Wow, congratulations on twins! It’s wonderful that you are taking steps to make sure you are eating a healthy diet while nursing them.
It is important that you eat enough to keep your milk supply up, but your energy needs are just a little higher than before pregnancy. Milk production can decrease in mothers if intake is suboptimal, and breast milk will reflect the nutrient diet of the maternal diet. Getting enough fluid (drink mostly water!) and adequate rest is also very important.