Careful with water and fruit in the heat?…summer health precautions for chronic kidney disease patients

 [Medical News · Ilgan Bosa] Summer heat causes sweating and dehydration that can place a strain on the kidneys. Patients with chronic kidney disease, whose kidney function is already reduced, need to be especially careful, as even a large amount of water drunk without thinking or summer fruit can become a threat to their health.

Chronic kidney disease is a condition in which reduced kidney function or kidney damage persists for three months or more. It is known to affect one in every seven or eight people in Korea, and related treatment costs exceeded KRW 2.83 trillion in 2024, the third largest for any single disease. A recent analysis also found that Korean patients with chronic kidney disease have about a 1.66 times higher risk of declining kidney function than patients in the United States. 

For patients with chronic kidney disease, overlapping seasonal risk factors can make a decline in kidney function in summer even more likely.

The kidneys are the organs that filter waste products out of the blood and excrete them in the urine while maintaining the balance of body fluids and electrolytes. They also play an important role in maintaining the body's homeostasis, for example by regulating blood pressure and hormones.

Chronic kidney disease is classified by the degree of loss of kidney function, from stage 1, which is close to normal, to stage 5, at which dialysis must be considered. The higher the stage, the greater the risk of complications including cardiovascular disease, and if it progresses to end-stage renal disease, dialysis or a kidney transplant may be required.

The problem is that there are almost no clear symptoms in the early stages even as kidney function declines. Many patients are unaware of the decline until protein is detected in a urine test or an abnormality is found on blood or imaging tests.

Not every patient with chronic kidney disease deteriorates at the same rate, however. Only some patients experience a meaningful decline in kidney function, and the level of risk and of treatment differs according to the stage of the disease and any accompanying conditions.

Diabetes and hypertension in particular are leading causes of chronic kidney disease, so patients with those conditions should have their kidney function checked regularly.

Fluid and fruit intake in a heat wave must suit the patient's condition

Summer heat waves are even more dangerous for patients with chronic kidney disease. If heavy sweating causes dehydration, the volume of blood flowing to the kidneys falls, which can lead to acute kidney injury or worsening of the existing disease. When the effects of medications such as diuretics are added, the risk of dehydration and electrolyte imbalance can rise further.

When a heat wave causes dehydration, blood flow to the kidneys falls and the risk of acute kidney injury and of worsening chronic kidney disease can rise. Research has also found that in high-temperature environments the risk of kidney disease and of related hospital admissions and emergency room visits increased by about 30%.

Care is also needed with summer fruit. Korean melon, watermelon and bananas are high in potassium, so eating large amounts when kidney function is reduced can cause hyperkalemia, an abnormally high concentration of potassium in the blood.

Hyperkalemia can cause muscle weakness or abnormal sensation and, in severe cases, can affect the heartbeat. Patients with chronic kidney disease should therefore keep to the intake their medical team recommends rather than eating fruit to excess in the belief that it is a health food.

Juices and sports drinks are not automatically safe either. Depending on the product they can be high in sugar, potassium and sodium, so the ingredients and the amount consumed should be checked. Salty food and excessive caffeinated or alcoholic drinks also place a strain on the kidneys and blood pressure and are best avoided.

Fluid intake also has to be matched to the patient's condition. Thirst makes it easy to drink more water than usual in summer, but patients with reduced kidney function cannot excrete excess fluid properly, which can lead to edema or shortness of breath.

Conversely, restricting fluid intake too severely raises the risk of dehydration and acute kidney injury. It is better to drink in several smaller amounts rather than a large volume at once, and to discuss the appropriate daily intake with the medical team, taking kidney function, urine output and any swelling into account.

The daily rules for patients with chronic kidney disease in summer are: △controlling the amount of high-potassium fruit such as Korean melon, watermelon and bananas △cutting down on salty food △drinking water in divided amounts rather than a large volume at once △limiting juice, sports drinks, caffeine and alcohol △watching for changes in the body such as urine volume and color and fatigue.

If dehydration continues, if urine output suddenly falls, if the urine is darker than usual, or if extreme fatigue and swelling appear, these should not be dismissed as simply the effects of the heat. Kidney function may have deteriorated sharply, so a specialist should be consulted.

Patients with chronic kidney disease must be more careful than anything about dehydration and declining kidney function in summer. Rather than simply drinking a lot of water or taking restorative foods and fruit, it is important to manage fluid intake and diet in line with one's own kidney function and disease status.

Source: Medical Newspaper (https://www.bosa.co.kr)