Is there a downside to taking collagen supplements? A closer look at the risks

October 5, 2025 •

4 min read

While often marketed as a beauty and joint health miracle, a 2020 Clean Label Project report found that nearly 30% of tested collagen supplements contained alarming levels of heavy metals. This raises a critical question: Is there a downside to taking collagen supplements, or are the risks purely a matter of product quality?

Quick Summary

Potential downsides of collagen supplements include sourcing and quality concerns, a lack of FDA regulation, and possible digestive discomfort. Allergic reactions, contamination, and interactions with certain medications are other important considerations for consumers.

Key Points

Digestive issues are common: Some people experience bloating, gas, heartburn, or diarrhea when taking collagen, especially at high doses or with less-hydrolyzed forms.
Heavy metals are a concern: Due to poor sourcing and a lack of regulation, some supplements have been found to contain toxic heavy metals like lead and cadmium.
Allergy risk is present: Collagen derived from animal products can trigger allergic reactions in those sensitive to fish, shellfish, or eggs.
Kidney stone risk exists: The hydroxyproline in collagen can convert to oxalate, increasing the risk of kidney stones for susceptible individuals.
Regulation is inconsistent: The supplement market lacks tight FDA oversight, leading to variable product quality and inaccurate dosage claims.
Cost vs. benefit: High-quality collagen supplements can be expensive, and a balanced diet is a more cost-effective and reliable way to support natural collagen production.

For years, collagen supplements have been touted as a go-to for improving skin elasticity, strengthening hair and nails, and supporting joint health. However, beneath the glowing testimonials and marketing promises, a number of potential downsides exist that are important for consumers to understand before adding these products to their daily routine. From digestive discomfort to serious concerns about contaminants and regulatory oversight, the full picture is more complex than it appears.

Potential Health Side Effects

Despite being generally well-tolerated, some individuals experience a range of side effects when taking collagen supplements. The severity of these issues can depend on dosage, product quality, and individual sensitivity.

Digestive Discomfort

One of the most frequently reported complaints is gastrointestinal distress. For some, this manifests as a feeling of fullness or heaviness in the stomach, while others experience more pronounced symptoms.

Bloating and gas are common, often linked to how the body processes the increased protein intake from the supplement.
Nausea and heartburn have also been noted, particularly when taking high doses or supplements with a poor absorption profile.
Diarrhea or constipation can occur, sometimes related to high protein levels without enough fiber or fluid.

These digestive issues are more likely with less-hydrolyzed collagen, which is harder for the body to break down, and may be exacerbated by other additives in the product.

Allergic Reactions

Because most collagen supplements are derived from animal sources—such as bovine (cow), marine (fish), or porcine (pig)—they can trigger allergic reactions in susceptible individuals. Those with pre-existing allergies to fish, shellfish, or eggs must be particularly vigilant about checking the product’s source. Symptoms can range from a mild rash or itching to more severe reactions requiring immediate medical attention.

The Risk of Kidney Stones

Collagen contains the amino acid hydroxyproline, which is converted to oxalate in the body. Excessive intake of oxalate can increase the risk of calcium oxalate kidney stones, especially for those with a history of them. While moderate intake is unlikely to cause issues in healthy individuals, those with kidney problems or a predisposition to stones should consult a doctor and monitor their intake.

Sourcing, Quality, and Contamination Concerns

Beyond the physiological effects on the body, the supplement industry's lack of strict regulation introduces significant risks regarding product quality and contamination.

Heavy Metal Contamination

A major and potentially serious downside is the risk of heavy metal contamination. Studies have exposed that some popular collagen products contain measurable amounts of heavy metals like arsenic, lead, and cadmium. These metals accumulate in animal tissues, and since supplements are often made from animal bones and hides, they can become a source of these toxic substances. Consumers should seek third-party tested and certified products to minimize this risk.

Inconsistent Potency and Ingredients

Unlike pharmaceuticals, the U.S. Food and Drug Administration (FDA) does not regulate supplements for safety or efficacy before they are sold. This means that the amount of collagen and the quality of other ingredients can vary significantly between brands. Consumers may purchase products that contain more or less of the stated ingredients, or unnecessary additives and fillers, which can affect both the product's effectiveness and safety.

