Why coffee became the world's favorite drink? Effects, Benefits, Risks, and What the Science Says

What is Coffee?

Coffee is one of the world’s most popular beverages, loved by millions for its dark color and rich, bitter-acidic taste.

Picture: Coffee

Credit: Pinterest

In terms of total volume, the United States is expected to be the world leader, consuming about 1.7 million tonnes in 2025 [1]. However, when measured per person, the Central African Republic tops the list. According to the 2022 data from the International Coffee Organization, the average person there consumed 52.1 kg of coffee per year, making it the highest per capita consumption country [1].

More recent data from Voronoi and Cafely place Luxembourg at the top of global coffee consumption in 2025, with around five cups per person per day, far exceeding larger economies [2] [3]. Coffee prices also vary widely across countries. Denmark has the most expensive coffee, averaging USD 5.40 per cup, while Ethiopia has the lowest, at around USD 0.78 [3].

Europe dominates global coffee culture. All of the top ten coffee consuming countries by per capita intake are European, ranging from about 5.3 to 1.6 cups per person per day [3]. In contrast, although coffee is popular in countries such as the United States, Australia and Japan, larger single serve sizes may contribute to lower per capita figures compared with Europe’s smaller but more frequent servings [3].

Coffee is made from roasted and ground coffee beans. While it was originally served hot and plain, today it is also widely enjoyed iced, and mixed with various ingredients, such as milk, milk alternatives, syrups, and creams, resulting in the dazzling classic and signature drinks of the modern era.

Story time…Who found the coffee? [4]

The discovery of coffee is wrapped up in several legends and historical theories. Even without the firm historical evidence, it is still fun to explore colorful stories that explain how coffee first woke up the world.

The most famous tale involves Kaldi, an Ethiopian goatherd who noticed his goats became unusually energetic after eating red berries from a wild bush. Kaldi tried the berries himself and felt the same stimulating effect. He took them to a monk, who disapproved and tossed them into a fire. As the beans roasted, a rich, pleasant aroma filled the air. This delicious smell is what supposedly led the monk to retrieve the beans and try brewing them into a drink. Although this might be the most widely known story about the origin of coffee, historians now believe the tale is a later invention, likely created in the 17th century and popularized in Europe.

Picture: Kaldi and his Dancing Goats

Credit: Alamy

Another idea links coffee’s origin to civet cats. According to the writings of J. Lewis Krapf, the civet cat helped spread coffee by eating the coffee berries and dispersing the undigested seeds in their droppings as they moved from central Africa to the Ethiopian highlands, where the Galla people later cultivated the plant.

Picture: Civet cat eating coffee berries

Credit: The telegraph

Many others credit the Galla people of Ethiopia with first discovering coffee's stimulating effects. They didn't initially drink it, however. Instead, they would grind up the wild coffee cherries, mix the pulp with animal fat, and roll the mixture into energy-rich balls. These were used as food rations for long journeys or raids, much like energy bars used by modern soldiers.

A brief history [4] [5]

Human use of coffee most likely began in Ethiopia, where the Coffea arabica plant grows naturally. Although stories of its discovery by a goat herder are popular, the earliest reliable evidence shows that by the 15th century people in East Africa were cultivating coffee and trading it across the Arabian Peninsula.

But references to coffee’s stimulating effects appear much earlier, in writings from the 9th and 10th centuries in the Arab world. Physicians such as Rhazes (854–932) and Avicenna (980–1037) described a plant called bunn and a drink called buncham, both of which match what we now recognize as coffee. Avicenna’s Canon of Medicine, one of the most influential medical texts in the Islamic world and medieval Europe, includes one of the earliest known discussions of a coffee-like substance and its medicinal properties.

In Yemen, Sufi monks (Muslim mystics) drank coffee to help them stay awake during long nights of prayer. Their use of the drink eventually inspired the first coffee gatherings, which soon expanded beyond religious circles. These early meetings evolved into public coffeehouses, lively places where people came to talk, tell stories, play games, listen to music, and share news.

By the early 1500s, coffee had spread from Yemen to major Islamic cities such as Cairo, Mecca, Constantinople, and Aleppo. Coffee stalls and dedicated coffeehouses quickly multiplied, drawing people from many different backgrounds and becoming central hubs of urban social life.

Europe encountered coffee in the late 16th century, when travellers described it as an exotic dark drink with energizing effects. Because it required boiling water, its preparation also helped reduce waterborne illnesses, much like tea. As these beverages spread, they encouraged safer drinking habits that supported social and economic development in the regions that adopted them.

Coffeehouse in Europe [4] [5]

Coffeehouses arrived in Europe in the 17th century, inspired by long-established cafés in the Middle East. Venice was one of the first European cities to adopt them, and by the mid-1600s they had spread to England.

The first English coffeehouse opened in Oxford in 1650, followed two years later by London’s first shop, run by Pasqua Rosée in St. Michael’s Alley. These venues quickly became important public gathering places where people exchanged news, debated ideas, and conducted business.

Picture: The Grand Café: the very first coffeehouse in England

Credit: The Grand Café

In London, many coffeehouses developed distinct identities. Merchants, scientists, and writers gathered at their preferred spots, and several major institutions, such as Lloyd’s of London and the London Stock Exchange, grew out of these communities. Because entry cost only a penny, they were often called “penny universities,” offering affordable access to information and discussion across class lines.

Picture: Interior of a London Coffee-house, 17th century

Credit: Wikimedia Commons

Coffeehouses also became hubs for political conversation. Their influence occasionally worried governments, leading to brief attempts at regulation or suppression. In France, similar spaces later played a role in spreading revolutionary ideas.

