The gut contains hundreds of trillions of bacteria to help us digest and get nutrients from our food. In order to do this, stomach bacteria can alter our genes to create digestive enzymes. As NPR's Jon Hamilton explains, “When people in Japan began eating seaweed with their rice and fish, they ingested some bacteria from the ocean. And as these ocean bacteria passed through the intestine, they exchanged bits of genetic code with the gut bacteria.” Even though the introduction of seaweed in the Japanese diet happened around 40,000 years ago, they found the ocean bacteria present in Japanese digestive systems today. North American stomachs were also tested, but lacked the bacteria.
So, unless you are Japanese, you aren’t breaking down seaweed. And because of how we process foods in the modern age, today's nori isn't bacteria-ific enough to be messing with your genes, so if you weren't born with the special seaweed powers, you're not getting them.
Image source: CHOW.com