I have a day book. I've kept one each year since 2003. I write down what happens that day, keep track of birthdays and important appointments. That kind of thing. I also record what I eat. Not every single day. But most. They are short entries normally:
Tuesday February 9
So anxious. Went home and made spectacular, elaborate aubergine wrapped ricotta gnocchis with brown butter sage sauce. Divine, esp. on a tuesday.
Saturday March 6
Up so early! Bought an octopus, jeans, made a pie!
Friday July 16
A date night that wasn't. Both home late & tired so we ordered indian and watched television.
If we have a particularly epic meal I will do my best to write a full description of what everyone ate. If I make some particularly delicious but can't remember where the inspiration came from I'll record that too, just in case.
I write food down because it helps me remember. I may not remember what the weather was like or what was going on in politics, but if I've written down the food I can usually pull up a pretty good picture, visuals, smell, of the day. It's like the moment gets captured in the food and saved there. It's likely it acts as an aide-mémoire for me because sitting down to eat requires you to slow down and breathe and relax, even for a few moments.
The reason I bring it up is because of this lovely short article in the New Yorker about a man who also wrote down what he ate.