Coffee itself symbolized a shift toward clear thinking and productivity, similar to how tea coincided with China’s Tang dynasty cultural peak. Its stimulating effects contrasted with alcohol and aligned well with the values of rationalism and the Enlightenment. Writers and thinkers such as Voltaire, Diderot, and Balzac embraced coffee as a tool for creativity and focus.

Coffee break [5]

The modern “coffee break” took shape in the early 20th century, though the idea existed in various forms beforehand. Some workplaces offered coffee but no break time, while others allowed breaks but did not provide the coffee itself.

The version we recognize today, paid time paired with free coffee, first appeared at Los Wigwam Weavers in Denver. When the company noticed a drop in worker productivity, it introduced two short daily coffee breaks. The result was a marked improvement in efficiency and employee morale.

A later legal case confirmed that these short pauses counted as paid work time because they ultimately benefited employers. This decision helped establish the paid coffee break as a common feature of American workplaces.

The phrase “coffee break” became widely known in 1952, when the Pan-American Coffee Bureau launched an advertising campaign celebrating coffee as a simple way to refresh workers during the day.

Picture: Pan American Coffee Bureau, 1953 ad.

Credit: Reddit

Etiology [4]

Historical and linguistic evidence indicates that the English word coffee derives from the Arabic qahwa, through the Turkish kahveh and European forms, for example, French café, Italian caffé and Dutch koffie.

Picture: Qahwa Arabic Coffee

Credit: Archanas kitchen

The origin of qahwa itself is a bit of mystery, with several competing theories. One widely supported view suggests qahwa comes from an Arabic root meaning “to diminish desire,” which first referred to wine, but was later applied to other psychoactive beverages, potentially including coffee among Sufi communities. Another idea connects the term to khat, a stimulating beverage in Yemen, suggesting that coffee adopted the same name. Other proposals link qahwa to Arabic words meaning “strength” or associate the term with Kaffa, a region in Ethiopia often cited as an early center of coffee cultivation.

Farm Log: How Does a Cherry Become a Bean? [6]

A little bit of botany

Coffee generally comes from one of two main species: Coffea arabica (Arabica) and Coffea canephora (Robusta). Arabica accounts for the majority of global coffee production and is grown in dozens of countries within the tropics. Over 120 coffee species exist, but Robusta is the only other species produced in significant quantities, making up about 40% of the world's annual production.

Picture: Arabica vs. Robusta

Credit: Pio Gastro Bistro

Robusta was discovered in the late 19th century and named for its attributes: it is robust. It can grow at lower altitudes, in higher temperatures, and is more resistant to disease than Arabica, making it substantially cheaper to produce. But it doesn’t taste as good as Arabica.

Robusta beans contain much more caffeine, typically around 22 to 27 mg per gram, while Arabica contains about 12 to 15 mg per gram [7]. Arabica also has nearly twice the sugar content and about 60% more lipids than Robusta, which contributes to its sweeter, smoother flavor and greater popularity [7].

Some high-quality Robusta are favored by the traditional Italian espresso, but most Robusta today are destined for the instant coffee, where price is prioritized over flavor.

Harvesting, Processing, and Roasting

Great coffee depends on altitude, the right harvest timing, and high-quality processing.

Machine harvesting and strip picking collect ripe and unripe cherries together, along with leaves and twigs, offering speed but limited precision. In contrast, hand-picking allows workers to select only ripe cherries and access steep terrain, where high-quality coffee is typically grown.

Picture: Coffee fruits picking

Credit: Firebird Coffee

Coffee processing refers to the series of steps used after harvest to turn fresh cherries into dried green beans. This stage has a major influence on final cup quality and commercial value. The main goals are to minimise defects and dry the beans to a safe storage level of 11–12% moisture. Producers choose processing methods based on quality targets, available resources, and environmental conditions.

Different processing methods create distinct flavor profiles and carry different risks of defects. Problems can arise from improper processing, insect damage, or biochemical reactions, leading to undesirable flavors such as fermentation, phenolic notes, or “barnyard” characteristics.

Among these issues, mold and heavy metal contamination raise not only quality concerns but also potential health risks. Certain molds can infect coffee cherries before harvest and spread during processing if drying is uneven or beans are exposed to moisture again. Under these conditions, fungi may produce mycotoxins such as ochratoxin A and aflatoxins, which are naturally occurring carcinogens.

Picture: OTA

Credit: Ncausa

Mycotoxins are relatively resistant to heat, meaning they can survive roasting and brewing. While these steps can reduce their levels, often by around 40-65% depending on roast and brewing method, they may not remove them completely [8]. Small amounts have been detected in roasted coffee, instant coffee, and brewed drinks [8].

Table 1: Global Regulatory Limits for Ochratoxin A (OTA) and Total Aflatoxins in Coffee

Coffee plants can also absorb heavy metals from soil, water and fertilisers [9]. Although most commercial coffee is considered safe due to strict regulations, choosing well tested, high quality products adds an extra layer of reassurance. Improved post harvest practices and regular testing greatly reduce the risk of contamination.

Availability varies by region. In the US, brands such as Lifeboost, Natural Force, Purity Coffee, and Holistic Roasters (also available in Canada) are well known for their focus on quality and transparency. In the UK, Mindful Coffee, Balance Coffee, and Exhale are commonly cited options.

In regions where regulation is less consistent, it’s worth checking individual roasters’ websites for certificates of analysis or third party lab testing details before purchasing.

