How can I make a reactive array from a Meteor collection?

I want to take a list of item names from a collection as a simple array to use for things like autocompleting user input and checking for duplicates. I would like this list to be reactive so that changes in the data will be reflected in the array. I have tried the following based on the Meteor documentation:

    setReactiveArray = (objName, Collection, field) ->
        update = ->
          context = new Meteor.deps.Context()
          context.on_invalidate update
          context.run -> 
            list = Collection.find({},{field: 1}).fetch()
            myapp[objName] = _(list).pluck field
        update()

    Meteor.startup ->
        if not app.items?
            setReactiveArray('items', Items, 'name')

    #set autocomplete using the array
    Template.myForm.set_typeahead =  ->
       Meteor.defer ->
        $('[name="item"]').typeahead {source: app.items}    

This code seems to work, but it kills my app's load time (takes 5-10 seconds to load on dev/localhost vs. ~1 second without this code). Am I doing something wrong? Is there a better way to accomplish this?