Dietary supplements
Dietary supplements encompass a wide range of substances that individuals consume alongside their regular diet, as defined by the U.S. Food and Drug Administration (FDA). This category includes vitamins, minerals, botanicals, amino acids, enzymes, and certain animal-derived products. Many people turn to dietary supplements to support health, particularly in the context of cancer treatment and prevention, although the effectiveness of many claims remains unproven. Vitamins and minerals are essential for human health; however, excessive intake, especially of fat-soluble vitamins, can lead to serious complications. Botanicals, including herbs like ginseng and green tea, are rooted in traditional practices but often lack rigorous scientific validation for their efficacy.
Dietary supplements are regulated as foods rather than drugs, meaning manufacturers are not required to prove safety or effectiveness before marketing. The FDA does impose certain regulations, such as requiring labels to state that claims have not been evaluated. Despite their common use, safety and effectiveness can vary widely based on type, purity, dosage, and individual health conditions. Concerns also exist regarding potential side effects and interactions with medications, especially in cancer patients. Therefore, it is recommended that individuals consult healthcare professionals before incorporating supplements into their health regimen.
On this Page
Subject Terms
Dietary supplements
DEFINITION: Dietary supplements are a broad category of materials that are defined by the US Food and Drug Administration (FDA) as substances consumed in addition to a person’s normal diet. Subclasses of this group are vitamins, minerals, botanicals, amino acids, enzymes, and certain animal-derived products.
Cancers treated or prevented: Dietary supplements are often taken in an adjuvant mode to help fight many types of cancer, although their effectiveness is rarely proven. Perhaps even more often, supplements are taken for cancer prevention or to boost the immune system.
Delivery routes: Oral in the form of tablets, caplets, capsules, powders, and liquids such as extracts and teas.
How these agents work: Supplements range from familiar multivitamin tablets to unusual substances like snake venom. Some dietary supplements (such as vitamins and minerals) have accepted roles in conventional medicine and complementary and alternative uses. Other dietary supplements, including most botanicals, are used almost exclusively in complementary and alternative medicine. Complementary medicine supplements traditional Western medical care, while alternative medicine seeks to replace traditional Western medical care.
Some dietary supplements, especially vitamins and minerals, are embraced by traditional Western medicine and play an important role in maintaining health, especially among individuals with cancer or other diseases that affect the body’s metabolism. Thirteen different vitamins are essential to human health. The body cannot make these compounds. They must be obtained from food or dietary supplements. The fat-soluble vitamins are vitamins A, D, E, and K. The water-soluble vitamins are vitamins B1 (thiamine), B2 (riboflavin), B3 (niacin), B5 (pantothenic acid), B6 (pyridoxine), B7 (biotin or vitamin H), B9 (folate or folic acid), B12 (cobalamin), and vitamin C. Vitamins are generally safe when taken in amounts less than the upper safe limit set by the US Institute of Medicine. Megadosing, or taking large quantities of vitamins, can cause serious health complications, especially with the fat-soluble vitamins that build up in the body. Minerals are inorganic compounds found in the earth that are necessary in small amounts for human health. Like vitamins, many minerals are safe and effective unless taken in mega doses.
Botanicals (herbs) are dietary supplements derived from plants. Botanicals have been used for centuries in traditional Chinese medicine, Ayurvedic or traditional Indian medicine, pre-nineteenth-century Western medicine, and homeopathy. The National Center for Complementary and Alternative Medicine (NCCAM) conducts rigorous investigations and clinical trials of many botanicals. Common botanicals that are claimed to treat cancer or cancer symptoms include apricot pit, foxglove, ginseng, green tea, and reishi mushroom. These claims have not been proven to the satisfaction of Western medicine.
Amino acids are molecules that are the building blocks of proteins. Humans require twenty amino acids, twelve of which the body can produce for itself. The rest must be obtained through diet or supplementation. Enzymes are proteins made in the body that regulate metabolic reactions. Prescription enzymes and amino acids are used in Western medicine when they replace compounds that the body is unable to make because of genetic defects. These substances are also sold as dietary supplements, some of which claim to treat cancer. Most traditional physicians do not accept these claims.
Animal-based supplements include products such as fish oil, bee pollen, and bear bile. Many of these products are used in alternative medicine and claim to prevent or treat disease. Practitioners of Western medicine generally acknowledge the benefits of some dietary supplements, such as vitamins, minerals, and fish oils, but question extreme claims.
In relation to cancer, people generally take dietary supplements for four reasonsto prevent a particular type of cancer; to meet the needs for a particular substance that they cannot acquire from their diet because of their cancer (vitamin supplements); to boost the immune system and help it fight their cancer (ginseng); and to reduce specific symptoms associated with their cancer (ginger for nausea). The American Cancer Society cautions individuals with cancer to choose dietary supplements with care and with the knowledge and advice of their physician. Much misinformation and many unproven anecdotal claims about dietary supplements and cancer exist on the Internet and in some fad medicine books.
