Kidney health is a big concern for a lot of people, and there are many rumors flying around about whether tea and coffee are safe for this part of the body. Will your morning cup of tea give you kidney stones? Can coffee cause kidney failure? Should you give up caffeine to protect your body?

Many err on the side of caution and think they should avoid all tea and coffee to be safe, but there are many teas that are perfectly fine for kidneys, and you shouldn’t have to miss out!

In this post, I’ll be answering the questions:

 

• What is the connection between caffeine and kidneys?
• Is black tea bad for your kidneys?
• Is coffee bad for your kidneys?
• Is yerba mate tea good or bad for kidneys?
• Which tea is best for kidneys?

 

We chose to research and write this article in particular because so many tea drinkers we meet in person and talk with online have told us they used to be coffee drinkers, and due to kidney issues their doctors told them to switch to tea. That said, kidney infections, kidney stones, and kidney disease are different conditions which come with their own recommendations so always talk with your physician before any dietary changes.

Read on to get the facts!

 

Before We Start: Defining Some Basic Kidney Terms

Your kidneys are truly amazing. A healthy set of kidneys filters about ½ cup of blood every minute! They remove excess water and wastes from the blood (K1). 

Kidney infections occur when bacteria from the gut travel through the bladder and up to the kidneys (K2). These are usually treated with antibiotics, and if you talk to your doctor, you may be able to add herbs to your treatment regimen to help ease pain and other symptoms. 

Kidney stones are made up of crystal-forming substances, such as uric acid, calcium, oxalate, or cysteine. High levels of these in the urine and too little fluid to dilute them can cause stones (K3, K4). Drinking more fluids, changing the diet, and sometimes medication are used as preventative approaches (K3). 

Kidney disease or failure involves the loss of kidney function. Some causes include: 

 

• Inflammation of the filtration units within the kidneys
• Inflammation of other structures in the kidneys
• Recurring infections
• Obstructions (such as from recurrent stones) (K5). 

 

Now, let’s find out how your favorite beverages might play into all this.

 

 

 

High Caffeine and Kidneys: Let's Explore Some Popular Drinks

Unfortunately, the effect of caffeine on the kidneys isn’t great. Caffeine consumption is a risk factor for kidney disease, and can cause scarring of the glomeruli - that is, the vessels in the kidneys that filter blood (Ca1, Ca2).

Caffeine may also lead to kidney stones, and it increases strain on the kidneys (Ca3). However, some caffeinated beverages, like coffee, may be safe in small amounts due to certain plant constituents (C1).

One review found that the data is inconclusive regarding caffeine and kidney stone risk; however, the researchers pointed out that coffee and decaffeinated coffee, but not other caffeinated beverages, actually had a protective effect on the kidneys (Ca4). 

The bottom line, though, is that you probably shouldn’t overdo it when it comes to caffeine. Let's look at some classically high caffeine drinks: black tea and coffee:

 

What About Black Tea and Kidneys?

In my kidney stone definition earlier, I mentioned that stones are caused by substances that crystallize in the kidneys. One of those crystal-forming substances is oxalate.

Well, black tea has a higher oxalate content than many other beverages. Drinking it leads to more oxalates in the urine, and it can promote stone formation if you consume too much (BT1).

One particularly memorable case of this occurred in 2014, when a man developed renal failure because he was drinking a gallon of black tea daily, which led to a heavy load of oxalates (BT2). Turns out there can be too much of a good thing!

 

How Much Black Tea Is Safe?

Of course, having a cup of black tea every so often is perfectly safe for most people. Even though black tea contains higher oxalate levels than most teas, it’s generally not enough to worry about.

One study looked at the amount of oxalates in (Iranian) black tea and found quite low levels. They concluded that drinking 4 cups of black tea would not pose a risk to kidney stones, and for kidney stone patients they recommended not to consume anything with more than 10 mg of oxalate, which is just over two 8oz mugs according to this study (BT3). 

Whether you can consume black tea with a kidney condition depends on how severe your condition is, how much you’re consuming, and your doctor’s instructions. While most people can drink reasonable amounts of black tea with no problem, be sure to check with your healthcare professional first if you have issues with kidney health.

 

 

Is Coffee Bad for Your Kidneys?

Let’s turn our attention to your morning cup of joe. This one’s a little more complicated than a yes or no answer when it comes to its effect on kidney health.

First of all, drinking multiple cups of coffee increases levels of potassium in your bloodstream - which your kidneys have to work to filter out. In addition, the creamer you might put in your coffee contains phosphates, which should be avoided by those with kidney disease (C2).

Furthermore, drinking lots of coffee (five or more cups) does not hydrate you, so make sure you are drinking enough water along with it to decrease the risk of stones (C3).  

