Do antioxidant micronutrients protect against the development and progression of knee osteoarthritis?

McAlindon TE, Jacques P, Zhang Y, Hannan MT, Aliabadi P, Weissman B, Rush D, Levy D, Felson DT · Arthritis and Rheumatism

The observation the whole vitamin C joint literature is built on. Among people who already had knee osteoarthritis, the middle and highest tertiles of vitamin C intake each carried a threefold lower risk of radiographic progression (adjusted OR 0.3, 95% CI 0.1-0.8 and 0.1-0.6), driven predominantly by less cartilage loss (OR 0.3, 95% CI 0.1-0.8), with less new knee pain too. Incident osteoarthritis showed no association with any nutrient, and the non-antioxidant control vitamins showed nothing — which is the internal control that makes the result interesting.

Population

Framingham Osteoarthritis Cohort, knees radiographed roughly a decade apart

Intervention

Dietary vitamin C, beta carotene and vitamin E intake by food frequency questionnaire, ranked in sex-specific tertiles

Limitations

Observational, with intake measured once by questionnaire and outcomes read from plain radiographs. Eighty-one incident and 68 progressive knees is a small number of events for tertile analysis. High vitamin C intake tracks fruit and vegetable intake, education and body weight, and no adjustment fully separates them. The authors call the findings preliminary and ask for confirmation; thirty years later a randomized confirmation still does not exist.