You can definitely lower the carbs and calories in German Christmas bread and make it more suitable for diabetics. Firstly, use a zero-calorie, zero-carb sugar replacement such as monk fruit or erythritol. Secondly, since raisins are high in sugar and carbs, you can omit them or reduce them and instead add a few more blanched, sliced almonds. That will help make your Stollen more diabetic-friendly.