Coffee, roasted from coffee beans, contains phytonutrients and stimulating compounds, such as caffeine, that have a variety of effects on your body. Too much coffee can have detrimental effects on your body, including your kidneys, mostly related to the amount of caffeine contained within coffee beans. Talk to your doctor about the use of coffee and caffeine if you suffer from kidney disease or have weakened kidneys due to illness.
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A single cup of coffee contains about 120 mg of caffeine on average, which is enough to effectively stimulate your central nervous system and increase energy and alertness. Caffeine turns on adenosine and adenine receptors in your brain, which in turn increases the production of adrenal hormones that increase your heart rate, blood flow, and blood vessel diameter. An increase in blood flow throughout your body increases the rate in which blood is carried to your kidneys, where toxins and other metabolites get filtered out of your blood and are excreted in your urine.
Renal System Stress
By stimulating blood flow to your kidneys, caffeine may increase the stress placed on your entire renal system, the system that includes your kidneys and is responsible for filtering your blood. In a 2002 study published in the journal, "Kidney International," researchers claim that long-term caffeine consumption can increase your risk of kidney failure by affecting your kidney's ability to filter insulin present in your bloodstream. According to Health-Science-Spirit.com, long-term coffee drinking can increase the amount of calcium excreted through your kidneys, causing a calcium deficiency.
The caffeine contained in coffee is well-known to increase your risk of dehydration, according to the book, "Nutritional Supplements in Sports and Exercise." The National Library of Medicine states that dehydration is the biggest risk factor that contributes to the formation of kidney stones, which are painful calcium deposits in your kidneys that can cause extreme pain and sometimes require surgery. Drinking more than one or two cups of coffee daily can increase your risk of becoming dehydrated because your body will lose water too quickly, according to the National Kidney and Urologic Diseases Information Clearinghouse.
University Health Services at the University of Michigan states that up to 200 mg of caffeine, or about 1 large cup of coffee, is relatively harmless. However, a higher daily intake can increase your risk of mild side effects, including anxiety, irritability, insomnia, intestinal discomfort and headache. Long-term caffeine intake upwards of 600 mg per day, or 3 or more cups of coffee daily, can significantly increase your risk of developing kidney stones and other kidney abnormalities that may be detrimental to your health.