Every individual responds to substances differently.
Vitamin C is no exception. Admittedly, there were relatively few older patients in my practice. Infants, small children, and teenagers tolerate ascorbic acid well and can take, proportionate to their body weight, larger amounts than adults. Older adults tolerate lesser amounts and have a higher percentage of nuisance difficulties. Patients with multiple food intolerances may have more difficulties but should attempt taking ascorbate because of benefits often obtained.