What classifies a hot drink? Exactly what temperature does a beverage become hot? Is iced tea or coffee permissible? 
 
It's all a bit bonkers!

The point, my dears, is not whether or not there is any definite scientific evidence which points in any particular direction. Science is not always conclusive, and (especially in the case of coffee) has ofttimes disagreed with itself on the health aspects of these substances. 
 
Yes, the fact that these substances are addictive plays into the decision to abstain from them. Many LDS people take this a level further and abstain from or curb use of as many addictive substances as they find -- cf. Mormons who don't drink Coke, Pepsi, or other caffienated drinks.  
 
However, the real issue at hand is the fact that we have received a commandment from a source we consider to be extremely trustworthy, and we will follow it; indeed, is it not written, "faith is not to have a perfect knowledge of things"?  
 
Of course, this brings up the topic of blind faith -- which none of us (intelligent) LDS agree with. We are proponents of personal revelation, whereby anyone -- member or not -- may pray about something and seek to know its veracity (or to use LDS terminology seek to "gain a testimony of it"). 
 
Hence, upon learning of the Word of Wisdom, conscientious investigators seek testimony of it. The WoW is just as much a test of faith as it is for our health. 
 
If you're still having trouble, consider the Mosaic Law, which prohibited the ancient Jews from consuming pork or other items which were not kosher. Was it for their health? It almost certainly aided them in this regard, as pigs are extremely dirty animals and will consume, quite literally, almost anything. However, it was the test of faith which it represented that was most important. 
 
*bows, exits stage left*

the reason for no coffee or tea has nothing to do with caffine it is a tarnic acid that is found in coffee and some teas i may be wrong im going to ask a missionary but i believe that all organic teas are ok because they do not have the acid in them hope this helped

Ok, so here's my thought.  
 
The word of wisdom says no hot drinks, correct? It's not specific, leaving it open for interpretation. Or not? 
 
Maybe it means exactly that, what it says... no hot drinks. However, if people say, "well it means caffeine, or tannic acid", then we're moving into shaping the word of wisdom to fit our lives the way we want it to. That is, if I'm looking at this objectively.  
 
In a religion such as the LDS church, where it literally fills your life with callings and duties to and with our families, maybe it's time to follow the word of wisdom as stated, and stop trying to make it so difficult.  
 
No hot drinks, period. If you take a sip of a warm drink, but it turns out it's hot and you burned your tongue, don't do that again. Seems simple enough. If this isn't what the Prophet meant (I'm assuming it was a Prophet who gave the WoW in the first place), then there needs to be an addendum of some sort. It seems that it would be best to clarify and make it so there is no doubt as to what the members are to do.  
 
Then, when practicing our Agency (free will), we'll know what we're doing and have no doubt about whether or not our choices are seen as right or wrong, by the LDS church. 
 
Would help me, anyway. :)

“ ‘[Tea and coffee] are what the Lord meant when He said “hot drinks” ’ ” (Joseph Smith, as quoted by Joel H. Johnson, A Voice from the Mountains [Salt Lake City: Juvenile Instructor Office, 1881], p. 12). There are people who think the issue is over caffeine. That is not the issue. In the Revelation, it never says anything about caffeine, nor has the Church of Jesus Christ of Latter Day Saints ever said anything "Doctrinally" about caffeine. Here is what was published in a church magazine by a church authority: (H. Burke Peterson, “Q&A: Questions and Answers,” New Era, Oct. 1975, 36–37) "Two of the tests we can employ as we question the use of any food or beverage are: Is it wholesome? Is it prudent? As we know, some of us need more rest than others. These same principles imply that we should not tax our bodies beyond good judgment. Finally, remember that the Lord has counseled: 
 
“For behold, it is not meet that I should command in all things; for he that is compelled in all things, the same is a slothful and not a wise servant; wherefore he receiveth no reward.” (D&C 58:26.) 
 
We know that cola drinks contain the drug caffeine. We know caffeine is not wholesome nor prudent for the use of our bodies. It is only sound judgment to conclude that cola drinks and any others that contain caffeine or other harmful ingredients should not be used." 
 
Sound judgement. It's also sound judgement not to hit your thumb with a hammer. Not a Commandment. You won't be kept from heaven cuz you drink your Mountain Dew.  
 
Yes, Herbal teas are okay. “And again, verily I say unto you, all wholesome herbs God hath ordained for the constitution, nature, and use of man—  
 
“Every herb in the season thereof, and every fruit in the season thereof; all these to be used with prudence and thanksgiving.”

Great Great Grandpa Joel had a powerful testimony of the meaning of the Word of Wisdom. I have read his testimony many times. In it he tells how he was present when the Word of Wisdom was given. And he expresses his Testimony of the Word\'s meaning. Granpa Joel said that Coffee and Tea were \"unwholesome herbs\", and he said many other things. 
 
Perhaps I misremember. I clearly remember the quote \"Tea and coffee are what the Lord meant when He said “hot drinks\". I don\'t remember that he ever said those were Joseph\'s words.  
 
Great Great Grandpa Joel was always very careful in quoting Joseph Smith. For example, here is a quote from his diary: 
 
\"I attended the conference held in the town of Orange in Ohio in the month of October where I first beheld the face of the Prophet and Seer, Joseph Smith. When I was introduced to him, he laid his hands upon my shoulder and said unto me, \"I suppose you think that I am a great, green, lubberly fellow.\" \" 
 
Notice, Joel carefully makes clear who was speaking and to whom. I don\'t remember any similar quotation of Joseph\'s words in Joel\'s Testimony of the Word Of Wisdom. However, my last reading of his Testimony was 18 months ago. Perhaps, I missed it.  
 
Forgive me if this upsets you. My thrust and wish is that you not rely upon my Great Great Grandfather\'s testimony, but develop your own.  
 
Too often we use our personal interpretations of the Word of Wisdom to exclude the interest of our brothers and sisters. The calling is to invite, to teach, and to lead. We have no calling to scorn, nor judge. 
 
And not frequently enough have people, even members, bothered to read and investigate the Word for themselves. Sadly, many know only their neighbor\'s, or father\'s, or mother\'s beliefs of the meaning of the Word, and fail to develop their own. In truth, often their neighbor, father, or mother themselves did not read and develop an understanding of the Word themselves, but blindly accepted still another person\'s views. 
 
For all of you who have questions about the Word of Wisdom, I invite you to read it for yourselves. Study it. Think about it. Discuss it. And when you believe you have reached a conclusion, pray about it and ask for guidance. If you have done your part to investigate the Word of Wisdom and its meaining yourself, I promise you will have an answer. 
 
I believe that the words \"hot drinks\" were used intentionally. And I believe the vagueness of the language is to reinforce the principle of the Iron Rod.  
 
For the curious, the iron rod is a feature in a dream that bears a valuable lesson on life. You can read about it in the Book of Mormon in 1 Nephi chapter 8, and again in chapter\'s 11 and 13. The chapters are short. It is a good story. And, as I said, it carries a valuable and lesson in clear language. 
 
The Word of Wisdom is adapted to the capacity of the weakest. But from the disagreement here, even among members and non-members alike, I am confident it is clear to all that there is no intention to command in all the details of the Word.  
 
And I am confident that when you determine to investigate the Word of Wisdom for yourselves, with an open heart, truly wanting to know the answer, whatever answer you may find, that you will learn several valuable lessons. And in the investigation, from the discord over interpretation, I hope you will discover tolerance and forgiveness, respect for those further on the path than you, and gentle, non-judgemental but firm disagreement for those who journey behind you.