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On the grocery-store shelf, a bottle of turmeric capsules states that the product “promotes the body’s natural healthy inflammation response.” A multivitamin marketed at adults over the age of 50 claims to provide “energy and heart health support” and “anti-aging defense.” A website selling hemp oil promises “natural therapeutic benefits,” by stimulating receptors in the body involved in mood and memory.

What do these claims have in common?

None of the claims are required by law to be proven true before they’re made!

Dietary supplements are regulated by the U.S. Food and Drug Administration (FDA). However, for regulatory purposes, supplements are treated like food, not drugs.1 They are supposed to be sold to supplement nutrients that might be lacking in a person’s diet, not to prevent or treat any medical condition.

But the Dietary Supplement Health and Education Act, commonly abbreviated as DSHEA and passed by Congress in 1994, expanded the definition of dietary supplements from vitamins and minerals to include herbal and botanical products. It also gave supplement manufacturers permission to promote their products with so-called “structure/function” statements.2

These statements can claim that the product supports the normal workings of the body’s organs and systems, but manufacturers do not have to provide the FDA with rigorous proof that they do so before making such claims.

In contrast, drugs sold in the U.S. must go through a long, standardized clinical trial process before they can be marketed, showing that a product improves health and that its side effects are acceptable and well understood.

Supplement makers “aren’t supposed to lie. And the FDA can go after them for supplements that don’t have what they say they have on the label,” says Marion Nestle, PhD, MPH, professor emerita of Nutrition, Food Studies and Public Health at New York University. “That does happen, but not often.”

The bar for intervention is very high, she explains, and the FDA cannot step in unless a complaint is received from the public or if people are obviously in danger from a product. “In general, the FDA leaves supplements alone, because Congress has been so clear that they want the FDA to leave supplements alone,” she continues.

So maybe you’re thinking that dietary supplements—vitamins and herbs—sound like a healthy addition to your nutrition and wellness plan to prevent cancer or reduce the risk of a cancer recurrence?

Some supplements may offer benefit, but there can be more to these unassuming capsules than you realize. Dietary supplements can actually cause serious side effects, including negative interactions with prescription medication. It’s therefore very important that you discuss any supplements you are considering with your doctor.

According to Richard Tsong Lee, M.D., medical director of the integrative medicine program at the University of Texas MD Anderson Cancer Center, “Herbs and supplements should be treated like prescription medication in that they have the potential to affect the body in both helpful and harmful ways.” Included in the potential risks of supplement use, according to Dr. Lee, are toxic effects at highly concentrated doses and interactions with prescription medications. Remember “Herbs and supplements are not regulated by the FDA, which means companies are not required to demonstrate efficacy, safety, or quality of the product made,” says Dr. Lee.

Americans spend $27 Billion on Supplements Annually

A glance at the vitamin and supplement aisle in any grocery or drug store is proof: the nutritional supplement market is booming. (1,2)

So why the rush to supplement? Many people believe that supplements can improve health, protect against disease, and, at worst, do no harm. But many of the claims made by manufacturers cannot be supported by science, and consumers are often unaware of drug interactions and other potential risks of using these products without a physician’s supervision.

Consider Food First

What many people seeking to improve their health with nutritional supplements may not know is that a balanced diet is adequate to provide most of us with the nutritional support we need. Supplements are not the same as food; they cannot replace a well-rounded diet made up of real food that includes a large volume of fruits and vegetables. And while many of us pop supplements to counter poor food choices, the fact is that no supplement has all the properties found in real food; there are more than 8,000 known bioactive compounds in fruits and vegetables alone, offering a treasure trove of protective benefits.

More Is Not Always Better

While it may seem like a good idea to boost our health by adding more of a beneficial nutrient, problems, including cellular toxicity or poor absorption of other nutrients, can arise when you take a higher concentration of a particular nutrient in supplement form. A nutritional compound that may be beneficial as one component of a food can have a potentially negative impact in a higher, concentrated dose. It is a double-edged sword: a supplement we take in an effort to do our bodies good may actually interfere with protective processes that occur naturally. More is not always better.

Questionable Science

When a supplement is recommended, a specific scientific study will often be cited that describes the purported benefits of the supplement. But the studies referred to are not always based on sound science. For example, if we were to examine the fact that Japanese men have a much lower rate of prostate cancer and assume that it is because they consume a large amount of soy, that may not be correct. They also consume large amounts of fish, vegetables, and fruit—all which may be factors in the lower prostate cancer risk.

