I would love to have the ability to keep a portion of my food diary private so the items count toward overall nutrition numbers, but folks can't actually see what it was that was eaten.

I have some vitamins and medications that I would like to keep track of, but I don't necessarily want people to see and comment on them.

You could just use the quick tools, quick added calories

Within the current system in order to "do" that you might find it easier to go to
my home > check in > track additional measurements
add a line per vitamin / med you take, decide how you want to track them.. 1 if you take 1... 2 if you take 2... 1 to represent you've taken your allotment for the day however many you take etc. Measurements can't be viewed by friends... So other than what you've already logged in your diary which they could go back through the days and see...

You could use code words! Sorry, I know you're making a suggestion and not looking for workarounds, but they are really slow to make changes here.

I would like the ability to track things that have nutritional value so they apply to my recommended daily allowances without actually appearing in the public portion of the diary. Logging then as measurements would only help for tracking quantity.

Some things have no calories, so a quick add won't work either.

Thank to all for the suggestions though

Add the medication to the database as a new food. Give it a name of your choice that you'll remember, and use that.