Reduced pain from osteoarthritis in hip joint or knee joint during treatment with calcium ascorbate. A randomized, placebo-controlled cross-over trial in general practice

Jensen NH · Ugeskrift for Laeger

The one randomized placebo-controlled trial of vitamin C with an osteoarthritis pain endpoint. Intention-to-treat, calcium ascorbate beat placebo on the 100 mm pain scale by a median 4.6 mm (95% CI 1.2-8.0, p=0.0078 by analysis of variance), with the Lequesne function index 0.56 (95% CI 0.04-1.08, p=0.036) and patient preference (p=0.012) following. The author's own reading is in the paper: the effect is less than half what is commonly reported for NSAIDs, and the finding would be of interest if it reproduced at a dose people could sustain.

Population

Patients with radiographically verified symptomatic hip and/or knee osteoarthritis, ten general practices in Denmark

Intervention

2 g calcium ascorbate daily, one gram twice a day, for 14±3 days

Comparator

Identical coated placebo tablets, crossover with a 7-day washout

Limitations

Blinding was incomplete and the author says so: the taste of the ascorbate and placebo dragées could be told apart if a participant chewed them, leaving bias unexcludable. He also calls the sample not quite large enough, and participants stayed on their usual analgesics instead of a defined escape medication, with six changing analgesic use during the trial. The dose is above what the paper itself calls acceptable for long-term treatment — it names one gram a day as the ceiling almost everyone tolerates, with urinary stones from hyperoxaluria and hyperuricaemia the reason. Fourteen days per arm is far too short for a structural claim and short for a symptomatic one, and a 4.6 mm difference sits well below the 15-20 mm usually treated as the minimal clinically important difference. One 88-year-old man withdrew with severe joint pain while on ascorbate. Published in Danish with an English abstract; the calcium in calcium ascorbate is an uncontrolled co-intervention. The trial was prompted by letters users sent the product's distributor, and follows an unpublished pilot of 54 people.