; the individual (purusha) and the universe (loka) stay in constant interaction with each other and also derive and draw materials from each other in order to maintain their normalcy and homeostasis. This interaction and exchange continues in a normal way such as by breathing the air, eating foods available in nature, etc.
So long as this interaction is wholesome and optimum, the man is in optimum health. When this harmonious process breaks down, a disease state starts. Hence in Ayurveda the main principle of treatment will be to restore the harmonious exchange between Purusha (individual) and Loka (universe).