Stability of thiamine and vitamins E and A during storage of enteral feeding formula.

The content of thiamine (vitamin B(1)), vitamin E (alpha-, gamma-, and delta-tocopherol) and vitamin A (all-trans-retinol and 13-cis-retinol) in five commercial enteral feeding formulas was studied. These formulas provide a large amount of vitamins: 2.5--3, 3.1, and 1.6-fold above the U.S. daily recommendations (U.S. RDA) for thiamine, vitamin E, and vitamin A, respectively. The stability of thiamine and vitamins E and A of two of the enteral feeding formulas was followed throughout 9 months of storage in the dark at 4 degrees, 20 degrees, and 30 degrees C. According to our results in all of the storage conditions studied, the enteral formula covered the U.S. RDA levels for thiamine and vitamin E, but in the case of vitamin A the U.S. RDA requirements are met only when the enteral sample has been kept in storage less than 3 months. After 6 months of storage, the decrease in vitamin A was so drastic that the level of vitamin covered only 0.9--0.3-fold of the U.S. RDA and after 9 months it covered only 0.2--0.0-fold of U.S. RDA. The manufacturer shelf life of the formula studied was 1 year; and, because enteral feeding solutions are often placed in storage conditions of uncontrolled temperature and humidity, these results should be taken into consideration with regard to the shelf life.