Picture: Coffee Roasting

Credit: Caffé Prima

Once dried, coffee beans remain enclosed in their parchment layer, which protects them once their moisture content is sufficiently low for safe storage. This is a traditional step believed to prevent “green” off-flavors and help the coffee age well during shipment. At the dry mill, the parchment is removed and the beans are sorted by size, color, and overall quality to eliminate defects before export.

Roasting transforms green coffee beans into the aromatic brown beans we use for brewing. Flavor depends on both the final roast level and how quickly the beans reach it. Two coffees roasted to the same color can taste completely different if one roast was fast and the other slow. Roast development affects the main components of flavor: longer or darker roasts reduce acidity and increase bitterness. Sweetness peaks in the middle, between high acidity and high bitterness.

Roasting also changes coffee’s nutritional profile. It mainly reshapes antioxidants, minor phytochemicals, and some B vitamins, while caffeine and minerals are only slightly affected. Light roasts retain more chlorogenic acids, but darker roasts still contain antioxidant compounds such as melanoidins [10]. Overall, total antioxidant capacity gradually declines as roasting becomes darker.

Although dark roasts are often perceived as “stronger” because of their bold flavor, caffeine is quite stable at high temperatures, so the caffeine difference between light and dark roasts is small [11].

During roasting, some niacin (vitamin B3) precursors are converted into niacin, meaning medium to dark roasts can provide more available vitamin B3 than green coffee beans [12] [13]. In contrast, other heat sensitive B vitamins present in raw beans are largely lost during roasting.

Because of these dynamics, the broad range of coffee flavors can be produced through different roasting techniques and roast profiles. Very dark roasts, like French Roast and Italian Roast, are known for their strong body and bitterness, but they suppress origin-specific character, making them less suitable for showcasing high-quality coffees.

Table 2: Partly detailed overview of technical differences between light, medium, and dark roast coffee

Credit: Colipse Coffee

Coffee and Global Inequality [4] [5] [6]

Coffee is one of the world’s most traded crops, ranking alongside cotton, sugar, corn and wheat [14]. Yet behind its popularity is a long history of unequal power dynamics, first through colonial expansion, and today through economic systems that still disadvantage the people who grow it.

In the 1600s, European demand for coffee surged. At the time, Arab traders controlled the trade and tried to protect their monopoly by exporting only roasted beans, which could not be planted. This changed in 1616, when live coffee plants were smuggled from the port of Mocha to Amsterdam. The Dutch cultivated these plants on the island of Java, creating the origin of the famous “Mocha Java” blend.

Picture: Dutch engraving of Port of Mocha, 1692

Credit: Wikimedia Commons

A century later, coffee plants descended from the Dutch stock were taken to France and then to the French colony of Martinique in the Caribbean. By the 1730s, French territories were exporting large amounts of coffee to Europe. These early movements of plants shifted coffee production away from Arabia and into European-controlled colonies, a change that shaped global trade for centuries.

Picture: Gabriel De Clieu transporting coffee to Martinique

Credit: Wikimedia Commons

Most coffee farmers today are smallholders in tropical regions, often working only a few acres. They typically earn just a tiny share of the price consumers pay. Global price swings, controlled by commodity markets in London and New York, can push their income below the cost of production.

Attempts to stabilize prices existed, such as the 1962 International Coffee Agreement, which set export quotas to protect farmers. But its collapse in 1989, followed by deregulation and the rise of powerful multinational buyers, shifted control even further away from producing countries.

Picture: International Coffee Agreement Signed at UN Headquarters

Credit: United Nation Photo

Today, a handful of corporations control much of the global coffee trade, while millions of farmers continue to struggle with low and unstable incomes. Programs like Fairtrade and premium-price sourcing (e.g., Starbucks Reserve) offer some improvements, but they do not fully address the deeper structural inequalities built into the system.

What’s in a Cup of Coffee?

According to the USDA, a cup (8 ounce/237g) of brewed coffee made with tap water contains about 94.8 milligrams of caffeine [15]. Caffeine is the psychoactive compound responsible for coffee’s stimulating effects.

Coffee also contains many other naturally occurring substances, including polyphenols such as chlorogenic acids, diterpenes like cafestol and kahweol, as well as carbohydrates, lipids, proteins, organic acids, minerals, alkaloids and a wide range of aromatic compounds. Together, these components shape the drink’s body, mouthfeel, flavor and taste.

The exact chemical makeup of a cup of coffee depends on how the beans are roasted, since roasting triggers the Maillard reaction that creates many of coffee’s characteristic flavors [16]. Grinding and brewing methods also influence the final composition [16]. In addition, genetics and gut microbiome also influence individual bioavailability [16].

Credit: Effects of Coffee and Its Components on the Gastrointestinal Tract and the Brain–Gut Axis

Mainstream vs. Alternative Views

Mainstream

Coffee is generally considered safe for most adults, and research suggests it may provide benefits for several health conditions, including type 2 diabetes, cognitive decline, weight management, certain cardiovascular outcomes and some cancers. These effects are often mistakenly attributed to caffeine alone, but many come from coffee’s other bioactive compounds, such as polyphenols and antioxidants, which also play important roles in its overall health profile.

What the science says

Coffee is one of the most widely studied beverages in the world, and scientists have examined its effects on a broad range of health outcomes. Large cohort studies and meta-analyses, such as the European Prospective Investigation into Cancer and Nutrition (EPIC) and the Framingham Heart Study, suggest that moderate coffee consumption may be linked to lower risks of several chronic diseases, although the biological mechanisms behind these effects are not yet fully understood [17] [18].

