Dietary Supplements

Nutrition & Health Info Sheets for Health Professionals - Herbal and Dietary Supplements

Nutrition & Health Info Sheets contain up-to-date information about nutrition, health, and food. They are provided in two different formats for consumer and professional users. These resources are produced by Dr. Rachel Scherr and her research staff. Produced by Brittany M. Loofbourrow, Anna M. Jones, PhD, Rachel E. Scherr, PhD.

What are Herbal and Dietary Supplements?

Congress defines dietary supplements as a product that:

  • Is intended to supplement the diet;
  • Contains one or more dietary ingredients (vitamins, minerals, herbs or other botanicals, amino acids, and other substances), or their constituents;
  • Is intended to be taken by mouth as a pill, capsule, tablet, or liquid; and
  • Is labeled on the front of a package as being a dietary supplement. [1]

Who Uses Herbal and Dietary Supplements?

Supplement use has increased in the last ten years with approximately 75% of Americans reporting use of at least one supplement. The most cited reason for taking supplements across age groups is overall wellness and the most commonly consumed supplement type are multivitamin and multimineral supplements. [2] This use has also expanded to youth under the age of 19, with 1 in 3 reporting use of supplements. [3]

What are the Recommendations for Herbal and Dietary Supplement Use?

According to the Dietary Guidelines for Americans 2015-2020 supplements can help certain individuals meet dietary needs in some cases. [4] However, supplements are not intended to replace foods that are important to a healthy diet. [5]

Examples of cases where supplements may be helpful:

  • Vitamin D: Supplemental Vitamin D may be helpful as it is limited in the food supply. This vitamin is unique in that humans are able to make vitamin D in the skin with adequate sun exposure, however in some cases this exposure may be limited due to latitude, climate, or sunscreen use. [4]
  • Iron: Iron is a mineral that can be commonly deficient in many people’s diets. Groups who may require an iron supplement to meet recommended amounts include adolescent girls, as well as women who are pregnant. [4]
  • Folate (Folic Acid): Folate, one of the B vitamins, has been fortified in grain products in the US since 1998. This vitamin has a role in decreasing the risk of neural tube defects in infants. Because of this, women of child-bearing age are advised to consume 400 mcg of synthetic folic acid from fortified foods and/or supplements. [4]
  • Omega-3 Fatty Acids: Omega-3 fatty acids, frequently found in fish oil supplements, may be beneficial for some individuals with heart disease. [5, 6]

Generally, supplement use of all kinds should be discussed with a medical professional to determine proper dose, length of time to consume the supplement, potential interactions with other supplements or medications, and any other concerns of the individual or medical professional. [5]

Are the Claims on Herbal and Dietary Supplements Accurate?

Supplement labels cannot claim the product treats, cures, mitigates, or prevents any disease – only FDA-approved medications can make these types of claims. Supplement labels are permitted to make health claims, which describe how the supplement may be related to health, or structure-function claims, which describe how the product affects the structure or function of the body. [7]

Health claims describe a relationship between an ingredient in the supplement and a reduced risk for disease or condition. A claim reading, “Calcium may reduce the risk of the bone disease osteoporosis,” is a health claim: it notes the ingredient and the reduced risk of a related disease.

Structure-function claims describe the ability of an ingredient to support the body’s normal structure or function. A claim reading, “Calcium builds strong bones,” is a structure function claim: it notes the ingredient and the supported body structure associated with it.

Advertising for herbal and dietary supplements may come in many forms, including packaging, television/internet ads, and increasingly the use of “social media influencers.” [8] The Federal Trade Commission (FTC) regulates all forms of advertising, and is charged with ensuring that advertising claims are not deceptive or misleading. If a product is suspected of advertising using misleading information, or the product is noted to cause harmful side effects, consumers are urged to notify the FDA and the FTC, in order to have the product removed from the market. To report a product, consumers can contact the FDA at 1-800-FDA-1088 (1-800-332-1088), and the FTC at [9]

Due to the stringency of health and structure-function claim requirements, the use of vague statements about the effects of supplements in advertising may be used to promote the product. [14, 15] Because of this ambiguity, it is important that consumers communicate with their healthcare providers to discuss any possible benefits or hazards associated with using a supplement.

What are the Benefits of Using Herbal and Dietary Supplements?

Dietary supplements can be used to ensure that some consumers meet their needs for certain nutrients, like vitamins and minerals. [4] For example, specific supplements and supplement combinations may be beneficial at mitigating the onset of conditions such as age-related macular degeneration in adults aged 65 years and older. [16] Most consumers, however, use supplements as a way to “maintain health” or “supplement the diet,” and less than a quarter of these consumers use supplements based on the advice of a healthcare professional. [17]

What are the Dangers of Using Herbal and Dietary Supplements?

