Unfiltered Coffee Can Raise Cholesterol | The Most Dangerous Brewing Method Explained

 One cup wakes you up. Two cups keep you going. The bitter, aromatic taste is hard to resist. Among all the things that stimulate the brain and create mild dependence, coffee is arguably one of the healthiest. A morning cup, an afternoon cup, one more before work begins—this is everyday life for countless coffee lovers.

But what many people don’t realize is that choosing the wrong coffee—or brewing it the wrong way—can quietly work against your health. Certain types of coffee can actually raise total cholesterol and LDL cholesterol levels. The hidden culprit?
Unfiltered coffee.

Let’s start with a quick explanation of LDL cholesterol, often referred to as “bad cholesterol.” Unlike HDL (“good cholesterol”), which helps clear cholesterol from blood vessels, LDL transports cholesterol from the liver throughout the body. When LDL levels are too high, it can penetrate blood vessel walls, become oxidized, trigger inflammation, and gradually form plaques. These plaques narrow arteries and increase the risk of cardiovascular disease—earning LDL its reputation as a silent killer.

This helps explain a puzzling situation many people face: they eat low-fat, low-salt diets, exercise regularly, even limit eggs—yet their LDL cholesterol still comes back elevated on blood tests. Stranger still, some people see their levels return to normal months later. The reason?
They stopped drinking coffee.

The idea that “drinking coffee the wrong way can raise blood lipids” isn’t just internet rumor—it’s backed by solid scientific evidence. Studies show that brewing method makes a dramatic difference, and the key factor affecting cholesterol is whether the coffee is filtered.

Unfiltered coffee refers to coffee brewed without paper filters. This includes espresso from home or office machines, French press coffee, moka pot coffee, Turkish coffee, boiled coffee, and similar methods.

A meta-analysis of 14 randomized controlled trials found that compared with paper-filtered coffee, long-term consumption of about 900 ml of unfiltered coffee per day increased LDL cholesterol by an average of 17.8 mg/dL, translating into an estimated 11% increase in cardiovascular disease risk. These findings have been repeatedly confirmed by umbrella reviews in The BMJ and studies supported by the NIH. For people who already have high cholesterol, the effect is even more pronounced.

So where does the problem actually come from?
Not the milk in milk-based drinks—but coffee oils, which many people assume are beneficial.

Coffee bean oils contain two compounds that act behind the scenes: cafestol and kahweol. These diterpenes make up about 1% of coffee bean content. They are easily extracted by hot water, but they do not pass through paper filters. As a result, boiled or unfiltered coffee contains especially high concentrations.

These two compounds interfere with the body’s cholesterol regulation system by blocking the excretion pathways of bile acids and neutral sterols. When cholesterol that should be eliminated stays trapped in the body, LDL levels gradually rise.

The amount of these diterpenes varies dramatically by brewing method:

Unfiltered methods (moka pot, French press)

Office coffee machines / chain café coffee
Paper-filtered coffee (pour-over, drip coffee, filter bags)

Most office espresso machines use metal filters, which trap only part of the oils. In other words, they “filter—but not very well.” A Swedish study revealed that coffee from office machines contained 15–18 times more diterpenes than home-brewed paper-filtered coffee. Some espresso samples had cafestol levels as high as 2,447 mg/L. In contrast, boiled coffee filtered through paper saw these compounds drop from 939 mg/L to just 28 mg/L—a 97% reduction.

No need to panic—coffee lovers don’t have to give up their daily lifeline. Just remember two principles: moderation and the right brewing method.

Most of the documented risk comes from long-term consumption of 900 ml or more of unfiltered coffee per day. One regular cup a day is generally not a problem.

More importantly, choose safer brewing methods. Cold brew and paper-filtered coffee are the simplest and most affordable ways to reduce risk. They remove nearly all cafestol and kahweol, preventing LDL cholesterol from rising.

