Introduction

Drug stores and supermarkets stock multiple aisles of nutritional supplements, ranging from multivitamins, probiotics, memory enhancers, hair growth supplements, to protein powders and sleep aids. 

American consumers are bombarded with supplement advertisements on television, social media and online. Since the Covid 19 pandemic, supplement use has surged as Americans look to control their health.  

According to the National Institutes of Health (NIH) Office of Dietary supplements, over half of all United States (U.S.) adults take at least one dietary supplement on a regular basis. For those over 60, the number increases to more than 70%, and both Millennials and Generation Z are increasingly using probiotics, collagen powders and energy supplements. The U.S. supplement industry has a market size between $68 to $78 billion per year.

While supplements can be a vital part of becoming and staying healthy, it’s important to understand their role. For example, probiotics can be a great supplement to regulate the gut, if there are problems with diarrhea or constipation. Many healthcare providers recommend over the counter supplements such as Vitamin D, calcium, or magnesium if inadequacies exist. 

Supplements, however, can be overused and can have dangerous side effects, particularly if they interact poorly with other medications. This fact sheet provides background and general guidance on supplement use, to allow consumers to understand the benefits and risks.

How Are Supplements Regulated?

In the United States, dietary supplements are regulated by the Food and Drug Administration (FDA) and the Federal Trade Commission (FTC).

FDA

The FDA regulates dietary supplements under the Dietary Supplement Health & Education Act of 1994 (DSHEA), as a category of food, not drugs. This means that the FDA is not authorized to review dietary supplements for safety or effectiveness before they are sold to the public. 

The FDA can pull a supplement from the market as a recall if deemed unsafe or mislabeled, but it must prove that the product is harmful or adulterated. Even with voluntary recalls, many harmful supplements may remain on the market for extended periods. 

The FDA has established current good manufacturing practices (CGMPs) to ensure the product’s purity, strength, and composition. In terms of labeling, manufacturers are prohibited from claiming that a supplement can diagnose, treat, cure, or prevent any disease. Companies can make claims about how a supplement affects the structure or function of the body (for example, ‘calcium builds strong bones’).  These claims must be substantiated with evidence.

FTC

The FTC regulates the advertising and marketing of dietary supplements, ensuring that claims made in promotional ads are truthful, not misleading, and supported by scientific evidence. The FTC handles claims made in ads, websites, and other marketing materials.

Limitations

• The after-the-fact approach means that a potentially harmful or mislabeled products can be on the market for a long period of time before the FDA becomes aware of it;
• Manufacturers do not need to prove that their supplements are effective before marketing them;
• There is considerable consumer confusion about structure/function claims being interpreted to mean that supplements treat or cure disease, when they are not regulated to do so;
• Some supplements can be contaminated with heavy metals, bacteria, illegal drugs or other prescription medications.

Independent third-party organizations like U.S. Pharmacopeia (USP) or NSF International offer quality testing and seals of approval. 

While these seals indicate that a product was manufactured properly, contains the ingredients listed on the label, is free from contaminants, they do not guarantee effectiveness.

Types of Supplements

Supplements can be in liquid, extract, powder, gummy, capsule or tablet form.

• Vitamins and minerals (as a complete supplement or single dose vitamin or mineral);
• Botanicals and herbs, such as echinacea, garlic, turmeric;
• Joint health, such as glucosamine;
• Eye health;
• Brain health;
• Probiotics and prebiotics;
• Fish oils;
• Protein powders;
• Collagen;
• Melatonin and sleep aids;
• Cardiac supplements such as beet powder;
• Amino acids;
• Hair growth;
• Fiber.

Do Supplements Work?

The available evidence of whether dietary supplements work is mixed. Some dietary supplements do what their manufacturers claim, while others don’t work as advertised. Some research into the health benefits of supplements is promising. 

For example, fiber supplements can relieve chronic constipation and lower cholesterol levels. Vitamin D supplementation does raise vitamin D levels in the blood and correct deficiency. 

The most effective supplement classes are generally those that address common deficiencies or have significant research backing, including vitamins (especially Folic Acid, D, C, & B12), minerals (such as magnesium, iron & calcium), Omega 3 Fatty Acids, Probiotics, and Creatine. It is important to look at the scientific research behind a supplement claim to assess the veracity of effectiveness.

 Megadosing on supplements is not recommended as this can pose significant risks including potential toxicity and adverse health effects. Tolerable Upper Intake Levels (ULs) have been established for vitamins and minerals to avoid these risks; for other supplements ULs don’t exist as there is limited data to establish the maximum safe dose.

