In the case of nuts, the definition of a vieno in so many spoonfuls is fairly accurate. This is done only as an illustration, and not continued throughout the table. The student should use only the second column of the table for rough work, and to help him figure the approximate amount of one vieno.
The third column of the table, which gives the number of vienos or the amount of heat-energy in one pound, is the column to which the student should refer in his work. A pound of food referred to in this column invariably means one pound of the edible portion.
Simple method of reducing food to vienos
The way for the student to calculate the amount of food in one vieno is to take a pound of the food that he is to use and divide it equally into as many portions as the number in the third column. For example: If one pound of wheat is given as equal to sixteen vienos, the student should weigh a pound of wheat and divide it into sixteen portions, and each of these portions will equal one vieno.
The nitrogen factor simplified
The fourth column of the table gives the approximate nitrogen factor; that is, the percentage of nitrogen by weight in one vieno. This column is to be used for computing the amount of nitrogen in the diet under all ordinary circumstances. The student should take the total number of vienos of each food and multiply this number by the nitrogen factor. The product will be the approximate amount of the nitrogen consumed, expressed in grams. This is the direct method of ascertaining the amount of available nitrogen in food.
Grams reduced to vienos
If in reading other works, the student finds the amount of nitrogen given in decigrams, he needs only to divide by ten in order to reduce it to this system, as a decigram is one-tenth of a gram. Likewise, protein can be reduced to grams, or decigrams, by a simple process of multiplication and division, as follows: Sixty grams of protein contains practically ten grams (one hundred decigrams) of nitrogen. Divide the amount of protein by six to change protein to the nitrogen unit. That is (Protein ÷ 6) = amount of nitrogen in grams.
The old-fashioned food table gave the amount of protein in per cent by weight, making it necessary to weigh the food, figure the amount of protein by multiplying the weight by the per cent, and then reducing this according to the rule given above. I explain this so that the student may be able to compare results expressed in the old table, with the vieno method, but in all practical work the student should use only this direct method which is much more simple and accurate.