To wrap up, here are some practical tips:

• At home, choose pour-over or drip machines with paper filters

• At chain cafés, opt for cold brew—or ask if the coffee is paper-filtered

• In the office, consider pooling resources for pour-over gear, or stock filter coffee bags and paper filters

• If you really enjoy espresso or French press coffee, keep portions in check—no more than 900 ml per day (roughly two large cups)

Drink smart, and let coffee work with your health—not against it.

Indonesian Coffee Review: A Clean, Comforting Cup from Father’s Coffee Roastery

 This was my first encounter with Father’s Coffee. Their full name is Father’s Coffee Roastery, a roasting brand founded in 2018 in Ostrava, the third-largest city in the Czech Republic.

They are a family-run business—but not in the traditional sense of just parents and children. Instead, they see “family” as a group of coffee lovers brought together by shared values. They place a strong emphasis on coffee quality and freshness, while also deeply caring about transparency in sourcing. Father’s Coffee actively shares the stories behind each coffee, striving to build long-term relationships with producers. This mutual trust allows them to better oversee the entire process—from harvest and processing to export.

Since 2023, they’ve also been involved in several projects that directly support coffee-growing regions. One such project funds a professionally equipped quality control lab in the beautiful Mount Elgon area of eastern Uganda. This initiative benefits not only the coffee producers themselves, but also farmers across the surrounding region. Sustainability, transparency, and honest work are clearly values that run through every aspect of their coffee operations.

Even in their brand story, you can feel a deep sense of warmth and familial connection. They believe that family is the source of all values and endless inspiration—and perhaps that’s the most touching form of teamwork there is.

The People Behind Father’s Coffee

Father’s Coffee was originally founded by a husband-and-wife team. The husband, Petr, is a former head barista at Berlin’s Five Elephant—a name I haven’t heard in a long time, which instantly brought back memories. One of these days, I really should revisit their beans.

In the early days of Father’s Coffee, Petr handled almost everything in the roastery himself. Today, he’s primarily responsible for green coffee sourcing, roast profile development, and quality control.

His wife, Marie, is the soul of Father’s Coffee. The brand name itself came from her inspiration. She mainly oversees social media communication, brand storytelling, and marketing copy.

Perhaps it’s because of this female perspective, but I consistently find a sense of warmth and sincerity in Father’s Coffee’s writing. That emotional tone naturally made me excited to try their beans. From the moment I placed my order to the day it arrived, I waited over two weeks—and my anticipation only grew stronger.

I deliberately chose a coffee from a relatively simple yet often overlooked origin and variety. I’ve tasted beans from this region before, and they left a deep impression on me. This time, I wanted something uncomplicated and grounded—a flavor that brings a sense of calm and reassurance to everyday life.

The Coffee: Indonesia Pegasing, Team Pegasing Station

This coffee comes from the Pegasing region of Indonesia, processed at the Team Pegasing station. It’s a natural (sun-dried) process coffee made from a blend of Tim Tim and Gayo 1 varieties.

The processing station sits at an altitude of 1,300–1,500 meters and is a family project led by Hendra and his father, Hamdan. They specialize in experimental coffee processing. Hendra purchased the farm in 2006, and since then they’ve built a small innovation hub, collaborating with over 70 local farmers and processing up to 40 tons of coffee each year.

This particular coffee uses the natural process—one of ten different processing methods employed at the station. Ripe coffee cherries are dried for 20–25 days on raised beds inside covered tents. Temperature is carefully monitored, and the cherries are regularly turned to ensure even drying. Once drying is complete, all defective or underripe cherries are meticulously hand-sorted so that only beans meeting the highest professional standards move forward.

About the Varieties: Tim Tim & Gayo 1

I’ve introduced Tim Tim before in previous tastings. It’s a hybrid variety discovered on the island of Timor in 1917, resulting from a cross between Arabica and Robusta. One of its most distinctive traits is its large, elongated bean shape—so large that even after roasting, it still stands out. Some people even call it “long-bean Mandheling.”

Thanks to its strong disease resistance, Tim Tim has become one of the most widely cultivated varieties and serves as a genetic foundation for many modern hybrids.

