Sodium nitrite change in US meat curing practices resulted in a 69% decrease in average nitrite content. This event preceded the beginning of a dramatic decline in gastric cancer mortality. Around 1970, it was found that ascorbic acid (vitamin C), an antioxidant, inhibits nitrosamine formation. Consequently, the addition of at least 550 ppm of ascorbic acid is required in meats manufactured in the United States. Manufacturers sometimes instead use erythorbic acid, a cheaper but equally effective isomer of ascorbic acid. Additionally, manufacturers may include α-tocopherol (vitamin E) to further inhibit nitrosamine production. α-Tocopherol, ascorbic acid, and erythorbic acid all inhibit nitrosamine production
Vitamin time it was shown that not all vitamins are amines, the word was already ubiquitous. In 1920, Jack Cecil Drummond proposed that the final "e" be dropped to deemphasize the "amine" reference, after researchers began to suspect that not all "vitamines" (in particular, vitamin A) have an amine component. In 1930, Paul Karrer elucidated the correct structure for beta-carotene, the main precursor of vitamin A, and identified other carotenoids. Karrer and Norman Haworth confirmed Albert Szent-Györgyi's discovery of ascorbic acid and made significant contributions to the chemistry of flavins, which led to the identification of lactoflavin. For their investigations on