Wow this is amazing. Definitely the best biology video I've seen.

Edit: this is cool enough to deserve it’s own post, Im going to submit it: https://news.ycombinator.com/item?id=46405855

Agreed. If this isn't hacking then I don't know what is.

̶I̶ ̶t̶h̶i̶n̶k̶ ̶h̶e̶ ̶a̶c̶t̶u̶a̶l̶l̶y̶ ̶g̶e̶n̶e̶t̶i̶c̶a̶l̶l̶y̶ ̶e̶n̶g̶i̶n̶e̶e̶r̶e̶d̶ ̶h̶i̶s̶ ̶g̶u̶t̶ ̶b̶a̶c̶t̶e̶r̶i̶a̶ ̶r̶a̶t̶h̶e̶r̶ ̶t̶h̶a̶n̶ ̶a̶n̶y̶ ̶o̶f̶ ̶h̶i̶s̶ ̶o̶w̶n̶ ̶c̶e̶l̶l̶s̶ ̶t̶h̶e̶r̶e̶,̶ ̶r̶i̶g̶h̶t̶?̶

EDIT: Above is false. Went back and checked and I had mis-remembered the video.

From the video, it sounds like he engineered his own cells. Using a virus that is known for transferring genetic material into other organisms, he added a gene for producing lactase, and then ate it. I suppose that would affect both his gut bacteria and his own cells. But it lasted for ~1.5 years, which probably indicates that it truly was his cells. Also he seems to know what he's talking about, and he claims it was his own cells.

You're right, thanks!

Could be placebo though?

Is there a reason why I'm seeing squares between each of the characters in your message? It's making it pretty hard to read...

I'm using Chrome on Android

Firefox on iOS, I see strikethrough but the strikes are at varying heights.

The text is crossed out using Unicode combining characters of a strikethrough. This allows it to display without any specific formatting support, but it does require that the font support those characters. The font you're using doesn't support the characters, so it displays boxes, instead.

I thought (maybe mistakenly) that your body developed immunity to the adenovirus used to edit your own DNA, and so this trick could only be used once? Am I wrong?

In this specific instance the code he built used a non-human lactase-enzyme producing gene, which he states in the retrospective is very likely the reason why his immune cells started attacking. There was also the matter of some of the other coding pieces being non-ideal.