Those Mysterious USDA Nutrient Data

April 23, 2004

Hi folks:

Does anyone have an answer to this one?

(I have previously noted an apparent error in the USDA's database.

When I pointed it out to them by email they did not reply. Is this

another? If so, is the database littered with errors? And if so, is

there much point in relying on these data to tell us what we want to

know? Lots of 'if's here. Perhaps there is a simple explanation and

the following is not an error.)

I took the nutrient data for 1700 calories-worth of broccoli from

Fitday.com, which presumably uses the data from the USDA. This is

what it showed for grams of macronutrients, along with the standard

multipliers and associated calories. (I have tried to 'force' this

table to format better).

----------------- grams multiplier kcals

----------------- ------ --------- ------

Fat -------------- 21.25 ----9---- 191.25

Protein --------- 180.93 ----4---- 723.72

Carbohydrate ---- 307.22 ----4--- 1228.88

Carb, minus fiber 131.15 ----4---- 524.60

Fiber, if ignored 176.07 ----0?----- 0.00

Fiber, if counted 176.07 ----4---- 704.28

Now as I said above, this data is for 1700 calories-worth of

broccoli, as was indicated near the top of the Fitday data table.

If you add up the calories for fat, protein and total carbohydrate

you get 2143.85 - 26.1% higher than the 1700 number for total

calories.

But if, instead, you assume the total carbohydrate grams number

includes the fiber, and that the fiber is not included in the calorie

total, and then add up the fat, protein and the 'carbohydrate minus

fiber' calorie numbers, you get 1429.57 calories, or 15.3% less than

the 1700 total.

Can someone please enlighten me as to what it is I am missing here?

These are not small discrepancies and appear much too big to be

accounted for by minor variations in the 'energy per gram' conversion

factors. Nor are these discrepancies confined to broccoli. All the

half dozen or so vegetables I checked have similar types of

discrepancies, but not, it seems, all the same percentage.

Rodney.

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