Cross-cultural communication （117）　

117) Grapefruit Juice
When my three sons were children, a song called “My Mixed Juice” was popular on the children's TV show “Okaasan to Issho” (roughly translated as “With Mother”). The chorus of the song went “If you drink this all in one go, something good might happen to you”. In my case, from the time I can remember, this was not mixed juice, but grapefruit juice. After I became a doctor (that is, after I was able to spend money freely myself), I always kept some in the fridge.

When I started living in New York as a resident doctor in my late 20s, I often stayed in hotels both in Japan and overseas for trips and conferences. At hotel breakfasts, there are usually several types of juice available, but grapefruit juice is always available wherever you go in the world. After drinking down that slightly bitter, cold glass of GFJ in the morning, I would eat a croissant with cafe au lait and a soft-boiled egg for a final meal, and I would be full of energy and able to handle any conference or presentation.

I often buy grapefruit juice at the convenience store near my home in Kobe, where I have lived for over 30 years, but after 2018, it disappeared from the shelves. I did some research and found that the majority of grapefruit in Japan is imported from the United States, and more specifically, from Florida. In the autumn of 2017, a hurricane hit Florida, and from the following year, the amount of grapefruit harvested there decreased dramatically. I was relieved to see it on the shelves of convenience stores from July 2021.

From around the second half of 1980, there were a succession of reports of business people who were travelling around the world becoming dizzy and fainting after drinking grapefruit juice at their hotel breakfasts. After investigating the matter, it was discovered that almost all of the people who had this symptom were taking a type of antihypertensive drug called calcium antagonist. Further research has shown that the bitter components of grapefruit juice interfere with the breakdown of this blood pressure medication in the liver, causing the medication to be too effective and resulting in low blood pressure attacks. Calcium channel blockers are still a highly effective blood pressure medication, so many people take them. For this reason, doctors and pharmacists always warn patients who are starting to take this medication to avoid grapefruit juice. As a result, this is now almost common knowledge for people with high blood pressure.

I myself turned 73 on my birthday in 2024, but fortunately my blood pressure is normal, and I can expect to be able to drink down a lot of grapefruit juice and do something good from now on.

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