Buyer Beware Where Is The Medical Evidence for Supplements and Herbal Products

I am a checklist fiend. Upon awakening, I perform my awake checklist. “I am alive, and my bodily functions are good.” I proceed to my meditation and enjoy my day. Once a week, I teach Physician Assistant students. 

I will introduce the indications, side effects, drug interactions, and evidence-based guidelines for the pharmacologic agents for the disease state assigned each week. My students understand their mission is to prescribe efficacious, safe, and affordable medications that lead to positive outcomes. The path of prescribing requires incorporating medication trials and treatment guidelines into their prescribing checklist. This paradigm is different for supplements and herbal products.

The overseer for prescribed medications is the Food and Drug Administration (FDA). The role of the FDA is to protect public health by ensuring that the drugs available on the US market meet specific standards for both safety and efficacy. Every new medication must undergo a rigorous evaluation that includes randomized controlled trials, adverse events during the studies, and what patient populations benefit the most from the disease state studied. Post-marketing of a new medication, Phase IV studies are initiated to evaluate and ensure the medications have a benefit in real-life use versus the results of the randomized controlled trials after FDA approval. If adverse events occur after marketing, a new medication can be voluntarily taken off the market or mandated to be removed from the market by the FDA.

Supplements and herbal products are regulated by the FDA’s Center for Food Safety and Applied Nutrition (CFSAN), the agency that oversees herbs and supplements. The FDA does not approve dietary supplements or their labeling but may evaluate specific claims by the dietary supplement manufacturer that require premarket review. The health claims include how a supplement can reduce the risk of a disease or health risk, function claims on the effects on the structure of the body, and nutrient claims, the amount of the nutrient in a supplement. The Federal Trade Commission (FTC) regulates advertising, including infomercials and advertising in e-articles for dietary supplements, so the FDA is generally responsible for safety, quality, and labeling, and the FTC is typically accountable for advertising.

The FDA will intervene when supplements or herbal products have been reported to have caused public health emergencies, injury, or illness. Another priority for the FDA is investigating products suspected of being adulterated, fraudulent, or violating the law. The remaining resources of the FDA are used to analyze product samples after marketing for their claimed content.

The FDA does not review structure or function claims. Labels containing a structure or function claim must include the disclaimer, “The Food and Drug Administration has not evaluated this statement. This product is not intended to diagnose, treat, cure, or prevent any disease.” For the general consumer, it is easy to misunderstand structure or function claims. For instance, people with benign prostatic hypertrophy (BPH) may have read that saw palmetto can help with their prostate problems. A statement on the saw palmetto bottle may read, “helps maintain a healthy prostate gland.”

Prescribed medications are evaluated and studied through rigorous, double-blind, randomized controlled trials. Supplements and herbal products lack such research. The primary source of herbal product data comes from the Commission E Report, a report that was started in Germany in the 1990s. This report compiled 380 monographs to evaluate the safety and efficacy of herbs for prescribing physicians in Germany. The monographs are a collection of official documents compiled over nearly two decades by a committee of twenty-four scientific experts. The committee was set up in 1978 and over the past twenty-five years, some small observational trials have been published that have shown conflicting data on safety and efficacy in patients. Most of the observational trials studied a very small group of patients. Many of the results of these trials could have been due to random chance. Small trials are not powered enough to confidently say that a particular herb makes a significant clinical difference in a study of patients’ disease states.

Supplements and herbal products do not need a prescription to be purchased by the consumer. The responsibility to administer herbs and supplements is on you. You need to educate yourself, weigh the risks versus the benefits, and consider the costs of purchasing these products. If you are taking prescription medications with supplements or herbs, there may be synergistic side effects, adverse reactions, allergic reactions, and drug interactions. The combination of prescription and OTC medicines plus herbs can cause a significant event that may require hospitalization. I had a patient come into the ER with a very rapid heart rate, which turned out to be a severe cardiac arrhythmia (ventricular tachycardia). She was on hypertension medications. Her labs and cardiac workup were all normal. She was admitted to the coronary care unit. I was consulted to evaluate all of her medications. She became very short of breath and went into ventricular tachycardia for a second time, which required defibrillation after passing out. Twenty-four hours after the patient stabilized, I asked her if she was taking any OTC, herbs or supplements. She confided in me that she was ingesting chincona bark (a quinine derivative) for nocturnal leg cramps. This herb turned out to be the cause of her event.