Unsubstantiated Health Claims

Aggressive marketing often oversells the benefits of collagen supplements, claiming dramatic improvements for issues like hair growth, gut health, and brain function. The scientific evidence for some of these claims is limited or based on small, industry-funded studies. A healthy, balanced diet rich in protein, vitamin C, and zinc is a proven, less expensive, and more reliable way to support the body's natural collagen production.

Comparison of Collagen Supplement Risks vs. Benefits


Aspect	Potential Downside (Risks)	Potential Upside (Benefits)
Digestive System	Bloating, gas, nausea, heartburn, diarrhea, constipation.	May aid in regulating gastric acid and supporting gut lining healing in some cases.
Allergies	Risk of allergic reactions if allergic to source (fish, shellfish, eggs, beef).	None, as allergies are an adverse reaction.
Kidney Health	Increased risk of calcium oxalate kidney stones for susceptible individuals due to hydroxyproline conversion.	None, potential risks outweigh any theoretical benefits.
Heart Health	High protein levels may interfere with blood pressure medications like propranolol.	Some studies show potential for improved markers of heart health, but evidence is not conclusive.
Product Quality	Risk of heavy metal contamination and inconsistent potency due to limited regulation.	High-quality, tested products can deliver on a portion of their claims for skin and joints.
Cost	Can be expensive, and results may not be more effective than a balanced diet and healthy lifestyle.	Cost is subjective and depends on perceived benefits and financial situation.

Who Should Be Cautious About Taking Collagen?

Certain groups of people should approach collagen supplementation with caution and consult a healthcare provider before starting:

Individuals with allergies: Anyone with allergies to fish, shellfish, eggs, or beef should avoid supplements derived from those sources.
People with kidney disease: The protein load from supplements can put extra strain on compromised kidneys.
Those with a history of kidney stones: Due to the risk of oxalate conversion.
Pregnant or breastfeeding women: The safety of collagen supplements for this population has not been extensively studied.
People taking certain medications: Specifically, those on blood pressure medications or anticoagulants should consult a doctor due to potential interactions.

Conclusion

While collagen supplements may offer some benefits for skin, hair, and joint health, they are not without potential downsides. Consumers should be aware of the risks, including digestive issues, allergic reactions, potential heavy metal contamination, and an increased risk of kidney stones for predisposed individuals. The lack of stringent FDA regulation means that product quality can be highly variable. For those considering collagen supplements, prioritizing high-quality, third-party tested products and consulting with a healthcare professional is crucial. Ultimately, a balanced diet rich in protein, fruits, and vegetables remains a reliable and often more cost-effective way to support the body's natural collagen production.

The True Content and Faces Behind America's Best-Selling Collagen (source link: https://cleanlabelproject.org/wp-content/uploads/Organic-Consumers-Assoc-White-Paper_Updated.pdf)

Frequently Asked Questions

The most common side effects include mild digestive issues such as bloating, gas, nausea, and a feeling of fullness. These are often related to dosage or individual sensitivity and may decrease over time.

For healthy individuals, moderate collagen intake is unlikely to cause kidney stones. However, for those with a history of kidney stones or kidney disease, the hydroxyproline in collagen can convert to oxalate and increase the risk of forming calcium oxalate stones.

Yes, it is a significant risk. Because supplements are not strictly regulated by the FDA, some products have been found to contain heavy metals like lead, arsenic, and cadmium, which can accumulate in animal tissues used for sourcing.

If you have allergies to common animal-derived sources like fish, shellfish, or eggs, you should carefully check the product's label to avoid an allergic reaction. Marine collagen, for instance, should be avoided by those with fish or shellfish allergies.

There is some evidence that high protein intake, including from collagen, could interfere with the effectiveness of certain medications, such as some blood pressure medications. Always consult your doctor before starting any new supplement, especially if you are on prescription medication.

While collagen offers some benefits, a healthy, balanced diet rich in protein, vitamin C, and zinc provides the necessary building blocks for your body to produce collagen naturally. For many, this is a more cost-effective and reliable approach than relying on expensive supplements.

Most collagen supplements are animal-derived, making them unsuitable for vegans and vegetarians. However, some newer vegan options are available, though they may not be based on collagen peptides directly.

To enhance safety, choose reputable brands that use high-quality sourcing and provide evidence of third-party testing for contaminants like heavy metals. Look for certifications from organizations that verify product quality and purity.