Here is an example of a possible connection: most causes of heartburn are actually caused by low stomach acid. Low stomach acid in the stomach often makes its way into the esophagus through the gastro-esophageal valve (the valve between the esophagus and the stomach that normally prevents stomach acid from making its way into the esophagus). When stomach acid, virtually any amount, that makes its way into the esophagus will cause varying degrees of inflammation of the esophagus or esophagitis; a person may have no symptoms to symptoms of heartburn, chest pain, nausea or coughing just to make a few.
Too much stomach acid in the wrong place (i.e., the esophagus) can cause a wide variety of symptoms. Low stomach acid, resulting from continual use of antacids (i.e. PPIs and H2-blockers), autoimmune conditions and other causes, can impair the use of calcium in the body. Calcium that is not properly ionized (activated) by stomach acid can accumulate in various tissues such as the breast.
Calcium-laden breast cysts are a known precursor, meaning they commonly develop into, breast cancer. Low stomach acid, causing heartburn symptoms or no symptoms at all, has also been linked to a greater incidence of osteoporosis (loss of calcium in bone), atherosclerosis (accumulation of calcium in arteries) and arthritis (calcium accumulation in joints) - all of these conditions, like breast cancer, can be caused or perpetuated, by impaired calcium metabolism.
Also, when stomach acid is low fewer hydrogen ions, an element in stomach acid, make their way into the tiny blood vessels within the stomach lining and into general circulation. Fewer hydrogen ions in the blood circulation cause a blood pH higher than it should be. Normally, blood pH, or relative hydrogen ion concentration) is around 7.3. With fewer hydrogen ions the in circulation, the blood pH increases (meaning that it is less acidic and more on the alkaline side) and this can cause calcium to come out of bones and from elsewhere in the body. The released calcium from various body tissues can then accumulate where it does not belong as in the breast, and other soft tissues such as the blood vessels themselves, tissues surrounding joints and out of bones.
In short, esophagitis is always an important health problem that deserves serious attention.