Iodine circulating in the blood is captured by numerous tissue sites and ends up in mucus secretions. These tissues include the salivary glands, nasal secretions, lungs and stomach. Tissues and mucus products containing iodine defend against invasion by bacteria and viruses. Respiratory and oral transmission are key pathways for viral infections. With enough supplementation, iodine can be ever-present and ready to defend in both the upper- and lower-respiratory systems as well as in the stomach.
As medical technology advanced, scientists gained enough insight to begin studying the causes of disease and two schools of thought emerged. One showed immediate and promising results while the other was more holistic in nature and, though sound in theory, could not readily offer the same clear evidence in terms of results. This dialogue began in Europe in the early 1800s and still continues in present times.