Are there any negatives to taking collagen? A closer look at the risks and downsides

October 5, 2025 •

4 min read

While often marketed for its benefits to skin and joint health, recent data indicates that collagen supplements are not without potential downsides. Understanding these negatives is crucial for making an informed decision about whether to add collagen to your diet.

Quick Summary

Despite its popularity, collagen supplementation carries risks including potential digestive upset, allergic reactions, and kidney-related complications, especially for individuals with pre-existing conditions. Quality control issues, unpleasant tastes, and potential for interaction with other supplements also exist, requiring careful consideration and informed choices.

Key Points

Digestive Upset: Some individuals report mild side effects like bloating, nausea, or diarrhea, often due to additives or poor digestibility of the supplement.
Allergy Risk: Allergic reactions are possible, especially for those with sensitivities to the animal sources (fish, beef, chicken) from which collagen is derived.
Kidney Health Concerns: People with kidney disease or a history of kidney stones should be cautious, as the amino acid hydroxyproline can increase oxalate levels, potentially leading to stone formation.
Contamination Issues: Because the supplement industry is not strictly regulated, products may contain heavy metals or other contaminants, highlighting the need for third-party tested brands.
Ingredient Interactions: Collagen supplements sometimes contain additional ingredients that could interact with medications or cause adverse effects in specific populations, like pregnant women.
Questionable Efficacy for Specific Needs: Since the body breaks collagen into amino acids and uses them as needed, there is no guarantee that supplements will directly benefit the intended area, such as skin elasticity.
Unpleasant Taste: Many unflavored collagen powders can have a persistent, unpleasant aftertaste, particularly those from marine sources.

Collagen supplements have surged in popularity, promising improvements for skin, hair, nails, and joints. While generally considered safe for most healthy individuals, it is important to understand the potential downsides that can arise from their use. Side effects range from mild digestive issues to more serious risks, including allergic reactions and potential complications for individuals with underlying health conditions. The unregulated nature of the supplement industry, potential for contamination, and formulation with additional ingredients also present notable concerns.

Potential Side Effects and Adverse Reactions

Digestive Issues

Some of the most common complaints associated with taking collagen supplements are digestive problems. These can include feelings of fullness or heaviness, bloating, diarrhea, or mild gastrointestinal upset. For most people, these symptoms are temporary and can be mitigated by adjusting the dosage or taking the supplement with food. However, for those with pre-existing conditions like irritable bowel syndrome (IBS) or a sensitive gut, collagen may exacerbate these issues. The source and type of collagen can also affect digestibility; for instance, hydrolyzed collagen is generally easier to absorb.

Unpleasant Taste

Unflavored collagen powders, particularly those from marine sources, can leave an unpleasant, lingering aftertaste. While this is not a health risk, it can be a deterrent for continued use. To mask the taste, manufacturers often add flavorings, which may contain artificial ingredients or sweeteners. Alternatively, users can mix the powder with smoothies, coffee, or other flavorful beverages.

Allergic Reactions

One of the most significant risks is the potential for allergic reactions, particularly for those with existing food allergies. Since collagen is typically sourced from animals, like fish (marine collagen), cows (bovine collagen), or chicken, individuals with allergies to these sources should avoid specific types. Symptoms can range from mild skin rashes and hives to more severe reactions like swelling of the face or throat and difficulty breathing. Anyone with known allergies should read product labels carefully and, if concerned, opt for hypoallergenic alternatives or consult a doctor.

Serious Health Considerations

Risks for Individuals with Kidney Issues

For most people with healthy kidneys, moderate collagen consumption is safe. However, individuals with a history of kidney stones or chronic kidney disease should exercise caution. Collagen contains the amino acid hydroxyproline, which is converted to oxalate in the body. High levels of oxalate can lead to the formation of kidney stones. The kidneys are also responsible for filtering waste products from protein metabolism, and excessive protein intake can increase their workload. Those with compromised kidney function should consult a healthcare provider before supplementing.

Concerns over Contamination

Dietary supplements, including collagen, are not strictly regulated by the FDA, meaning there's less oversight regarding their purity and safety. This lack of regulation raises concerns about potential contaminants, such as heavy metals (like arsenic, lead, and cadmium) that can accumulate in animal tissues. A Clean Label Project report even found that nearly 30 collagen supplements tested positive for heavy metals. To mitigate this risk, consumers should choose reputable brands that perform third-party testing and provide certificates of analysis.

