Adventists believe the key to wellness lies in a life of balance and temperance. Nature creates a wealth of good things that lead to vibrant health. Pure water, fresh air and sunlight—when used appropriately—promote clean, healthy lives.

A well-balanced vegetarian diet that avoids the consumption of meat coupled with intake of legumes, whole grains, nuts, fruits and vegetables, along with a source of vitamin B12, will promote vigorous health.

Throughout the world the Seventh-day Adventist Church runs a wide network of hospitals, clinics, lifestyle centers, and sanitariums. These play a role in the church's health message and worldwide missions outreach.

The largest medical school and hospital in North America is Loma Linda University and Loma Linda University Medical Center. AdventHealth is the largest not-for-profit Protestant health care provider in the United States. It is sponsored by the Seventh-day Adventist Church and cares for over 5 million patients yearly.

en.wikipedia.org/wiki/Seventh-day_Adventist_Church#Health

There are several reasons that Adventists believe in and promote this diet. The original diet given to Adam and Even in the Garden of Eden was fruits, grains, and nuts. "God said, 'See, I have given you every herb that yields seed which is on the face of all the earth, and every tree whose fruit yields seed, to you it shall be for food" (Genesis 1:29 NKJV).

After the fall, when Adam and Eve disobeyed God's command and ate from "the tree of the knowledge of good and evil" (Genesis 2:9), God added vegetables to their diet. "You shall eat the herb of the field" (Genesis 3:18 NKJV).

God did not withhold meat from the Hebrews in the wilderness simply to show His authority, but for their good, that they might preserve physical and moral strength. He knew that the use of animal food strengthens the animal passions and enfeebles the intellect. He knew that the gratification of the appetite of the Hebrews for flesh meats would weaken their moral powers and induce such an irritable disposition that the vast army would become insubordinate, that they would lose the high sense of their moral obligations and refuse to be controlled by the wise laws of Jehovah.

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But Daniel purposed in his heart that he would not defile himself with the portion of the king’s delicacies, nor with the wine which he drank; therefore he requested of the chief of the eunuchs that he might not defile himself. 
So Daniel said to the steward whom the chief of the eunuchs had set over Daniel, Hananiah, Mishael, and Azariah, “Please test your servants for ten days, and let them give us vegetables to eat and water to drink. Then let our appearance be examined before you, and the appearance of the young men who eat the portion of the king’s delicacies; and as you see fit, so deal with your servants.” So he consented with them in this matter, and tested them ten days.
And at the end of ten days their features appeared better and fatter in flesh than all the young men who ate the portion of the king’s delicacies. Thus the steward took away their portion of delicacies and the wine that they were to drink, and gave them vegetables. (Daniel 1:8,11-16)

In Revelation 21:1,4, the Apostle John tells us, "Now I saw a new heaven and a new earth, for the first heaven and the first earth had passed away. ... 'And God will wipe every tear from their eyes: there shall be no more death, nor sorrow, nor crying. There shall be no more pain, for the former things have passed away.'" This indicates that there will be no eating of animal flesh, because there will be no more killing of animals.

The Apostle John also relays God's promise, "'To him that overcomes I will give to eat from the tree of life, which is in the midst of the Paradise of God'" (Revelation 2:7). If you plan to have eternal life in heaven, spend your remaining time on Earth preparing yourself for the diet that you will encounter there.

Or do you not know that your body is the temple of the Holy Spirit who is in you, whom you have from God, and you are not your own? For you were bought at a price; therefore glorify God in your body and in your spirit, which are God’s.

1 Corinthians 6:19,20 (NKVJ)

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