He investigated the metabolism of tumors and the respiration of cells, particularly cancer cells.

“Cancerous tissues are acidic, whereas healthy tissues are alkaline. Water splits into H+ and OH- ions,
if there is an access of H+, it is acidic; if there is an excess of OH- ions, then it is alkaline.”

In his work The Metabolism of Tumors he demonstrated that all forms of cancer are characterized by
two basic conditions: Acidosis and Hypoxia (lack of oxygen). Lack of oxygen and acidosis are two sides
of the same coin: where you have one, you have the other.

"All normal cells have an absolute requirement for oxygen, but cancer cells can live without oxygen -
a rule without exception." - Dr. Otto Warburg

"Deprive a cell 35% of its oxygen for 48 hours and it may become cancerous."

Otto Warburg. Dr Warburg has made it clear that the prime cause of cancer is oxygen deficiency
(brought about by Toxemia).  Dr Warburg discovered that cancer cells are anaerobic
(do not breathe oxygen) and cannot survive in the presence of high levels of oxygen.

Notice how Dr. Warburg states that healthy tissues are alkaline whereas cancerous tissues are acidic.
Cancer cannot survive in an alkaline state!  What Dr. Warburg discovered is that Alkalinity and
longevity go hand in hand.