"There's essentially no difference in the fiber or nutrient content of rolled and steel-cut oats" - Diabetic Gourmet Magazine
The only difference is in how they are processed. Steel cut oats are chopped into little pieces, whereas rolled oats are steam-softened and then flattened. Steel cut oats provide a chewier, denser textured oatmeal, but take longer to cook - usually an overnight soaking.
Choosing between the two is a matter of personal taste preference. A nice in-between alternative is a "thick" rolled oat, usually available in the bulk aisles of natural food stores like Wild Oats.
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