Fructose Intake and Kidney Disease - Effects & Guidelines

Fructose is the primary nutrient in fruits and honey, giving them a sweet taste. There are two important sources of fructose in the diet.

• Refined Sugar: The first source of fructose is refined sugar, it is made from sugarcane, sugar beets, and palm. Recently, intake of refined sugar in the diet has increased. Refined sugar has sucrose, which is made of glucose and fructose. Refined sugar is added to sweets, desserts, alcohol, soft drinks, and other common foods.
• High Fructose Corn Syrup (HFCS): The second source of fructose in the diet is high fructose corn syrup (HFCS). It is derived from corn. The advantage of HFCS is it crystallizes less compared to refined sugar. Because of this feature, it is added to frozen foods.

Refined sugar & high fructose corn syrup are usually added to soft drinks, desserts, processed food, and baby foods. Fructose is also generated in the body in a few conditions. There is high fructose generation in the body in patients with diabetes, high salt diet, high sugar diet, Gout, metabolic syndrome, dehydration, and kidney disease. High fructose intake can lead to various deleterious effects on our bodies.

Sugar (sucrose) and high fructose corn syrup in the diet are broken down in the intestines, and fructose is released. Fructose is absorbed from the intestines into the blood and transported to the liver. Fructose is metabolized in the liver. Fructose metabolism in the liver can produce glucose and lactate. At the same time, fructose decreases the energy levels inside the cells. Because of this decrease in energy levels inside the cells, more uric acid is generated. This uric acid is the main reason for the harmful effects associated with high fructose intake. Uric acid can cause lead to -

• Increases the oxidative stress inside the cells.
• Diabetes
• High blood pressure (hypertension)
• Obesity
• Liver disease
• Kidney injury

Fructose and Its Effects on Kidney

High fructose intake, leading to diabetes, hypertension, obesity, and metabolic syndrome, increases the chronic kidney disease risk. Uric acid may directly damage the kidneys by causing scarring in the kidneys. It can lead to increased pressures inside the glomeruli (functioning units of the kidney) which can have harmful effects on the kidney.

In patients suffering from chronic kidney disease, it can worsen the protein loss in the urine (proteinuria). More than or equal to 2 servings of soda or drink with fructose can increase the risk of kidney disease.

Guidelines for fructose intake in kidney disease patients

• Food with high refined sugar or high fructose corn syrup can increase insulin resistance, obesity, and fatty liver.
• The risk is heightened with products containing sugar in liquid forms, like soft drinks, power drinks, sugary teas, and fruit punches. So, it is better to avoid them.
• Natural fruits have less fructose and contain fiber, which delays fructose absorption. Fruits also contain certain chemicals which are protective of the body.
• Fruit juices can have high fructose content, so it is better to avoid them.
• If fruits or sweet taste is desired, it is better to take natural fruit after discussing with a nephrologist and dietician, which are acceptable. 
• In dialysis patients, salt and sugar increase thirst and excess weight gain between dialysis sessions. So, they are recommended for both salt restriction and avoiding excess sugar intake. 
• Refined sugar recommendations are six teaspoons (25 grams) for women and nine teaspoons (37.5 grams) for men in a whole day. 

Department of Nephrology