One in seven people in Korea has chronic kidney disease…avoid high-potassium fruit in summer

 [Sports Chosun, reporter Jang Jong-ho] Summer is the season when heat and dehydration raise the risk of kidney disease.

In Korea in particular, where the number of patients with chronic kidney disease (CKD) is considerable, managing kidney health in the summer heat is all the more important. Korea has one of the highest prevalence rates of chronic kidney disease in the world. Related annual treatment costs were also more than KRW 2.83 trillion as of 2024, the third largest for any single disease. The Korea National Institute of Health and the Korean Society of Nephrology recently announced that Korean patients with chronic kidney disease have about a 1.66 times higher risk of declining kidney function than patients in the US CRIC cohort and are more likely to progress to end-stage renal disease.

Lee Ji-yeon, Chief of Nephrology at St. Peter's Hospital, explained, "In people with chronic kidney disease, seasonal risk factors overlap in complex ways, so the risk of declining kidney function in summer is also more likely to increase."

◇One in 7 to 8 people has ‘chronic kidney disease’… no early symptoms even as kidney function declines

The kidneys are a key organ that keeps the body's internal environment stable. Their main role is to filter waste products out of the body and cleanse the blood through millions of glomeruli made up of tiny capillaries. In doing so they maintain fluid and electrolyte balance and regulate hormones, preserving the body's homeostasis. If kidney function declines continuously for three months or more, or damage is confirmed, a diagnosis of chronic kidney disease is made.

Chronic kidney disease affects one in seven or eight people in Korea, and its prevalence is rising worldwide as populations age. It is divided according to the degree of decline in kidney function, from stage 1, which is close to normal, through to stage 5, at which dialysis must be considered; the higher the stage, the greater the likelihood of complications such as cardiovascular complications. Once it progresses to end-stage renal failure, the prognosis is often poor and mortality rises sharply.

The problem is that most patients have no noticeable symptoms in the early stages even as kidney function declines. Chief Lee Ji-yeon said, "Most patients do not realize that their kidney function has fallen until protein is detected in a urine test or an abnormal finding shows up on imaging or other examinations."

However, kidney function actually declines significantly in only about 5–7% of patients with chronic kidney disease, and the severity and the level of treatment vary greatly depending on the patient's stage and condition. That makes it important to detect the disease early and to prevent it from worsening through consistent management. Diabetes and hypertension in particular are regarded as major causes of chronic kidney disease, so extra care is needed if you have these conditions.

◇Cut potassium intake in summer and keep fluid intake right for the individual

What patients with chronic kidney disease need to be especially careful about is looking after their kidney health in summer. Summer heatwaves are in themselves a factor that places a burden on the kidneys of patients with chronic kidney disease. Excessive heat can cause dehydration and electrolyte imbalance, and when the effects of medications such as diuretics are added, this risk can become even greater.

Chief Lee Ji-yeon said, "Extreme heat can reduce blood flow to the kidneys through dehydration, which raises the risk of acute kidney injury and can worsen the symptoms of chronic kidney disease," explaining, "Meta-analyses have in fact reported that in high-temperature environments the risk of kidney disease and of related hospital admissions and emergency room visits increases by about 30%."

An even bigger problem is summer eating habits. Summer fruits high in potassium, such as Korean melon, watermelon, and banana, place a burden on the kidneys and carry a risk of causing hyperkalemia, so intake must be kept under control. It is also advisable to refrain from consuming excessive amounts of juice or sports drinks. Excessive salt intake of more than 5 g a day and consumption of caffeinated and alcoholic drinks are likewise best avoided.

Appropriate fluid intake, matched to kidney function and disease status, is also important. In summer, sweating increases and it is easy to drink more water than usual to quench thirst, but patients with chronic kidney disease need to take care, as excessive fluid intake can in fact place a burden on the kidneys. It is also recommended to drink in several smaller amounts spread over time rather than a large volume at once. The guidance on heatwave precautions for vulnerable groups released by the Korea Disease Control and Prevention Agency in early July this year likewise stresses that patients with kidney disease should keep to the fluid intake that is appropriate for them individually.

In addition, if abnormal symptoms such as persistent dehydration, changes in urine volume or color, or extreme fatigue appear, it is best not to dismiss them as simply the effects of the heat but to consult a specialist.

Chief Lee Ji-yeon advised, "Patients with chronic kidney disease must be more careful than anyone about dehydration and declining kidney function in summer," adding, "Rather than simply drinking water or taking restorative foods, they need to discuss the matter with their medical team and manage their condition carefully, taking their own kidney function and disease status into account."