Almost every food product comes with nutritional information including the calorie content per serving. How much variation is likely to occur in the actual calorie content of the serving you would eat. For example, let’s say a loaf of bread defines a serving as one slice and states that there are 100 calories in a slice. Since every loaf of bread is made with different wheat, the actual calorie content of the slice will not be exactly 100. What is the likely range of variation? 90-110 calories? 80-120? Higher?
I’m not specifically only interested in bread, but in any food which is likely to vary in calorie content per serving.
My WAG is that if you went to the trouble to figure out what the caloric content of any given piece of bread, it would turn out to be fairly close to what is stated on the package +/- 2-3%. Why? Because they have to have done some rigorous testing and averaging to arrive at the value they print.
They probably analyzed dozens (hundreds?) of pieces to arrive at whatever value they chose. While there are some variations in production, the basic ingredients are the same so that answer for any given piece can’t be too far off the mark.
Food labeling falls under the FDA’s jurisdiction, so they probably have rules regarding this. I spent a few minutes searching their website and didn’t see anything.
More than you would ever want to know about how the FDA wants manufacturers to analyze & label your food can be found here. Basically, it boils down to the following:
[ul][li]Nutrients such as vitamins, minerals, protein, total carbohydrate, dietary fiber, other carbohydrate, polyunsaturated and monounsaturated fat, or potassium that occur naturally in the product must be present at 80% or more of the labeled value to be in compliance. [/li][li] Nutrients such as vitamins, minerals, protein, dietary fiber, or potassium that are artificially added to foods must be present at 100% or more of the labeled value to be in compliance. [/li][li] Nutrients such as calories, sugars, total fat, saturated fat, cholesterol, and sodium—in other words, stuff you don’t want to get too much of—must be present at 120% or less of the labeled value.[/li][/ul]
Now, of course, you’re correct in saying that food is a natural product, and doesn’t roll off an assembly line with exactly 6.523 grams of sugar in it. So what the FDA recommends that manufacturers do is test samples of their food, figure out roughly what the spread is, and then label their foods such that 95% (19 out of 20) of their packages will be in compliance with the guidelines.
It depends, if your MegaConglomorateCorp selling a million units of an item per day, then you can afford to have fairly sophisticated techniques. If your IttyBittyHippieCommune, then you might not have the resources to do it properly. You only get fined if you get caught and the FDA doesn’t routinely do it’s own, independant analysis so some companies can try and skate under the radar.
a calorie is a unit of heat. to get the calories in a particular food that food is placed in a fancy box and burned completely. the composition of the food and such is hashed out in another process. the key here is that calories are heat from breaking down food.
if you eat a double quarter pounder with cheese with 700 calories did your body absorb all 700 calories worth of energy? i bet if you were to fish out that brick and dry it off there would still be energy to burn in there.
the point is, 10 calories here or there in error on product labels is not a big deal. use the calorie counting tools available to you and track for changes or trends. accept the grey area.
one calorie counting site i like a great deal is www.fitday.com. it’s free and great for tracking treands.
for thought…
say you eat a 5-gallon bucket of corn…how many calories do you think your body really absorbed?