Interpreting Macronutrient Percentages and Converting Their Format

[DocHolliday]

Hi.

 

I need some math help/clarification.

 

I'm writing about some nutritional issues and searching for some research on the macronutrient content (protein/fat/carbohydrate) of wild fruits so I can compare them to commercially grown fruits.

 

I've found an excellent study looking at exactly what I want. You can read the PDF here: 2008 Milton, K. Macronutrient Profiles of 19 Fruit Species from Barro Colorado Island, Panama. Neotropical Primates 15 (1):1- 5. http://nature.berkeley.edu/miltonlab/pdfs/neotropical.pdf

 

However, the numbers don't work, as I need them in a percentage of calories model, which is how most macronutrient info is presented. The study lists the fruits macronutrient content as a percentage of dry weight.

 

To confuse me even more, for some reason the percentage of dry weight from the three categories doesn't add up to 100 percent. The water is all evaporated out of it, which leaves only the flesh. There are only three macronutrients, so if the weight isn't a carb/protein/fat, then what is it?

 

So first, can anyone explain the above lack of 100 percent total question.

 

Second, is there any way I can convert this information into a percentage of calories model?

 

If it helps, there are 4 calories per gram of protein and carbs, and 9 calories per gram of fat.

 

If this is just too complicated and you think I should ditch this study and look for something else, let me know. Math is not my area, so I'm a bit out of my league.

 

Thanks in advance.

 

-Andrew

 

 

[Xittenn]

Your first question is really entirely a question about biochemistry. The note above the chart clearly states the percentage of dry weight(Total Nonstructural Carbohydrates) so you might first want to find the definition of a nonstructural carbohydrate.

 

The second part is pretty simple mathematics. If you have the percentage by weight and you know what the weight translates to in terms of calories it follows to do a simple conversion.

 

1) decide on a set quantity of the dried fruit mass in terms of dry weight

 

2) multiply this weight by the percent that is each constituent(in decimal form .10 == 10%)

 

3) multiply each constituents weight by the amount of calories that 1 unit of the constituent would theoretically possess

 

4) sum the calories of each constituent

 

5) divide the calories of a selected constituent by the total calories of the mass to get the decimal fraction

 

You might want to find somebody who can help you set up a spreadsheet to quickly do the conversion for you. I don't know if this really helps though, if your document isn't presenting all of the information that you require.

[John Cuthber]

"There are only three macronutrients, so if the weight isn't a carb/protein/fat, then what is it?"

Bone, fibre, minerals, anything else that was round the place at the time.