A major milestone came in 2002, when a large epidemiological study first reported that people who drank more coffee had a lower risk of developing type 2 diabetes [19]. In a group of more than 17,000 participants, people who drank seven or more cups of coffee per day had about half the risk of developing type 2 diabetes compared with non-coffee drinkers, even after accounting for factors such as race, gender and location. However, the study did not define what constituted a “cup,” which can vary widely from an espresso to a full mug of filter coffee. Later studies confirmed this pattern and suggested a possible protective effect, with some research showing stronger associations in adults under 60, although findings on age differences remain mixed [20] [21] [22].

Coffee has also been studied in relation to brain health. One of the most influential long-term studies on lifestyle and brain health, the Australian Imaging, Biomarkers and Lifestyle (AIBL) study found that people who drank more coffee experienced slower decline in attention and executive function and were less likely to progress from normal cognition to mild cognitive impairment or Alzheimer’s disease during the study period [23]. Broader evidence suggests that moderate consumption of caffeine-containing drinks can offer short-term improvements in attention, vigilance, reaction time and certain aspects of memory, especially when individuals are tired or sleep-restricted [24]. Some studies link regular coffee intake with lower risks of dementia, including in people already showing early signs of impairment [25].

Figure: Higher habitual coffee intake was associated with slower cerebral Aβ-amyloid accumulation.

Graphical representation of mean change in cerebral Aβ-amyloid accumulation, ± SD, over 126 months, across tertiles of coffee intake.

Credit: Higher Coffee Consumption Is Associated With Slower Cognitive Decline and Less Cerebral Aβ-Amyloid Accumulation Over 126 Months: Data From the Australian Imaging, Biomarkers, and Lifestyle Study

However, these findings are not entirely consistent. After statistical adjustments, several studies indicate that the strength of the association can vary by gender (often more pronounced in women), age (mixed results) and length of follow-up (short-term studies tend to report positive associations, whereas longer studies sometimes show null or negative findings) [25] [26]. Importantly, many studies find that the apparent cognitive benefits become weaker or disappear once factors such as socioeconomic status, education, childhood IQ, or health history are taken into account [27] [28]. This suggests that part of the observed benefit may reflect differences in lifestyle or background rather than the effects of caffeine itself.

The “coffee paradox” refers to the observation that caffeine can temporarily raise blood pressure, yet people who drink coffee regularly tend to have a lower risk of developing hypertension. A large Norwegian study from 1989, involving around 30,000 adults, found that daily coffee drinkers generally had lower systolic and diastolic blood pressure [29]. Among people who already have hypertension, research shows that caffeine can cause a brief rise in blood pressure, but this effect usually fades quickly as the body develops tolerance. Importantly, studies have not found a link between caffeine intake and increased cardiovascular mortality in people with high blood pressure.

Across cardiovascular research, research points to a dose-response relationship between coffee and cardiovascular disease: moderate coffee consumption is consistently associated with lower risk, while evidence for heavy consumption remains mixed, partly due to limited data [30]. For heart failure, pooled results from large cohort studies such as the Framingham Heart Study and the Cardiovascular Health Study report a 5–12% lower risk for each additional cup consumed per day [31]. More recent evidence from a UK Biobank analysis (over 500,000 participants) links moderate coffee intake to reduced risks of arrhythmia and hypertension, with some findings suggesting that drinking coffee in the morning may support vascular function by aligning with the body’s circadian rhythms [32] [33].

Most large-scale studies show that moderate coffee consumption remains associated with lower cardiovascular risk even after adjusting for major confounders. Some variations exist by sex (with stronger effects in women), smoking status (benefits clearer in non-smokers), genetic differences in caffeine metabolism (greater advantages in fast metabolizers) and coffee preparation methods (will be specified in later section), but the overall protective pattern is consistent [30] [34] [35] [36].

Coffee consumption has also been studied in relation to cancer. Most large studies and meta-analyses show a strong and consistent protective association between coffee consumption and the risk of liver and endometrial cancers. Dose–response analyses indicate that each additional two cups per day is linked to a substantially lower risk of both cancers [37] [38]. There is also early evidence of a small protective effect for prostate cancer. For lung and bladder cancers, the associations become weaker once factors like smoking are taken into account [37] [38]. For several other cancers, including breast, pancreatic, kidney, ovarian and gastric cancers, the current evidence indicates no meaningful association with coffee intake [30] [39].

Lifestyle factors such as smoking, sedentary lifestyle, high BMI and poor diet play a significant part in developing and progressing chronic disease, but these influences do not fully diminish the potential protective patterns observed with moderate coffee intake [40]. At the same time, most studies share similar limitations. They rely on observational designs and self-reported coffee habits, and do not always account for differences in cup size, brewing method or additives such as milk and sugar. These factors make it difficult to determine cause and effect and may introduce bias.

Alternative

Alternative health perspectives on coffee often center on its effects on hormones, gut health and metabolism. These views commonly highlight concerns that coffee may disrupt hormonal balance, act as an inflammatory or overly acidic food, or stress the digestive system. At the same time, some proponents claim that coffee can support detoxification or stimulate metabolism, though evidence for these effects is mixed or limited.

Within the biohacker community, figures such as Ray Peat have raised additional concerns related to nutrient status, suggesting that frequent coffee consumption may contribute to deficiencies in minerals or vitamins such as calcium, magnesium, vitamin B1 and iron. These ideas remain outside mainstream scientific consensus but are influential in certain wellness circles.

