I read the following interesting snippet in the health section of a newspaper:

"Vitamin C is needed for the production of collagen. Each disc in the spine contains collagen and this is largely responsible for the strength and resilience of the intervertebral discs. ... Researchers discovered that people who suffered from back pain because of damaged discs found their pain reduced after taking Vitamin C daily. ... Research suggests that for this to be effective high daily doses of 1,500-2,000mg are needed."

Perhaps this explains the puzzle of why high doses of Vitamin C (like other collagen-building supplements such as glucosamine) are said by some people to be bad for Dupuytren's patients.