Adverse Reactions

For most people, taking common dietary supplements is safe and doesn’t pose serious health risks. Evidence of the unfavorable effects of supplement use continues to accumulate, however. 

An estimated 23,000 emergency room visits in the U.S. every year are attributed to adverse events related to dietary supplements. Visits commonly involve cardiovascular manifestations from weight loss and energy products among young adults, and swallowing problems associated with large pill supplements among older adults. 

In addition, it’s estimated that 20% of drug-induced liver toxicities in the U.S. are related to herbal and dietary supplements. Anyone can have an adverse reaction to a supplement, particularly if you take a large dose, use not as directed, or combine many supplements.  

Adverse reactions could include:

• Stomach pain;
• Nausea and vomiting;
• Lightheadedness or fatigue;
• Chest pain;
• Difficulty breathing;
• Rapid heart rate;
• Difficulty urinating or dark urine;
• Diarrhea;
• Loss of appetite;
• Unintended weight loss;
• Anxiety; 
• Reflux.

If you are allergic to a supplement or supplement ingredients, you may experience an allergic reaction. This can present as rash or hives, itching and swelling in the throat, tongue or lips,

Drug Interactions

Certain supplements may have harmful interactions with medications and other supplements.  Taking multiple supplements or combining supplements with prescribed medications can increase the risk of side effects or make your medication less effective. This is particularly true for senior citizens who are taking multiple prescription medications.

Safe Use of Supplements

There are some things you can do to make sure you are using supplements safely and appropriately.

• If you are taking more than a multivitamin supplement, on multiple supplements and/ or prescription medications talk to your healthcare provider before use;
• Take supplements exactly as directed;
• If you experience any side effects from a supplement, stop taking it immediately;
• Purchase supplements from reputable manufacturers;
• Choose supplements with the USP or NSF seal;
• If a marketing claim sounds too good to be true, research the supplement for scientific evidence of claims;
• If scheduled for surgery, let your health care provider know which supplements you are taking.  Some can interfere with anesthesia or risk post-operative bleeding;
• Be aware that multi-ingredient weight loss and bodybuilding supplements and herbals such as green tea extract, kava, ashwagandha and turmeric taken in high doses can cause liver toxicity or liver failure.

Conclusion

The rise in supplement use among American consumers will continue to grow as people try to improve their health and well-being. Some supplements are a useful adjunct to a person’s diet, either to correct a deficiency or address a health problem.

While most supplements are not harmful when taken appropriately, it is important to not overuse them and be mindful of their use when taking prescription medications. Consumers should talk to their health care provider for guidance before supplementing, and research the benefits before spending money. It is important to understand the benefits and risks of supplement use and research them beyond the marketing hype to avoid harm or wasting money.

Resources

Using dietary supplements wisely. (February 2020). NIH National Center for Complementary & Integrative Health. https://www.nccih.nih.gov/health/dietary-and-herbal-supplements 

Supplement use is on the rise. (August 30, 2021).  Jonas, W., Psychology Today https://www.psychologytoday.com/us/blog/how-healing-works/202108/supplement-use-is-the-rise 

Assadourian, J., Peterson, E. & Navar, A. (2025). Label statements and perceived health benefits of dietary supplements. JAMA Netw Open. 2025;8(9):e2533118. doi:10.1001/jamanetworkopen.2025.33118 

Three-quarters of Americans take dietary supplements: Most users agree they are essential to maintaining health (October 5, 2023). CRN https://www.crnusa.org/newsroom/three-quarters-americans-take-dietary-supplements-most-users-agree-they-are-essential 

Wierzejska RE. Dietary Supplements-For Whom? The Current State of Knowledge about the Health Effects of Selected Supplement Use. Int J Environ Res Public Health. 2021 Aug 24;18(17):8897. doi: 10.3390/ijerph18178897. PMID: 34501487; PMCID: PMC8431076. 

Geller, A.,Shehab, N., Weidle, N., Lovegrove, B. Wolpert, B., Timbo, B.,Mozersky, R. & Budnitz. D. Emergency department visits for adverse events related to dietary supplements (2015). New England Journal of Medicine. https://www.nejm.org/doi/full/10.1056/NEJMsa1504267 

Navarro VJ, Khan I, Björnsson E, Seeff LB, Serrano J, Hoofnagle JH. Liver injury from herbal and dietary supplements. Hepatology. 2017 Jan;65(1):363-373. doi: 10.1002/hep.28813. Epub 2016 Nov 17. PMID: 27677775; PMCID: PMC5502701.