Corn Syrup

Corn syrup is glucose produced by breaking down cornstarch with enzymes. High-fructose corn syrup (HFCS) is then enzymatically converted so that 42% or 55% of the sugars are fructose instead of glucose — roughly the same ratio as table sugar, but cheaper and easier for food manufacturers to use. It's in most sweetened sodas, many sauces, packaged baked goods, breakfast cereals, and condiments.

Why fructose matters

Glucose can be used by almost every cell in your body. Fructose is metabolized almost exclusively in the liver. In small doses (a piece of fruit) that's fine. In large doses from sweetened drinks and processed food, the liver converts excess fructose into fat — driving non-alcoholic fatty liver disease, raising triglycerides, and worsening insulin resistance. Liquid sugar is the most concerning form because there's no fiber to slow absorption.

Blood sugar and mood

Drinks sweetened with HFCS deliver a fast glucose spike followed by a crash — felt as a slump in energy, irritability, and renewed hunger an hour or two later. Over time, repeated spikes blunt insulin sensitivity. People who cut sweetened drinks usually notice steadier energy within a week or two.

For people with IBS, the fructose in HFCS is also a FODMAP — when intake exceeds what the small intestine can absorb, it ferments in the colon, causing bloating and loose stools. Reading labels is the main lever: HFCS hides under names like "glucose-fructose syrup" and "isoglucose" outside the US.