For millions of people, coffee is simply part of the morning routine. It may be the first thing they reach for after waking up, a drink they enjoy during the workday, or a small source of energy when the afternoon slump arrives.
But because everything we eat and drink eventually has to be processed by the body, it raises an interesting question: What does drinking coffee every day actually do to the kidneys?
The kidneys are two small organs with an enormous job. They continuously filter the blood, removing waste and extra water that eventually leave the body as urine. They also help control important minerals and electrolytes and play a role in maintaining healthy blood pressure.
When kidney function becomes damaged over time, a person can develop chronic kidney disease, commonly called CKD. In severe cases, the kidneys may eventually lose so much function that treatments such as dialysis are needed to help remove waste and excess fluid from the blood.
Fortunately for coffee drinkers, research so far does not suggest that moderate coffee consumption is harmful to healthy kidneys. In fact, several studies have found that coffee may actually be associated with certain kidney benefits.
Coffee May Be Linked to a Lower Risk of Kidney Disease
One of the more encouraging findings involves chronic kidney disease itself.
Research has found that people who regularly drink coffee may have a lower chance of developing CKD compared with people who don’t drink it. One large analysis found that people drinking two or more cups per day had about a 14% lower risk of developing kidney disease.
That doesn’t necessarily mean coffee directly prevents kidney disease. Studies like these can identify a connection between two things, but they cannot always prove that one causes the other.
Still, scientists have some ideas about why coffee could potentially be helpful.
Coffee is much more complicated than caffeine alone. It contains more than 1,000 naturally occurring compounds, including polyphenols, chlorogenic acids and melanoidins. Many of these substances have antioxidant and anti-inflammatory properties.
Antioxidants help protect cells against damage caused by unstable molecules produced naturally in the body. Long-term inflammation and oxidative stress can contribute to many chronic diseases, including conditions affecting the kidneys.
This could help explain why some of coffee’s possible health effects appear to extend beyond caffeine.
It also means decaffeinated coffee may offer some similar benefits. Decaf still contains many of coffee’s naturally occurring plant compounds while providing considerably less caffeine.
Research has even suggested possible benefits for some people who already have kidney disease. Coffee consumption has been associated with a lower risk of worsening kidney disease, protein appearing in the urine, end-stage kidney disease and death.
However, people who already have CKD should discuss their individual diet and coffee habits with a health care professional because kidney disease can affect people very differently.
Coffee May Also Be Connected to Fewer Kidney Stones
Kidney stones develop when certain substances in urine become concentrated enough to form crystals. These crystals can eventually grow into hard deposits that may cause severe pain when they move through the urinary tract.
There isn’t one single cause. Genetics, diet, hydration, certain medical conditions and other factors can all influence a person’s risk.
Interestingly, regular coffee consumption has been associated with a lower risk of kidney stones.
One possible explanation is surprisingly simple: fluid.
Drinking enough liquid increases the amount of urine the body produces. That makes the urine more diluted, reducing the concentration of minerals that could otherwise come together and form stones.
Coffee contributes to a person’s daily fluid intake. Caffeine can also temporarily increase urine production, which researchers believe could contribute to coffee’s association with reduced kidney stone risk.
However, coffee shouldn’t replace water.
For people trying to prevent kidney stones, getting enough total fluid throughout the day remains one of the most important dietary strategies. Coffee can contribute to that total, but water should still make up a significant portion of daily fluid intake.
There Is One Important Concern: Blood Pressure
Although moderate coffee consumption appears safe for most people, caffeine can have an effect that deserves attention.
It may temporarily raise blood pressure.
High blood pressure is one of the major risk factors for kidney disease. Over time, excessive pressure can damage the small blood vessels responsible for delivering blood to the kidneys.
As kidney function becomes impaired, the kidneys may have more difficulty controlling fluid and blood pressure. This can create a damaging cycle in which high blood pressure harms the kidneys while declining kidney function makes blood pressure more difficult to control.