The second variety in this blend, Gayo 1, was officially recognized by Indonesia’s Ministry of Agriculture in 2010 as a high-quality variety. It may share genetic roots with Tim Tim, making the two highly complementary. Together, they create a harmonious balance of chocolatey depth and fruity brightness.

Roast Level & Aromatics

When I first opened the bag, I was pleasantly surprised—the roast was noticeably light in color. Light-roasted Indonesian coffees are truly worth trying, and this one sits beautifully within a soft, approachable range.

As expected, the beans are impressively large—much bigger than most African coffees, even after roasting. Each bean is uniform and well-shaped, and visually, I find these large beans especially appealing.

Once ground, the dry aroma is quite distinctive. As a classic natural-process coffee, it carries a signature sweetness. I picked up notes of apple pie, Ceylon cinnamon, and smoked plum, layered with a hint of milk chocolate. There’s something undeniably cozy about it—almost winter-like.

Brewing Notes & Tasting Experience

For brewing this light-roasted, large-bean coffee, I recommend a 92°C (198°F) water temperature with a fine grind and fast drip method.

My recipe:

• Coffee: 15 g

• Water in: 251 g

• Final yield: 212 g

• Brew ratio: approx. 1:14

• Brew time: 1 minute 49 seconds

At this ratio range, you’ll get very consistent results. This coffee doesn’t try to impress you with flashy flavors. In fact, at higher temperatures, it may even seem a bit understated. But once it cools to a medium temperature—that’s when it truly shines.

The wet aroma reveals cooked apple notes. On the palate, the cup is exceptionally clean and refreshing. Gentle acidity gradually emerges, the body is smooth and round, and the acidity reminds me of plum jam with a touch of blackberry. The finish carries a pleasant tea-like quality.

Cold Brew Impression

I also tried this coffee as a cold brew:

• Coffee: 20 g

• Water: 335.5 g

• Brew time: ~6 hours (refrigerated)

• Final yield: 262.5 g

• Ratio: approx. 1:13

Compared to the hot pour-over, the cold brew is even cleaner and more refreshing. The fruit acidity becomes more prominent yet softer, while the body is lighter and juicier. No matter how you brew it, the core profile remains consistent—clean, crisp, and gently fruity.

This is a coffee that feels playful yet restrained. It may not shout for attention, but before you know it, your cup is empty. For me, it’s an excellent everyday coffee—comforting, reliable, and quietly satisfying.

Coffee Bean Blending Guide: How to Create Unique Pour Over & Espresso Flavors at Home

 Whenever I get tired of the coffee sitting in my jars, I like to approach those beans in a more creative way. By “reworking” them through blending, I can give familiar coffees completely new flavors and textures—essentially refreshing the entire drinking experience.

Many of you have probably guessed it already: this “creative method” is blending. By combining two or more different coffees, you can create an entirely new cup with a distinct personality. For a long time, blending was mainly associated with espresso. Back when espresso dominated the market, roasters relied on blends to ensure consistency over time. But in recent years, it’s easy to see that more and more brands—and even competition-level brewers—are using blended coffees for pour-over, cold brew, and other manual brewing methods.

The reason is simple. Blending isn’t just about consistency. As I mentioned earlier, it can also create something entirely new. A new experience might mean novel flavor combinations, or a coffee that excels across the board—a true “all-rounder.” In short, blending allows us to achieve a 1 + 1 > 2 effect and enjoy coffee in ways that a single origin sometimes can’t provide.

That said, blending isn’t as simple as throwing different beans together. A good blend requires intention. You need to think about your goal, your base coffee, and the proportions. Random combinations can easily result in a cup that falls short of expectations—or is even worse than the original base coffee on its own.

So today, I want to share how to approach coffee blending: what to pay attention to, how to think about your goals, and a few blending “recipes” I personally use.

