New Findings on Ascorbic Acid and Osteoarthritis

In an article published in the June issue of Arthritis & Rheumatism, researchers found that prolonged high doses of ascorbic acid worsened the severity of spontaneous osteoarthritis in male guinea pigs. Based upon results from previous studies suggesting ascorbic acid might be protective against OA by slowing its progression, it was hypothesized that pathologic cartilage degradation in OA could be prevented by ascorbic acid supplementation. The researchers studied the effects of eight months of exposure to low, medium, and high doses of ascorbic acid in relation to the development of histological OA. The low-dose group received 2.5 to 3mg of ascorbic acid daily, which previous studies had shown to exceed the minimum amount needed to prevent scurvy. The medium-dose group received 30mg/day, the standard amount of ascorbic acid in guinea pig chow, and resulted in plasma levels comparable with those of a person consuming 200mg/day (5 fruits and vegetables daily). The high-dose group received 150mg/day, the amount previously shown to slow the progression of OA in guinea pigs. Ascorbic acid was shown to activate latent transforming growth factorβ (TGFβ), which has been shown to cause OA-like changes following prolonged intraarticular exposure. Therefore, it was concluded that TGFβ might be responsible for the negative effects of prolonged, high-dose ascorbic acid supplementation. With this in mind, the authors suggested that ascorbic acid intake not be supplemented above the current recommended dietary allowance of 90mg/day for men and 75mg/day for women. Kraus V, Huebner J, Stabler T, et al. Ascorbic acid increases the severity of spontaneous knee osteoarthritis in a guinea pig model. Arthritis & Rheumatism. 2004;50:1822-1831. Return to Top