One reason for the jump to attribute scientific studies to various supplements is the potential financial returns on supplements in the lucrative US market; manufacturers want to cite studies to help market the supplements, so they push the results of studies that are sometimes incomplete, lack outcome data, and are not based on the rigorous human studies needed. For studies to be valid in nutritional science, they need to be complete and conducted over a sufficiently long period to offer results that can actually make a valid claim as to benefit or harm. Even the rather prolific research on multivitamins does not show a direct correlation to greater longevity. The bottom line: don’t assume that the studies used to market supplements are reputable or rigorous; think critically about any scientific claims made, and always discuss supplements with your physician.

Be a Savvy Consumer

As with claims about scientific studies related to various supplements, other marketing approaches should also be evaluated with a critical eye. When you see a claim on a package that states something like “supports breast health,” ask yourself, What does that actually mean? In all likelihood, at this time, there is no good evidence that it can lower the risk of breast cancer.

The nutritional supplement market has our attention, but research does not necessarily support the marketing claims about these products. Until we have more sound scientific proof that taking supplements provides real benefit, it may behoove us to focus more on the most optimal diet possible. Using real food instead of searching for a “magic pill” will likely provide more long-term benefit for our overall well-being.

Moderation and variety in the diet give us the nutrition we need. If you do feel the need for a supplement, consult your physician to avoid harmful interactions with other drugs you may be taking. If your physician approves, keep supplementation to a level that is found in food, avoid the “mega” levels often seen in nutritional supplements, and stay within the bounds of the daily recommended intake. Do not base your decisions on retailers; even more importantly, focus on what we do know about nutrition: a lifestyle that includes a high intake of fruits and vegetables and regular exercise to maintain a healthy weight is generally the best choice.

Supplements Can Have Negative Effects in Cancer Patients

What are some potential negative outcomes associated with popular supplements? Dr. Lee cites two examples: beta-carotene (in supplement form) and Saint-John’s-wort. Beta-carotene, he says, has been associated with an increased risk of lung cancer, and Saint-John’s-wort (an herb thought to relieve mild depression) may interact adversely with the chemotherapy drugs Camptosar® (irinotecan) and Gleevec®(imatinib mesylate) as well as with the hormonal therapy tamoxifen (Nolvadex®).

Tell your doctor about current or planned supplement use if you are undergoing surgery—some supplements may cause side effects related to surgery. Certain supplements, for example, increase the risk of bleeding; these include garlic, ginkgo biloba, ginseng, and vitamin E. Others, such as kava and valerian, may need to be avoided because they can increase the sedative effects of anesthetics.

The two chief take-home messages about dietary supplement use are: First, never assume a product is safe, even if it’s labeled “natural.” Second, always talk with your doctor before trying any dietary supplement. With proper guidance and with safety as a priority, you may find that certain herbs and vitamins are a great addition to your wellness plan.

When do Supplements Make Sense?

While most of us can get the nutrients we need by eating a balanced diet that includes a high volume of fruits and vegetables, the following individuals may benefit from nutritional supplements:

  • Those who have a medical condition that restricts the intake of a healthy diet or that interferes with the absorption of nutrients, such as food allergies, gastrointestinal disease, or liver disease
  • Those on calorie-restricted diets, generally below 1,500 calories per day
  • Women who are pregnant or planning to become pregnant—a prenatal vitamin ensures adequate intake of certain nutrients
  • Those with very little exposure to the sun who may need vitamin D
  • Those over 50 who may need a Vitamin B 12 supplement due to reduced absorption with age.
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Common Supplements & Their Interactions


Used for: Depression

May interact with: Anti-cancer drugs (such as Camptosar® [irinotecan]), birth control medication, HIV/AIDS drugs, drugs used to prevent rejection of organ transplant, anticoagulants (drugs to prevent blood clotting), heart medication

Potential side effects: May increase sun sensitivity, anxiety, dry mouth, dizziness, fatigue, headache, gastrointestinal symptoms, sexual dysfunction


Used for: Inflammation and arthritis-related pain, liver function, digestion, menstrual irregularities, heartburn, stomach ulcers, gallstones, cancer treatment and prevention

Potential side effects: Indigestion, may worsen gallbladder disease


Used for: Migraines, fevers, headaches, stomachaches, rheumatoid arthritis, psoriasis, allergies

Potential side effects: Canker sores, irritation and swelling of lips and tongue, nausea, bloating, digestive problems, allergic reactions; should not be taken by women who are pregnant due to risk of miscarriage and preterm delivery

