Does Christianity have any dietary guidelines?

Yes, there are some restrictions. Here is what I know the Bible says on the topic. Yes, the Bible lays out restrictions on food that make sense (e.g. for health reasons) in the Old Testament. This was definitely the law for Israel before Jesus came, and there is open debate on whether or not this still applies today to all Christians. In the law of Moses, the Bible lays out some specific permissions and restrictions to Israel, and is displayed here:

[Leviticus 11:2-47 NASB] 2 "Speak to the sons of Israel, saying, 'These are the creatures which you may eat from all the animals that are on the earth. 3 'Whatever divides a hoof, thus making split hoofs, and chews the cud, among the animals, that you may eat. 4 'Nevertheless, you are not to eat of these, among those which chew the cud, or among those which divide the hoof: the camel, for though it chews cud, it does not divide the hoof, it is unclean to you. 5 'Likewise, the shaphan, for though it chews cud, it does not divide the hoof, it is unclean to you; 6 the rabbit also, for though it chews cud, it does not divide the hoof, it is unclean to you; 7 and the pig, for though it divides the hoof, thus making a split hoof, it does not chew cud, it is unclean to you. 8 'You shall not eat of their flesh nor touch their carcasses; they are unclean to you. 9 'These you may eat, whatever is in the water: all that have fins and scales, those in the water, in the seas or in the rivers, you may eat. 10 'But whatever is in the seas and in the rivers that does not have fins and scales among all the teeming life of the water, and among all the living creatures that are in the water, they are detestable things to you, 11 and they shall be abhorrent to you; you may not eat of their flesh, and their carcasses you shall detest. 12 'Whatever in the water does not have fins and scales is abhorrent to you. 13 'These, moreover, you shall detest among the birds; they are abhorrent, not to be eaten: the eagle and the vulture and the buzzard, 14 and the kite and the falcon in its kind, 15 every raven in its kind, 16 and the ostrich and the owl and the sea gull and the hawk in its kind, 17 and the little owl and the cormorant and the great owl, 18 and the white owl and the pelican and the carrion vulture, 19 and the stork, the heron in its kinds, and the hoopoe, and the bat. 20 'All the winged insects that walk on all fours are detestable to you. 21 'Yet these you may eat among all the winged insects which walk on all fours: those which have above their feet jointed legs with which to jump on the earth. 22 'These of them you may eat: the locust in its kinds, and the devastating locust in its kinds, and the cricket in its kinds, and the grasshopper in its kinds. 23 'But all other winged insects which are four-footed are detestable to you. 24 'By these, moreover, you will be made unclean: whoever touches their carcasses becomes unclean until evening, 25 and whoever picks up any of their carcasses shall wash his clothes and be unclean until evening. 26 'Concerning all the animals which divide the hoof but do not make a split hoof, or which do not chew cud, they are unclean to you: whoever touches them becomes unclean. 27 'Also whatever walks on its paws, among all the creatures that walk on all fours, are unclean to you; whoever touches their carcasses becomes unclean until evening, 28 and the one who picks up their carcasses shall wash his clothes and be unclean until evening; they are unclean to you. 29 'Now these are to you the unclean among the swarming things which swarm on the earth: the mole, and the mouse, and the great lizard in its kinds, 30 and the gecko, and the crocodile, and the lizard, and the sand reptile, and the chameleon. 31 'These are to you the unclean among all the swarming things; whoever touches them when they are dead becomes unclean until evening. 32 'Also anything on which one of them may fall when they are dead becomes unclean, including any wooden article, or clothing, or a skin, or a sack--any article of which use is made--it shall be put in the water and be unclean until evening, then it becomes clean. 33 'As for any earthenware vessel into which one of them may fall, whatever is in it becomes unclean and you shall break the vessel. 34 'Any of the food which may be eaten, on which water comes, shall become unclean, and any liquid which may be drunk in every vessel shall become unclean. 35 'Everything, moreover, on which part of their carcass may fall becomes unclean; an oven or a stove shall be smashed; they are unclean and shall continue as unclean to you. 36 'Nevertheless a spring or a cistern collecting water shall be clean, though the one who touches their carcass shall be unclean. 37 'If a part of their carcass falls on any seed for sowing which is to be sown, it is clean. 38 'Though if water is put on the seed and a part of their carcass falls on it, it is unclean to you. 39 'Also if one of the animals dies which you have for food, the one who touches its carcass becomes unclean until evening. 40 'He too, who eats some of its carcass shall wash his clothes and be unclean until evening, and the one who picks up its carcass shall wash his clothes and be unclean until evening. 41 'Now every swarming thing that swarms on the earth is detestable, not to be eaten. 42 'Whatever crawls on its belly, and whatever walks on all fours, whatever has many feet, in respect to every swarming thing that swarms on the earth, you shall not eat them, for they are detestable. 43 'Do not render yourselves detestable through any of the swarming things that swarm; and you shall not make yourselves unclean with them so that you become unclean. 44 'For I am the LORD your God. Consecrate yourselves therefore, and be holy, for I am holy. And you shall not make yourselves unclean with any of the swarming things that swarm on the earth. 45 'For I am the LORD who brought you up from the land of Egypt to be your God; thus you shall be holy, for I am holy.'" 46 This is the law regarding the animal and the bird, and every living thing that moves in the waters and everything that swarms on the earth, 47 to make a distinction between the unclean and the clean, and between the edible creature and the creature which is not to be eaten.

