It says that the same individual will be prone to various diseases that reflect their individual make-up. Therefore Ayurveda can provide a treatment that covers not only a specific illness but all the potential diseases that the individual is likely to get. Modern medicine is realizing the importance of disease prevention. It is not enough to treat diseases after they arise. That is like putting out a fire after it has already started and done some damage.
Real treatment is to prevent disease from happening in the first place.
And many diseases that are difficult to treat once they are fully developed can be prevented, if caught early enough. According to Ayurveda, disease arises mainly from a breakdown of the balance of internal energies in a person, not merely from external pathogens, however powerful these may be. This is similar to modern medicine's effort to strengthen the immune system, which is the energy of our body to defend itself from outside attacks. But Ayurveda has a better understanding of this internal energy and its connections with mind and consciousness. It views our vital energy not merely as a biochemical phenomenon but as a product of the mind and prana which are not limited to our physical structure.