Query: In which year were nutrients categorized into their two respective categories?
Context: The list of nutrients that people are known to require is, in the words of Marion Nestle, "almost certainly incomplete". As of 2014, nutrients are thought to be of two types: macro-nutrients which are needed in relatively large amounts, and micronutrients which are needed in smaller quantities. A type of carbohydrate, dietary fiber, i.e. non-digestible material such as cellulose, is required, for both mechanical and biochemical reasons, although the exact reasons remain unclear.