The Dietary Supplement Health Education Act of 1994 defines a dietary supplement as “any product (except tobacco) – in pill, capsule, or liquid form – containing a vitamin, mineral, herb, or other plant product, amino acid, or other know dietary substance that is intended as a supplement to the normal diet.” This obviously covers a great range of ingestible substances. Supplements are the most commonly used complementary or alternative therapy, since they are widely available and obtainable without a prescription.
When it comes to cancer, there are two general motivations behind the use of dietary supplements: prevention and treatment.
Some dietary supplements are taken for their reputed ability to boost health and prevent cancer from occurring in the first place. A variety of products claim to lower the consumer’s risk of cancer, and evaluating these claims can be difficult. Antioxidants – substances that are thought to prevent cell damage caused by a type of unstable molecule called free radicals – are currently a popular preventative treatment. They can be found in a variety of foods, but are often sold in pill form. Other supplements said to prevent cancer include vitamins such as A, C, or E, and minerals like selenium.
Other dietary supplements may be used alongside or instead of standard cancer treatments like radiation and chemotherapy. Some of these supplements, like Iscador (an extract of the mistletoe plant), are thought to boost the effectiveness of chemotherapy. Others purport to enhance the immune system, though the immune system plays a relatively minor role in the treatment of cancer. Many supplements are used to mitigate the unpleasant side effects of chemotherapy or radiation if standard medicines prove ineffective or unpalatable.
A Word of Caution
The American Cancer Society, the National Institutes of Health, and the Mayo Clinic all advise caution when it comes to choosing and taking dietary supplements and strongly warn against replacing standard treatment with these supplements. Before 2007, the FDA did not require the makers of these supplements to report major adverse health effects. Additionally, combinations of supplements with each other or with radiation and chemotherapy can have unintended interactions that may produce unpleasant or even dangerous side effects. These organizations recommend consulting with a health care professional before beginning any course of treatment, including dietary supplements.