Prolonged exposure to high doses of vitamin C seems to make osteoarthritis worse. This suggests that people should not exceed the recommended dietary allowance for vitamin C. Previous short-term studies have indicated that vitamin C might be protective against osteoarthritis, but long-term treatment with vitamin C has not been studied, the researchers note in the medical journal Arthritis & Rheumatism.
Dr. Virginia B. Kraus from Duke University Medical Center in Durham, North Carolina, and colleagues investigated the effects of 8 months’ exposure to low, medium, and high doses of vitamin C on the development of knee arthritis in guinea pigs.
The low dose was the equivalent of the amount needed to prevent scurvy, the medium dose represented that obtained by a person consuming five fruits and vegetables daily, and the high dose to match that shown in a previous study to slow the progression of arthritis in guinea pigs.
The guinea pigs exposed to the highest dose in the current study had more severe arthritis than the animals exposed to low or medium doses, the investigators report.
This study highlights the potential drawbacks of long-term, high-dose vitamin C intake on joint health.
Dietary intake should not be supplemented above the currently recommended dietary allowance (90 mg/day for men and 75 mg/day for women).
In addition to a balanced diet, one multivitamin per day is sufficient to achieve the recommended amount of vitamin C.
Besides the association with arthritis, long-term use of high dose vitamin C has been linked with diarrhea, iron problems, and kidney stones, Kraus added.