Can only Japanese people digest seaweed? No, that's not true: Some studies say that the Japanese and East Asians have specific enzymes that help them digest seaweed, but this is just the ability to digest a type of polysaccharide contained in seaweed and does not describe seaweed as a whole. Even in the studies, this specific enzyme was not found in the intestines of all the Japanese looked at. The ability to digest seaweed is a function of the intestinal bacteria that coexist within the body and is not part of the Japanese DNA.
The claim appeared in a video (archived here) on TikTok on February, 13, 2024. The video opened (translated from Japanese to English by Lead Stories staff):
Only Japanese people can digest seaweed.
This is what the post looked like on TikTok at the time of writing:
(Source: TikTok screenshot taken on Thu Feb 22 00:00:14 2024 UTC)
The connection between Japanese people and digesting seaweed was examined in two papers. One is from a 2010 Nature article, "Transfer of carbohydrate-active enzymes from marine bacteria to Japanese gut microbiota" (archived here), the other from a 2022 Cell Host Microbe article, "Diverse events have transferred genes for edible seaweed digestion from marine to human gut bacteria" (archived here).
These papers found that the fermentation process in the large intestine is extremely efficient for Japanese people, but this is just the ability to digest a type of polysaccharide contained in seaweed, and this specific enzyme was not found in the intestines of all Japanese examined. This is not part of the Japanese DNA.
