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What are collagen peptides?
Collagen is the most abundant structural protein in the human body. It is found in bones, cartilage, tendons, ligaments, skin and many other connective tissues.
As we age, the body produces less and less of it, and this is evident: the skin loses its elasticity, the joints become stiffer and muscle recovery slows down.
Collagen peptides are the most easily absorbed form of collagen. They are obtained through enzymatic hydrolysis: this process breaks down the long protein chains of intact collagen into much shorter fragments — dipeptides and tripeptides — which the gut absorbs easily and releases into the bloodstream.
Once in the blood, these fragments reach the target tissues where, according to available data, they are thought to stimulate fibroblasts to produce new endogenous collagen.
The difference between collagen and collagen peptides
In its native form, collagen is a huge molecule: a triple helix of protein chains with such a high molecular weight that the gut can hardly absorb it as it is. Consuming it in this form — as is the case with edible gelatine or bone broth — therefore provides a modest amount of amino acids, but not the bioactive peptides that we are specifically seeking to obtain.
Collagen peptides, by contrast, have short chains, dissolve in water and pass easily through the intestinal barrier. It is this difference in molecular structure that determines a product’s true effectiveness.
Another point to bear in mind: not all sources of collagen are created equal. The raw material – whether marine or bovine – determines the amino acid composition, the profile of bioactive peptides and the bioavailability of the finished product. Comparing marine and bovine collagen helps you decide which is best suited to your own goals.
Health benefits of collagen peptides
The documented benefits of collagen peptides extend to several systems in the body — not just the skin, which is usually the first thing that springs to mind when this supplement is mentioned.
As regards the skin, the available data suggestthat regular intake can improve dermal hydration, increase skin density and reduce the depth of wrinkles. These effects are measurable and generally become apparent after 8 to 12 weeks of continuous use. However, it is amongst athletes that the scope of application is widest.
Tendons and ligaments are composed mainly of type I collagen. In these tissues, supplementation with bioactive peptides appears to support regeneration: it is thought to shorten recovery times following microtrauma caused by training and to strengthen the mechanical resistance of connective tissues in the long term. At the muscular level, the glycine, proline and arginine they contain aid recovery after exercise and, when combined with resistance training, are thought to promote greater gains in lean body mass than those observed with a placebo.
The skeleton is another well-established area of interest. In cases of reduced bone mineral density, collagen peptides can provide useful support — provided they form part of a comprehensive management plan, and without ever replacing medical treatment. The article on collagen for bones and osteoporosis details the clinical applications in this field.
Collagen peptides also support hair quality by providing the building blocks needed to synthesise the structural proteins that make up the hair shaft. For further information, the guide on collagen for hair offers practical advice on products and how to use them.
Finally, to complement supplementation with targeted joint support, the bone and joint health section brings together the most suitable products.
Side effects and contraindications of collagen peptides
Collagen peptides are generally well tolerated. We are not talking here about a pharmacologically active substance in the traditional sense: it is a dietary protein, and its safety profile in healthy adults is very favourable. As with any supplement, however, there are a few situations that warrant attention.
The most commonly reported adverse effects — though they remain rare — are digestive in nature: mild nausea, a feeling of heaviness, and bloating. These mainly occur in the first few weeks, or when high doses are taken on an empty stomach. In most cases, these symptoms resolve on their own by adjusting the time of day the supplement is taken or by splitting the daily dose into smaller portions.
Contraindications for marine collagen
Marine collagen offers the best bioavailability of all sources, but it comes with one very specific contraindication: allergies. It is extracted from the skin, scales or bones of fish, so anyone allergic to fish or shellfish must check the source before buying a marine collagen product. In the event of a confirmed allergy, bovine or porcine collagen is a safe alternative, to be discussed with your doctor.
Allergies are not the only point to be mindful of: other clinical conditions warrant a more thorough examination of the safety profile — kidney conditions, drug interactions and specific metabolic disorders. For a comprehensive and up-to-date overview, the article on the contraindications of marine collagen reviews the risks and side effects in sufficient detail to enable you to make an informed decision.
Risks associated with food allergies
Food allergies represent the main practical risk associated with collagen peptides. It is the raw material that determines the product’s allergenic profile: marine collagen derived from fish, bovine collagen, porcine collagen and chicken collagen do not pose the same risks depending on an individual’s allergies or intolerances.
People with a nickel allergy should be wary of products that combine collagen with plant-based vitamin C: some of these sources may contain traces of nickel. The best course of action is still to read the entire label and, if in any doubt, seek advice from a doctor or allergist before starting. Reputable products, such as those from TN Pharma, always specify the source precisely and clearly indicate any allergens present or likely to be present due to cross-contamination.
Answers to the most common concerns about organs and metabolism
There are many ideas circulating about collagen: some are well-founded, others far less so. Here are the answers to the most frequently asked questions concerning the liver, weight, the thyroid and the heart.
Is collagen bad for the liver?
