Hi,
I'm new here. Since I'm intolerant to gluten and lactose I am a severe label reader and content researcher. I found online that some Protein drinks/mixes/supplements have monosodium glutamate ( MSG) which can cause headaches for some people. Here's a list of some not-so-evident forms of MSG's I've found online: Anything "hydrolyzed", Any "hydrolyzed protein", Calcium caseinate, Sodium caseinate, Autolyzed yeast, Gelatin, Textured protein, Soy protein, soy protein concentrate, Soy protein isolate, whey protein, whey protein concentrate, Whey protein isolate.
I get headaches from MSGs however, I don't hedaches from all of the above (soy protein products, gelatin are okay).
So look on your labels and see what you have.
Hope this helps!
My surgery is August 8th and I've just started my pre-op diet.