One could argue that since we are not living in Israel, this does not apply to us (e.g. the first portion says "Speak to the sons of Israel...". Some argue that since we are grafted in through Jesus, this does apply to us. However, some argue that since we are under the New Covenant, this no longer applies to us. There are verses in the New Testament that one can interpret to say that all meat is okay, for example, this passage:

Acts 11:7-9 “And I heard a voice saying to me, ‘Rise, Peter; kill and eat.’ “But I said, ‘Not so, Lord! For nothing common or unclean has at any time entered my mouth.’ “But the voice answered me again from heaven, ‘What God has cleansed you must not call common.’

However, if you read the whole chapter, it becomes apparent that this is a vision that illustrated to Paul that he is supposed to preach to the Gentiles. Whether or not it is also saying it is okay for us to eat anything is a point of debate. Many nutritionists, even non-Christian ones claim that many (if not all) of the prohibited foods are unhealthy to eat (e.g. it really is unclean).

This passage in Acts is what I believe applies to us today:

[Acts 15:19-20 NASB] 19 "Therefore it is my judgment that we do not trouble those who are turning to God from among the Gentiles, 20 but that we write to them that they abstain from things contaminated by idols and from fornication and from what is strangled and from blood.

This passage talks about not doing things that could trip up those around us:

Romans 14:21-23 It is good neither to eat meat nor drink wine nor do anything by which your brother stumbles or is offended or is made weak. Do you have faith? Have it to yourself before God. Happy is he who does not condemn himself in what he approves. But he who doubts is condemned if he eats, because he does not eat from faith; for whatever is not from faith is sin.

If we believe it is sin and we do it anyway, it is sin. I personally am not fully convinced the law of Moses does not apply to us. However, we can be forgiven for all our sins, just by believing on Jesus for our salvation and asking Him to save us:

1 John 1:8-9 If we say that we have no sin, we deceive ourselves, and the truth is not in us. If we confess our sins, He is faithful and just to forgive us our sins and to cleanse us from all unrighteousness.

John 3:16-18 “For God so loved the world that He gave His only begotten Son, that whoever believes in Him should not perish but have everlasting life. “For God did not send His Son into the world to condemn the world, but that the world through Him might be saved. “He who believes in Him is not condemned; but he who does not believe is condemned already, because he has not believed in the name of the only begotten Son of God.

As far as kudos for eating kosher go, you will probably be healthier, and I believe God will also reward your devotion here on earth and in Heaven. This will not earn your way into Heaven, you already have that gift if you know Jesus as your Savior (see John 3:16 above).

^{Disclaimer: I'm not a Mormon. If I misportrayed something, please edit.}

For Mormons, the following are forbidden:

• wine(except for sacraments)
• strong drinks
• tobacco
• hot drinks

These commandments arise from Doctrine and Covenants, Section 89 (which is Mormon-specific scripture):

5 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.
6 And, behold, this should be wine, yea, pure wine of the grape of the vine, of your own make.
7 And, again, strong drinks are not for the belly, but for the washing of your bodies.
8 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.
9 And again, hot drinks are not for the body or belly.

And some Christians (notably the Witnesses) refuse to eat blood because of the restriction in Acts 15:29.

As a precept of the Catholic Church, in America, we are obliged to fast from meat on Fridays in Lent and fast completely on Ash Wednesday and Good Friday. Bishops in the U.K. are re-adopting this guideline starting Advent 2011 for all fridays. In America we're supposed to maintain some sort of penitential observance, although we get to choose what.

But on the whole, there are no dietary restrictions, except as Richard says rightly, in eating food sacrificed to Idols or cannibalism.