Communion has been the subject of some recent high-profile debates, ranging from calls to deny the sacrament to Democratic presidential candidate John F. Kerry to a decision to revoke the first Communion of an 8-year-old girl Roman Catholic girl because she ingested a non-wheat wafer.

The reality is that the meaning of Communion and the way it is practiced have been sources of dispute since the early centuries of Christianity. Those debates continue but rarely reach the national stage because they involve often-subtle changes made by church hierarchies or conflicts within individual congregations.

Yet such discussions are important because they go to the heart of the Christian faith, say clergy and denominational officials. They affect the way believers perceive and take part in one of the most sacred events in Christian history: the meal Jesus shared with his disciples the night before his crucifixion. And they affect efforts to foster unity among Catholics, Protestants and Orthodox Christians and end theological and liturgical disputes that have created deep divisions in Christianity.

For those with a goal of unity, success could be far in the future, with Communion practices becoming more diverse as congregations search for new ways to accommodate the lifestyles and sensibilities of their members.

Juleen Turnage, spokeswoman for the Assemblies of God, said some megachurches in her denomination -- including her own 6,000-member church -- have found it unwieldy to offer Communion during packed Sunday morning services and now do so only during the lesser-attended Sunday night services. "It's a matter of practicality," she said.

John Revell, spokesman for the Southern Baptist Convention, said many churches now use Communion kits, which consist of a wafer and a small plastic cup of grape juice. The prepackaged kits, which are passed through the pews on cardboard instead of silver trays, make breaking up crackers and filling hundreds of tiny glasses -- and washing them afterward -- a thing of the past.

The United Methodist Church passed a resolution at its general conference in May urging congregations to shed generations of tradition by offering Communion weekly rather than monthly. The effort is to "reshape the focus on Communion by urging people to celebrate the Eucharist more often," said denomination spokesman Stephen Drachler.

Moving toward weekly Communion also has been a goal of many Lutherans for more than 30 years, said the Rev. Michael Burk, director of worship for the Evangelical Lutheran Church in America. One reason was the adoption of a book of worship in 1978 that placed more emphasis on Communion; another is the church's use of a common lectionary developed in recent years by Roman Catholic and mainline Protestant leaders, he said.

And the Presbyterian Church (USA) has been moving slowly from monthly to weekly Communion, said the Rev. Joseph Small, director of the church's office of theology and worship. Small said he knows of at least 400 Presbyterian churches, out of about 8,000, that offer Communion weekly.

A more evident change among Presbyterians, whose Reformation forebears rejected many Catholic Communion practices, has been an increase in the number of congregations that prefer taking Communion at the altar rail rather than in the pews, Small said. Many now use wine instead of grape juice and prefer the method of intinction, in which a piece of bread is dipped into a common chalice, then consumed.

One thing that hasn't changed for most Protestants is their rejection of transubstantiation, the Catholic teaching that the elements -- bread and wine -- are transformed during the Eucharist into the body and blood of Jesus and remain so. In the Roman Catholic Church, any leftover wine must be consumed by the priest, and the leftover hosts or wafers must be kept in a receptacle known as a tabernacle.

Burk said Evangelical Lutherans believe that the bread and wine are transformed into the body and blood of Jesus, but only for that meal. Any leftovers are "bread that was used in Holy Communion," not the body and blood of Jesus, he said.

But most Protestants view the bread and wine as a symbol of Jesus's presence, placing less emphasis on the elements' physical makeup and more on the communal sharing of bread and wine (or grape juice). For some, monthly Communion isn't merely adequate but preferred.

The Rev. Ronald Braxton, pastor of Metropolitan AME Church in Northwest Washington, said that African Methodist Episcopalians believe that Communion is a "renewal of our relationship with the Savior," not a "physical taking of Christ into our body."

"The way we live our lives, the way we execute our faith every day is our participation in Christ," he said. That means daily prayer, meditation, Bible study and weekly worship with other believers. Taking Communion is important, but once a month is sufficient, he said.

Braxton's denomination was drawn into the fray over Kerry's Communion practices when the nominee took Communion on Palm Sunday at Charles Street AME Church in Boston. Some Catholic leaders and pundits criticized Kerry, a Roman Catholic, for taking part in a Protestant ritual.

Monsignor James P. Moroney, executive director of office of liturgy for the U.S. Conference of Catholic Bishops, said the church generally does not condone the participation of Catholics in non-Catholic Communion, but he said it's a matter of degree of theological difference and a decision to be made by the local bishop.

"If a Catholic goes to an Orthodox Church and receives Holy Communion, are we concerned with that? No," Moroney said. "If he went to a Baptist church, that would be considered inappropriate."

The greater outcry involving Kerry concerned several Catholic bishops' statements in the spring that they would not offer Communion to Kerry because he supports a woman's right to abortion. A majority of American Catholics support abortion rights, and many were outraged at the suggestion that Kerry was guilty of a "serious sin" -- the primary reason for a priest refusing to give Communion. The U.S. Conference of Catholic Bishops issued a statement that the decision to refuse Communion was the prerogative of each bishop, not a matter of national policy.

Last month, some Catholics were upset that the bishop of the Diocese of Trenton in New Jersey declared invalid the first Communion of Elizabeth Pelly-Waldman. The 8-year-old has celiac sprue disease, a digestive disorder that prevented her from consuming the wheat wafers required by the church. Her priest gave her a rice wafer, and the bishop revoked the Communion.

Moroney said the church does insist on the use of unleavened wafers but understands that thousands of Catholics suffer from celiac sprue disease. It offers alternatives, including a recently developed wafer that is 0.01 percent wheat and the use of only wine in Holy Communion.

Although both elements must be consecrated and consumed by the priest during Mass, the taking of one element -- bread or wine -- is sufficient for lay communicants, he said.

Moroney said reuniting disparate branches of Christianity would be impossible without a common doctrine of Communion.

He said he understands that the growing practice among Protestants to invite all professing Christians to the Communion table is an effort to break down theological barriers. But a common liturgy of Communion must be the result of dialogue and understanding, not a tool for unification, he said.

That does not mean the Catholic way of offering Communion is the right and only way, he added. "Liturgical expression has evolved through the years and will continue to evolve," he said.