Catholics believe that during Communion, bread and wine become the body and blood of Jesus Christ, though they continue to appear unchanged to the human eye.
But there have been a handful of rare and debated cases in which the sacred elements appeared to take on a far more literal, physical form.
Reports from churches in Poland, Mexico, Argentina and Italy have described consecrated wafers and wine allegedly bleeding or developing red, flesh-like tissue during or after Mass.
One of the earliest recorded cases dates back to around 700 AD in Lanciano, Italy, where a monk claimed to have witnessed bread turn into flesh and wine into blood during the consecration.
According to the account, the substance coagulated into visible clumps, marking what many consider one of the first documented Eucharistic miracles.
More recent cases included a 2013 incident in Poland, where a consecrated host placed in water after falling during Mass reportedly failed to dissolve and instead developed a red substance.
Five scientific investigations published between 1971 and 2014 subjected samples from such events to forensic testing, including microscopic and biochemical analysis.
In each case, researchers said the material was consistent with human heart muscle, and where blood was detected, two investigations identified it as the rare AB type.
One of the earliest recorded cases dates back to around 700 AD in Lanciano, Italy, where a monk is said to have witnessed bread turn into flesh and wine into blood during the consecration (PICTURED)
Scientists and skeptics have cautioned that such extraordinary claims require rigorous, reproducible evidence, noting that many Eucharistic phenomena lack controlled conditions and have not been widely published in leading peer-reviewed journals.
Critics have also pointed to more conventional explanations, such as contamination or misidentification of biological material, emphasizing that without strict chain-of-custody protocols, such findings remain disputed within the scientific community.
However, the scientists who studied the samples argued that traditional scientific standards, such as repeatable experiments and peer review, are difficult to apply because the events are spontaneous and cannot be recreated in a laboratory setting.
They also claimed that stigma surrounding supernatural phenomena has discouraged broader scientific investigation, though critics maintain these limitations leave the findings unverified.
‘Fraud in all five events would require an elaborate conspiracy orchestrated by the scientific investigators and Church officials, a painstaking amount of work, and airtight collusion among multiple institutions across continents spanning several decades,’ the team said.
Communion was modeled after the Last Supper, which the Bible says was the meal Jesus shared with his 12 Apostles before the crucifixion.
According to Matthew 26:26–28, Jesus told his apostles: ‘Take and eat; this is my body. Drink… this is my blood.’
Ordinarily, the Eucharist used during Mass looks and behaves like ordinary bread and wine.
Pictured are the samples from the 700 AD case, which monks claimed the wine turned into blood
But throughout history, there have been reports of so-called Eucharistic phenomena, events in which consecrated hosts appear to transform into flesh or blood.
A report examining five such cases, spanning 40 years and three continents, claimed that each withstood extensive testing.
The samples were examined by teams of pathologists, forensic specialists and medical researchers across multiple countries, including university laboratories in Poland and independent experts in Mexico, Argentina and Italy.
The case in Italy was revisited by Professor Odoardo Linoli in 1970, who was permitted to analyze the ancient relic.
Following the reported transformation in 700 AD, monks preserved the bread and wine, which were later placed in a sacred vessel and chalice on display for pilgrims.
The first modern case occurred in Sokolka, Poland, on October 12, 2008, when a priest placed a consecrated host in water after it fell during Mass, following standard disposal practice
Linoli, who worked at the Santa Maria Sopra i Ponti Hospital in Arezzo, examined the samples under a microscope and conducted various assays over several months, concluding that the flesh was human heart muscle and that the clots were human blood, both of blood type AB.
He claimed that the histological structure of the flesh within the wafer was heart muscle tissue.
Ruggero Bertelli, a professor of human anatomy at the University of Siena, also examined the slides and agreed that the tissue appeared to be myocardial.
In Buenos Aires, Argentina, a discarded host found on a candleholder in 1996 developed a red substance after being placed in water.
In 1999, a sample was examined by Dr Frederick Zugibe, a forensic pathologist in New York.
He identified the material as cardiac tissue and noted that the presence of intact white blood cells after years in water was highly unusual.
