Long before the medicinal value of plants and roots was understood by modern science, the Nephite and Lamanite “medicine men” made good use of the only pharmacy available to them. Since then, science has found that plant derived medicines have many uses: quinine is an effective treatment for malaria, opium is a powerful pain killer, digitalis stabilizes the heart’s rhythm, and belladonna is used to make atropine, a drug with many medicinal uses.
Hugh Nibley
“They were able to control fevers because of the very good remedies they had from these tropical plants. Quinine wasn’t discovered until 1840. Nobody knew that the quinine bark would cure these fevers until then. They didn’t know what could cure them. They didn’t know about mosquitoes or anything else. Again, here we have a wonderful insight. There are these occasional flashes of background in the Book of Mormon, which for the most part concentrate intently on the issues of salvation. But here it just happens to note in passing (it’s good to note) that it was fever country and there were diseases to which men were subject by the nature of the climate, which was tropical and humid. The fevers were held under control by the most excellent quality of the plants.” (Teachings of the Book of Mormon, lecture 62, p. 65)
Bruce R. McConkie
"There are two opposite and almost equally unsound views held by many people as to the value and place of physicians in society. Most people rely entirely on doctors and medical science where health is concerned and make no attempt to seek the healing power of the Lord. (2 Chron. 16:12.) Some others reject hospitalization and medicinal aid, supposing that it is only by divine aid that health will or can be restored.
“Actually, of course, the Lord intends that men should exercise faith in him so as to be healed, but he also intends that men should use the agency and intelligence he has given them, in both preventing and curing sickness. It is proper that the sick should ’be nourished with all tenderness, with herbs and mild food.’ (D. & C. 42:43.) The Book of Mormon speaks ’of the excellent qualities of the many plants and roots which God had prepared to remove the cause of diseases.’ (Alma 46:40.)” (Mormon Doctrine, p. 573)