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Ask Doctor DawnAn hour of medical questions, answers, debate, dialogue, discussion, & health in the news. Author: Dr. Dawn Motyka - JivaMedia.com
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A Guided Tour of the Upper GI Tract, Pancreatic Cancer's Protective Microenvironment, and Herman Ponzer's Energy Expenditure Research
Thursday, 5 February, 2026
Broadcast from KSQD, Santa Cruz on 3-05-2026: >ul> Dr. Dawn presents a whimsical "theme park tour" of the upper gastrointestinal tract, from saliva production triggered by sight and smell of food, through the esophageal sphincter's iris-like opening, into the stomach's pH-1 acid bath where parietal cells produce 3,000 mg of hydrochloric acid per meal. She explains protective mechanisms including the bicarbonate layer beneath stomach mucus, H. pylori's role in ulcers, and how H2 blockers and proton pump inhibitors work—cautioning about long-term PPI effects on B12 and calcium absorption. The tour continues through the pylorus into the duodenum where pancreatic enzymes and bile converge, then along the 23-foot small intestine with its tennis-court surface area of villi absorbing nutrients, iron in the duodenum, most nutrients in the jejunum, and B12 requiring intrinsic factor in the ileum. Dr. Dawn explains why pancreatic cancer—projected to become the second leading cause of cancer death by 2030—is so deadly, using a medieval castle metaphor. The tumor microenvironment acts as an impenetrable moat of desmoplastic stroma made of fibroblasts, collagen, and hyaluronic acid that blocks drugs and immune cells. Over 90% of cases have K-RAS mutations acting as growth accelerators that also thicken this protective barrier and increase CD47 "don't eat me" signals. She discusses emerging treatments including K-RAS inhibitors, PARP inhibitors for BRCA mutations, and combination immunotherapies showing 67% response rates, while noting that CAR T-cell therapy and checkpoint inhibitors alone fail because they cannot penetrate the stroma. Dr. Dawn summarizes Duke researcher Herman Ponzer's work using doubly-labeled water to measure total energy expenditure, revealing that humans burn 20-60% more calories than other great apes when adjusted for body mass. His surprising finding: Hadza hunter-gatherers walking 8-14 kilometers daily burn the same calories as sedentary Americans—the body compensates by reducing energy spent on inflammation and stress responses. This "constrained energy expenditure" model explains why exercise alone doesn't cause weight loss, though it remains crucial for preventing weight gain, reducing disease risk, and potentially tamping down harmful stress responses.
