A recent review by nutrition researcher Emma Beckett from the Australian Catholic University, published in late September 2026, outlines several surprising effects of coffee on the body that are not primarily due to caffeine. These findings highlight how various compounds in coffee, beyond the well-known stimulant, can influence bodily functions in ways that are not yet fully understood. For about three out of ten people, drinking coffee can trigger the urge to go to the toilet within half an hour. This effect is also observed with decaffeinated coffee, indicating that caffeine is not the cause. Other compounds in coffee directly stimulate the colon, which is already more active upon waking. The addition of milk, sugar, or sweeteners can enhance this effect. Coffee also activates the entire digestive system. Even without food, it prompts the pancreas to release trypsin, an enzyme that breaks down proteins. Decaffeinated coffee produces the same response, making it difficult to determine whether coffee suppresses or increases appetite. These effects on digestion occur independently of caffeine. Drinking coffee too close to taking medication can alter the drug's action. It reduces the absorption of levothyroxine, used for thyroid treatment, and alendronate, a treatment for osteoporosis. It also slows the elimination of clozapine, an antipsychotic. Conversely, an antibiotic such as ciprofloxacin can slow the degradation of caffeine and prolong its effects. In most cases, spacing the intake of coffee and the drug by a few hours can avoid these issues. Coffee affects the absorption of iron. Its polyphenols and chlorogenic acids bind to plant-based iron and block a large part of it. This is particularly important for individuals with low iron reserves or those following meat-free diets. Delaying coffee consumption by an hour after a meal can significantly reduce this effect. Two compounds in coffee, cafestol and kahweol, increase total cholesterol and bad cholesterol (LDL). However, these same molecules also lower lipoprotein(a), another marker of cardiovascular risk. Chlorogenic acids seem to slightly dilate blood vessels, but the overall impact on heart health remains uncertain. In the intestine, chlorogenic acids feed the gut flora, similar to melanoidins formed during roasting, which bacteria ferment. Small studies indicate that the composition of the microbiota can change with each cup of coffee. Caffeine temporarily raises the pressure inside the eye, which is a concern for individuals with glaucoma. It can also worsen existing acid reflux. Many of these findings are based on limited studies, and experts are calling for further research on larger groups.