Interactions with Medications

While there are no widely reported direct interactions between collagen and medications, other ingredients often found in collagen supplements could pose a risk. Many formulations include added vitamins, minerals, and herbal extracts that may interfere with commonly prescribed medications, especially blood thinners. It is crucial to discuss any supplements with a healthcare professional, particularly if taking other medications, are pregnant, or nursing.

Limited Scientific Evidence for Certain Claims

Despite the robust marketing, scientific evidence for some of collagen’s purported benefits is limited or mixed. For instance, the body breaks down ingested collagen peptides into amino acids, which are then used where the body needs them most, not necessarily where the user intends, such as a specific area of the skin. Additionally, many studies showing benefits were funded by collagen manufacturers, which may have influenced the outcomes. A healthy diet rich in protein, vitamin C, and zinc often provides sufficient resources for the body's natural collagen production without the need for supplements.

Comparison of Potential Negatives by Collagen Source


Potential Negative	Bovine Collagen	Marine Collagen	Chicken Collagen
Allergen Risks	Risk for those with beef or bovine allergies.	Risk for those with fish or shellfish allergies.	Risk for those with poultry or egg allergies.
Taste Issues	Can have a neutral to slightly savory taste; unflavored versions may be noticeable.	Can have a more pronounced, fishy aftertaste, especially unflavored.	Generally has a neutral taste; less common source of supplements.
Heavy Metal Risk	Potential for contamination depending on animal's diet and environment.	Higher potential risk if sourced from fish in polluted waters; need to check for purity tests.	Potential for contamination, requiring vetting of the source and manufacturer.
Sourcing Concerns	Ethical concerns related to animal husbandry.	Concerns related to sustainable fishing practices and sourcing.	Concerns related to poultry farming conditions.
Contraindications	Avoided by vegans/vegetarians and those with religious dietary restrictions (e.g., Kosher/Halal).	Avoided by vegans/vegetarians and those who avoid seafood.	Avoided by vegans/vegetarians and those with poultry restrictions.

Conclusion: Making a Mindful Choice

Before taking collagen, consider these potential negatives against the promised benefits. For most healthy individuals, mild side effects like digestive upset are manageable. However, for those with kidney disease, allergies to animal products, or who are pregnant or nursing, the risks can be more significant. Concerns over supplement regulation and potential contamination underscore the importance of choosing a reputable brand that provides purity testing. A balanced diet and healthy lifestyle can effectively support natural collagen production, offering a potentially safer and less expensive alternative. As with any dietary supplement, consulting a healthcare professional is the best way to determine if collagen is right for your individual health profile and needs.

For more detailed information on collagen and nutrition, you can consult authoritative health resources like Healthline's article on Collagen.

Frequently Asked Questions

For individuals with healthy kidneys, moderate intake is unlikely to cause issues. However, collagen contains hydroxyproline, which the body converts to oxalate. For those with a history of kidney stones or kidney disease, excess oxalate can increase the risk of stone formation.

People with specific allergies to the animal sources (fish, beef, chicken), those with kidney problems, and individuals who are pregnant or nursing should consult a healthcare provider first. Vegans and vegetarians also need to avoid animal-sourced collagen.

There is no conclusive evidence that one source is universally better than another. Marine collagen is generally considered more bioavailable and is often rich in Type I collagen, but it may carry a higher risk of heavy metal contamination and is a common allergen.

Common side effects include mild digestive upset such as bloating, nausea, or diarrhea. Some may also experience a persistent, unpleasant taste.

To minimize side effects, start with a small dose, stay well-hydrated, choose a brand with third-party purity testing, and consult your doctor to ensure no contraindications exist based on your health history or other medications.

No, the FDA does not regulate dietary supplements like collagen. It is the manufacturer's responsibility to ensure the safety and accurate labeling of their products, which raises concerns about potential contaminants.

While uncommon, some users have reported skin issues like rashes or acne. This could be due to individual sensitivity or potential reactions to other ingredients in the supplement. Always monitor your body's response and consult a dermatologist if problems persist.

Yes, contraindications may include pregnancy, breastfeeding, certain autoimmune disorders, significant kidney or liver diseases, and allergies to the source material.