The Purpose of Blending and Bean Selection

Since most of you reading this are buyers of roasted coffee (rather than roasters), we don’t need to worry about green-bean blending versus post-roast blending. When you decide to create a blend, I strongly recommend starting by defining your goal—what kind of cup do you want to drink? Once that’s clear, you can select suitable beans from what you already have. This approach saves money and helps you arrive at an ideal blend much more efficiently.

For pour-over blends, the goals usually fall into two categories:

1. Creating a completely new flavor profile, or

2. Building a well-rounded coffee with both excellent flavor and mouthfeel.

If your goal is the former, you’ll prioritize distinctive flavor characteristics. If it’s the latter, you’ll need to carefully balance both flavor and texture through bean choice and ratios.

If you’ve browsed my Taobao or Tmall flagship store, you may have noticed that I offer quite a few blends. In addition to espresso-focused blends, there are also blends designed specifically for pour-over and cold brew. One blend name appears across multiple categories: Strawberry Candy. While the name stays the same, the beans and roast profiles change depending on the intended brewing method.

Strawberry Candy · Geisha (For Pour-Over & Cold Brew)

The Strawberry Candy · Geisha blend is designed for flavor-driven brews like pour-over and cold brew. My goal was a cup with intense fruitiness and pronounced floral aromas. To achieve that, I blended:

• A Costa Rica Mirazu Estate honey-processed coffee with rich strawberry and mixed-berry notes, and

• A washed Geisha from Boquete, Panama, known for its elegant jasmine aroma.

The result is a blend bursting with both fruit and floral character. In the cup, you can clearly taste sweet strawberry and berry notes, elegant jasmine florals, and a refreshing oolong tea–like finish. The overall profile leans toward bright sweetness and acidity, with a smooth mouthfeel and a long, lingering aftertaste.

Strawberry Candy · Espresso

The espresso-focused version, Strawberry Candy · Espresso, is a blend I mention quite often. My goal here was different: I wanted an espresso with floral and fruity notes, low acidity, sweetness as the core flavor, and a solid, weighty mouthfeel.

To achieve this, I blended:

• A berry-forward Strawberry Candy component,

• A Colombia Huila coffee with chocolate, cookie, and caramel notes and a full body, and

• An Ethiopian heirloom variety to add aromatic complexity.

Pulled as espresso, this blend delivers flavors of strawberry, subtle florals, chocolate, and caramel. The cup is sweet, rich, and full-bodied, with a long finish. When paired with milk, it even develops a unique strawberry wafer–like flavor—an unexpectedly delightful result.

Why Goals Come First

As you can see, different goals lead to different bean choices—and even different roast levels. Compared to the pour-over blend, the espresso version uses a slightly darker roast. This helps reduce perceived acidity while enhancing body and sweetness.

By now, it should be clear why setting a goal before choosing your beans is so important.

When selecting beans for a blend, keep these two points in mind:

First: the roast levels should be similar.
Some difference is fine, but avoid extremes. Beans roasted to different levels extract at different speeds. Darker roasts have a more porous structure, so their soluble compounds are extracted more quickly. If you blend a very dark roast with a very light roast, uneven extraction becomes almost inevitable.

With high extraction efficiency, the dark roast can easily over-extract; with lower efficiency, the light roast may under-extract. This makes brewing far more difficult. Choosing beans with similar roast levels helps minimize extraction differences and makes it much easier to brew a great cup.

Beyond that, there aren’t many hard rules. Feel free to experiment. Mix coffees from different origins, processing methods, or flavor profiles, and you’ll quickly discover entirely new expressions. If you want to highlight a specific characteristic, simply increase the proportion of the bean that carries it.

Ratios and Brewing Parameters

Using Strawberry Candy · Geisha as an example again:

• If I want the floral notes to stand out more, I might use a 4:6 ratio of Costa Rica to Panama Geisha.

• If I want more fruit intensity, I might reverse it to 6:4.

Set your ratios based on your goal, then fine-tune them based on taste.

As for brewing parameters, simply base them on the average roast level of your blend. If both coffees are light-roasted, use standard light-roast parameters. If one is light and the other medium, choose a middle-ground approach. The same logic applies across the board.

