Nutrition Facts Determining Calories from fat

[hazelrah]

Hi Jeff,

Sorry to bother you with yet another in my perpetual list of tedious questions. I'm wondering how this is actually determined. Does the laboratory actually take the food and chemically break it down into the fat/carb/protein components and then burn the fat portion separately to measure the calories?, do they break them down into the componets and just weigh them and calculate the equivalent calories from the weight?,...
I'm looking at a label and the portion size is 30g, but the total of the fat, carb and protein grams is only 23g. I'm wondering what the other 7g are. Is it all minerals?

Thanks.

Mark

[JeffN]

The problem is that you and I think they are using an exact system when in fact, they are using one of several systems and all of the systems have some range of error built into them and some of them round off numbers.

If you do the math on the Carbs, Proteins and Fats on most Nutrition Facts labels and use the standard 4/4/9, you will always find discrepancies. Even just going from grams of fat to calories from fat.

These articles/discussions will help...

http://www.nutribase.com/449.html

https://www.accessdata.fda.gov/scripts/ ... on%20label

https://www.fda.gov/regulatory-informat ... n-labeling

http://ajcn.nutrition.org/content/86/6/1649.full

This is the most descriptive

http://www.gpo.gov/fdsys/pkg/CFR-2004-t ... c101-9.xml

It says…

(1) “Calories, total,” “Total calories,” or “Calories”: A statement of the caloric content per serving, expressed to the nearest 5-calorie increment up to and including 50 calories, and 10-calorie increment above 50 calories, except that amounts less than 5 calories may be expressed as zero. Energy content per serving may also be expressed in kilojoule units, added in parentheses immediately following the statement of the caloric content.

(i) Caloric content may be calculated by the following methods. Where either specific or general food factors are used, the factors shall be applied to the actual amount (i.e., before rounding) of food components (e.g., fat, carbohydrate, protein, or ingredients with specific food factors) present per serving.

(A) Using specific Atwater factors (i. e., the Atwater method) given in Table 13, “Energy Value of Foods—Basis and Derivation,” by A. L. Merrill and B. K. Watt, United States Department of Agriculture (USDA) Handbook No. 74 (slightly revised, 1973), which is incorporated by reference in accordance with 5 U.S.C. 552(a) and 1 CFR part 51 and is available from the Office of Nutritional Products, Labeling and Dietary Supplements (HFS-800), Center for Food Safety and Applied Nutrition, Food and Drug Administration, 5100 Paint Branch Pkwy., College Park, MD 20740, or may be inspected at the Office of the Federal Register, 800 North Capitol St. NW., suite 700, Washington, DC.;

(B) Using the general factors of 4, 4, and 9 calories per gram for protein, total carbohydrate, and total fat, respectively, as described in USDA Handbook No. 74 (slightly revised 1973) pp. 9-11, which is incorporated by reference in accordance with 5 U.S.C. 552(a) and 1 CFR part 51 (the availability of this incorporation by reference is given in paragraph (c)(1)(i)(A) of this section);

(C) Using the general factors of 4, 4, and 9 calories per gram for protein, total carbohydrate less the amount of insoluble dietary fiber, and total fat, respectively, as described in USDA Handbook No. 74 (slightly revised 1973) pp. 9-11, which is incorporated by reference in accordance with 5 U.S.C. 552(a) and 1 CFR part 51 (the availability of this incorporation by reference is given in paragraph (c)(1)(i)(A) of this section;

(D) Using data for specific food factors for particular foods or ingredients approved by the Food and Drug Administration (FDA) and provided in parts 172 or 184 of this chapter, or by other means, as appropriate; or

(E) Using bomb calorimetry data subtracting 1.25 calories per gram protein to correct for incomplete digestibility, as described in USDA Handbook No. 74 (slightly revised 1973) p. 10, which is incorporated by reference in accordance with 5 U.S.C. 552(a) and 1 CFR part 51 (the availability of this incorporation by reference is given in paragraph (c)(1)(i)(A) of this section).

And, of course, to put it all in perspective, my article on it...

http://www.jeffnovick.com/RD/Q_%26_As/E ... alues.html

In Health
Jeff

[hazelrah]

Thanks,

As I was reading the label I was just remembering my quant chemistry courses and kind of wondering if the machinery had become so good that it could be trusted. It's a long time ago, but I would not like to bet my life on the quantitative output that came out of any of my labs. I guess I figured the whole process would be so automated and that so much checking would be done to ensure that things balanced out that I was surprised to see the number of grams did not add up.

Thanks again for the response. It's more curisoity on my part than any attempt to come up with some kind of scheme using the details on the label. According to a book I had, some guy was trying to determine how cold he needed to make his whiskey so that the amount of heat needed to bring it to body temperature would offset the number of calories in the whiskey. But he did not realize the calories in food were actually KIlocalories so he was off by a factor of 1000. The whole discussion of the numbers on labels always reminds me of that.

Mark