According to “The Guardian”, the average American eats about 17 teaspoons of added sugar per day.  And the American Heart Association warns that the maximum daily allowance of added sugar is 9 teaspoons for men (36 grams) and 6 teaspoons for women (25 grams). 
Surprising or not, sugar is added not only to sweets and candy, but also to processed, semi-processed, and packaged foods, dairy products and canned foods.
That being said, very few people watch their daily sugar intake, which can contribute to diabetes, heart disease, hypertension, chronic diseases, chronic inflammation, and weight gain. 
While sugar consumption will not directly harm your kidneys if your blood sugar levels are normal, consistently eating too much added sugar may cause diabetes and associated high blood glucose. High blood glucose may cause kidney damage and impraired blood filtration efficiency.
Now let’s dive into the details!
Does too much sugar cause kidney disease?
Added sugar is strongly associated with a whole host of chronic health conditions including diabetes, heart disease, hypertension, metabolic syndrome and some cancers. One very important distinction is that only added sugar is associated with negative health effects. Naturally occurring sugar, what is found in fruit, is not connected with harmful health effects.
The healthy fiber, vitamins, minerals and antioxidants found in fruit significantly outweigh the small amount of sugar that it has. So go ahead and enjoy fruit as a way to healthfully sweeten up your day!
Too much sugar may cause kidney disease.
If you are healthy, follow a balanced and diverse diet, and have an overall healthy lifestyle, a little added sugar is unlikely to cause kidney issues. This is because a healthy lifestyle will reduce your risk of increased blood sugar, prediabetes and diabetes. So in this case, occasionally eating foods with added sugar is unlikely to harm your kidneys.
High blood sugar
According to the National Kidney Foundation, blood sugar levels higher than 180mg/dl may damage the blood vessels in the kidneys, impairing their filtering function. 
Besides, the source suggests that the degree of kidney damage increases proportionally to the blood sugar levels. Meaning, the higher your blood sugar, the greater is your risk of kidney damage.
This way, continuous overconsumption of (added) sugar, especially if you have diabetes, may lead to high blood sugar which can cause kidney disease. Kidney disease is characterized by inefficient blood filtration, as well as salts, water, waste materials, and minerals buildup in the blood.
Evidence suggests that continuous high sugar intake is associated with significant increase in systolic blood pressure.  And hypertension is one of the leading causes of chronic kidney disease, as it may increase the intraglomerular pressure (pressure in the blood vessels around the kidney) and impair the filtering mechanism of these important organs.
Taking into account that these two health conditions are associated with impaired kidney function and chronic kidney disease, overconsumption of sugar is indirectly (yet dangerously) related to kidney disease development.
Does sugar cause kidney stones?
According to a 2018 study published in the BMC Nephrology, high fructose and sucrose intake may increase the formation of kidney stones by lowering the acidity (pH) of the urine and increasing urine oxalate.  In addition, it has been established that too much added sugar can increase urine calcium, which is the biggest driver of kidney stone formation. 
This way, the overconsumption of foods high in added sugar may significantly increase the risk of kidney stones formation.
Diet for diabetes and kidney disease
While the typical diet for diabetes focuses on counting carbs and fats, a kidney disease diet is focused on foods low in animal proteins, sodium and may require changes to how much potassium and phosphorous you eat.
But if you simultaneously suffer from diabetes (or high blood sugar) and kidney disease, it may feel like your food options are be limited.
Find out foods suitable for diabetic renal diet in the blog post written by Melanie Betz MS, RD, CSR, CSG, LDN
That being said, the Centres of Disease Control and Prevention provide general guidelines for a joint diabetes and kidney disease diet  :
- Fruits: berries, grapes, cherries, apples, plums
- Veggies: cauliflower, onions, eggplant, turnips
- Proteins: lean meats (poultry, fish), eggs, unsalted seafood
- Carbs: bagels, sandwich buns, unsalted crackers, pasta
- Drinks: water, clear diet sodas, unsweetened tea
If you are a diabetic and suffer from KD, consult your dietitian for more food and meal options, as well as a tailored meal plan.
Disclaimer: This information is meant for educational purposes only. It is not intended to replace the counsel of a medical doctor.