How do I calculate nutrient intake from food and dietary supplement sources combined?

Overview
If dietary supplement use was assessed using the Dietary Supplement Assessment Module (DSAM), nutrient intakes from food and dietary supplement sources combined may be calculated using Output File data in File 04 (Intake Properties Totals File) and File 12 (DSAM Total 24-hour Supplement Intake File). File 04 contains total daily nutrient intake estimates from the 24-hour dietary recall record (e.g., total daily vitamin C intake from the 24-hour dietary recall record). File 12 includes total daily nutrient intake estimates from the DSAM interview (e.g., total daily vitamin C intake from the 24-hour dietary supplement recall interview). By summing nutrient intake estimates from File 04 and File 12, total daily intake of nutrients from food and supplement sources may be calculated (e.g., vitamin C intake from 24-hour dietary recall record + vitamin C intake from 24-hour dietary supplement recall interview = total vitamin C intake from all sources combined).
 
Nutrients and Food Components for Which Totals May be Calculated
Nutrients with common units and definitions in File 04 and File 12 may be combined to calculate total intake estimates. A listing of variable names and file locations (column numbers) for nutrients with the same units in File 04 and File 12 are provided herein to assist in this process (pdf).  Comments are provided to explain the rationale for some of the combinations.

 

It is important to note that File 04 contains some nutrients and food components that are not included in File 12. For example, the variable ‘maltose’ is included in File 04 but is not available in File 12. Conversely, File 12 contains some nutrients and dietary supplement components that are not included in File 04. For example, the variable ‘chromium’ is included in File 12 but is not available in File 04. Consequently, total intake estimates from food and dietary supplement sources combined may not be calculated for these nutrients and food components.
 
It is also important to note that nutrients with different units or descriptions should not be combined unless conversion factors are available (see the Alerts and Footnotes in the pdf). For example, multiply the Synthetic Folate (folic acid) value in Supplements by a factor of 1.7 to convert to Dietary Folate Equivalents in Supplements or divide the Omega-3 Fatty Acids value in Supplements by 1000 to convert from milligrams to grams.
 
Dietary Supplement Intake Data Caveats
All nutrient values and other components assigned to dietary supplements in the DSAM database are limited to the information provided on the product’s Supplement Facts panel. Dietary supplement manufacturers have some discretion with respect to the information they provide on this panel. Most notably, they are not required to list on the Supplement Facts panel all of the nutrients the product contains. Since NCC does not calculate or impute nutrients for dietary supplements, the level of completeness for some nutrients and components may therefore be low. Due to this limitation, the nutrient totals may be under-estimated for some nutrients because the DSAM database does not contain the usual relationships to other nutrients or components.
 
Some examples of nutrients and other supplement components for which completeness may be an issue are as follows:
 
Amino Acids
The amount of protein contained in a ‘serving’ of a dietary supplement must be provided on the Supplement Facts panel if a product contains protein. The individual amino acids in a protein containing supplement may be listed, but inclusion on the Supplement Facts panel is not mandatory. As a result, amino acid information for protein containing products may be incomplete.
 
Fatty Acids
The amount of fat contained in a ‘serving’ of a dietary supplement must be provided on the Supplement Facts panel if a product contains fat. Likewise, the total saturated and trans fatty acid content must be listed. Other classes of fatty acids and individual fatty acids do not have to be provided. However, manufacturers may provide this information if they wish. Consequently, fatty acid information for fat containing products may be incomplete.
 
Soluble and Insoluble Fiber
The amount of fiber contained in a ‘serving’ of a dietary supplement must be provided on the Supplement Facts panel of fiber containing supplements. The amounts of soluble and insoluble fiber do not have to be provided. However, manufacturers may provide this information if they wish. As a result, soluble and insoluble fiber information may be incomplete for some fiber containing products.
 
Total Vitamin A
Starting in 2016 when the FDA published the final rule for the new Nutrition Facts panel for foods and Supplement Facts panel for dietary supplements, vitamin A could be included on product labels in either Retinol Activity Equivalents (RAE) (mcg) or International Units (IU).  The new Supplement Facts panel, which manufacturers could begin using anytime between the final rule and mandatory implementation in 2020, requires vitamin A to be listed on the label in the unit of mcg RAE whereas the old label required listing vitamin A in IU.  As a result of this labeling change, starting in NDSR 2020 vitamin A containing products in the DSAM database may include vitamin A values in either mcg RAE or IU.
 
There is no direct conversion factor from the vitamin A declared on labels in IU to mcg RAE, only individual conversion factors for provitamin A carotenoids and pre-formed vitamin (https://www.fda.gov/media/129863/download).  Consequently, Total Vitamin A Activity (International Units) (IU) from Files 04 and 12 can be combined and Total Vitamin A Activity (Retinol Activity Equivalents) (mcg) from Files 04 and 12 can be combined but the two cannot be combined to calculate one Total Vitamin A value from foods and supplements.
 
Total Vitamin E
Starting in 2016 when the FDA published the final rule for the new Nutrition Facts panel for foods and Supplement Facts panel for dietary supplements, vitamin E could be included on product labels in either Total Alpha-Tocopherol (mg) or International Units (IU). The new Supplement Facts panel, which manufacturers could begin using anytime between the final rule and mandatory implementation in 2020, requires vitamin E to be listed on the label in the unit of Total Alpha-Tocopherol (mg) whereas the old label required listing vitamin E in IU.  As a result of this labeling change, starting in NDSR 2020 vitamin E containing products in the DSAM database may include vitamin E values in either Total Alpha-Tocopherol (mg) or IU.
 
Without knowing the form of vitamin E (i.e. natural RRR-α-tocopherol vs. synthetic all-rac-α-tocopherol), there is no direct conversion factor from the vitamin E declared on labels in IU to mg of Total Alpha-Tocopherol.  Consequently, Vitamin E (International Units) (IU) from Files 04 and 12 can be combined and Vitamin E (Total Alpha-Tocopherol) (mcg) from Files 04 and 12 can be combined but the two cannot be combined to calculate one Total Vitamin E value from foods and supplements.