There is also growing interest in novel coffee-related products, such as unroasted “green” coffee, bulletproof coffee and herbal-based coffee replacement. These are often promoted for weight management or appetite control, contributing to their popularity in some alternative health communities.

What the science says

Concerns such as “adrenal fatigue” are based on the idea that chronic stress can exhaust the adrenal glands, but this concept is not supported by mainstream medical research. Coffee dose temporarily increases cortisol and catecholamines, affecting short-term glucose and insulin responses [41] [42]. However, these effects tend to diminish in habitual drinkers, and long-term studies do not show harmful hormonal disruption [41]. Research on sex hormones, including testosterone and estradiol, has shown mixed and generally non-significant effects from caffeine [43] [44] [45]. Some differences appear across racial groups, but the findings are inconsistent and limited [46].

Cortisol naturally peaks within the first 30 to 45 minutes after waking [47]. Drinking coffee immediately upon waking, especially on an empty stomach, adds a caffeine driven cortisol rise on top of this natural peak [48]. For people who are sensitive to caffeine, this may prolong elevated cortisol levels and increase feelings of jitteriness or anxiety. Consuming coffee with food, particularly protein or carbohydrates, slows caffeine absorption and reduces peak blood levels.

At present, there is little direct evidence linking the timing of coffee consumption to meaningful changes in sex hormones. Most research focuses on total caffeine intake rather than when coffee is consumed [41]. This is likely because caffeine’s primary short term hormonal effects act through the stress response system, including cortisol and adrenaline, rather than through direct regulation of sex hormones.

Thyroid research has reached similar conclusions. Large population studies, including National Health and Nutrition Examination Survey (NHANES) and Mendelian randomization analyses, report no association between coffee consumption and the risk of either hyperthyroidism (overactive thyroid gland) or hypothyroidism (underactive thyroid gland), nor is there consistent evidence that coffee triggers or worsens autoimmune thyroid diseases. However, coffee can interfere with the absorption of levothyroxine (LT4), the synthetic hormone commonly prescribed for hypothyroidism. This interaction does not affect thyroid hormone production itself; rather, the concern is that drinking coffee too soon after taking LT4 can reduce the medication’s absorption and effectiveness [49] [50].

Concerns are sometimes raised about whether coffee might disrupt gut health, since foods and beverages can directly shape the gut microbiota. Animal and human studies consistently show that regular coffee consumption is associated with increases the amount and abundance of beneficial taxa such as Actinobacteria, Bifidobacterium species and often Faecalibacterium, along with reductions in potentially harmful groups like Proteobacteria and certain E. coli strains [51] [52] [53] [54].

Coffee does stimulate gastric acid and can slightly relax the muscle at the lower end of the esophagus [55] [56]. These effects occur with both caffeinated and decaffeinated coffee [57]. Even so, moderate consumption, generally fewer than four cups a day, is not associated with a higher risk of gastroesophageal reflux disease [58]. Higher intakes may increase discomfort in people who are already sensitive [58].

Coffee also speeds up bowel movements, a finding repeatedly observed in research [59]. This likely contributes to the lower rates of constipation seen in regular coffee drinkers. It may also help the gut recover after surgery: several clinical studies show that coffee can promote the return of normal bowel function and shorten the duration of postoperative ileus after colorectal or gynecological operations [60].

Coffee can influence how the body absorbs certain nutrients, but the effects vary by nutrient and are usually small in people with a balanced diet. One of the more consistent findings is that coffee can reduce the absorption of non-heme iron, the type mainly found in plant foods. For example, drinking a cup of coffee with a hamburger meal has been shown to reduce iron absorption by about 39% [61]. Furthermore, both drip and instant coffee lowered iron absorption from roughly 5–6% to around 1–2%, with stronger instant coffee causing even greater reductions [61].

Coffee can also bind to divalent (carrying two electrical charges) minerals such as magnesium, zinc, and calcium, and it may slightly increase urinary excretion of these minerals as well as some water-soluble B vitamins. Observational research suggests that heavy coffee drinkers (around four or more cups per day) sometimes show lower blood levels of certain B vitamins, such as folate, B6 and riboflavin, although this may partly reflect overall diet patterns [62]. For most people, these effects are small and can be easily compensated by a normal diet. For example, the minor decrease in calcium absorption from coffee can be offset by adding just 30–50 millilitres of milk [63]. Similarly, the loss of water-soluble vitamins through increased urinary excretion is generally not large enough to cause deficiency in healthy individuals who eat a varied diet.

Coffee is widely known for boosting energy and alertness, and many people also find that it improves their exercise performance. Because of these effects, some believe that coffee may support weight management. Research in humans shows that caffeine can temporarily raise the resting metabolic rate for several hours. In some studies, a dose of eight milligrams per kilogram of body weight increased the amount of free fatty acids in the blood and promoted fat oxidation, especially in people with a normal body weight [64]. In simple terms, this means the body shifts toward burning fat rather than glucose for fuel. These findings suggest that coffee may act as a helpful supportive tool for weight management, though it is unlikely to cause weight loss on its own.

Green, unroasted coffee beans contain higher levels of chlorogenic acids (CGAs), which have antioxidant and anti-inflammatory properties (will be further explained in later section). A 2010 industry-sponsored review of randomized controlled trials found that green coffee bean extract (GCBE) was linked to small reductions in body weight and BMI compared with a placebo [65]. However, stronger and higher-quality evidence is still needed to confirm these effects.

