One of the reasons study results are often wrong – more likely wrong than right in fact – is because there are so many confounding variables. For example, we can’t tell whether the cephalic insulin response to artificial sweeteners is meaningful and unhealthy, because most of the population is already in metabolic shambles.
The cephalic insulin response occurs when your body secretes insulin in anticipation of a meal. Even the smell of food can cause your body to release insulin. This response also occurs when you first chew and swallow food, before blood glucose levels rise.
The unknown of artificial sweeteners is: if your body thinks you’re in the process of having a meal, how much insulin is released, even in the absence of glucose? Does your body produce enough insulin under these conditions to impact your long-term metabolic health? Do artificial sweeteners in coffee or zero calorie sodas break a fast? What about sugar free gum?
One scientist who looked at this issue for a decade and gave up, said: “The literature is messy because people who are prone to be overweight are the biggest consumers of artificially sweetened beverages.” In short, obesity may cause metabolic problems unrelated to the sugar-free substances. Or, excess insulin from sugar substitutes might cause or amplify metabolic problems/obesity.
On this and other biomedical controversies, we have no idea which way the causation arrow is pointing. Take cholesterol for example. Your body sends cholesterol as a healing compound to the site of inflammation. Yet cholesterol is blamed for being on the scene after sugar already committed the crime. Same with TMAO. This metabolite is hyped by the anti-meat crowd because it is elevated in people with heart disease. Nevertheless, TMAO is produced by the gut whether you eat red meat, eggs, fish, or vegetables.
The bottom line is, the next time someone waves a new study in your face to make some esoteric point, remember: wet streets cause rain.