This is one of the most widespread concerns, particularly amongst those who are already taking other supplements or medication and fear overburdening their liver. The answer, broadly speaking, is no: in a healthy person and at standard doses, collagen peptides have no toxic effect on the liver. This organ naturally plays a part in protein metabolism, and an intake of hydrolysed collagen does not place an abnormal strain on it.
However, caution is advised in three situations: where a liver condition has already been diagnosed, where hepatotoxic medicines are being taken, or where the recommended doses are significantly exceeded over a long period. Medical advice is therefore essential. The article ‘Is collagen bad for the liver? ’ analyses the available scientific data and assesses the actual risk.
Does collagen cause weight gain?
No, collagen does not cause weight gain. Collagen peptides are a source of protein, and protein is the macronutrient with the highest thermic effect: the body expends energy simply to digest and metabolise them. For an equivalent calorie intake, a higher protein content increases satiety and preserves lean body mass — two factors that help manage weight rather than complicate it.
Collagen contains no significant amounts of fat or carbohydrates. Powdered formulations generally provide 35 to 40 kcal per serving, which is far too low to have any significant impact on your daily calorie intake. The only situation in which it might indirectly contribute to weight gain is when it is sold in a product high in added sugars or hidden calories: in such cases, the problem lies with the product itself, not the collagen. The report ‘Does collagen make you put on weight?’ debunks the main myths, backed up by figures.
Is collagen bad for the thyroid?
There is no evidence that collagen peptides disrupt thyroid function in a healthy person. The thyroid is not a target organ for collagen, and no known biochemical mechanism justifies general concern on this point.
The situation is slightly different for people taking levothyroxine (Levothyrox): as with many supplements, it is recommended to space out the timing of taking the medication and the supplement to avoid any interference with absorption. This is not specific to collagen; it is a precaution that applies to any supplement taken alongside hormone therapy. Any changes to your dosage schedule must be approved by your doctor or endocrinologist. The article ‘Is collagen bad for the thyroid? ’ examines the actual links and specific contraindications for patients undergoing treatment.
Is collagen bad for the heart?
Here again, the available data show no negative effects of hydrolysed collagen on cardiovascular health. Some studies even suggest the opposite: improved integrity of vascular connective tissue, where collagen plays a major structural role, could have beneficial long-term effects on arterial health. However, this research remains preliminary and does not allow for any firm conclusions.
People taking anticoagulants or other medicines that affect blood clotting should consult their doctor before adding a concentrated protein source, including collagen. Not because any direct interaction has been documented, but because the overall treatment regimen warrants assessment. For the rest of the population, collagen peptides at standard doses have no known cardiovascular contraindications.
Vegan collagen and contraindications
There are products on the market marketed as ‘vegan collagen’ or ‘vegan collagen boosters’. It is best to know exactly what you are buying, as this is a completely different category from conventional collagen peptides.
Plant-based collagen does not exist: collagen is, by definition, an animal protein that only organisms in the animal kingdom can synthesise. Vegan products marketed as alternatives actually contain precursors and co-factors for endogenous synthesis — vitamin C, zinc, silicon, plant-based amino acids such as glycine and proline — whose role is to encourage the body to produce more of its own collagen. The mechanism is therefore indirect: it depends on each individual’s biological response, rather than on the intake of pre-formed bioactive peptides.
Those following a vegan diet who wish to support their collagen synthesis should maintain realistic expectations regarding these products: they provide valuable nutritional support, but they do not match the direct action of hydrolysed peptides.
Frequently Asked Questions
What are the side effects of collagen peptides?
Side effects from collagen peptides are rare and usually mild. The most common are digestive in nature: nausea, bloating or a feeling of heaviness during the first few weeks, particularly if the product is taken on an empty stomach or in high doses. Simply splitting the dose or taking it with a light meal is usually enough to resolve the problem.
Allergic reactions remain the most serious contraindication: if you are allergic to fish, avoid marine collagen; if you are allergic to bovine proteins, avoid bovine collagen. Apart from these cases, this is a supplement with a sound safety profile for healthy adults.
Who should not take collagen?
Certain people should exercise greater caution, or even avoid taking it altogether without a medical recommendation. Those withallergies to animal proteins should check the ingredients before making a purchase. Those with a diagnosed kidney condition should consult their doctor: increasing total protein intake is not without implications for managing the workload on the kidneys.
Pregnant or breastfeeding women should discuss any supplementation with their GP, even though there are no documented specific contraindications for collagen during these periods. As for healthy children, they generally have no need for supplementation: their natural production of collagen is abundant whilst they are growing.
What are the best collagen peptides?
The quality of a collagen supplement is assessed on the basis of a few specific criteria: the source of the raw material (marine or bovine), the type of hydrolysis used, the average molecular weight of the peptides stated on the label, and the presence of independent certifications attesting to purity and the absence of contaminants. The best products display all this information transparently, rather than simply stating ‘hydrolysed collagen’ without further details.
To help you navigate the range of products available, our blog’s guide to the 5 best collagen supplements selects the most effective products based on the quality of the raw materials, the transparency of the formulations and the available data.
