Really? The contrary is the case during Eucharistic Miracles like that of Lanciano. Science rather confirms the Real Presence. This historical miracle is described here:
"In 1970-'71 and taken up again partly in 1981 there took place
a scientific investigation by the most illustrious scientist Prof. Odoardo Linoli, eminent Professor in Anatomy and Pathological Histology and in Chemistry and Clinical Microscopy. He was assisted by Prof. Ruggero Bertelli of the University of Siena.
The analyses were conducted with absolute and unquestionable scientific precision and they were documented with a series of microscopic photographs.
These analyses sustained the following conclusions:
- The Flesh is real Flesh. The Blood is real Blood.
- The Flesh and the Blood belong to the human species.
- The Flesh consists of the muscular tissue of the heart.
- In the Flesh we see present in section: the myocardium, the endocardium, the vagus nerve and also the left ventricle of the heart for the large thickness of the myocardium.
- The Flesh is a "HEART" complete in its essential structure.
- The Flesh and the Blood have the same blood-type: AB (Blood-type identical to that which Prof. Baima Bollone uncovered in the Holy Shroud of Turin)."
http://www.therealpresence.org/eucharst/mir/lanciano.html
These are Miracles which serve to confirm faith. But
"blessed are those who have not seen, but yet believed" (Jn 20:29) by faith alone. In normal cases, we are to rest content with faith in God's Word, which
"is assurance about things what we do not see" (Heb 11:1).