The FDA has the power to remove a product from the market if there is evidence that it is unsafe for consumers. However, it should be noted that unlike medications, dietary supplements do not have to be proven safe or effective before entering the market. [1] It is possible that after reaching consumers, supplements may be found to be unsafe for use. As an example, dietary supplements which contained ephedrine alkaloids were marketed as supplements that promoted weight loss and energy-enhancement. [18] However, in 2004 the FDA banned the sale of dietary supplements containing these compounds, due to increased risk of heart attack, stroke, seizure, and death. [18, 19]

To assess the safety of supplements, some dietary supplements may be assessed by third party agencies, such as NSF International and US Pharmacopeia (USP) [20, 21]. These agencies work to confirm that supplements contain the ingredients listed on labels, as well as certify that there are no contaminants in the supplement. The agencies do not, however, assess efficacy of dietary supplements. [20]

The Dietary Supplement Health Education Act of 1994 (DSHEA) gives the ability for the FDA to remove a product from the market if it is found to be unsafe for consumers and requires that dietary supplements include the following statement on product labels if they include beneficial claims: “This statement has not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.” [22]

Some supplements may cause harmful side effects or interact with medications. For example, vitamin K can reduce the effectiveness of warfarin, which is taken as a blood thinner, and antioxidant supplements (including vitamins C and E) may reduce the effectiveness of some cancer chemotherapies. [5] Other potential interactions include ginseng and chamomile, which can decrease the anticoagulant effect of warfarin. [23] Common herbal supplements and their drug interactions are noted in Table 1. All individuals considering the use of an herbal or dietary supplement should consult with a healthcare professional before beginning use, especially if that individual is a member of an at-risk group, or if they are currently using any other supplements or drugs. [5]

Table 1. The Most Common Herbal Medicines Reported in Herb-Drug Interactions [23]



Herb-Drug Interaction

St. John’s Wort

  1. Cyclosporine, Midazolam, Tacrolimus, Amitriptyline, Digoxin, Indinavir, Warfarin, Phenprocoumon, Theophylline, Irinotecan, Alprazolam, Dextromethorphan, Simvastatin
  2. Oral Contraceptives
  3. Sertraline, Paroxetine, nefazodone
  4. Antidepressants or serotonergic drugs
  1. Decreases blood concentrations of these drugs
  2. Breakthrough bleeding and unplanned pregnancies
  3. Serotonin syndrome
  4. Gastrointestinal disorder, allergic reactions, fatigue, dizziness, confusion, dry mouth, photosensitivity


  1. Saquinavir
  2. Warfarin sodium
  3. Acetaminophen
  4. Chlorpropamide
  1. Decreases blood concentration of saquinavir
  2. Alters bleeding time
  3. Changes in breakdown time
  4. Hypoglycemia


  1. Phenelzine sulfate
  2. Estrogens or Corticosteroids
  1. Induction of mania and blood concentration reduction of alcohol and warfarin; headache; trembling
  2. Enhanced effects


  1. Warfarin
  1. Enhances anticoagulation and bleeding


  1. Warfarin, aspirin, ticlopidine, clopidogrel, dipyridamole
  2. Thiazide diuretic
  3. Trazodone
  4. Levodopa
  1. Bleeding
  2. Raises blood pressure
  3. Coma
  4. Increases “off” periods in Parkinson’s patients


  1. Alprazolam
  2. Cimetidine and terazosin
  3. Benzodiazepines
  1. Semicomatose state or coma
  2. Lethargy and disorientation
  3. Coma

Milk Thistle

  1. Indinavir
  1. Decreases circulating concentrations


  1. Spironolactone
  1. Decreased effectiveness

Echinacea, kava, ginkgo, ginseng, garlic, St. John’s Wort

  1. Anticancer drugs
  1. Interference and decreased effectiveness


  1. Anabolic Steroids, Amiodarone, Methotrexate, and Ketoconazole
  1. Hepatotoxicity

Feverfew, garlic, ginkgo, ginger, ginseng

  1. Warfarin sodium
  1. Alteration of bleeding time


  1. Barbiturates
  2. Central nervous system depressants
  1. Excessive sedation
  2. Increased drug effects

Ma Huang (Ephedra)

  1. Caffeine, decongestants, and stimulants
  1. Hypertension, insomnia, arrhythmia, nervousness, tremor, headache, seizure, stroke, heart attack

