Vitamin C - How Much is Too Much?

The recognition that adequate amounts of vitamin C are vital for health was made a long time ago when Captain Cook demonstrated that citrus fruit prevented scurvy in his sailors.

The recommended daily allowance (RDA) is 60 mgs though there is now much debate about whether higher daily doses will provide benefits for adults, such as prevent cataract and reduce certain types of cancer.

An important and unresolved issue is defining the dosage that produces the maximum level of vitamin C in the blood or other bodily tissues. Some studies have found that intakes higher than 90 to 150 milligrams (mg) do not continue to raise levels of the vitamin in the body, suggesting that higher doses are useless. However, two other recent analysis have identified 200 mg as the highest effective dose.

Traditionally, taking too much of a water soluble vitamin like vitamin C in supplement form was not a concern, since health professionals believed any excess amount would be excreted harmlessly in the urine. Recently, however, large (greater than 1,000 mgs daily) doses were found to increase urinary excretion of a substance called oxalate, raising the risk of kidney stones. As a result, the National Institutes of Health has listed an upper supplement-safety limit of 1,000 mg of vitamin C daily.

There is now some concern that even 1000 mgs a day may be too high. Recent research found that vitamin C supplements in doses of 500 mg functioned both as an antioxidant to prevent genetic damage that could lead to cancer, and as a pro-oxidant that promoted DNA damage.

Summary
At this time, a vitamin C supplement of no more than 200 mgs per day seems appropriate. If you feel compelled to take more, then it would be wise for you to consult a doctor or registered dietitian before you do.

Rather than taking higher doses we think it is preferable to commit to eating more fruits and vegetables, which provide not only vitamin C but also countless other beneficial nutrients. Those rich in vitamin C include kiwi, oranges, strawberries, grapefruit, cantaloupe, broccoli, cauliflower and bell peppers.

Hopefully you recall the current recommendations for five or more daily servings of fruits and vegetables for overall good health.