Similarly, bulletproof coffee, a trendy drink made by blending coffee with medium-chain triglycerides (MCT) oil and grass-fed butter or ghee, is popular in alternative health circles and among followers of keto lifestyles. Supporters claim it can suppress appetite, increase alertness and serve as an ideal meal replacement. The drink was popularized by Dave Asprey, who drew inspiration from butter tea consumed in Tibet.

Some studies do show that bulletproof coffee can reduce hunger, largely because it is high in fat and calories [66]. However, this also leads to criticism: a single cup can contain a significant amount of saturated fat, and when added to a normal diet, it may contribute to excess calorie intake [67]. There is also no strong evidence that bulletproof coffee improves cognitive performance compared with regular coffee [66].

Interest in mushroom-based coffee alternatives has grown as more people look for ways to enjoy a coffee-like experience without the jitters that caffeine can cause. Popular blends often combine Lion’s Mane with Chaga or Reishi, and are marketed as offering a roasted, coffee-adjacent flavor along with a calmer, more balanced energy boost. However, scientific evidence for their benefits remains limited. Most research on medicinal mushrooms has been carried out in animals or in lab settings rather than in humans [68] [69]. Human trials, where they exist, tend to involve small sample sizes and short study periods, making it difficult to draw firm conclusions about long-term health effects [68] [69] .

There are also considerations on the sensory side. Studies testing medicinal mushroom powders in food products have reported negative impacts on taste, texture, colour and overall flavor, especially when mushrooms are added in crushed or powdered form. While mushroom coffee blends are generally considered safe to consume in moderate amounts, their health claims are still preliminary, and their sensory quality can vary widely.

Another well-known substitute is chicory root coffee, which is made from roasted chicory and contains no caffeine. It brews like coffee and is naturally rich in inulin, a type of prebiotic fiber that supports gut health. Animal studies suggest that chicory root may also help regulate blood sugar, reduce inflammation and support aspects of brain health, though these findings still need confirmation in long-term human research.

Coffee enemas is an alternative practice by inserting a liquid made from brewed coffee into the rectum using an enema kit. In detox-focused wellness communities, it is believed to “cleanse” the liver and remove toxins. Study in Thai male participants did not find beneficial antioxidant effects by coffee enemas [70].

Claims such as “coffee brewing removes heavy metals from water” can be misleading. Scientific studies do show that spent coffee grounds, when processed into engineered filters containing about 60% coffee grounds and silicone, can remove up to 99% of lead and mercury from still water over long contact times [71]. However, this does not mean that everyday coffee brewing removes heavy metals in any meaningful way. These filtration effects occur only when coffee grounds are specifically treated and used as a filtration material, not when making a regular cup of coffee.

Coffee is a plant that is easily affected by pests and diseases, especially the widely grown Arabica variety [6]. This vulnerability often leads to the use of pesticides during cultivation, raising concerns about possible residue in the final product. A recent study from Egypt examining 881 coffee samples found pesticide residues in some green beans, roasted beans and capsules, with most levels still below EU safety limits [72]. Brewing, especially espresso, reduced these residues even further. It is also important to note that coffee goes through multiple processing steps, such as high-temperature roasting, removal of the outer layers, and water extraction, before it reaches the cup, all of which help lower the amount of pesticide residue that ends up in the beverage.

Deeper understanding: Potential mechanisms

The protective effects may come from caffeine, which blocks adenosine receptors and may help reduce inflammation in the brain, as well as from other compounds in coffee that have antioxidant properties. Interestingly, decaffeinated coffee showed similar patterns, suggesting that the benefits may not depend on caffeine alone.

Coffee contains a wide range of bioactive compounds that may contribute to its potential health benefits. One of the most studied groups is chlorogenic acids (CGA), a type of polyphenol with antioxidant properties. These compounds help protect cells from oxidative damage and may play a role in reducing neuroinflammation, which has been linked to conditions such as insulin resistance and cognitive decline [73] [74].

CGA and other compounds in coffee also appear to help lower chronic inflammation, a key factor in many long-term health conditions. Studies have found that higher coffee consumption is associated with lower levels of inflammatory markers such as high-sensitivity C-reactive protein [20]. These anti-inflammatory effects may come not only from CGA but also from melanoidins, antioxidant-rich compounds formed during the roasting process [75] [76].

Coffee’s polyphenols may support metabolic health in several ways. Some research suggests that CGA can slow the absorption of glucose during digestion and improve insulin response by influencing enzymes involved in carbohydrate breakdown [20]. However, this mechanism remains debated, as CGA levels in the bloodstream after drinking moderate amounts of coffee may be too low to exert large direct effects [77]. Even so, other pathways, such as improved hormone signaling, enhanced mineral availability and possible prebiotic effects on gut bacteria, may still contribute to better insulin sensitivity [78].

Coffee may also benefit vascular health. CGA has been shown to improve endothelial function, supporting nitric-oxide–mediated vasodilation and reducing arterial stiffness [79]. Better vascular function is closely linked to improved cardiovascular outcomes and overall metabolic health.

Coffee’s potential health effects are linked to several biological mechanisms, many of which involve caffeine but not all. One of the best-understood pathways is caffeine’s role as an adenosine-receptor antagonist in the brain. By blocking adenosine, a chemical that promotes fatigue, caffeine increases alertness, supports attention and memory, and can temporarily enhance cognitive performance. Animal studies show that blocking specific adenosine receptors may also counteract age-related cognitive decline and influence pathways related to amyloid buildup and tau tangles, both key features of Alzheimer’s disease [23]. These effects suggest a possible protective role for coffee in long-term brain health.

