Coffee's Effect on the Kidneys

The ever-growing worldwide popularity of coffee as a beverage of choice also makes it a subject of intense study into its health effects. Science has investigated how coffee impacts everything from our immune system to the risk of heart disease and cancer.

The debate about whether coffee is good or bad for you has raged on for over a thousand years, ever since coffee was first discovered (possibly) in Ethiopia. It is hard to imagine today, but at times coffee was even banned in certain parts of the world, for health or religious reasons.

Studies on Coffee and Kidney Disease

Population-based epidemiological studies have tended to show an association between consumption of coffee and possibly a protective effect on kidney function.

A Korean study of more than 2,600 women showed that consumption of coffee was associated with a decreased risk of kidney disease, including in diabetic women. As we know in medicine though, population-based surveys are not enough to draw hard conclusions.

Therefore, given the pertinent and possibly controversial nature of the topic, a meta-analysis published in 2016 attempted to answer this very question. This meta-analysis showed no association between coffee consumption and increased risk of kidney disease in male patients.

Interestingly, it actually noted the possibility of a reduced risk of kidney disease in women who drink coffee. The conclusion regarding coffee, at least based on these data could be: harmless on male kidneys, and possibly beneficial to women's.

The results of the above meta-analysis are similar to another study from another part of the world, specifically the Pacific Coast of Nicaragua where the lower prevalence of chronic kidney disease in coffee growing villages has been noted.

Coffee and Genetic Kidney Disease

In the past, basic science studies have indicated that caffeine could increase the risk of growth of kidney cysts in patients with autosomal dominant polycystic kidney disease (PKD).

However, in more current clinical studies, consumption of coffee was not noted to be a risk factor for PKD progression.

Risk of Kidney Stones

Beyond medical diseases of the kidney, there are still special situations where intake of coffee might need to be moderated. One such scenario is people who form kidney stones.

Oxalate stones are one of the commonest varieties of kidney stones, and it just so happens that one of the main sources of oxalate in our diet is regular coffee (black tea being the other culprit).

Therefore, patients with kidney stones, especially those with calcium oxalate stones, should still regard coffee as a possible risk factor.

Risk of Kidney Cancer

The evidence regarding this is quite mixed. Studies have typically indicated a reduced risk of renal cell carcinoma with coffee consumption. However, for some reason, this association seems to be true for caffeinated coffee only.

Decaffeinated coffee consumption seemingly increases the risk of clear cell renal cell carcinoma subtype, a particular kind of kidney cancer, but more studies need to be done to better understand this potential link.

Coffee, Hypertension, and Kidney Disease

As discussed in other articles, high blood pressure (after diabetes) is the biggest cause of kidney disease. 

There is some evidence that drinking caffeinated coffee could cause a short-lasting increase in blood pressure, with the effects seemingly exaggerated in older patients and people who are not regular drinkers of coffee.

Given this possible link between coffee intake and elevated blood pressure, the concern is often raised about coffee's ability to cause damage to the kidneys. Despite this plausibility, there is evidence to the contrary.

Data shows that as long as daily consumption of coffee does not exceed 3 to 4 cups (with each 8-ounce cup having anywhere between 100-200 mg of caffeine), there is no increase in the risk of kidney disease in healthy young subjects.

Decaf and Hypertension

Almost counterintuitively, coffee has been found to increase nervous system activity as well as blood pressure, independent of its caffeine content. 

Therefore, the effect of an increase in blood pressure is even seen with decaffeinated coffee, making it appear that there might be something other than caffeine in coffee that could be responsible for this blood pressure elevation.

A Word From Verywell

Given the current weight of available evidence, it appears that while coffee could have a blood pressure increasing effect in non-habitual drinkers of coffee and in people with pre-existing hypertension, that does not seem to translate into an increased risk of kidney disease.

In fact, there is mixed evidence pointing to a possible protective role of coffee on kidney disease, especially in women. Patients with calcium oxalate kidney stones might still want to moderate their coffee intake given its oxalate content.

The evidence that coffee could increase or reduce the risk of kidney cancer remains controversial at best.