In the 16th century, the Dutch sailors knew that eating citrus fruits prevented scurvy. But it wasnt until 1920s when it was recognised that the active ingredient in citrus fruits was vitamin C (ascorbic acid).
The next big development for vitamin C came in 1974. A research paper was published with careful description of the responses of 50 consecutive patients with advanced, untreatable cancer to high-dose intravenous and oral vitamin C.
Most patients in this group of 50 did not respond to high doses of vitamin C. But extraordinary things happened to a significant minority of them. These included several cases of tumour regressions.
This report generated some controversy. In 1991, a panel set by the US National Cancer Institute, reviewed 25 of the 50 patients who had complete remission of the tumour. The panel found that in each and every case, there were alternative explanations for the observed remissions.
So, what do we know about vitamin C and its usefulness in cancer prevention and treatment?
Vitamin C is known to play an important role in the synthesis of collagen (fibrous protein of connective tissue), to promote wound healing and to influence many immunological and biochemical reactions in the body.
In laboratory animals, vitamin C has been shown to have a range of effects that could be beneficial to cancer patients, including tumour regression, the inhibition of tumour growth and increased survival on animals with implanted cancer.
There is some evidence that populations whose dietary intake of vitamin C is high have a decreased risk of some types of cancer, cardiovascular disease and cataracts. Vitamin C supplements are generally well tolerated. In adults, a dose of one gram per day is safe with minimal toxicity. Very minimal toxic effects have been reported even at much higher doses.
Vitamin C can interfere with absorption of many other medications: blood thinners, iron, vitamin B12, and vitamin E.
Humans cannot manufacture vitamin C. We have to obtain it from dietary sources. It is found in many fruits such as oranges, grapefruit, strawberries, raspberries and kiwi fruit, and in vegetables such as cabbage, tomatoes and bell peppers.
Canadas Food Guide, prepared by Health Canada, sets guidelines for the recommended daily intake (RDI) of vitamins and minerals. Most people who eat a balanced diet that is made up of a variety of foods and that is rich in fresh fruits and vegetables will meet the RDI of vitamins and minerals.
Advocates of mega dose vitamins often recommend combining vitamins A, C, and E and claim that these vitamins improve general well being, strengthen the immune system and may delay the development and progression of serious disease.
Is this information good enough to make a strong case for vitamins in the management of cancer patients?
In 1998, the Canadian Medical Association Journal (CMAJ) ran a series on Unconventional therapies for cancer. The article on Vitamin A, C and E says: There is some laboratory evidence and some clinical evidence that vitamins A, C and E, given separately or on combination, may have value in the management of cancer. However, there is a lack of solid scientific evidence of the sort required to support a recommendation that cancer patients take vitamin supplements.
In the last few years, rational guidelines fro testing biological agents like vitamin C have been developed, says the CMAJ. And hopefully new information on the benefits of vitamin C should be forthcoming. The good thing about vitamin supplements is that they are readily available, can usually be self-administered and are relatively inexpensive and non-toxic for most adults. And hopefully, there will be more good news in the years to come.
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