Dandruff is usually due to a poorly-functioning immune system. A common cause of that is a lack of zinc relative to copper. That's why Head and Shoulders shampoo works in many instances (it is rich in zinc).
Too much sugar can cause dandruff. Sugar does raise the metabolic rate, but at the same time, you are draining vitamins and minerals at a faster rate, so consuming a lot of sugar as Peat says will lead to vitamin and mineral deficiencies unless you're eating a good amount of liver. But liver has more copper than liver, so it's not good for the zinc/copper situation.
Too much sugar can cause dandruff. Sugar does raise the metabolic rate, but at the same time, you are draining vitamins and minerals at a faster rate, so consuming a lot of sugar as Peat says will lead to vitamin and mineral deficiencies unless you're eating a good amount of liver. But liver has more copper than liver, so it's not good for the zinc/copper situation.