Is Coffee Beneficial or Harmful to Your Health?

Coffee contains numerous biologically active compounds that can significantly impact long-term health. Regular coffee consumption has been linked to a reduction in overall mortality and cardiovascular disease (CVD) risk, and it also appears to provide protection against conditions such as diabetes, heart disease, neurodegenerative disorders, liver diseases, certain cancers, and asthma. Additionally, coffee may have a positive effect on fertility. Consuming three to four cups a day is generally considered safe and is associated with the most beneficial outcomes from coffee. However, most studies on coffee are observational in nature, with few randomized controlled trials to provide conclusive evidence.

What Are the Active Compounds in Coffee?

Coffee contains several biologically active compounds, including polyphenols, alkaloids, and diterpenes. Among the most notable polyphenols are chlorogenic acids, found in green coffee beans, and caffeic acid, present in roasted beans. Other significant compounds include caffeine, trigonelline, and diterpenes like cafestol and kahweol. These compounds have overlapping health effects, contributing to coffee's overall health benefits.

Green coffee beans are rich in chlorogenic acids, a group of polyphenols that have shown various health-promoting properties. Chlorogenic acids are often concentrated in supplements as green coffee extract. These compounds have been shown to help lower blood pressure, improve mood, and reduce blood sugar levels. They also exhibit antibacterial properties. Specifically, chlorogenic acid can lower both systolic (~2.5 mmHg) and diastolic (~1.5 mmHg) blood pressure without affecting nitric oxide production or endothelial function. Instead, they inhibit an enzyme called alpha-glucosidase, which is involved in the breakdown of carbohydrates and sugars in the small intestine, thus reducing glucose absorption during digestion.

A small study conducted on older adults found that decaffeinated coffee with high chlorogenic acid content improved mood, although other studies have produced mixed results. Chlorogenic acids also show antibacterial effects by inhibiting the enzyme sortase A, which plays a critical role in the formation of bacterial cell walls. This disruption in bacterial cell structure is particularly harmful to Staphylococcus aureus, but it may also affect beneficial gut bacteria, like enterococci.

Caffeic acid, which is abundant in roasted coffee beans, possesses antioxidant, anti-inflammatory, anti-cancer, and anti-viral properties. It may also provide protection against chemotherapy and radiation-related toxicity, reduce the risk of developing diabetes, combat exercise-induced fatigue, and help delay the onset of neurodegenerative diseases. The anticancer effects of caffeic acid are primarily due to its antioxidant and pro-oxidant properties, which stem from its chemical structure.

Coffee and Obesity

Several compounds in coffee, such as chlorogenic acid, caffeine, trigonelline, and magnesium, have been shown to have anti-obesity effects. A meta-analysis of studies on coffee drinkers revealed conflicting results, but it suggested that men may experience modest weight loss benefits from regular coffee consumption.

Coffee's Side Effects

While coffee has many potential benefits, its high caffeine content can also lead to some negative side effects. These include anxiety, insomnia, headaches, shakiness, and heart palpitations. Excessive coffee consumption may also increase the risk of fractures in women. During pregnancy, drinking coffee can raise the likelihood of low birth weight and preterm labor.