109. Post Hoc Reasoning

(da “Informal Logic, a pragmatic approach”, D. Walton, second edition,  pag. 279 - 282, Examples of drawing causal conclusion from scientific studies)

Example 8.17

Researchers reported in the Circulation Journal of the American Heart Association that drinking as little as one can soda pop per day, whether it is regular or diet, is associated with a 48% increased risk of a predecessor of heart disease and diabetes called metabolic syndrome. Metabolic syndrome is a cluster of symptoms including excessive abdominal fat, high blood pressure, high blood sugar level, and lower levels of cholesterol (….) The findings of the study suggested the conclusion that drinking as little as one can of regular or diet soda per day is a cause of metabolic syndrome, a syndrome known to be associated with heart disease and diabetes”

(…) still there is a danger of committing the POST HOC FALLACY when interpreting such experimental findings and trying to express them in causal terms (….) Dr. Ramachandran S. Vasan of Boston University School of medicine said that it is unlikely that an ingredient in soda causes the effect. He added that it is more likely that consuming these drinks is ‘simply a marker for the poor eating habits of the participants.’ This remark suggest that those who drink soda beverages regularly also consume other foods of poor nutritional value, and it is all their diet choices as a whole tha cause conditions, such as being overweight and having high blood pressure, that are known to have adverse consequences for diabetes and heart problems. To jump to the conclusions that drinking soda causes metabolic syndrome would be an instance of incorrect POST HOC reasoning. To single out drinking soda regularly as the cause of thes unhealtthy outcomes, there would need to be an additional experimental investigation that studied whether people with otherwise healthy diets, but who regularly consume diet o regular soda, also have metabolic syndrome”