National Nutrient Database for Standard Reference.
FoodData Central API is a free Health API that requires apiKey authentication, is served over HTTPS and has unconfirmed CORS support.
USDA FoodData Central produces thorough resources for navigating and understanding nutritional info to support dietary choices and nutritional analysis.
Details from fdc.nal.usda.gov.

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The FoodData Central API is provided by USDA FoodData Central (fdc.nal.usda.gov). USDA FoodData Central produces thorough resources for navigating and understanding nutritional info to support dietary choices and nutritional analysis.
Yes. The FoodData Central API is listed in the Health category of the public-apis directory, which only includes APIs that are free or have a free tier. Check its documentation for rate limits and paid plans.
Yes. The FoodData Central API uses apiKey authentication, so you need to register for credentials before making requests.
CORS support for the FoodData Central API is unknown. Test a request from the browser, and fall back to a server-side call if it is blocked.
Yes. The FoodData Central API is served over HTTPS, so it's safe to use in production.