Gentle and Non-Acidic. Non-Acidic. Unique Vitamin C Formula. 24-Hour Immune Support. American health. Ester-C is a unique, breakthrough Vitamin C formula containing naturally occurring metabolites. Metabolites help enhance the retention of Vitamin C by your white blood cells, an important part of your immune system. Ester-C s water-based manufacturing process neutralizes pH, making it non-acidic and gentle on the stomach. In a daily 1,000 mg dose, Ester-C delivers 24-hour immune support so once a day is all you need.