Although millions of Americans use dietary supplements daily, the safety and effectiveness of these products vary depending on the type of supplement, the purity of the manufacturing process, the dosage, the health of the individual, and how the supplement interacts with other supplements and drugs. In the United States, dietary supplements are regulated under the 1994 Dietary Supplement Health and Education Act (DSHEA). This act regulates supplements as foods rather than as pharmaceutical drugs. Under the act, dietary supplement manufacturers do not need to prove that their products are either safe or effective before they are marketed. This contrasts with over-the-counter and prescription drugs, which cannot be sold until extensive testing (clinical trials) proves them to be safe and effective in treating specific conditions.
DSHEA limits the health claims that can be made for dietary supplements. Supplements cannot legally claim to treat or cure a particular disease. They are, however, allowed to make general claims, such as “helps build strong bones” or “helps lower cholesterol.” Any structure or function claims made for dietary supplements must have on the label the exact words, “This statement has not been evaluated by the FDA. This product is not intended to diagnose, treat, cure, or prevent any disease.” The packaging does not have to contain any warnings about potential side effects.
Additional FDA regulations have been added since the original 1994 law. By the end of 2007, all supplement manufacturers were required to report consumer complaints, including complaints of adverse reactions, ineffectiveness, and contaminated products, to the FDA. Before 2007, there was no requirement to inform the FDA of any problems reported by consumers. In June 2007, new FDA regulations established stronger good manufacturing practices for dietary supplements that required manufacturers to test for the identity, purity, strength, and composition of their products. These regulations were intended to help consumers determine exactly what is in the supplement and to certify that it is free from contamination by bacteria, fungi, glass, pesticides, heavy metals, and nonapproved additives.
The new manufacturing regulations resulted from findings by independent laboratories and the FDA of many contaminated supplements, as well as those that contained material other than what was listed on the label or that contained less or none of the labeled ingredients. Manufacturers are still not required to make any statements on the packaging about potential side effects, nor are they required to prove that a supplement is safe or effective.
Side effects: The side effects of many dietary supplements have not been studied and are unknown. Megadosing with supplements that are generally safe at lower doses, however, may cause the supplement (if fat-soluble) to build up in the body and interfere with the absorption or metabolism of other supplements or pharmaceutical drugs. Botanicals may also change the way in which other drugs or supplements act in the body by speeding up or inhibiting their actions. For example, antioxidants like vitamins C and E can reduce the effectiveness of chemotherapy medicines. Several cancer treatments are negatively impacted by the use of St. John's wort, and Vitamin K increases the risk of blood clots. Additionally, some supplements can contribute to the increased risk of developing cancer.
In addition, many natural plant substances (such as foxglove, hemlock, or ephedra) can be dangerous or life-threatening. According to the American Association of Poison Control Centers, thousands of people in the United States are treated each year in a healthcare facility because of ingesting dietary supplements.
Finally, dependence on dietary supplements to treat cancer or any serious disease may deprive the individual of effective traditional drugs and medical care that can save or prolong life. Individuals interested in taking dietary supplements as part of their cancer treatment regimen should research information carefully and discuss their findings with their oncologist before beginning a supplement.
Bibliography
"Are Dietary Supplements Safe?" American Cancer Society, 6 Sept. 2023, www.cancer.org/cancer/managing-cancer/treatment-types/complementary-and-integrative-medicine/dietary-supplements/safety.html. Accessed 20 June 2024.
Dew, Kevin. Complementary and Alternative Medicine: Containing and Expanding Therapeutic Possibilities. Routledge, 2021.
"Dietary Supplements: Background Information." Office of Dietary Supplements. Natl. Institutes of Health, 11 Mar. 2020, ods.od.nih.gov/factsheets/DietarySupplements-Consumer. Accessed 20 June 2024.
"Dietary Supplements." MedlinePlus, National Library of Medicine, 2018, medlineplus.gov/dietarysupplements.html. Accessed 20 June 2024.
Ernst, Edzard. So-Called Alternative Medicine (SCAM) for Cancer. Springer, 2021.
"FDA 101: Dietary Supplements." FDA, 6 Feb. 2022, www.fda.gov/consumers/consumer-updates/fda-101-dietary-supplements. Accessed 20 June 2024.
Gopi, Sreeraj. Clinical Studies on Nutraceuticals and Dietary Supplements. CRC Press, 2023.
Hiam, Deirdre S. The Gale Encyclopedia of Alternative Medicine. 5th ed., Gale, a Cengage Company, 2020.
Idzikowski, Lisa. The Effectiveness of Alternative Medicine. Greenhaven Publishing, LLC., 2019.
Jabbari, Parnian, et al. “Supplement Use and Increased Risks of Cancer: Unveiling the Other Side of the Coin.” Cancers, vol. 16, vol. 5, 22 Feb. 2024. MDPI, doi.org/10.3390/cancers16050880.
Quillin, Patrick. Beating Cancer with Nutrition. 5th ed., Nutrition Times Press, 2020.