A personal answer from Gale.
The first prophet of The Church of Jesus Christ of Latter-day Saints, Joseph Smith, received a revelation from the Lord in February, 1833, regarding the care of the body and nurturing of the spirit. As with many of the revelations received by Joseph Smith, this one was an answer to an inquiry from the Prophet. Certain events led up to this revelation. Brigham Young (second prophet of the Church) recorded the following:
“The brethren came to that place [in Kirtland, Ohio] for hundreds of miles to attend school in a little room probably no larger than eleven by fourteen. When they assembled together in this room after breakfast, the first they did was to light their pipes, and, while smoking, talk about the great things of the kingdom, … and as soon as the pipe was out of their mouths a large chew of tobacco would then be taken. Often when the Prophet entered the room to give the school instructions he would find himself in a cloud of tobacco smoke. This, and the complaints of his wife at having to clean [the] floor, made the Prophet think upon the matter, and he inquired of the Lord relating to the conduct of the Elders in using tobacco” (Journal of Discourses, 12:158).
The introductory verses in Doctrine and Covenants, section 89, where the revelation is recorded, read as follows:
“A Word OF Wisdom, for the benefit of the council of high priests, assembled in Kirtland, and the church, and also the saints in Zion—
“To be sent greeting; not by commandment or constraint, but by revelation and the word of wisdom, showing forth the order and will of God in the temporal salvation of all saints in the last days—
“Given for a principle with promise, adapted to the capacity of the weak and the weakest of all saints, who are or can be called saints” (Doctrine and Covenants, 89:1-3).
As you can see, this revelation came “not by commandment or constraint,” and so originally, it was considered counsel rather than a direct commandment. It took awhile for the new rules of health to sink in, but by the time Brigham Young was prophet, most Latter-day Saints had made changes to their eating and drinking habits. In 1851 President Young proposed to the general conference of the Church that all members formally covenant to keep the “Word of Wisdom.” His proposal was unanimously sustained by the membership of the Church, and since that day the revelation has been a binding commandment for all Church members. Keeping the Word of Wisdom is part of the prerequisite for temple attendance.
Verse 4 of section 89 explains why the commandment was given:
“Behold, verily, thus saith the Lord unto you: In consequence of evils and designs which do and will exist in the hearts of conspiring men in the last days, I have warned you, and forewarn you, by giving unto you this word of wisdom by revelation—
This is an interesting statement made by the Lord in 1833. Especially in light of what we know today about health and the companies that have conspired against our good health in order to reap profits. The revelation goes on to say,
“That inasmuch as any man drinketh wine or strong drink among you, behold it is not good, neither meet in the sight of your Father, only in assembling yourselves together to offer up your sacraments before him.
“And, behold, this should be wine, yea, pure wine of the grape of the vine, of your own make. And, again, strong drinks are not for the belly, but for the washing of your bodies” (Doctrine and Covenants 89:5-7).
Thus, observant Mormons do not drink beer, wine, or any alcoholic drinks. In fact, Mormons use water for the sacrament, since a revelation to Joseph Smith recorded in Doctrine and Covenants, section 27:
“For behold, I say unto you, that it mattereth not what ye shall eat or what ye shall drink when ye partake of the sacrament, if it so be that ye do it with an eye single to my glory ─ remembering unto the Father my body which was laid down for you, and my blood which was shed for the remission of your sins. Wherefore, a commandment I give unto you, that you shall not purchase neither wine neither strong drink of your enemies; Wherefore, you shall partake of none except it is made new among you” (vs 2-4).
The Word of Wisdom goes on to say the following:
“And again, tobacco is not for the body, neither for the belly, and is not good for man, but is an herb for bruises and all sick cattle, to be used with judgment and skill.
“And again, hot drinks are not for the body or belly.”
Thus, observant Mormons do not smoke or chew tobacco. “Hot drinks” have been defined by our prophets to mean coffee and tea. At the time the Word of Wisdom was given, science had not discovered the dangers of most of these products. More recent science, however, has discovered much in these substances that is harmful. In addition to containing harmful substances, all of these “food products” are addictive. The concept of “free agency” is extremely important in the Mormon faith, and men are counseled to do nothing that would compromise freedom of choice and the ability to make sound decisions. Anything that is addictive robs us of our freedom. In recent years, Mormon prophets have added addictive drugs to the list of destructive substances Mormons should avoid.
The proper care of the body also makes it a worthy temple to house the Holy Ghost, and the Holy Ghost cannot dwell in a body corrupted by sin or addictive substances. The Holy Ghost helps us make inspired decisions, so his presence is highly desirable.
The Word of Wisdom then goes on to tell us what is good for our bodies and commends “wholesome herbs” in season, fruits, vegetable, and grains. It also counsels us to eat meat, but to do so sparingly. The Word of Wisdom recommends eating more meat during the winter, or in times of famine. Elsewhere in the Doctrine and Covenants, the Lord condemns the wasting of flesh, which translates to hunting animals for sport, rather than for food. It is interesting how many of these principles correspond with the Law of Moses in the Old Testament, and yet how currently applicable they are.
Some people bring up current science to site the benefits of some of these products, especially green tea. All types of tea (green, black, and oolong) are produced from the Camellia sinensis plant using different methods, so there really isn’t much difference between tea products except processing. All the benefits found in tea and coffee can be obtained from other foods without the negative ingredients included.
Some people have cited caffeine as the undesirable ingredient in tea and coffee, and thereby avoid caffeine for religious reasons in other products, such as cola drinks. Doctor Lindsay R. Curtis said the following:
“We have been admonished repeatedly by our General Authorities to leave this section  as it is, neither adding to it, as many food faddists are inclined to do, nor interpreting it so liberally that it loses all significance. Let us use good judgment. If we are still uncertain about certain products and feel keenly about it, let us make it a matter of prayer and fasting. We will find the proper interpretation—for us. But we should not feel that this is the answer for everyone else.
“We could speculate as to what the Lord might say in a 1971 version of the Word of Wisdom, but he hasn’t seen fit to elaborate on the original revelation. And he doesn’t need to. We’ve been given the basic guidelines; our bodies are holy tabernacles and we are to use wisdom and all the good judgment we possess in caring for them. In that sense, we can live the Word of Wisdom as fully now as when it was given in 1833” (Q&A: Questions and Answers,” New Era, Feb 1971, 5).
The Word of Wisdom is called “a principle with a promise”:
“And all saints who remember to keep and do these sayings, walking in obedience to the commandments, shall receive health in their navel and marrow to their bones; And shall find wisdom and great treasures of knowledge, even hidden treasures; And shall run and not be weary, and shall walk and not faint. And I, the Lord, give unto them a promise, that the destroying angel shall pass by them, as the children of Israel, and not slay them. Amen” (Doctrine and Covenants 89:18-21).