Which of the following are examples of adulterants that are commonly found in dietary supplements?

January 13, 2026 •

3 min read

According to the FDA, hundreds of dietary supplements have been found to contain undeclared, unapproved pharmaceutical ingredients, posing a serious public health risk. This guide explains which of the following are examples of adulterants that are commonly found in dietary supplements and the dangers they present to consumers who believe they are taking safe, 'natural' products.

Quick Summary

This article examines the various types of adulterants hidden in dietary supplements, details their associated health risks, and provides strategies for identifying potentially contaminated products.

Key Points

Hidden Drugs: Many dietary supplements are adulterated with undeclared, unapproved pharmaceutical ingredients like Sibutramine (for weight loss) and Sildenafil (for sexual enhancement).
Heavy Metal Contamination: Environmental contaminants like lead, arsenic, and cadmium are frequently found in protein powders and other botanical supplements due to soil and processing issues.
Banned Steroids: Muscle-building supplements are often spiked with illegal anabolic steroids or related compounds, which can cause severe health problems.
Microbial Risks: Poor manufacturing hygiene and contaminated raw materials can introduce dangerous bacteria and fungi into dietary supplements.
Third-Party Verification: The best way to ensure supplement safety is to purchase products verified by independent organizations like USP, NSF, or ConsumerLab.com.
Exaggerated Claims: Be cautious of marketing that promises dramatic, rapid results, as this is a common red flag for adulterated products.
Dangerous Side Effects: Adulterated supplements can cause serious adverse health events, including heart attacks, strokes, liver damage, and drug interactions.

Common Categories of Adulterants

Adulteration in dietary supplements can be intentional, often motivated by economic gain, or unintentional, resulting from poor manufacturing practices. The types of adulterants can vary widely depending on the supplement's market and intended effect. Key categories include:

Active Pharmaceutical Ingredients (APIs): Illegal or unapproved prescription drugs are often secretly added to boost a supplement's effectiveness and achieve faster results.
Heavy Metals: Contamination can occur from soil, water, or manufacturing processes, especially in plant-based supplements.
Microbiological Contaminants: Bacteria and fungi can enter products due to improper harvesting, storage, or hygiene during manufacturing.
Herbal Contaminants and Substitutions: Cheaper, incorrect, or even toxic herbs are sometimes substituted for legitimate, often more expensive, botanical ingredients.

Adulterants in Targeted Supplements

Weight Loss Supplements

Supplements marketed for rapid weight loss are notorious for containing dangerous, undeclared substances. The FDA has issued numerous warnings about this category. Common adulterants include Sibutramine, a withdrawn appetite suppressant linked to increased heart attack and stroke risk, Phenolphthalein, a laxative with potential carcinogenic risks, and the antidepressant Fluoxetine, which can cause serious side effects.

Sexual Enhancement Supplements

These products are frequently adulterated with ingredients found in prescription erectile dysfunction drugs. Examples include Sildenafil (active ingredient in Viagra) and Tadalafil (active ingredient in Cialis). Manufacturers also use chemically similar compounds (analogues) that haven't been tested for safety or efficacy.

Muscle-Building Supplements

Products for strength and performance are often contaminated with illegal steroids. This includes undeclared synthetic steroids or steroid-like ingredients, which pose severe risks like liver injury and cardiovascular problems. Other stimulants like DMAA and Higenamine, linked to cardiovascular events, have also been found.

Unintentional Contaminants

Supplements can also be contaminated with environmental and microbial agents unintentionally.

Heavy Metals: A review of protein powders found many contained heavy metals like lead, arsenic, cadmium, and mercury, which are linked to cancer and other health issues.
Microbial Growth: Poor conditions can lead to bacterial and fungal contamination. One analysis found bacteria in all 138 herbal products they investigated.
Pesticides: Residues from farming pesticides can end up in finished products.

Comparison of Common Adulterants by Supplement Category


Supplement Category	Common Adulterants	Key Health Risks	Intentional or Unintentional?
Weight Loss	Sibutramine, Phenolphthalein, Fluoxetine	Cardiovascular events, cancer risk, drug interactions	Primarily intentional
Sexual Enhancement	Sildenafil, Tadalafil, PDE-5 analogues	Dangerous drop in blood pressure, vision issues, priapism, drug interactions	Primarily intentional
Muscle Building	Anabolic steroids, synthetic stimulants (DMAA)	Liver damage, kidney damage, cardiovascular issues, hormonal disruption	Primarily intentional
Herbal/Protein	Heavy metals (Lead, Mercury), Pesticides, Microbes (bacteria, fungi)	Cancer, neurological damage, kidney and liver problems, infections	Often unintentional, but can be intentional

Protecting Yourself from Adulterated Supplements

Since dietary supplement manufacturers are not required to prove safety or efficacy to the FDA before marketing a product, consumers must take proactive steps. The most reliable method is to look for third-party verification marks from independent testing organizations.

Third-Party Certification: Look for seals from reputable organizations like United States Pharmacopeia (USP), NSF International, or ConsumerLab.com. These certifications verify that the product was tested for purity, potency, and contaminants.
Scrutinize Marketing Claims: Be cautious of products that promise rapid, unbelievable results. Claims like "miracle cure," "fast-acting," or "100% natural" can be deceptive.
Consult a Healthcare Provider: Always discuss any supplements you plan to take with a doctor or registered dietitian, especially if you have pre-existing conditions or are on other medications.
Report Adverse Effects: If you experience any adverse reactions, report them to the FDA's MedWatch Program. These reports help the FDA identify problematic products.
Be Aware of the Source: Consider the retailer and the country of origin. Products sold online from obscure sellers or imported from regions with lax regulations carry higher risk.

Conclusion

Many dietary supplements contain harmful adulterants, ranging from intentionally added banned drugs and steroids to unintentionally included heavy metals and microbes. These adulterants pose substantial health risks. Understanding what to look for and choosing products with third-party certification are key steps consumers can take to make safer choices. For more information, visit the FDA's official website on avoiding products with hidden ingredients.

Frequently Asked Questions

Sibutramine is one of the most commonly identified adulterants found in weight loss supplements, despite being withdrawn from the market due to increased cardiovascular risk.

It is difficult to know if a product is adulterated just by looking at it, as illegal ingredients are hidden. The most reliable method is to look for third-party verification seals from organizations like USP or NSF on the product label.

Heavy metals such as lead and mercury can cause severe and lasting health problems, including cancer, neurological damage, and kidney or liver damage.

Manufacturers may illegally add pharmaceutical drugs to boost the perceived efficacy of a supplement and ensure consumers see faster results. This is often done for economic gain.

Yes, herbal supplements can be unintentionally contaminated with heavy metals absorbed from soil, pesticides used during farming, and microorganisms like bacteria and fungi due to poor handling or processing.

No, the FDA does not approve dietary supplements for safety or efficacy before they are sold. The responsibility lies with the manufacturers to ensure their products are safe and accurately labeled, and the FDA only takes action after a product is on the market.

If you suspect a supplement is contaminated or have an adverse reaction, stop using it immediately and consult a healthcare professional. You should also report the issue to the FDA's MedWatch Program.