A Few Personal Blending Recipes

To wrap things up, here are a couple of my personal blending combinations. If you happen to have these beans on hand, I highly recommend giving them a try—you might be surprised by the results:

• Colombia Sidra × Ethiopia Guji — 4:6

• Panama Boquete Geisha × Ethiopia Alo × Colombia Pink Bourbon — 3:5:2

Happy blending—and enjoy discovering entirely new cups of coffee. ☕

Ice Water Cold Brew Hack: Why This Method Tastes Sweeter, Smoother, and More Refreshing

 Cold brew, as the name suggests, is coffee made with cold water at low temperatures. The most common method is to soak ground coffee in room-temperature water, refrigerate it, and wait for the cold water to slowly pull out the flavors. After steeping, simply filter out the grounds and you’re done.

But here’s something fun: cold brew doesn’t have to be made with room-temperature water. You can actually make it with ice water—a mix of ice cubes and water brewed together with the coffee grounds. The big question is: Does it taste better?

Two Ways to Make Cold Brew

For this comparison, I made two batches of cold brew—one with room-temperature water and one with ice water. I kept all other variables as consistent as possible so I could really taste the difference.

1. Room-Temperature Cold Brew

I used my Colombian “Big Belly Button” beans, measured out 20g, and ground them to a coarse, sugar-like texture. Using a 20-mesh sieve, the grind had an 80% pass rate. (For reference: EK43s at 9.5, Comandante C40 at 24 clicks.)

Since this coffee has a fruity profile and doesn’t need a high concentration, I went with a 1:12 coffee-to-water ratio.

I added 20g coffee grounds and 240g filtered water to a clean, sealable container, stirred well, sealed it, and let it steep in the fridge for 12 hours. After that, I filtered out the grounds.

2. Ice-Water Cold Brew

Ice water extraction is just as easy. I again weighed out 20g of beans, but because ice water extracts more slowly at lower temperatures, I made the grind a bit finer—82% pass rate through the same 20-mesh sieve. (EK43s at 9, Comandante C40 at 22 clicks.)

Since the ice cubes I normally use are fairly large and melt slowly, I increased the proportion of liquid water and reduced the ice. My final ratio was:

1 : 8 : 4 (coffee : water : ice)
= 20g coffee, 160g water, 80g ice.

I combined everything, stirred, sealed, steeped for 12 hours, and filtered as usual.

Ice Water vs. Room Temperature—Which One Tastes Better?

Room-Temperature Cold Brew

• Deeper color

• Notes of blueberry, grape, and grapefruit

• Medium fermentation aroma

• Fuller body with a slightly bitter finish

Ice-Water Cold Brew

Because the ice didn’t fully melt during steeping, there were still small crystals left on the filter—which also meant the final yield was lower. Still, the result surprised me:

• Bright flavors of grape, pineapple, orange, and cherry

• Clean, sweet, juice-like body

• Almost no bitterness

• Refreshing and memorable, like a mixed fruit juice

Honestly, the ice-water version tasted shockingly good.

Why Does Ice-Water Cold Brew Taste So Different?

Temperature plays a huge role in coffee extraction. Higher temperatures speed up the release of soluble compounds; lower temperatures slow everything down. Compared to room-temperature water (around 18–27°C / 64–80°F), ice water sits between 0–10°C (32–50°F), making extraction noticeably slower. This means ice-water cold brew naturally contains fewer dissolved solids under the same steeping time.

But it’s not just about quantity—it’s about what gets extracted.

Coffee contains hundreds of compounds, all with different solubility characteristics. Some dissolve quickly, some slowly, and some only at certain temperatures.

In general, coffee flavors extract in this order:
acidity → sweetness → bitterness

Aromatic, fruity, and floral compounds tend to release first. Sweet caramel-like compounds follow. Bitter, heavier molecules usually come last.