Let’s look at the data for the top two most asked questions by pilots on this subject.

Spatial disorientation with motion sickness is a significant problem in aviation. The Air Force has their pilots fill out a motion sickness history questionnaire. Fifty percent of the Air Force pilots experienced motion sickness (“Spatial disorientation in aviation. Progress in astronautics and aeronautics Series,” p. 203,American Institute of Aeronautics and Astronautics, 2004). Many flight instructors have asked what I can recommend for their student pilot’s motion sickness. The answer is, “I am sorry, there are no prescribed or over-the-counter medications available that are allowed by the FAA.” OTC medications like dimenhydrinate (Dramamineâ) or antivert (Bonineâ) are not approved for use by the FAA. Both drugs cause drowsiness.

Ginger has been studied for motion sickness. The trials cited did not have very many participants and the study results were not statistically significant. This study was a double-blind, randomized, placebo-controlled trial. Eighteen healthy volunteers with a history of motion sickness induced by automobile, boat, or airplane travel (8 men and 10 women aged 18–40) were recruited. The participants were put into a circular spinning device. They were evaluated on how long it took for the study patients to become nauseous. For the patients who did not get ginger, nausea began at 2.5 minutes. For the patients administered ginger 1,000 mg, the nausea onset was 8.5 minutes. Ginger significantly reduced the severity of nausea up to 45 minutes after cessation of circular vection (March 1, 2003, American Journal of Physiology).

The two most common causes of vision loss worldwide are age-related macular degeneration (AMD) and cataracts. AMD is an eye disease that causes blurring of a person’s central vision. Aging causes damage to the macula, which controls the sharpness of forward vision. The macula is part of the retina that is light-sensitive. AMD does not cause complete blindness. You may also notice a blurry area near the center of your vision. Over time, this blurry area may get more prominent, or you may see blank spots. Colors may also seem less bright than before, and you may have more trouble seeing in low lighting. These symptoms are usually not seen until reaching the late stage of AMD.


Two trials have studied supplements to slow the progression of vision loss in AMD patients. The AREDS (The Age-Related Eye Disease Study) was a double-blind, randomized controlled trial of 4754 AMD enrollees, evaluating four treatments of daily antioxidants, which included vitamin C, vitamin E, beta carotene, zinc, and copper. The study’s endpoints were the progression of AMD and a decrease in 15 letters on the visual acuity score. The AREDS supplements reduced the risk of progression from intermediate to advanced AMD by about 25 percent. The AREDS2 trial studied 4302 enrollees randomized to a combination of lutein, zeaxanthin, and omega-3 fatty acids or placebo in age-related macular degeneration patients. The primary endpoint of the study was progression of AMD. Most patients were also on the antioxidants utilized in the AREDS trial. AREDS2 supplements reduced the risk of progression from intermediate to advanced AMD by about 25 percent, but did not prevent AMD onset. AREDS and AREDS2 supplements did not affect patients with cataracts. The supplement manufacturers derive their products from the antioxidants, lutein and zeaxanthin and note “AREDS2” on their labels. There is no medical evidence that using these AREDS2-derived products can prevent AMD.


People who are at risk for AMD have a family history of AMD and are smokers. A study in JAMA Ophthalmology gave the AREDS2 supplements to first-generation children of parents with AMD. After six months, there was no increase in optical density uptake of lutein and zeaxanthin (JAMA Opthalmal.2017;135(11):1259-1266). The thought was that higher levels of lutein and zeaxanthin in the macula would protect subjects from developing AMD. Lutein and zeaxanthin are the most common xanthophylls that are found ingreen leafy vegetables (kale, spinach, broccoli, peas, and lettuce) and egg yolks. These combination supplements can run from $60-$84.


The decision to ingest an herbal or supplement is multifactorial. I recommend you consult your healthcare provider. A brilliant cardiologist taught me about his medication checklist: “Efficacy check, safety check, cost check.” When you see the statement, “may improve…,” become a Missourian. Show me the medical evidence. Be well and fly safely.

Larry M. Diamond, PharmD, CFII
Larry Diamond has a Doctor of Pharmacy Degree and has been a pharmacist for 37 years. Larry’s pharmacy practice has been as a Clinical Pharmacy Specialist in Cardiology, Orthopedic Surgery Specialist and most recently Clinical Pharmacy Coordinator. He is a CFII, a pilot for 33 years and has been an AOPA member since 1984.

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