Calculating food Carb %
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Janet & Binky (GA)
Active Member
Well, I disagree with the assertion that you'll get reliable results using the guaranteed minimum values. But if it's used with the actual values, the calculations seem to be reasonably correct. (They seem to be using 8.7 kcals/g for fat rather than the standard 8.5, but that's not a big deal.)
I have an Excel sheet which calculates percent of calories from each of the components at http://binkyspage.tripod.com/foodfaq.html.
-- Janet
I have an Excel sheet which calculates percent of calories from each of the components at http://binkyspage.tripod.com/foodfaq.html.
-- Janet
Seattlebrian
Active Member
I was thinking that since it uses the min values from the can, that it would yield a "Max" carb %. Not the actual carb %.
Might be useful for companies that absolutely refuse to give real numbers.
I was also thinking, I could look at the javascript "guts" of it and rewrite a different version that would be more useful to people here. I could see people getting % of carbs confused with % of calories from carbs.
Might be useful for companies that absolutely refuse to give real numbers.
I was also thinking, I could look at the javascript "guts" of it and rewrite a different version that would be more useful to people here. I could see people getting % of carbs confused with % of calories from carbs.
Monique & Spooky
Very Active Member
Here is the "formula"
When we talk about "less than 10% carbs" we are reffering to the fact that the food has say 8% of it's calories from carbohydrates. The actual carbohydrate amount (scientifically Nitrogen free extract=NfE) in the orginal or dry substance is calculated as follows using as fed values (not the Minimum and maximim given on most labels)
Subtract the as fed values of protien, fat, ash, fiber, and moisure from 100%
100% - crude protien% - crude fat% - ash% - crude fiber% - moisture% = NfE (carbohydrate)%
example canned food: 100% - 10% - 5,5% - 2,5% - 1,0% - 79% = 2% NfE
example dry food: 100% - 30% - 10% - 6,5% - 2,5% - 9% = 42% NfE
To calculate the carbohydrate content in the dry substance
canned food: 100% - 79% moisture = 21% dry matter (DM) = 0,21
dry food: 100% - 9% moisture = 91% dry matter (DM) = 0,91
Then divide the carbohydrate procent by the DM
canned food: 2% NfE / 0,21 = 9,52% carbs in the dry substance
dry food: 42% NfE / 0,91 = 46,15% carbs in the dry substance
To calculate calories each component has a differnt calorie value (depending on digestability typically the modified Atwater-Factor is used:
Protein: 3,5 kcal/g, Fat: 8,5 kcal/g, NfE (carbohydrates): 3,5 kcal/g
The Energy in kcal / 100 g Food is calculated as follows:
(%Protein * 3,5 kcal/g) + (%Fat * 8,5 kcal/g) + (%NfE * 3,5 kcal/g)
When we talk about "less than 10% carbs" we are reffering to the fact that the food has say 8% of it's calories from carbohydrates. The actual carbohydrate amount (scientifically Nitrogen free extract=NfE) in the orginal or dry substance is calculated as follows using as fed values (not the Minimum and maximim given on most labels)
Subtract the as fed values of protien, fat, ash, fiber, and moisure from 100%
100% - crude protien% - crude fat% - ash% - crude fiber% - moisture% = NfE (carbohydrate)%
example canned food: 100% - 10% - 5,5% - 2,5% - 1,0% - 79% = 2% NfE
example dry food: 100% - 30% - 10% - 6,5% - 2,5% - 9% = 42% NfE
To calculate the carbohydrate content in the dry substance
canned food: 100% - 79% moisture = 21% dry matter (DM) = 0,21
dry food: 100% - 9% moisture = 91% dry matter (DM) = 0,91
Then divide the carbohydrate procent by the DM
canned food: 2% NfE / 0,21 = 9,52% carbs in the dry substance
dry food: 42% NfE / 0,91 = 46,15% carbs in the dry substance
To calculate calories each component has a differnt calorie value (depending on digestability typically the modified Atwater-Factor is used:
Protein: 3,5 kcal/g, Fat: 8,5 kcal/g, NfE (carbohydrates): 3,5 kcal/g
The Energy in kcal / 100 g Food is calculated as follows:
(%Protein * 3,5 kcal/g) + (%Fat * 8,5 kcal/g) + (%NfE * 3,5 kcal/g)
Janet & Binky (GA)
Active Member
Correct, it would give you a max carbohydrate value, unless water, ash, and fiber (which are maximum values) were vastly overstated.
The real problem, I think, is that companies tend to seriously understate the fat value of the food. This has led to some really bad estimates -- for example, one food where the GA values indicated that the carbohydrate content was over 25% of calories, whereas in fact it was around 10%.
-- Janet
The real problem, I think, is that companies tend to seriously understate the fat value of the food. This has led to some really bad estimates -- for example, one food where the GA values indicated that the carbohydrate content was over 25% of calories, whereas in fact it was around 10%.
-- Janet
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