Caffeine’s influence extends beyond cognition. It can temporarily reduce appetite and increase energy expenditure, and may shift the body toward using more fat as fuel during these periods. Therefore, those following a ketogenic lifestyle often use black coffee as a potent metabolic catalyst to accelerate the transition into ketosis and enhance fat oxidation. Some population studies have also observed associations between regular caffeine intake and lower risks of depression and suicide, potentially linked to its stimulating effects on neurotransmitters. Increased alertness may even contribute indirectly to safety outcomes, such as reducing driving-related accidents.

Coffee’s impact is not limited to the brain. Since the gastrointestinal tract is the first system to encounter coffee, researchers have explored whether the drink affects gut microbiota. Although caffeine is often considered the main active component, some studies report similar changes in microbiota composition with both caffeinated and decaffeinated coffee, suggesting that other bioactive compounds in coffee may also play a role [80] [81]. This raises the possibility of a broader gut–brain interaction contributing to coffee’s health effects.

Both caffeine and estrogen are processed by the same liver enzyme, CYP1A2, which means caffeine intake could theoretically influence hormone levels. Animal studies suggest that caffeine may affect sex hormones by interfering with the maturation of egg cells or by altering enzymes involved in steroid and estrogen metabolism [82]. However, findings in human studies are inconsistent, and no clear pattern has been established [83] [84] [85].

Because of these uncertainties, some attention has also turned to the phytoestrogens found in coffee. These plant-based compounds may help supplement declining estrogen levels in postmenopausal women and have been linked to a lower risk of atherosclerosis [86]. This could partly explain why certain protective effects of coffee are more evident in women than in men.

For a comprehensive understanding of caffeine, check our caffeine overview article!

Diterpenes are natural oily compounds found in coffee, mainly cafestol and kahweol. They are known for their impact on cholesterol levels [87]. Studies show that cafestol, the more potent of coffee’s diterpenes, can reduce LDL receptor activity in the liver, leading to increases in total and LDL cholesterol as well as triglycerides [88]. Some long-term studies link heavy unfiltered coffee consumption to higher cardiovascular risk, although for most moderate coffee drinkers, the overall benefits of coffee still tend to outweigh these effects [87].

Interestingly, cafestol and kahweol may also have positive roles in the body. Early research suggests they can activate detoxification enzymes and promote pathways that trigger the death of damaged or abnormal cells, which may contribute to cancer-preventive effects [87] [89]. These findings are still developing, but they highlight the complex and multi-layered nature of coffee’s health profile.

Brewing, Roasting and Their Impact on Health

Coffee’s health effects are shaped not only by how much people drink but also by how the coffee is made. Brewing and roasting methods can meaningfully influence the compounds we consume. One important example is chlorogenic acids (CGA), a group of polyphenols known for their antioxidant and metabolic effects. CGA levels change depending on how the coffee is roasted, extracted and brewed [90] [91]. During roasting, some CGA is broken down into quinides, compounds that may help regulate blood glucose. Brewing methods also matter because different extraction techniques pull out these compounds in varying amounts.

Overall, filtered coffee tends to offer more health advantages than unfiltered or boiled coffee. Research has associated filtered and even decaffeinated coffee with lower risks of type 2 diabetes, reduced dementia risk and a more favorable cholesterol profile [92]. A key reason is that unfiltered or boiled coffee contains higher levels of diterpenes, naturally occurring compounds that can raise cholesterol. Boiled coffee can contain about 7.2 milligrams of these compounds per cup, whereas a paper filter removes most of the oils that carry them [93]. Some of the protective effects of filtered coffee are thought to come from phenolic acids that pass through the filter while the cholesterol-raising oils are retained.

To Milk or Not to Milk

Milk can change how coffee polyphenols behave by binding to them and altering their absorption, as well as their antioxidant and anti-inflammatory effects.

Milk proteins and fat can bind to coffee polyphenols, including chlorogenic acids, forming complexes that slow their release and absorption in the gut [94]. This interaction was long thought to reduce coffee’s antioxidant effects.

However, emerging research suggests the picture is more nuanced. One study found that with a specific amount of milk added (about 90 mg of protein/ml), the antioxidant activity rose from about 33.6-49.4% [95]. Cell based studies also show that polyphenol–protein complexes can be roughly twice as effective at reducing inflammatory responses in immune cells compared with polyphenols alone [96].

Because humans absorb only a small fraction of free polyphenols, binding them to proteins may actually improve both absorption and biological activity, a mechanism now being explored in further research [96]. But these effects can vary depending on the amount and type of milk used, the coffee’s phenolic profile, and the brewing method.

Who it might help and/or harm?

People sensitive to caffeine

For those sensitive to caffeine, if cutting it out completely feels difficult, consider switching to decaffeinated options. They offer the same variety of flavors, just without the jitters and shakes.

For a deeper and more comprehensive understanding of common decaffeinated options, check our Decaffeinated Alternatives Overview Articles.

Children and Adolescents

Soft drinks, tea, and chocolate are still the primary sources of caffeine for children. But with the growing popularity of coffee, children and adolescents may be encountering coffee earlier than we tend to expect. Evidence indicates that children can develop tolerance and experience withdrawal symptoms similar to those observed in adults [4]. Early exposure to caffeine has also been linked to increased impulsivity, sensation seeking, and risk-taking behaviors [97].

Therefore, general dietary guidelines recommend avoiding caffeine-containing foods and beverages in the diets of children and adolescents.