Zugibe said the sample was heart tissue that appeared damaged and contained a mix of immune cells, including white blood cells, suggesting inflammation.
‘When I was later told that the heart tissue was kept in tap water for about a month and transferred to sterile, distilled water for three years, I indicated that it would be impossible to see white blood cells or macrophages in the sample,’ he said in analysis notes.
‘Moreover, it would be impossible to identify the tissue per se as there would be no morphological characteristics.’
A similar event was reported in Legnica, Poland in 2013, about 400 miles from the previous case, after a host fell during Mass and was placed in water
On January 5, 2014, Father Andrzej Ziombra checked on the host and reported: Immediately, we noticed that the Host had not dissolved and that a red spot covering a fifth of its surface had appeared
The first modern case occurred in Sokolka, Poland, on October 12, 2008, when a priest placed a consecrated host in water after it fell during Mass, following standard disposal practice.
A week later, parish sacristan Sister Julia Dubowska discovered a red substance attached to the partially dissolved host and alerted other clergy.
After 18 days in water, the material was removed and sent for testing. In January 2009, two pathologists from the Medical University of Bialystok analyzed the sample independently and concluded it was heart muscle.
One of the scientists, Professor Stanislaw Sulkowski, described the unusual nature of the findings.
In Buenos Aires, Argentina, a discarded host found on a candleholder in 1996 developed a red substance after being placed in water
Sample from the Buenos Aires host, showing what experts claimed are cardiac fibers with significant degeneration
‘If we put the Communion wafer in the water, in the normal course of events it should dissolve in a short time,’ he told the Polish newspaper Nasz Dziennik in 2009.
‘In this case, however, part of the Communion, for some incomprehensible reason, did not dissolve… the tissue that appeared on the Communion was tightly connected to it.’
His colleague, Professor Maria Sobaniec-Łotowska, added: ‘This remarkable phenomenon… also demonstrates to me that there could be no human interference here… we are not able to explain the studied phenomenon solely based on natural science.’
A similar event was reported in Legnica, Poland in 2013, about 400 miles from the previous case, after a host fell during Mass and was placed in water.
On January 5, 2014, Father Andrzej Ziombra checked on the host and reported: Immediately, we noticed that the Host had not dissolved and that a red spot covering a fifth of its surface had appeared.
‘We decided to inform the Bishop, who established a special theological scientific commission to analyze the event.’
In 2006, a priest invited Father Raymundo Reyna Esteban to lead a retreat at a parish in Tixtla, Mexico. During Mass attended by hundreds, a nun reported seeing a consecrated host release a reddish substance resembling blood
Pictured are what experts said they saw in the Mexico wafers while looking under a microscope
Multiple laboratories examined the sample, ruling out bacterial or fungal contamination, while one concluded it was human heart muscle.
On February 10, the material was dried, and 15 samples were collected under strict documentation alongside control specimens.
Forensic testing ruled out contamination, and one lab identified the tissue as human heart muscle.
Cardiologist Dr Barbara Engel, who was part of the investigative committee, said: ‘For me, as for everyone who has seen this host up close, there is no doubt that it is a miracle.’
In 2006, a priest invited Father Raymundo Reyna Esteban to lead a retreat at a parish in Tixtla, Mexico.
During Mass attended by hundreds, a nun reported seeing a consecrated host release a reddish substance resembling blood. The sample was set aside for further study and sent to multiple independent laboratories.
Pathologists Dr Orlando Rodas Pernillo and Dr Elisa Hernández de Rodas said the sample showed structures consistent with heart muscle, along with fat cells and white blood cells. Separate testing confirmed the presence of human blood, identified as the rare AB-negative type.
Across all five cases, the report highlights striking similarities: the repeated identification of cardiac muscle and, when blood was present, the same rare blood type.
It also pointed to unexplained factors, such as tissue not decomposing as expected or appearing to be interwoven with the host itself.
Skeptics argued that extraordinary claims require extraordinary evidence. The report acknowledges limitations, including the inability to replicate the events under controlled laboratory conditions and questions about the chain of custody.
The Catholic Church itself has debunked other alleged miracles in the past, including cases involving paint or contamination.