Black Cohosh

Used for: Menopausal symptoms including hot flashes, night sweats, and vaginal dryness; menstrual irregularities and premenstrual syndrome; arthritis and muscle pain (also known as rheumatism)

Potential side effects: Liver complications, including abdominal pain, dark urine, or jaundice; reports of hepatitis and liver failure


Used for: Immune support, chronic hepatitis, common colds, and upper respiratory infections

May interact with: Medications to suppress immune system (such as those taken by cancer patients and patients undergoing organ transplant)

Potential side effects: Changes to blood pressure and blood sugar levels; some species can be toxic (not those usually found in dietary supplements, however)


Used for: Many health conditions; high cholesterol levels, menopausal symptoms, osteoporosis, high blood pressure, breast cancer, and prostate cancer

Potential side effects: Stomach irritation, including nausea, bloating, and constipation; allergic reactions; uncertain role in breast cancer and effects on estrogen levels—women at high risk of breast cancer are advised to discuss using soy with their healthcare providers.

Know how to choose safely

Alternative and integrative practices have come a long way in a short time, but how do people derive the benefits of dietary supplements without putting themselves at risk of potential problems such as the ones that regularly occur as a result of this after-the-fact regulation?

The following steps can help ensure safety when choosing among dietary supplements.

  • Bring up your medication and supplement use with all of your healthcare providers—including all dietary supplements such as vitamins, minerals, and herbs.
  • Review the label for any ingredients you may be allergic to or that might cause problems, including hormones, unfamiliar ingredients, a long list of ingredients, or ingredients that may trigger a rise in blood pressure or heart rate.
  • Tap into the knowledge of a pharmacist about different supplement choices and possible interactions with prescription drugs, foods, or other supplements.
  • Buy only as much as you are likely to consume before the expiration date, and store them properly.
  • Know that the more drugs and supplements you take, the greater the risk of interactions or bad reactions; question the need for multiple medications and herbals, aiming to simplify your regimen in consultation with your healthcare providers.
  • Stay away from supplements that advertise miracle cures or immediate results and those that promise to help you achieve something you know to be difficult, such as weight loss, super strength, a headful of hair, outsized sexual performance, or regained youth.
  • Remember that dietary supplements cannot be sold or advertised to cure or alleviate a disease, so steer clear of such claims and promises.
  • Certification by an independent laboratory may be as reliable as no certification at all when it comes to the specific bottle sitting in your medicine cabinet. Look for supplements that follow established, tested procedures, such as those bearing the USP Verified Mark.
  • Follow the label instructions; whether or not a product claims to be natural, more is not necessarily better, and more could be harmful.


People who care about their health are surprised to learn how many useful and safe integrative health choices are available; some of these might be less risky than certain conventional care options. Our wellness state, lifestyle choices, and diet sometimes fall out of balance. For some conditions high-touch, low-tech, and more-holistic approaches can be quite safe, effective, and less costly than many mainstream methods or treatments.

There is a common misperception that all supplements are good and that if a little is good, then more is better. To date, there has been little evidence that dietary supplements reduce the risk of cancer—and now new research indicates that high doses of some supplements actually increase cancer risk, according to a commentary published in the Journal of the National Cancer Institute.

In fact, the data indicates that the true biology of dietary supplements is complex—and that the value of any nutrient cannot be assessed in isolation. The nutrients in dietary supplements are essential and have value; however, they often have value in a certain balance with other nutrients.

The data indicates that nutrients like beta-carotene, selenium, and folic acid are fairly harmless, even when taken up to three times the recommended daily allowance; however, when taken at higher levels, these three supplements have been shown to increase the risk of certain cancers.

The researchers suggest that stricter regulation may be necessary in order to ensure safe doses of nutrients. The U.S. Food and Drug Administration (FDA) regulates dietary supplements as food; however some supplements can act more like drugs, especially when taken at high doses.

Individuals who are concerned about getting the proper balance of nutrients are advised to eat a healthy, balanced diet with a wide variety of fruits and vegetables. Most people who consume a healthy diet should not need to supplement.


  1. NCHS Data Brief. Centers for Disease Control and Prevention website. Available at: . Accessed October 1, 2013.
  2. 10 Surprising Dangers of Vitamins and Supplements. Consumer Reports website. Available at: . Accessed October 1, 2013.
  3. Martinez ME, Jacobs ET, Baron JA, et al. Dietary Supplements and Cancer Prevention: Balancing Potential Benefits Against Proven Harms. Journal of the National Cancer Institute. 2012; 104(10): 732 DOI: 10.1093/jnci/djs195