When the steeping temperature drops close to 0°C, extraction becomes much slower—particularly for the larger, more bitter compounds. As a result, ice-water cold brew emphasizes bright, juicy, fruity notes while holding back harsher flavors. The result is a refreshing, sweet, almost juice-like cup.

The Secret Behind Clear Coffee: How CLR CFF Made Coffee Completely Transparent

 Do you still remember CLR CFF, the colorless, crystal-clear coffee that went viral nearly a decade ago? I was lucky enough to actually try that “internet-famous” product back then. For so long, we all believed coffee could be reddish-brown, brown, or even red—but it never crossed our minds that coffee could exist as something completely transparent.

When CLR CFF was first released, it immediately caught the attention of coffee lovers. It became the world’s first colorless coffee drink, and its production process was always described in a vague, mysterious way—“made with methods never used before.” It sounded almost mythical, and no one ever seemed to crack the secret behind it. Today, the brand’s social media accounts have gone silent, its official website is no longer maintained, and similar products have essentially vanished. So how did they manage to make coffee completely clear? Let’s talk about this “mysterious” technology.

Simply put, the core idea is to keep the flavor and caffeine of the coffee while removing all substances that create color. The key technology behind this result is precise separation and recombination. Just like traditional coffee, the process starts with carefully selected beans that are roasted—usually lightly roasted to achieve a bright, fruity acidity while avoiding the heavy color and oils produced by dark roasts. Next comes the extraction stage, which is crucial for transparent coffee.

Cold brew is typically used to extract this type of colorless coffee. Using hot water would pull out more oils, acidic components, and suspended solids from the beans—substances that cause cloudiness and dark color. Cold brewing, on the other hand, gently extracts the volatile aroma compounds and caffeine while minimizing the release of pigments and oils. This means the initial coffee liquid is already much lighter in color compared to hot-brewed coffee.

The cold-brew concentrate then undergoes the second key step: a series of highly precise filtration processes. First comes ultrafiltration, which removes large molecules such as proteins, polysaccharides, and some pigments. Next is nanofiltration, capable of filtering out even smaller molecules, including most of the components responsible for color. After these two steps, the liquid undergoes reverse osmosis, which removes nearly everything except water molecules and the very smallest compounds. This process functions like a molecular-level sieve, leaving behind clear water, caffeine, and the aroma compounds that define flavor.

I remember that when I tasted this transparent coffee, if I had been blindfolded, I wouldn’t have known it wasn’t regular coffee. It had a refined and surprisingly full flavor, balanced and very similar to a typical cold brew. But with such extensive filtration, some volatile aroma compounds inevitably get lost. To solve this, manufacturers may use a technique similar to aroma recovery. During the early stages of extraction, they capture those volatile aromas and then reintroduce them back into the filtered, colorless liquid to ensure the final product still smells like coffee.

Finally, the processed clear coffee liquid, the recovered aromas, and any necessary components (possibly tiny amounts of natural flavorings to enhance taste) are blended and bottled. With all solids and oils removed, transparent coffee typically has very low acidity and an extremely clean, smooth mouthfeel. It was advertised as a zero-calorie or low-calorie beverage, and for people worried about coffee staining their teeth, its colorless nature made it stain-free. The refreshing taste also made it easy to mix with cocktails or sparkling water for unique “coffee-based” drinks—coffee flavor without coffee color, which naturally generated tons of buzz.

However, transparent coffee does have drawbacks. Its flavor is extremely simple—smooth and balanced, but thin, almost like “water with coffee flavor.” It’s also a highly processed beverage, much like how some people feel hesitant about decaf, believing it loses the soul of coffee and many of its natural qualities. But the biggest reason we rarely see CLR CFF or similar products today is the cost. The production process is extremely complex and expensive. Back in 2017, a 200 ml bottle of CLR CFF cost me nearly 80 RMB including shipping—far more expensive than a regular cup of coffee with a richer, more complex flavor.