The relationship between coffee and long-term blood pressure is complicated. Some studies have found that coffee drinkers don’t have an increased risk of hypertension, while other research suggests caffeine can temporarily increase blood pressure, particularly in certain people.
Individual sensitivity matters.
Someone who already has uncontrolled high blood pressure may need to be more cautious with caffeinated coffee. For these individuals, limiting intake to around one or two cups per day may be appropriate, depending on advice from their doctor.
Decaffeinated coffee may also be worth considering for people who enjoy coffee but are particularly sensitive to caffeine.
What You Put in Coffee Matters Too
The coffee itself isn’t always the biggest concern.
A plain cup of coffee contains very few calories and no meaningful amount of added sugar or saturated fat. The nutritional picture changes dramatically once large amounts of flavored syrup, sugar, heavy cream or sweetened creamer are added.
Some specialty coffee drinks contain extremely high amounts of added sugar.
Regularly consuming large quantities of added sugar can contribute to weight gain and metabolic problems that increase the risk of conditions such as type 2 diabetes. Diabetes and high blood pressure are two of the most important causes of chronic kidney disease.
Heavy cream and certain creamers can also add substantial amounts of saturated fat. Too much saturated fat can contribute to cardiovascular problems, which are closely connected with kidney health.
That doesn’t mean coffee must always be consumed black.
Using smaller amounts of sugar or gradually reducing sweeteners can make a meaningful difference. Low-fat or skim milk can also provide creaminess without as much saturated fat.
Another option is simply experimenting with different coffees. Light, medium and dark roasts can taste surprisingly different. Finding a coffee you genuinely enjoy may reduce the temptation to cover its flavor with large amounts of sugar and cream.
Even Black Coffee Should Be Consumed in Moderation
For most healthy adults, up to about 400 milligrams of caffeine per day is generally considered an amount that isn’t associated with negative effects. Depending on how strongly it is brewed, that is roughly the caffeine found in about four standard 8-ounce cups of coffee.
But “four cups” can be misleading.
A standard cup used in nutrition research is often only eight ounces. Many mugs, convenience-store coffees and café drinks are significantly larger, meaning someone can consume several cups’ worth of caffeine in a single drink.
People with kidney disease may have another consideration: potassium.
An eight-ounce cup of coffee contains roughly 100 milligrams of potassium. That amount may be perfectly reasonable for many people with CKD, but several large cups throughout the day can add up.
Some people with advanced kidney disease are instructed to limit potassium because damaged kidneys may have difficulty removing excess potassium from the blood. Dangerously high potassium levels can affect the heart.
This doesn’t mean everyone with kidney disease needs to avoid coffee or potassium. Dietary restrictions depend heavily on a person’s kidney function, medications and blood test results.
So, Is Daily Coffee Good or Bad for Your Kidneys?
For most people, there’s little reason to fear a normal morning cup of coffee.
Moderate coffee consumption has been associated with a lower risk of chronic kidney disease and kidney stones, and some research suggests it may even be associated with better outcomes among people who already have kidney disease.
The key word, however, is moderation.
Drinking enormous amounts of caffeine isn’t necessary to receive coffee’s potential benefits. Two or three standard cups per day may be perfectly reasonable for many adults.
It’s also important to consider the entire drink rather than coffee alone. A simple cup of coffee and an oversized beverage loaded with syrups, sugar and heavy cream may technically both contain coffee, but nutritionally they are very different.
People with uncontrolled high blood pressure, abnormal potassium levels or existing kidney disease should be especially careful. Their ideal amount of coffee may be lower, and switching partly or entirely to decaf may sometimes make sense.
For everyone else, current research offers some reassuring news: enjoying coffee every day doesn’t appear to be bad for the kidneys when it’s consumed sensibly. It may even come with a few unexpected benefits.
As with most things in nutrition, however, more isn’t necessarily better. The healthiest cup is usually the one that fits into an overall balanced diet without excessive caffeine, sugar or saturated fat.
Featured image: Magnific
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