I think Fizzlex is talking about the stricter diet, not the website diet.
I’ve seen people eat more eggs for more protein. If you can get through that first 12 days, you can add in chicken or fish and that will help. If you truly felt like you couldn’t function for 12 days on the other sources of protein, I guess I’d add in chicken. But I’d try to go as long as possible before doing so, just to give my digestive system the break it needs.