Limitations of Nutrition Facts Labels
Entering nutrition information for items that are not already in the USDA database starts with requesting the most complete nutrition data from the distributor, vendor or manufacturer of the product. Refer to the article Collecting Nutrition Data for details.
Request nutrition values for a 100g sample of the product. This is the standard for reporting nutrition data.
If the nutrition information reported is incomplete, the nutrition analysis of any recipe containing that ingredient will also be incomplete.
Total nutrient weight for a 100g sample should equal 100g. Deviations from 100g indicate incomplete nutrition data. See the article Nutrient Deviation for details.
Deviations in nutrition data are most often caused by unreported water and ash values. When requesting a 100g sample analysis of the product, ask for data that includes water and ash.
Nutrition Facts labels are inadequate as a source of nutrition information for the following reasons:
1. The values are rounded. This is a built-in inaccuracy.
2. The sample sizes are often very small. This causes some nutrients to be listed as 0, when they are actually present.
3. Not all of the nutrients are reported. This causes the total nutrient weight to deviate from the serving size.
Also, note that if a nutrition report says "<" (less than) or ">" (greater than), there is not enough information to report a specific value. You can mark it as n/a, or ask the supplier to clarify the value.