Is Green Tea Bad for your Kidney(s)?

You will probably recognize that one of the more recent trends in the world of foods and beverages is understanding what is healthy for the body. A quick search online reveals that there is much to know, not only about the body but also about the impact various substances have on it. The idea behind green tea is that it's healthy, and for some, this healthy component brings up important distinctions such as "catechins".

This article will review another area of green tea and our bodies, namely whether green tea is healthy or unhealthy for your kidney(s).

What do you know about your kidney(s)?

You have two kidneys, and they are approximately bean-shaped organs. The size of a fist that is situated below your rib cage on each side of your spine. Each kidney is made up of roughly a million units called nephrons. Each of your nephrons has a filter called the glomerulus and a tubule. The glomerulus filters your blood, and the tubule returns what is necessary to your blood. Blood flows to your kidneys via the renal artery, which is a large blood vessel that splits until your blood reaches the nephrons. Your kidneys filter approximately 150 quarts of blood a day; most of it is returned to your body.

In fact, your kidneys have higher blood flow than your brain and liver. It is a unique organ given that most of us start out with two yet only require one-half of a kidney to filter our body’s blood. In an odd relationship with your liver, your kidneys may also produce vitamin D if the liver cannot. Another important component of our kidneys is that they make hormones that directly help control blood pressure, create red blood cells, and keep your bones healthy.

Healthy kidneys are important. Due to the functions kidneys perform and the harmful substances that may move through them, they are susceptible to a number of issues, including kidney failure, kidney stones, uremia, and chronic kidney disease, among many others.

Green tea and your kidneys

Of course, drinking green tea affects your kidneys, but how?

We talked briefly about catechins and their impact viz-a-viz the liver. Let us spend a few more minutes on the most common catechin found in green teas and its support in preventing Chronic Kidney disease: Epigallocatechin-3-gallate, or EGCG. When discussing chronic kidney disease, we have a form of kidney disease that slowly yet progressively leads to a loss in renal function. One of the more common causes of chronic kidney disease is, yes, diabetes (As a quick note, green tea may actually help lower the risk of type-2 diabetes). However, it may also include hypertension, obstruction, and other issues. Kidneys can be exposed to harm like any other organ in the body. In fact, the kidneys of many people are at high risk of oxidative stress.

Oxidative stress can lead directly to chronic kidney disease and its progression. None of this sounds good, but EGCG has been shown to support your kidneys and help stave off renal decline. Further, The American Journal of Clinical Nutrition has also shown that green tea may actually help regulate blood sugar, which is not only good for staving off chronic kidney disease but also assists diabetics in their own struggles with blood sugar levels.

According to the Chinese Medicine Journal, a 2010 literature review noted that green tea consumption has been linked to the prevention of cancer in the kidneys (among many other parts and organs of the body). This is largely due to the sheer number of polyphenols, which are antioxidants. In this review, the authors also highlight that green tea has been linked to lower blood pressure, which directly benefits the overall functionality of our kidneys. Conversely, the Heart and Stroke Foundation states that over a given amount of time, relatively high blood pressure can cause the arteries around the kidneys to narrow, weaken, or harden. This may lead to an inadequate amount of blood being sent to the kidneys.

Of course, there are concerns related to kidney stones and green tea. A recent study in the journal Nutrients concluded that green tea consumption does not lead to kidney stones. Chinese researchers, in reply, have found that green tea extract, for example, changes the shape of calcium oxalate and makes it less likely to band together, making it easier to move through the kidneys. In fact, studies have shown that there is no link between the substance in green tea and damage to one’s kidneys.

Benefits of Green Tea for Kidneys

Green tea is well-known for its health benefits, and one of its most powerful components, Epigallocatechin-3-gallate (EGCG), plays a significant role in kidney health. Studies have shown that green tea can help in the prevention of chronic kidney disease (CKD) by reducing oxidative stress, which is a key factor in kidney damage.

Moreover, green tea may help manage blood sugar levels, which is crucial for people with diabetes—a leading cause of kidney disease. Research from the American Journal of Clinical Nutrition suggests that regular consumption of green tea could help control blood sugar, making it beneficial for people at risk of kidney disease​ [2].

Potential Risks of Green Tea for Kidney Health

Although green tea offers health benefits, excessive consumption can have harmful effects on the kidneys. The risks are often associated with its caffeine content, the presence of aluminum, and its impact on iron absorption. According to studies, high levels of caffeine can overstimulate the kidneys, causing potential dehydration and strain on kidney function [4].

Patients with chronic kidney disease or renal failure should be especially cautious. Green tea contains aluminum, which, if accumulated in the body, can lead to neurological issues, especially in individuals with impaired kidney function. Therefore, it is always best to consult a healthcare provider before increasing your green tea intake.

How Green Tea Interacts with Kidney Stones

A common concern among green tea drinkers is whether it causes kidney stones. Fortunately, research has shown that green tea does not contribute to the formation of kidney stones. In fact, a study published in the journal Nutrients reveals that green tea extract changes the shape of calcium oxalate, the compound responsible for kidney stones, making it less likely to clump together. This reduces the likelihood of stone formation, offering a potential protective benefit​ [1].

Expert Recommendations for Green Tea Consumption

To enjoy the health benefits of green tea while minimizing risks to your kidneys, it's important to consume it in moderation. Medical experts recommend limiting green tea intake to 2-3 cups per day, especially for individuals with pre-existing health conditions such as high blood pressure, kidney disease, or heart problems. Pregnant women and those with iron deficiencies should also monitor their green tea consumption, as it can interfere with iron absorption​.

Do I need to worry about its impact on my kidneys?

Green tea can, in fact, damage your kidneys. Like green tea and its impact on your liver, for example, too much green tea or green tea extract can be toxic. The harmful effects of green tea are often due to three major factors: Its caffeine content, the presence of aluminum, and, according to Chinese Medicine’s review, "the effects of tea polyphenols on iron bioavailability." Green tea should be avoided if your doctor states so or if you’re suffering from heart conditions or major cardiovascular problems. It is recommended that pregnant and breastfeeding women limit their green intake to two cups a day.

For those suffering from renal failure, high levels of aluminum can lead to neurological disease. For the more popular, up to 10 small cups of green tea a day is likely fine, according to Chemical Biology and Pharmacognosy Professor Chung Yan. At the end of the day, chances are most of us tea lovers do not need to worry, but it is important to know what impact green tea does have on the body!

Conclusion

Green tea, when consumed in moderation, offers numerous health benefits, including potential protection against kidney disease and kidney stones. However, it is important to monitor intake, particularly for individuals with pre-existing kidney conditions. The key takeaway is that green tea can be part of a kidney-friendly diet, but always consult with your healthcare provider for personalized advice.

References

1. "Green Tea Extract and Its Impact on Kidney Stone Formation" – The Journal of Urology
2. "Effects of Green Tea Catechins on Fasting Glucose and Cardiometabolic Health" – Frontiers in Pharmacology
3. "Chronic Kidney Disease Overview and Treatment" – Mount Sinai

"Severe Iron-Deficiency Anemia Associated with Moderate Green Tea Consumption in Women" – Heliyon