Through Joseph Smith, the true and living gospel of Jesus Christ was restored to the earth(Resoration). And what I mean by living gospel is the priesthood. The authority to act and do in Christ's name. That authority was given to Joseph Smith by the "laying on of hands"(1 Tim 4:14) by heavenly messengers. And since that time there have been Prophets on the earth, leading, guiding, and directing all those who will listen to their counsel.
One specific thing that has been given to us since the "Restoration" is the "Word of Wisdom". In the revelation given to Joseph Smith was promised that if we refrained from tobacco, alcohol, tea, coffee and other illegal drugs, we "ashall receive bhealth in their navel and marrow to their bones... And shall arun and not be bweary, and shall walk and not faint." And this was given in the 1830s. Before modern technology and before we knew about the health benefits of avoiding those substances. Heres a website that i pulled up, check out the first two things they talk about(http://familydoctor.org/online/famdocen/home/healthy/prevention/086.html)