Expert Warns Sugar, Not Salt, May Be Key Driver of High Blood Pressure and Explains Why Tonkatsu Twice a Week Can Still Be Acceptable
More dangerous than salt! Blood pressure and sugar trap
Hypertension is not something that only the elderly need to be careful about. Even ordinary daily habits, such as how you hydrate yourself, may potentially contribute to high blood pressure.
When it comes to preventing hypertension, “reducing salt intake” is considered essential. However, Dr. Minoru Kamata, Honorary Director of Suwa Central Hospital, issues a warning:
“Recently, it has become clear that sugar may be a greater cause of high blood pressure than salt.”
It is thought that fructose, which is contained in sugar, acts on the renal tubules in the liver and promotes sodium reabsorption, thereby raising blood pressure.
Sweetened beverages cause vascular aging
Sugars contained in liquids such as cola, juice, and sports drinks are considered to have a particularly strong effect on raising blood pressure, and are also associated with glycation.
Glycation is a process in which excess sugar binds with proteins in the body, producing AGEs (advanced glycation end products), which are said to degrade skin and blood vessels.
As a result, it can not only cause wrinkles and sagging skin, but also contribute to the deterioration of blood vessels, which in turn may lead to arteriosclerosis and become a factor in hypertension.
As the hot season approaches, hydration becomes essential. At such times, people tend to rely on sports drinks for heatstroke prevention, but Dr. Kamata points out:
“For heatstroke prevention, water or tea is also sufficient.”
Regarding sugar intake in beverages, there are warnings in materials from the Ministry of Health, Labour and Welfare that encourage caution against excessive consumption, asking essentially, “Would you drink sugar like that if you were thirsty?”
Although it varies slightly depending on the manufacturer and product, in terms of sugar equivalent (about 3g per stick of sugar), a 350ml cola contains the equivalent of about 14 sticks, a 220ml yogurt drink about 13.5 sticks, and a 350ml carbonated soft drink about 12.5 sticks—an astonishing amount.
Sudden death risk! The “Monday morning curse”
Hypertension has no noticeable symptoms, and if left untreated, it increases the risk of myocardial infarction, stroke, and dementia. It is estimated that there are about 43 million people with hypertension in Japan, but only about one-third of them are actually receiving treatment.
Even if a blood pressure reading at the hospital shows no issues, some patients experience a sharp rise in blood pressure only in the morning, known as a morning surge.
Dr. Kamata recommends measuring blood pressure five times a day, including in the morning, to detect such hidden hypertension in outpatients. In practice, this has led to the discovery of patients with morning surges.
“Cerebral infarctions and myocardial infarctions tend to occur more often in the morning. During sleep, dehydration can easily occur, making the blood thicker. In terms of weekdays, Monday carries a higher risk. It is better to keep Monday mornings in a good mental state and avoid placing too much workload at the start of the week.”
Losing 1 kg more than medication
The Japan Society of Hypertension has revised its hypertension treatment guidelines for the first time in six years, and in the 2025 revision, the target blood pressure has been unified across all ages to less than 130 mmHg systolic and less than 80 mmHg diastolic. Previously, the target for people aged 75 and older was somewhat more lenient, but it has now been standardized regardless of age.
For patients on the borderline of hypertension, Dr. Kamata explains his daily guidance:
“I tell them to lose just 1 kg.”
Obesity is a major risk factor for developing hypertension. Therefore, instead of immediately relying on medication, patients are advised to focus on reducing salt and sugar intake and managing their body weight in daily life.
Body fat is broadly divided into subcutaneous fat and visceral fat. Excess accumulation of fat around internal organs and in the abdomen is known as metabolic syndrome, which requires attention even among working-age adults, as it significantly increases the risk of arteriosclerosis. However, there is some good news: compared to subcutaneous fat, visceral fat is easier to reduce.
Tonkatsu OK! The truth about carbohydrate restriction
A notable paper on low-carbohydrate dieting was published in 2008. It was a study conducted in Israel on 322 participants over about two years, comparing the effectiveness of weight loss through diet across three groups:
① low-fat diet + calorie restriction
② Mediterranean diet + calorie restriction
③ low-carbohydrate diet (carbohydrate restriction) + no calorie restriction
As a result, it was found that group ③, the no calorie restriction + low-carbohydrate (sugar-restricted) diet, led to greater weight loss than the others.
Based on such research findings, Dr. Kamata recommends that reducing carbohydrates is beneficial for improving obesity.
Many people, in an effort to avoid fat, tend to reduce foods such as meat, but this is said to be a trap. In fact, Dr. Kamata himself, now in his late 70s, enjoys his favorite tonkatsu about twice a week while keeping his rice intake moderate. This is because rice contains a large amount of carbohydrates, and carbohydrates are mainly composed of sugars and dietary fiber.
“Eating delicious food is also important for maintaining mental stability.”
By maintaining moderate exercise and paying attention to the quality of daily diet, obesity and metabolic syndrome can be improved, and the risk of serious diseases caused by hypertension can steadily decrease.
Interview and text by： Hideki Asai PHOTO： Afro