Modern methods for measuring calories are technically advanced. Shelton is partially correct here. Humans cannot live well exclusively on refined foods, and we do need vitamins and minerals, for which vegetables and fruits are an excellent source. Back in Shelton's time, it appears that some conventional medical writers overemphasized the value of calories. Inasmuch as Shelton's criticism here is a reaction to now- outdated views extant during his time, we observe that Shelton's criticism is no longer important.
Calories are the least important nutritional factor.
Shelton goes on to say that calories measure only the combustible part of foods. Here Shelton is grossly overemphasizing that calories are only a partial measure, and this may lead the reader to the false conclusion that calories are worthless and can be ignored. This part of Shelton's writings borders on demagoguery, in my opinion. There is an additional irony here. In context, the preceding remark by Shelton was made concerning the limitations of the calorie measure.