Overall, I see CLR CFF as a fascinating achievement in food engineering—a product made through cold brew extraction, molecular-level filtration, and aroma management. But it was never destined to disrupt traditional coffee or become mainstream. Its disappearance from the market seems almost inevitable. In reality, products built on viral hype often become temporary trends. What truly stands the test of time are the simple, everyday coffees that people return to again and again.

Why Coffee Makes Some People Poop and Others Constipated: The Science Behind Caffeine’s Gut Effects

 “Every time I drink coffee, I have to run to the bathroom within half an hour—it’s like my body has an alarm clock.”

“I drink two cups of coffee every day, but I often feel bloated and constipated. Sometimes I even wonder if I should just give up coffee.”

On October 16, the hashtag “The first batch of coffee lovers has fallen victim” started trending online. Netizens shared their very different gut reactions to coffee—some experience diarrhea, while others get constipated.

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Caffeine’s Dual Effect: It Can Both Relieve and Cause Constipation

Why can the same cup of coffee produce two completely opposite effects?
According to Cui Jun, Chief Dietitian at Beijing Electric Power Hospital, coffee’s impact on digestion is the result of multiple factors—mainly caffeine stimulation and acidic compounds.

Caffeine stimulates stomach acid secretion and speeds up intestinal movement. A single intake of 100 mg of caffeine (roughly one espresso) can increase intestinal motility by nearly 30%, shortening the time food residues stay in the intestines and reducing water absorption. When things move too quickly, diarrhea follows.

Besides caffeine, organic acids like chlorogenic acid and quinic acid lower coffee’s pH to around 4.5–5.5, directly irritating the stomach lining and boosting stomach acid production.

On the flip side, some people develop constipation after long-term coffee consumption. Cui explains that the mechanism is quite different:
“Caffeine’s diuretic effect can cause mild dehydration. If you don’t drink enough water, your stool can become dry and hard.” In this case, the intestinal contents lose moisture, making it harder for the body to pass waste. Additionally, regular heavy coffee drinkers may build a tolerance to caffeine, weakening its bowel-stimulating effects over time.

As for the online claim that “coffee grounds absorb water and cause constipation,” Cui clarifies:
“There’s no scientific basis for that. Coffee grounds do absorb water—but only before brewing. Once you drink coffee, there are no actual ‘grounds’ entering your intestines, so this claim is inaccurate.”

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Gut Reactions Depend on the Individual — Smart Drinking Is Key

So why do different people react so differently to the same cup of coffee?
Cui points to individual differences as the main factor.

Your genes determine how quickly you metabolize caffeine. “Variations in the CYP1A2 gene can make caffeine metabolism differ by up to eightfold,” Cui explains. “People who metabolize caffeine more slowly experience longer and stronger effects.” Gut microbiota also play a role—people with unbalanced gut flora, due to poor diet or frequent antibiotic use, are more likely to have abnormal reactions like diarrhea or constipation after drinking coffee.

To enjoy coffee without upsetting your stomach, Cui suggests a few practical tips:

• Avoid drinking coffee on an empty stomach. It’s best consumed about an hour after a meal to reduce irritation to the stomach lining.

• Moderate your intake. For healthy adults, the recommended limit is 400 mg of caffeine per day—about 3–4 cups of 150 ml black coffee. Sensitive individuals should consume less.

• Choose the right type. People with sensitive stomachs should try coffees lower in acidity. “For example, cold brew coffee has over 40% less acid than hot brew. Low-caffeine or light-roast Arabica beans are also good options.”

• Pair it wisely. Drinking coffee with fiber-rich foods like whole-grain bread or oatmeal, and maintaining good hydration throughout the day, can ease its effects on your digestive system and counter dehydration.

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Caffeine affects everyone differently, so it’s important to listen to your body.
“If you experience insomnia, anxiety, or stomach discomfort after drinking coffee, it’s a sign you’ve exceeded your personal tolerance level,” Cui advises.

So, while the internet may be divided between “coffee causes diarrhea” and “coffee causes constipation,” there’s really no need to panic. The key is understanding your own body—and finding the way of drinking coffee that works best for you.