Dietary Supplements: Risks, Benefits and Other Information

Surviving a cancer diagnosis can mean a continuous battle to maintain health and to prevent recurrence. Surveys show that majority of survivors resort to dietary supplements with the hopes of cure and improving quality of life. Whereas some supplements offer health benefits, others have unintended adverse effects.  Therefore, it is important for patients to address the following:  Do they really need supplements?  What is the science behind it? Can it cause harm? Who is promoting it?

In this article, we will discuss some pros and cons of using dietary supplements and where to obtain reliable information.

Dietary supplements are considered natural products and are the most commonly used Complementary and Alternative Medicine modality worldwide. According to the Dietary Supplement Health and Education Act (DSHEA) of 1994, dietary supplements include vitamins, minerals, herbs and botanical formulas that are consumed orally. Unlike prescription drugs, they are not intended to treat or prevent diseases. However, many supplements are promoted to treat and prevent disease including cancer.

Dietary supplements are perceived as natural and safe.  And because they are relatively inexpensive and available without a prescription, they become popular choices. Surveys show that users tend to be young, educated, women with higher income level, and cite a sense of control over one’s health as the main reason for taking supplements. Some patients use them for religious and spiritual reasons as well.

Many dietary supplements, especially those from botanical sources, contain biologically active constituents. Some have been investigated for their anticancer effects. Following are a few examples that have shown promising results:

Soy – Epidemiological studies suggest that consumption of soy can help protect against breast cancer. However, constituents of soy such as genistein are known to have estrogenic effects and can be detrimental in patients with hormone-sensitive cancer.

Turmeric – A widely used culinary spice with applications in traditional medicine. Lab studies show that curcumin, an important constituent of turmeric, exerts antitumor effects through different mechanisms. Clinical studies are under way to examine its safety and efficacy as an anticancer treatment.

Green Tea – Green tea is known to have antioxidant effects. The active constituent, epigallocatechin-3-gallate (EGCG), is thought to account of its health benefits. A form of green tea extract is one of the first dietary supplement ingredients to be approved as a drug. Clinical trials are underway to investigate green tea as an agent to prevent and to treat cancer.

Mushrooms – Many edible mushrooms have medicinal properties. Extracts from maitake, shiitake, reishi, and coriolus have been studied in cancer patients in Asia and some have been incorporated in cancer treatments. These products contain beta-glucans that are thought to have immunomodulating effects.

Vitamin D – Vitamin D are used as supplements to maintain bone health. However, recent studies show vitamin D acts as a hormone that can affect the functions of other organs. Low serum vitamin D levels have been associated with increased risk of certain cancers, which suggest that it may have a protective effect. More studies are needed to determine its efficacy and the optimal dosage for disease prevention. Limited sun exposure leads to vitamin D deficiency. Cancer survivors are encouraged to have their vitamin D levels checked by a physician. The Institute of Medicine has recently increased the recommended intake of vitamin D to 600 IU for bone health.

Despite the popularity of dietary supplements, information about their efficacy to guide daily usage is lacking.  Several large scale clinical trials conducted to determine the preventive effects of dietary supplements yielded disappointing results. For example, previous studies suggested that selenium and vitamin E may reduce prostate cancer risk. However, a large prevention trial failed to find any benefits. Moreover, these products may increase the risk of cancer and diabetes.

Also, many dietary supplements are intended for oral consumption and the active constituents must be absorbed in the gastrointestinal tract in order to produce systemic effects. These products will have no benefits if not taken in sufficient amounts, whereas excessive use can be toxic. Unfortunately, the optimal dosages remain unclear as few products have been subjected to dose escalation studies.

Further, when used inappropriately dietary supplements can interfere with prescription drugs resulting in severe adverse effects.  For example, products that inhibit blood coagulation, have antioxidant effects, or act like estrogen are especially prone to interact with cancer treatments.

Additional concerns associated with dietary supplement use involve quality control.  Herbs are harvested from different parts of the world and are not standardized which makes it difficult to compare the potencies between batches. Independent tests found that many products do not contain the labeled amount of active ingredients. Some are even contaminated with heavy metals and microbes. Others contain undeclared prescription drugs. However, this may change as there are new regulations requiring dietary supplement manufacturers to meet certain quality control standards.

With the proliferation over the last two decades of web sites containing information about dietary supplements, it can be daunting to find a reliable source. Many promote supplements to patients using pseudoscientific jargon, unsubstantiated claims and false testimonials. To address the questions often raised by cancer survivors and by healthcare professionals, the Integrative Medicine Service at Memorial Sloan-Kettering Cancer Center developed a free to access website called  AboutHerbs. It provides unbiased information on over 250 dietary supplements and unproven anticancer treatments. The content is based on published scientific data and is updated frequently.

Other useful sources include Medline Plus – Herbs and Supplements Database and the National Library of Medicine – Dietary Supplements Labels Database which provides information on various  brand products  and their contents. lists independent quality test reports of many dietary supplements.

Finally, it is very important for patients not to delay conventional treatments and to communicate with their doctors about any dietary supplements they are using. Most mainstream oncologists agree that health can be maintained with exercise and a balanced diet, not dietary supplements.

Category: Experts Speak

Tags: AboutHerbs, anticancer treatments, dietary supplements, green tea, integrative medicine, Simon Yeung, soy, turmeric