Magnesium is needed to prevent sodium from increasing blood pressure. The ingestion of magnesium supplements inhibits the effectiveness of many medicines used to treat high blood pressure and heart disease. Compounds commonly used to treat hypertension and heart disease diminish the body's capacity to absorb and retain magnesium. As people age, their ability to metabolize magnesium deteriorates.
Researcher: Hard water contains more calcium and magnesium than soft water contains. Thus, those who drink mostly soft water incur an increased risk of heart disease, stroke, and hypertension, for people being treated for these conditions tend to have lower levels of magnesium in their blood.
Which one of the following, if true, most undermines the researcher's argument?