The Nutrition Dex

Dietary Assessment

SR Legacy

Also known as: Standard Reference Legacy, SR28

The frozen April 2018 final release of the USDA's Standard Reference database, preserved inside FoodData Central as the historical reference backbone for legacy research.

By James Oliver · Editor & Publisher ·

Key takeaways

  • SR Legacy is the archived final release (April 2018) of the USDA National Nutrient Database for Standard Reference.
  • It contains roughly 7,800 foods, each analysed or compiled under the pre-FDC methodology.
  • It is frozen — no new entries, no updates. Research reproducibility is the point.
  • For current analytical data, Foundation Foods has supplanted SR Legacy; for historical comparability, SR Legacy remains the anchor.

SR Legacy — formally, the Standard Reference Legacy release — is the April 2018 final version of the USDA's long-running National Nutrient Database for Standard Reference (NNDSR), preserved unchanged inside FoodData Central as the historical anchor dataset. It contains approximately 7,800 foods, each with compiled nutrient profiles drawn from USDA analytical work, industry submissions, and the scientific literature between 1950 and 2018.

Why it is frozen

When FoodData Central launched in April 2019, the USDA split the old NNDSR into two futures. The ongoing analytical programme moved into Foundation Foods, which applies stricter sampling and uncertainty documentation. The legacy content — seven decades of accumulated compilation — was archived as SR Legacy and will receive no further updates. The freeze is deliberate: research conducted against SR28 (the last NNDSR release) remains reproducible against SR Legacy indefinitely.

What it still gets used for

Two use cases keep SR Legacy live. First, any longitudinal dietary-assessment study that began before 2019 will be written against SR and should remain so — switching midway would introduce a dataset-discontinuity artefact into the time series. Second, foods never re-analysed for Foundation Foods remain available only through SR Legacy; most obscure produce items, regional specialties, and less-studied cuts of meat have no Foundation equivalent and still must be cited from SR.

Methodological caveats worth naming

The NNDSR assembly methodology, particularly for pre-2000 entries, is uneven. Some foods were analysed directly under USDA protocols. Others were imputed from analogues. Others were compiled from submitted industry data or foreign databases. Uncertainty estimates are sparse and inconsistent. Researchers working from SR Legacy figures should check the data type field on each entry — analytical, calculated, assumed, or borrowed — rather than treating all SR Legacy figures as equivalent. A 2018 review in Food Chemistry flagged pre-1980 SR entries for carotenoids and vitamin E as particularly stale.

When to cite it, when not

Cite SR Legacy for historical comparability, for foods absent from Foundation Foods and FNDDS, and for the portion of any paper that references the 2018-and-earlier literature. Do not cite SR Legacy as current state of the art — Foundation Foods supersedes it for every food Foundation covers, and the two should not be mixed in a single table without disclosure.

References

  1. "SR Legacy documentation". USDA FoodData Central .
  2. Haytowitz DB, Ahuja JKC, Wu X, Somanchi M, Nickle M, Nguyen QA, Roseland JM, Williams JR, Patterson KY, Li Y, Pehrsson PR. "USDA National Nutrient Database for Standard Reference, Legacy Release". USDA Agricultural Research Service , 2019 — doi:10.15482/USDA.ADC/1529216.

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