Pregnancy and Lactation

Pregnant women are advised to limit caffeine intake because slower maternal metabolism prolongs both maternal and fetal exposure. Fetuses and newborns are unable to metabolize caffeine efficiently, requiring 100–350 hours for complete elimination. Caffeine consumed during breastfeeding also passes into breast milk, exposing infants whose metabolism remains slow.

Therefore, health organizations generally recommend moderation, no more than about 200 mg of caffeine per day, during pregnancy and lactation [98] [99].

Cigarette smokers and people who plan to quit smoking [4]

Caffeine may help mitigate certain adverse pulmonary effects of smoking, such as chronic bronchitis and pulmonary edema, and could potentially delay the onset of chronic obstructive lung disease. However, as smoking itself is a major confounding factor in related studies, further research is required to establish definitive conclusions.

Smoking accelerates caffeine metabolism, causing smokers to consume larger amounts to achieve the same stimulant effects. Consequently, individuals who reduce or quit smoking are advised to lower their caffeine intake to avoid increased sensitivity and prolonged effects once tobacco use ceases.

People who are taking medication or have certain medical conditions

For people taking medication or managing certain health conditions, it’s always wise to inform your healthcare provider about your coffee drinking habits, including how many cups you drink, how often, and at what time of day, before starting any prescription or treatment. Caffeine is generally safe with most medications, but certain substances, such as ephedra, can increase the risk of high blood pressure, heart attack, stroke, or seizures in some individuals [100].

How to stack it?

Daily recommendation [100]

Most health authorities recommend a daily caffeine intake of up to 400 mg for adults, roughly the amount in four cups of brewed coffee, ten cans of cola, or two energy drinks. However, it’s always wise to check the caffeine content on pre-packaged drinks before consuming them.

Lethal dosage

Most death cases by caffeine overdose were due to ​​accidental overdoses in medical settings. A lethal dose of caffeine is around 10 grams. Since a shot of espresso contains about 100 milligrams, an overdose would require roughly a hundred of them.

For a deeper and comprehensive understanding of caffeine, read Caffeine Overview Article on Lifestack!

Common questions

What’s the difference between commodity coffee and specialty coffee? [6]

When buying coffee, you are generally choosing between two types:

Commodity Coffee: Think of this as the generic, everyday option. It is sold in huge volumes based on a global price, regardless of its quality or flavor. It is often just seen as a bitter, caffeinated product, and the details of how it was grown or processed are largely ignored.

Specialty Coffee: This is coffee where the flavor and quality comes first. It is carefully grown, harvested, and processed to achieve a superb taste. Its origin matters immensely, as the specific farm, soil, and climate directly shape its unique flavor.

What are the tips for purchasing the best coffee? [6]

There is no guaranteed method for selecting excellent coffee every time, but certain practices can significantly improve quality.

1. Buy coffee from specialty shops instead of supermarkets. Specialist shops generally offer fresher products, knowledgeable staff, and the possibility to sample or receive tailored recommendations.
2. Look for clear traceability on the package. Good coffee varies by country, region, farm, and processing method. Packaging that tells you where the coffee came from usually indicates higher-quality beans, and helps you learn what flavors you enjoy. Because traceability is expensive to maintain, it’s most often found on better-grade coffees.
3. Check the roast date and buy small amounts. Choose coffee that shows when it was roasted, and try to buy it within two weeks of that date. Only buy enough for one to two weeks at a time. Coffee tastes best in the first few weeks after roasting.

Note: Dark-roasted coffee loses freshness faster. The intense roasting process makes the beans more porous, so they absorb air and moisture more quickly.

Depending on where you live, availability will vary. Examples of brands that emphasize quality and transparency include:

• UK: Mindful Coffee, Exhale, Balance Coffee
• US: Lifeboost, Natural Force, Purity Coffee, Holistic Roasters (also available in Canada)
• EU: NoordCode Pure Coffee (Netherlands)

It is also worth checking individual roaster websites for certificates of analysis or lab testing details before purchasing.

Does coffee go stale? [6]

Surprisingly, yes. Even though many people don’t think of coffee as a “fresh” product, it absolutely is, and it can lose quality over time.

Polyphenols are sensitive to heat, and higher temperatures lead to greater losses. Processes like roasting speed up their degradation and reduce the levels of bioactive compounds in coffee [101]. Grinding intensifies this effect even further. When a coffee bean is ground for espresso, its surface area increases by more than 10,000 times, dramatically increasing exposure to heat and oxygen [102].

Therefore, to maximize the health benefits of coffee, make sure to use coffee that is recently roasted and freshly ground.

Coffee stales in two main ways:

1. Loss of aromatics. The fragrant compounds that give coffee its smell and flavor gradually disappear.
2. Exposure to oxidation and moisture. These speed up staling and create dull, unpleasant flavors often described as flat, woody, or like cardboard.

To keep your coffee tasting its best, check the roast date when you buy it, and if you can, grind your beans at home right before brewing.

Is keeping my coffee in the fridge a good way to slow the stale process? [6]

Not really. Storing coffee in the fridge doesn’t keep it fresh longer. Instead, it can cause the coffee to absorb smells from other foods, which affects the flavor.

If you need long-term storage, the freezer is a better option. Just make sure the coffee is sealed in an airtight container, and only defrost the amount you plan to use right away.

For everyday storage, the best way to keep coffee fresh is simple:

• Use an airtight bag or container.
• Keep it away from light, especially direct sunlight.
• Protect it from moisture.

These steps help slow down the staling process and preserve flavor as long as possible.

This article is for informational purposes only and does not constitute medical advice. Consult a healthcare provider before making changes to your health routine.