Bitter Melon, ginseng

  1. Diabetes mellitus drugs
  1. Blood glucose level effect

Lycium, mango, papaya

  1. Warfarin
  1. Anticoagulant effect increased


  1. Glipizide, Insulin
  2. Heparin, Ticlopidine, Warfarin
  1. Excessive decrease of blood sugar levels
  2. Bleeding

Gum guar, wheat bran

  1. Digoxin
  1. Plasma digoxin concentration decreased

Borage, evening primrose oil

  1. Anticonvulsants
  1. Seizure threshold lower


  1. Office of Dietary Supplements. Background Information: Dietary Supplements. NIH Office of Dietary Supplements. Published June 24, 2011. Accessed July 4, 2019.
  2. 2018 CRN Consumer Survey on Dietary Supplements. Council for Responsible Nutrition. Published October 18, 2018. Accessed July 4, 2019.
  3. Qato DM, Alexander GC, Guadamuz JS, Lindau ST. Prevalence of Dietary Supplement Use in US Children and Adolescents, 2003-2014. JAMA Pediatr. 2018;172(8):780–782. doi:10.1001/jamapediatrics.2018.1008. Accessed July 4, 2019. 
  4. U.S. Department of Health and Human Services and U.S. Department of Agriculture. Dietary Guidelines for Americans 2015–2020 8th Edition. 2015-2020 Dietary Guidelines. Published December 2015. Accessed July 4, 2019. 
  5. Dietary Supplements: What You Need to Know. NIH Office of Dietary Supplements. Published June 17, 2011. Accessed July 4, 2019.
  6. Bowen KJ, Harris WS, Kris-Etherton PM. Omega-3 Fatty Acids and Cardiovascular Disease: Are There Benefits? Current Treatment Options in Cardiovascular Medicine. 2016;18(11). doi:10.1007/s11936-016-0487-1.
  7. Using Dietary Supplements Wisely. National Center for Complementary and Integrative Health. Published January 15, 2019. Accessed July 18, 2019.
  8. Carnett L. Influencer marketing in the ingredient and dietary supplement space. Natural Products INSIDER. Published September 24, 2018. Accessed July 18, 2019.
  9. Dietary supplement concerns? Tell the FTC and FDA. Consumer Information. Published March 13, 2018. Accessed July 18, 2019.
  10. Pauling L. The significance of the evidence about ascorbic acid and the common cold. Proceedings of the National Academies of Sciences USA 1971;68:2678-81. Published November, 1971. Accessed 22 July, 2019.
  11. Office of Dietary Supplements - Vitamin C. NIH Office of Dietary Supplements. Accessed July 22, 2019.
  12. Hemila H, Chalker E. Vitamin C for preventing and treating the common cold. Cochrane Database of Systematic Reviews 2013. 2013;(1). doi:10.1002/14651858.CD000980.pub4. Published January 31, 2013. Accessed July 22, 2019.
  13. Institute of Medicine; Food and Nutrition Board, Panel on Dietary Antioxidants, Standing Committee, Scientific Evaluation of Dietary Reference Intakes. Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids. The National Academies Press. Published April 11, 2000. Accessed July 22, 2019.
  14. Royne MB, Myers SD, Deitz G, Fox AK. Risks, Benefits, and Competitive Interference: Consumer Perceptions of Prescription Drug Versus Dietary Supplement Advertising. Journal of Current Issues & Research in Advertising. 2016;37(1):59-79. doi:10.1080/10641734.2015.1119769. Published January 28, 2016. Accessed July 18, 2019.
  15. Rotfeld HJ. Health Information Consumers Can’t or Don’t Want to Use. Journal of Consumer Affairs. 2009;43(2):373-377. doi:10.1111/j.1745-6606.2009.01145.x. Published June 1, 2009. Accessed July 18, 2019.
  16. Age-Related Eye Disease Study Research Group. A Randomized, Placebo-Controlled, Clinical Trial of High-Dose Supplementation With Vitamins C and E, Beta Carotene, and Zinc for Age-Related Macular Degeneration and Vision Loss. Archives of Opthamology. 2001;119(10):1417-1436. doi:10.1001/archopht.119.10.1417. Published October, 2001. Accessed July 18, 2019.
  17. Bailey RL, Gahche JJ, Miller PE. Why Adults Use Dietary Supplements. JAMA Internal Medicine. 2013;173(5):355-361. Published March 11, 2013. Accessed July 18, 2019.
  18. Ephedra. NCCIH. Published November 9, 2011. Accessed December 31, 2019.
  19. Office of Dietary Supplements - Ephedra and Ephedrine Alkaloids for Weight Loss and Athletic Performance. Accessed December 31, 2019.
  20. Supplement and Vitamin Certification - NSF International. Accessed December 29, 2019.
  21. Dietary Supplements Verification Program – US Pharmacopeia. Accessed January 10, 2020
  22. Swann JP. The history of efforts to regulate dietary supplements in the USA. Drug Test Anal. 2016;8(3-4):271-282. doi:10.1002/dta.1919
  23. Skalli S, Zaid A, Soulaymani R. Drug Interactions with Herbal Medicines. Therapeutic Drug Monitoring. 2007;29(6):679-686. doi:10.1097/FTD.0b013e31815c17f6. Published December 2007. Accessed July 17, 2019.


Inquiries regarding this publication may be directed to The information provided in this publication is intended for general consumer understanding, and is not intended to be used for medical diagnosis or treatment, or to substitute for professional medical advice.

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