Nutrition has always been a part of conventional medicine, and “establishment” health care providers are trained in nutrition. However it appears that most doctors are cynical of patients willingness to consider it. Rather than tell a patient with Type-2 diabetes to undergo serious changes in diet and to get substantial amounts of exercise (since most patients would have done that already if they were so inclined), doctors prescribe medicines. If you tell your doctor you are nervous about drugs or surgeries and want to try changes in lifestyle, the doctor only needs to be convinced you are serious. By analogy, if a Ben Torah asks a shailoh of a Gadol,he’s quite likely to get, as an answer, a reference to the gemara or the Shulhan Arukh, since a Ben Torah really likes to know the real source of the answer to his problem. If a Baal ha-Bayis asks the question, he’ll get a “yes-no” answer since the Rav thinks him incapable of doing more. IF a doctor thinks you incapable of lifestyle changes, he’ll prescribe what he thinks you are capable of (having things done to you).
All medicines are natural. Antibiotics started out as moldy bread. Apsirin is from tree bark. What “Big Pharm” does it find a way of making it more cheaply. What many alternate medicine people do is advocate drugs that have already been tested and been found wanting.