Eat more fat. Seriously. You're body needs more fat and iron during that time. I like this breakfast in the mornings during my time: take an egg crepe and fill it with some smoked or baked wild salmon and melt some onion & chive cream cheese, add some mushrooms, garlic and chopped tomatoes and then put the cream cheese mixture over the crepe. Really, really good stuff. I've found that the more fat I eat the first few days before and druing my beastly time, I'm better off with.