Photo/IllutrationReduced-potassium melons (Provided by Sanwa Factory Co.)

  • Photo/Illustraion
  • Photo/Illustraion

MATSUE--Kidney disease means closely watching what you eat and drink, but researchers at Shimane University here found a way to make eating more pleasurable again for those with the condition.

People with diabetes and heart diseases can also benefit from the research.

The researchers developed a melon with a strikingly low potassium content that tastes as delicious as ordinary fruit bought at stores, and have begun commercial production.

Other researchers developed an app to help patients cook healthier meals more easily.


The special melon for dialysis patients is the brainchild of Toshiki Asao, 60, a horticultural professor at the university’s Faculty of Life and Environmental Sciences.

The fruit looks the same as normal melons and is as juicy and sweet. The only difference is that Asao’s melon contains half the amount of potassium.

Asao was granted a patent in 2014 for methodology to culture the reduced-potassium fruit.

Malfunctioning kidneys of dialysis patients are unable to disgorge potassium properly though urination. High levels of potassium accumulated in the body pose the risk of hyperkalemia that causes limb paralysis and an irregular pulse.

As a result, patients are urged to shy away from fruit and vegetables with high potassium levels.

The low-potassium melon enables those individuals to savor the sweet taste of fruit without getting overly anxious about how it will affect their health.

“I wanted to create something that can turn the stress of being unable to have what one really wants into the pleasure of actually eating it,” said Asao.

Trials are now under way to ascertain whether cabbage and various vegetables can be grown with hydroponics to lower potassium levels. The idea was to raise them in long and narrow pots with glass stones, instead of soil, by fine-tuning the injection of fertilizers through tubes connected to the pots. Tests are carried out in a greenhouse at the university’s Honjo Experimental Farm in Matsue.

The trick is to supply different fertilizers, such as potassium and calcium, through separate tubes. This makes it possible to stop the supply of potassium while continuing to provide other fertilizers in the culturing processes.

Potassium is essential to plant growth, and melon plants store potassium in their leaves before flowering. Inspired by this characteristic, Asao developed a technique to get the species to bear fruit using only potassium accumulated in its leaves by cutting off the supply after flowering.

He embarked on his melon quest in 2008 and began selling the fruit in quantity 10 years later.

Matsue city authorities offered the melon as a gesture of appreciation last year to taxpayers who took advantage of a tax incentive system called “furusato nozei” that allows them to choose to make a tax-deductible donation to a municipality, prefecture or cause they want to support, such as social and environmental programs.

Asao succeeded in commercializing the product after much trial and error.

If the potassium supply is terminated too early, the fruit loses its sweetness and taste. Stopping it too late results in the same potassium content as ordinary melons.

As factors such as temperature, hours of sunlight and weather conditions also determine when to suspend the potassium supply, Asao had to collect vast amounts of data to ensure quality remained stable.

Kunio Koshimura, 63, director of the Kumanoji Clinic in Shingu, Wakayama Prefecture, bought one of Asao's melons as a present for one of his dialysis patients.

“The patient was clearly excited at being able to tuck into such a delicious melon,” he said. “Dialysis puts a heavy burden on patients, mentally as well, because the treatment continues through their lives. The patient's stress levels were eased by eating the melon.”


In the same vein, Morihiko Nakamura, 61, a biochemistry professor at the university’s Faculty of Medicine and Office for Regional Collaboration and Innovation, developed a smartphone app that shows people with diabetes and heart diseases how to cut their intake of sugar and salt and cook healthy dishes easily.

Users can quickly concoct meals just by adding dedicated sauces with less sugar or salt to frozen ingredients based on the app’s instructions.

Armed with details of the patient's health problems, the app proposes meals combining foodstuffs and sauces registered in a database. All a patient has to do is microwave the ingredients and add the sauce of choice.

Fifty kinds of sauce, including tartar, curry taste and stew, are available. The cooked reduced-salt meals contain less than half the volume of salt compared with ordinary dishes.

Nakamura said his aim was to create meals with more flavor by getting professional cooks to adjust the taste of each dish with stock and spices.

“One can make an unlimited number of meals with the help of the app,” said Nakamura. “Eliminating the need to keep patients on a strict diet may help them develop a healthier appetite.”

Development of the app and dedicated sauces started in 2016, and Nakamura has applied for a patent. He is also working on a business plan to promote the system on a commercial basis. One of his concerns is how to deliver the ingredients and sauces to patients.