Interestingly, coffee may not be all bad for the kidneys! One study showed that consuming one to two cups of coffee may protect against end stage renal failure. The benefit could be due to a phytoestrogen in coffee called trigonelline (C1).

However, more studies are needed, as it is the only study of its kind so far that I found. In a genome-wide association study on coffee and kidney health, the authors also found support for the above conclusions. For now, the evidence so far seems to indicate that coffee has a protective effect (C4).

The University of Chicago notes that coffee contains low levels of oxalates which is part of the reason they also agree that overall it has a protective effect. But bear in mind the caffeine side described earlier (C5).

 

Is Yerba Mate Tea Good or Bad for Kidneys?

Yerba mate is an herbal tea native to South America with a smooth, woody flavor. It’s high in antioxidants and nutrients. We bring it up here because it has a caffeine content comparable to coffee, making it a popular coffee alternative for waking you up in the morning.

Despite yerba mate’s benefits, there is little research on its relationship to kidney health. It does contain oxalic acid, an oxalate, so it should be avoided in excess when experiencing kidney conditions (Y1). 

I have come across information that yerba mate may have properties which can help dissolve kidney stones. However, I have yet to verify this information with any reliable sources (Y2). At this time, I’d recommend speaking to your physician and moderating your consumption of yerba mate if kidney health is a concern for you.

What we do know is that the antioxidants in yerba mate really make an impact in how the body responds to the high caffeine - in a good way. A much healthier way to get your high caffeine kick. To learn more about yerba mate and its benefits, check out our spotlight post!

Coffee, Black Tea and the Kidneys: The Conclusion:

For those who like cups and cups a day of coffee or black tea, the caffeine and oxalates (respectively) should make you pause for thought if you care about your kidneys. BUT all is not lost, read on for...

 

 

The Solution: Which Teas are Best for Kidneys?

Not all teas are cause for concern when it comes to kidneys. There are plenty of tea types that haven’t been linked to kidney disease, and in fact may help improve kidney health! The key you may have learned by now is levels of caffeine and oxalates, and also other constituents like certain antioxidants which can actually be beneficial to kidney health.

 

Green Tea and Kidneys

Good news for green tea lovers! Green tea was found to help prevent the progression of kidney disease, due to the polyphenols and you probably already know it's not nearly as high in caffeine as black tea or coffee (we're talking 35mg versus coffee's 95mg+ read our Caffeine spotlight linked to at the end of the article to learn more).

Green teas also contain lower levels of oxalates than some other beverages, and higher levels of EGCG, which means green tea may help prevent kidney stone formation (GT1, GT2).

Furthermore, green tea does not contain creatinine - a waste product produced by the body that healthy kidneys filter from the blood. Unhealthy kidneys may not filter this chemical efficiently, causing creatinine levels in the blood to increase (GT3). But with green tea, there’s no need to worry about that.

To learn more about green tea’s benefits, including the difference between Chinese and Japanese green teas, check out our spotlight post.

 

Rooibos Tea and Kidneys

Rooibos is a cinch for kidneys to deal with - it’s low in tannins, and is caffeine and oxalate free (R1, R2)!

In one review of red and green rooibos, no negative effects were noted in a study where animals were given rooibos as the sole drinking fluid, and no negative effects on kidneys and creatinine were noted. In the human trial, no adverse effects or out-of-range clinical pathology reports were observed (R3).

Of course, speak to your doctor if you have any health concerns; but in general, the research seems to suggest that rooibos is safe for your kidneys.

To learn more about rooibos and its benefits, check out our Rooibos vs Honeybush spotlight post.

 

Chamomile Tea and Kidneys

Like rooibos, chamomile tea is caffeine free and low in tannins and oxalates (Ch1, Ch2). 

However, chamomile may have more than just a neutral effect on kidneys. In an animal study, animals with nephrotoxicity (toxicity of the kidneys which impairs function) were administered chamomile and it was found to improve kidney function (Ch3).

Chamomile also reduces kidney dysfunction as a result of high fat diets. Long story short, there’s pretty good evidence that chamomile is good for kidneys (Ch4)! That is a cup of good news. 

To learn more about chamomile and its benefits, read our chamomile spotlight post!

 

A Note from the Herbalist

Unless you’re planning to drink a gallon of oxalate-heavy black tea every day, your regular tea consumption will likely not cause any issues with your kidneys. However, it’s always good to enjoy everything in moderation, and to check with your doctor about any health concerns.

Interested in learning more about caffeine? Check out our article Caffeine in Coffee and Tea

If you’re interested in exploring some teas that will be kind to your kidneys, check out my selections below! All of Matcha Alternatives’ teas are ethically sourced, top quality, and super delicious.