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NCCIH Clinical Digest

for health professionals

Know the Science of Complementary Health Approaches:
What the Science Says

October 2017


Clinical Guidelines, Scientific Literature, Info for Patients: 

NCCIH has launched a new initiative called “Know the Science,” to help consumers better understand complex scientific topics related to health research so they can be discerning about what they hear and read and make well-informed decisions, especially about complementary and integrative health, where many approaches are readily available in the marketplace and are often selected for self-care. The Know the Science initiative covers topics such as drug-supplement interactions, the facts about health news stories, placebo effect, health-related risks, and the myths about “natural” products.

Here are 10 “Know the Science” facts to help your patients get to know the science of health:

Did You Know?

  1. Studies with large numbers of people generally get results that are more reliable than studies with small pools of participants. Larger studies can increase the accuracy of the study findings and reduce the probability that any effect observed in the study was due to chance. Too few participants may make the entire study a failure—it may only produce inconclusive results. Statisticians and scientists have tools to figure out how many volunteers are needed for a clinical study to be meaningful.
  2. Unless you read and understand the original sources for a health news story, it can be difficult to know whether a news story is misleading or has left out important information. But the likelihood that the story is correct increases if it comes from a media outlet that isn’t trying to promote a point of view or cause, was written by a science or health reporter trained to understand medical findings, and includes quotes from experts no connected to the study (for a more objective take on the findings or to show another point of view).
  3. Sometimes taking a prescription drug and dietary supplement together may increase the drug’s effects. The drug’s effects may become too strong, and unwanted side effects may increase. For example, the herb schisandra may slow down the processes in your body that change drugs into inactive substances. So, if you take this herb while you’re also taking a drug, the amount of the drug in your body may increase. As a result, the drug’s effects may be too strong.
  4. Sometimes taking a prescription drug and a supplement together may decrease the drug’s effects. This means that you aren’t getting the full benefit from the drug that your health care provider wants you to have. St. John’s wort is one popular herbal supplement that is especially known for decreasing the effects of drugs. It does this by speeding up the processes in your body that change drugs into inactive substances.
  5. When it comes to medicine, there is no official definition for use of the term natural. And it’s important to know that a medicinal product labeled natural does not always mean safe. For example, the herbs comfrey and kava may be considered natural products, but they can cause serious harm to the liver. An herbal or botanical supplement labeled natural may contain dozens of chemical compounds and all of its individual components may not be known.
  6. In clinical trials, researchers test new ways to prevent, detect, or treat disease. Treatments might be new drugs or combinations of drugs, new surgical procedures or devices, or new ways to use existing treatments. Clinical trials can also test other aspects of care, such as ways to improve the quality of life for people with chronic illnesses.
  7. The strength of a study depends on its size and design. New results may confirm earlier findings, contradict them, or add new aspects to scientists’ understanding. In the end, cause and effect are usually hard to establish without a well-designed clinical trial.
  8. Some people believe that “natural” products are safe because they believe these medicines are free of chemicals. For many, the word “chemical” has come to mean toxic or synthetic, something to be avoided. But everything is made of chemicals—the apple on your kitchen countertop, the ceramic mug in your cupboard, and even the air that you breathe. Natural medicines such as herbal and dietary supplements are made up of chemicals, too.
  9. Although many herbal or dietary supplements (and some prescription drugs) come from natural sources, “natural” does not always mean that it’s a safer or better option for your health. An herbal supplement may contain dozens of chemical compounds, and all of its ingredients may not be known. Scientists are studying many of these products to identify what ingredients may be active and to better understand their effects in the body.
  10. The strongest evidence about whether a treatment is useful and safe consists of results from several studies by different investigators. Rarely does a single study provide a final, definitive answer.  There is a need for a study to be replicated, which involves repeating a study using the same methods but with different volunteers and investigators. Replication of a study gives more confidence that the results are reliable and valid.  


NCCIH Clinical Digest is a service of the National Center for Complementary and Integrative Health, NIH, DHHS. NCCIH Clinical Digest, a monthly e-newsletter, offers evidence-based information on complementary health approaches, including scientific literature searches, summaries of NCCIH-funded research, fact sheets for patients, and more.

The National Center for Complementary and Integrative Health is dedicated to exploring complementary health products and practices in the context of rigorous science, training complementary health researchers, and disseminating authoritative information to the public and professionals. For additional information, call NCCIH's Clearinghouse toll-free at 1-888-644-6226, or visit the NCCIH Web site at NCCIH is 1 of 27 institutes and centers at the National Institutes of Health, the Federal focal point for medical research in the United States.


Content is in the public domain and may be reprinted, except if marked as copyrighted (©). Please credit the National Center for Complementary and Integrative Health as the source. All copyrighted material is the property of its respective owners and may not be reprinted without their permission.

This page last modified October 19, 2017