Do I need a special diet with porphyria?

No. There is no special or particular diet required or recommended for persons with porphyria. Rather, the principles of good and sensible nutrition apply. These principles call for a varied and balanced diet, particularly with avoidance of over-nutrition. Consumption of too many calories, in excess of daily needs for calorie and energy consumption, as well as too little can lead to exacerbations.
Probably not. There are different types of porphyrias and most of them are not affected by dietary manipulation. There is some evidence that a high carbohydrate diet will alleviate some of the acute attacks. All this should be coordinated through a physician who deals with this type of metabolic problem.