JOEL - Actually Annie, you already know the main reason why we should not drink wine. Because it is a commandment. At first it was just a "word of wisdom ... To be sent greeting: not by commandment or constraint"(D&C 89:1-2). However, the prophet Brigham Young later on declared that it should be a commandment. (Gospel Doctrine, 5th ed. p. 365). I guess it's one of those little tests God gives us to see if we will have enough faith to trust and obey Him, even though intellectually we might not think there is anything wrong with having a little sip of wine once in a while. But I don't think that's the answer you wanted to hear, so I will try to come up with a few more.
I am a scientist by profession. I can give you several health related reasons why drinking wine is not good for you. Science has shown that the alcohol in it dulls the senses, slows down reflexes, and can damage the liver. It can cause gastritis, pancreatitis, weakening of the heart, cancer, and can do permanent harm to a developing fetus. A person who does not know that he is an alcoholic and starts drinking it only occasionally may soon find himself hopelessly addicted to it. When this happens he can lose his family, his friends, his job, and eventually his life. On the other hand, I can also give one recently discovered reason why it is good for you. Scientists have decided now that a glass of red wine each day can greatly reduce the risk of cardiovascular disease. So as you can see there is some confusion in the scientific field about the benefits and risks of drinking wine, although the risks still definitely out weigh the benefits.
Your friend says it's OK to have a drink here and there as long as we don't abuse it. Sounds logical. However, what do you call abuse? People are different and have different tolerances to the effects of alcohol. What doesn't have much effect on one person may be destructive to another. The safest thing to do is to not have any at all, then you don't have to wonder about how much is too much. It is true that in Biblical times, Jesus and most everyone drank wine. However, it probably did not contain as much alcohol as the wines we have today. Also the amount of alcohol in other alcoholic beverages has been greatly increased by distillation. God knew that as time went further along man would invent more and more ways to abuse his body(durgs, stronger alcoholic drinks, etc). Because of this He decided it was time to give us instruction by revelation through the prophet Joseph Smith.
During the early years of the church the revelation was taken as simply a reccommendation for moderation in taking in the things listed. President Joseph F. Smith later taught that the Lord did not insist on strict compliance in the early years in order to allow a generation addicted to noxious substances some years to discard bad habits. The path leading to the present position on the Word of Wisdom began with the Presidency of Joseph F. Smith (1901-1918) and culminated in the administration of Heber J. Grant (1918-1945), who, more than any other Church leader, preached strict compliance.
God has told us that our bodies are like temples for our spirits(1 Cor. 6:19, D&C 93:35) and that no unclean thing may enter a temple or into His Kingdom(1 Ne. 10:21). Our latter-day prophets have told us what many of those unclean things are(including wine). When something unclean comes into our temple it can have a detrimental effect on our mind and spirit. President Hinckley said," Your body is the instrument of your mind. In your emotions, the spirit and the body come closest to being one. What you learn spiritually depends, to a degree, on how you treat your body."
The best reasons for closely following the Word of Wisdom are the promises the Lord makes to us for our obedience. We shall "receive health in our naval and marrow to our bones" We shall find wisdom and great treasures of knowledge, even hidden treasures; we shall run and not be weary, walk and not faint... and the destroying angel shall pass them by."(D&C 89) God always keeps His promises.
Elder A. Theodore Tuttle said, "Obedience to this law qualifies us to receive the promised blessings: we shall receive health, wisdom, strength and protection. (See D&C 89:18-21.) We do not worry. We have an inner peace and quietude. Even knowing the calamities we may face, we know we will have the promised blessings and protection of the Lord."
Elder Boyd K. Packer said, "The Word of Wisdom was revealed to the Prophet Joseph Smith in 1833. This revelation has been scrutinized and ignored, attacked and defended, ridiculed and praised. Meanwhile, faithful Saints have observed it as a token of their obedience to God. For many years, they could obey it only on faith, in much the same spirit that Adam offered sacrifice. An angel asked him, "Why dost thou offer sacrifices unto the Lord? And Adam said unto him: I know not, save the Lord commanded me" (Moses 5:6). Early members of the Church obeyed the Lord's counsel without the benefit of present medical knowledge, which has validated the physical benefits of their obedience. We now know by scientific evidence what the Saints have known by revelation for 158 years."
Is it OK to have an occasional glass of wine? Sure it is, if you don't want to be exalted in our Heavenly Father's Kingdom. Here's a good answer given by President Hinckley. "I recall a bishop's telling me of a woman who came to get a recommend. When asked if she observed the Word of Wisdom, she said that she occasionally drank a cup of coffee. She said, "Now, bishop, you're not going to let that keep me from going to the temple, are you?" To which he replied, "Sister, surely you will not let a cup of coffee stand between you and the house of the Lord."