The Diet Soda Kidney Damage Connection

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Diet Soda and Kidney Function Decline

Although very few research studies are available that link diet soda to kidney damage, most of them have confirmed that those who drink two or more than two diet sodas a day practically double their risk of kidney function decline. In other words, there is 30 percent decline in the kidney function associated with drinking diet soda. One such study led by researcher Julie Lin, assistant professor of medicine at Harvard Medical School and a staff physician at Brigham and Women’s Hospital in Boston, found that women who drank two or more diet sodas daily had a 3mL/min/year (3 milliliters per minute per year) decline in their GFR or the glomerular filtration rate. GFR is the measurement of kidney function, which estimates how much blood passes through the glomeruli, the tiny filters, in the kidneys each minute. Incidentally, the decline in kidney function is natural with aging – it declines about 1mL per minute per year after age 40.

What is in the diet soda that causes a decline in kidney functioning? The answer is simple: artificial sweetener, phosphoric acid and carbonation. Let’s check them out one by one.

The Artificial Sweeteners in Diet Soda

People usually turn to diet soda as part of their weight loss plan. Whether or not the diet soda helps you lose weight is another issue but the aspartame used in the diet soda actually accelerates kidney damage.

Aspartame mainly consists of methanol, phenylalanine and aspartic acid. Phenylalanine, an otherwise essential amino acid, can become dangerous in people who have chronic kidney failure. In such people, there is a deficiency of enzyme (phenylalanine hydroxylase) that breaks down phenylalanine into tyrosine. This results in an imbalance in the ratio of these two chemicals. Apart from damaging the kidney furthers, high levels of phenylalanine in the blood also cause alterations in brain function and behavior changes.

The Role of Phosphoric Acid in Kidney Damage

The artificial sweeteners are not the only culprits for kidney damage. The phosphoric acid in the soft drinks, diet or otherwise, double the chances of kidney disease. Phosphoric acid is generally added to give soda its tangy and acidic flavor. This acid also functions as a preservative and mold deterrent. Studies have shown a clear connection between carbonated beverages, especially cola beverages, containing phosphoric acid and urinary changes that promote kidney stones. This is because the salts of phosphoric acid and uric acid combine with calcium and/or magnesium and form kidney stones. For that matter, all kidney diseases are acid related. Unlike the liver, which can store acid, kidneys cannot store acids nor can they filter it out completely. The kidneys become so stressed they cannot even filter the normal by-products. The acids accumulate and eventually form kidney stones by combining with other salts or pave the way for other kidney diseases such as nephritis and uremic poisoning.

Acidity is measured in pH values. A pH of 7 is neutral and represents the acidity of pure water at room temperature. The lower the pH value the more acidic is the substance. Here are the pH values of some liquids.

Battery acid – 1

Colas – 2.5

Diet soda – 3.2

Branded beer – 4.7

Distilled water – 7

Filtered tap water – 8.4

Fresh vegetable juice – 8.9

Alkaline water – 10

No wonder nutritionists suggest a more alkaline diet to keep the kidneys functioning properly.

Does Carbonation Cause Kidney Damage?

Carbonation can also cause kidney damage according to some researchers. For example, urologists from the University of Rochester Medical Center, New York found evidence that changes in urinary magnesium, citrate and oxalate levels could contribute ‘to enhanced kidney stone formation in patients who drink large quantities of cola-flavored carbonated beverages’.

However, many studies did not find any direct association between carbonation and kidney damage, except that carbonation may increase acidity levels, which might affect kidney functioning.

Diet soda kidney damage can cause other concerns too. The National Kidney Disease Education Program (NKDEP), a subsidiary of NIH, suggests that if you are at risk for kidney disease, you must manage your diabetes, high blood pressure and heart disease as well. So, when it comes to health, the best bet would be to stick with natural and unprocessed beverages.


Diet Soda, Sodium Tied to Kidney Trouble: Studies -

Tina M. Saldana, Olga Basso, Rebecca Darden, and Dale P. Sandler (2007). “Carbonated beverages and chronic kidney disease”. Epidemiology 18 (4): 501–6.

pH of the Human Body is Critical for Health -

Weiss GH, Sluss PM, Linke CA. Changes in urinary magnesium, citrate, and oxalate levels due to cola consumption. Urology. 1992 Apr;39(4):331-3.