I have taken ascorbic acid (vitamin c) since age of 20 years, in various forms. I am now 67 years of age and only learnt 6 months ago that there are 2 different ascorbic acids in nearly all vitamin c supplements. One is of no use whatsoever and irritates the stomach, while the other, L ascorbic acid does the good and doesn't affect the stomach. I searched and found this product is pure L ascorbic acid only. I have been using it 1 capsule 3 time daily ever since. what a difference. No bad effect on the tummy and works extremley well in helping to prevent and fight of viruses and bugs.