Across 7 studies, 6 reported beneficial effects (predominantly small to moderate in size) on reducing pain. Evidence is strongest for post-surgical pain and clinical conditions such as carpal tunnel syndrome and oral health issues. Effects were observed at a median study duration of 60 days, with some studies showing benefit within days.
Caveats: Available evidence is overwhelmingly positive — clinical literature in this area is subject to publication bias (null-result studies are less likely to be published or indexed). Several studies used vitamin C in combination with other ingredients (e.g., vitamin E, curcumin), confounding the isolated effect. The neutral study suggests a possible dose-response threshold, with pain reduction only observed at higher intravenous doses (300–600 mg/kg/day) in cancer patients. Most studies were conducted in clinical populations, so results may not generalize to healthy individuals with nonspecific pain.
Vitamin C may be an effective substitute for glucocorticoids for reducing morphine use and the risk of nausea or vomiting and for improving joint function after THA without side effects causing blood glucose fluctuations.
from: Efficacy of Vitamin C as Glucocorticoid Substitute for Reducing Pain and Inflammation AfteThe vitamin C group reported lower pain and itching levels (itch: P = 0.02; pain: P = 0.00).
from: Gingival depigmentation by conservative injectable vitamin C in comparison with scalpel suThe vitamin C group reported lower pain and itching levels (itch: P = 0.02; pain: P = 0.00).
from: Gingival depigmentation by conservative injectable vitamin C in comparison with scalpel suNo major side effects were noticed.
from: Clinical usefulness of nutraceutics with acetyl-L-carnitine, α-lipoic acid, phosphatidylseEither treatment was associated with a significantly lower rate of postoperative nausea and vomiting.
from: Efficacy of Vitamin C as Glucocorticoid Substitute for Reducing Pain and Inflammation AftePain scores were significantly lower in the vitamin C group on day 2
Compared with patients in the control group, those who received vitamin C or dexamethasone reported a significantly lower VAS pain score on postoperative day 1
Supplementation with ... a combination of vitamin C and E significantly improved measures of pain
The vitamin C group reported lower pain and itching levels (pain: P = 0.00)
as well as BCTQ symptoms subscale, and the pain.
The administration of sodium ascorbate at dose of 100 to 300 ... showed statistically significant improvements in quality of life ... However, only the 300 to 600 mg/kg/day dose demonstrated a statistically significant reduction in pain
NBF gel may provide clinical benefits as an adjunct to non-surgical periodontal therapy, with reported improvements in pain-related outcomes