Coffee is a complex plant extract containing hundreds of bioactive compounds that can have various effects on the body. Beyond its well-known ability to increase alertness, coffee can influence digestion, medicine efficacy, and nutrient absorption. According to a recent study, these effects can occur even when consuming decaf coffee. The compounds present in coffee can interact with the body's digestive system, microbes, and medicines in unexpected ways.
One of the most immediate effects of coffee is its impact on bowel movements. A study found that about three in ten people experience the urge to poo shortly after drinking coffee, with this effect occurring quickly and with both regular and decaf coffee. While it's unclear which coffee compounds cause this, factors such as the addition of milk or sugar-free sweeteners can also affect bowel movements. Morning coffee consumption, when the colon is naturally more active, may also contribute to this effect.
Coffee can also affect reflux symptoms, eyes, and ears. For some people, coffee can worsen reflux symptoms, contributing to coughing, wheezing, and other respiratory issues. Caffeine can increase pressure inside the eye, which is a concern for individuals with glaucoma or ocular hypertension. Additionally, people with patulous Eustachian tube dysfunction, a condition affecting the ear, may be advised to limit caffeinated drinks and stay hydrated.
The relationship between coffee and medicine is complex. Coffee can interact with certain medications, such as thyroid medication and osteoporosis drugs, reducing their absorption. Caffeine can also slow the metabolism of certain medications, increasing their concentration in the blood. Conversely, some medications can affect how the body processes caffeine, prolonging its stay in the system.
Coffee's impact on cholesterol levels is also multifaceted. Compounds like diterpenes, cafestol, and kahweol can increase total and LDL ("bad") cholesterol. However, these compounds have also been shown to lower lipoprotein(a), which may indicate a lower risk of heart attack or stroke. Other coffee compounds, such as chlorogenic acids, may modestly lower blood pressure and improve blood vessel function.
Coffee may also have a prebiotic effect, feeding gut microbes and influencing the composition of the gut microbiome. Laboratory experiments suggest that coffee's chlorogenic acids can be broken down by microbes in the colon, producing other compounds. Small human studies have shown that drinking coffee can change the gut microbiome, but more research is needed to confirm this effect.
Finally, coffee can affect iron levels and gut hormones. Drinking coffee with a meal can reduce the absorption of non-haem iron, primarily due to polyphenols like chlorogenic acids. This effect is most significant for individuals with low iron stores or those relying heavily on plant-based iron sources. Coffee can also stimulate the pancreas to release trypsin, an enzyme involved in protein digestion, and affect gut hormones involved in appetite and fullness.
Key points
- Coffee's effects on the body go beyond just caffeine, with hundreds of bioactive compounds influencing digestion, medicine efficacy, and nutrient absorption.
