Complex sentence: Use of pure oats in a gluten-free diet remains controversial because a small proportion of people with celiac disease react to pure oats, but offers improved nutritional value from the rich content of oat protein, vitamins, minerals, fiber, and lipids.
Split into simpler sentences: Use of pure oats in a gluten-free diet remains controversial because a small proportion of people with celiac disease react to pure oats. The inclusion of pure oats in a gluten-free diet may increase the diet's nutritional value, because are an important source of proteins, vitamins, minerals, fibre, and lipids.