Collagen: what it is and its potential implications - Digestive health

Collagen supplements have been very popular for many years. Many potential benefits have been reported, but what does the science say? Do collagen supplements work?

Here's a series of blogs exploring its involvement in different aspects of health. This one focuses on digestive health.

The other two blogs are about SKIN HEALTH and the joint health.

What is collagen and what does it do?

Collagen is a protein found in various types of connective tissue in the body, including cartilage, tendons, bone and skin (2)(11). It accounts for around 25 to 35% of total proteins in the human body (2)(8). This compound therefore plays an important role in tissue structure, ensuring rigidity and integrity (8). As collagen begins to break down with age, a number of studies have looked at the benefits of supplements of collagen on health, including digestive health (3).

Collagen and digestive health

Anatomy 101

The gastrointestinal (GI) barrier is composed of epithelial cells held together by tight junction proteins (10). This physical barrier is important in separating the lumen of the intestinal tract from the bloodstream and body tissues (10). The GI barrier facilitates the transport of nutrients from the intestine to the bloodstream, and also limits the entry of potentially harmful elements such as pathogenic bacteria (1)(10).

When the barrier is disrupted, often referred to as leaky gut, a cascade of inflammatory events is triggered (1)(10). This disruption appears to be involved in the development of certain digestive conditions such as irritable bowel syndrome (IBS) (1)(10).

Thus, the hydrolyzed collagen seems worth studying to reduce this intestinal inflammation and maintain the integrity of the intestinal barrier through its content in amino acids (10). Collagen is therefore not directly present in the intestines. However, these compounds (amino acids) could help maintain a healthy intestinal barrier.

Within a cell study (in vitro), hydrolyzed collagen attenuated intestinal barrier dysfunction and reduced certain inflammatory markers (1, 10). In mouse, Hydrolyzed collagen consumption during GI injury reduced intestinal inflammation (10). These results suggest that hydrolyzed collagen may enhance enterocyte integrity by modulating tight junction protein expression and reducing intestinal inflammation (10). Another study in rats observed that a diet rich in collagen peptides increased the levels of two short-chain fatty acids (SCFA) in stools (6).

Unfortunately, no human studies has been done to replicate the results observed in the laboratory. What's more, no research shows that collagen supplementation «repairs» the intestinal mucosa.

One study evaluated the effect of a 20 g (2 x 10 g) bovine collagen peptide supplement per day for 8 weeks on the management of digestive symptoms in healthy women (1). The vast majority of women reported improvement in their digestive symptoms whose bloating and the intestinal regularity (1). However, this study has several limitations, including the small number of subjects (14 women) and the absence of a control group (1). Further research is needed to replicate these observations.

No study has evaluated the effect of supplements on the management of digestive symptoms in the context of irritable bowel syndrome nor for the Crohn's disease and the ulcerative colitis. Supplements are not recommended in this context.

Some studies have evaluated the benefits of collagen supplements on intestinal symptoms linked to physical activity (10). Indeed, intense activity can trigger gastrointestinal dysfunction leading to diarrhoea or intestinal cramps (10). An 8-week study of 20 athletes has observed no benefits The use of collagen supplements has been shown to reduce inflammation, intestinal permeability and digestive symptoms following exercise (10). So, although the theory seems interesting for the use of collagen in a sporting context, clinical results are not present.

Depending on the source, molecular weight and type, collagen can be classified into two main groups: the hydrolyzed collagen and the undenatured collagen (9). For digestive health, the hydrolyzed collagen, in the form of collagen peptides, is the most studied, being a «smaller» molecule and more easily absorbed in the small intestine (5)(9). Collagen peptides come from bovine, porcine, marine or poultry sources (1). Obviously, doses vary according to the type of collagen used. One study reports that the quantities of collagen peptides evaluated in the literature vary between 2.5 and 15 g per day (7).

Possible side effects and contraindications

Very few, if any, side effects have been reported in current studies with oral collagen supplements (3)(11). Some report an unpleasant taste, headaches or certain gastric disorders such as nausea, bloating, diarrhea and acid reflux (3)(4)(11). Of course, if you have an allergy to beef or fish, it's essential to avoid supplements containing it (2).

There appears to be no interaction with collagen supplements (11). It is important to validate with your pharmacist according to your medications and your health conditions.

Pregnancy and breastfeeding are contraindications for collagen supplements due to the lack of data demonstrating its safety during these periods (11).

Conclusion

Can collagen help digestive health?

In view of the lack of robust scientific studies, a collagen supplement not recommended for digestive health. Studies, mainly on cells and animals, show potential benefits. On the other hand insufficient data in humans and larger, long-term studies are needed. Furthermore, no studies have evaluated supplements in the context of digestive diseases (e.g. IBS, Crohn's disease, ulcerative colitis).

If you would like to know more about dietary supplements and their impact on digestive health, you can read the articles on peppermint and the apple cider vinegar.

References

(1) Abrahams et al (2022) Effect of a Daily Collagen Peptide Supplement on Digestive Symptoms in Healthy Women: 2-Phase Mixed Methods Study. JMIR Form Res May 31;6(5):e36339. https://pubmed.ncbi.nlm.nih.gov/35639457/ 
(2) Dewi et al (2023) Exploring the Impact of Hydrolyzed Collagen Oral Supplementation on Skin Rejuvenation: A Systematic Review and Meta-Analysis. Cureus Dec 9;15(12):e50231. https://pubmed.ncbi.nlm.nih.gov/38192916/ 
(3) Healthline (2024) What You Need to Know About the Health Benefits of Collagen. https://www.healthline.com/nutrition/collagen-benefits 
(4) Lin et al (2023) Analgesic efficacy of collagen peptide in knee osteoarthritis: a meta-analysis of randomized controlled trials. J Orthop Surg Res Sep 16;18(1):694. https://pubmed.ncbi.nlm.nih.gov/37717022/ 
(5) Martínez-Puig et al (2023) Collagen Supplementation for Joint Health: The Link between Composition and Scientific Knowledge. Nutrients Mar 8;15(6):1332. https://pubmed.ncbi.nlm.nih.gov/36986062/ 
(6) Mei et al. (2020) Effect of a high-collagen peptide diet on the gut microbiota and short-chain fatty acid metabolism, Journal of Functional Foods, 75;104278. https://www.sciencedirect.com/science/article/pii/S1756464620305028 
(7) Paul et al. (2019) Significant Amounts of Functional Collagen Peptides Can Be Incorporated in the Diet While Maintaining Indispensable Amino Acid Balance. Nutrients May 15;11(5):1079. https://pubmed.ncbi.nlm.nih.gov/31096622/ 
(8) Sibilla et al. (2015) An Overview of the Beneficial Effects of Hydrolysed Collagen as a Nutraceutical on Skin Properties: Scientific Background and Clinical Studies. The Open Nutraceuticals Journal 8: 29-42. https://benthamopenarchives.com/contents/pdf/TONUTRAJ/TONUTRAJ-8-29.pdf 
(9) Simental-Mendía et al (2025) Effect of collagen supplementation on knee osteoarthritis: an updated systematic review and meta-analysis of randomised controlled trials. Clin Exp Rheumatol Jan;43(1):126-134. https://pubmed.ncbi.nlm.nih.gov/39212129/ 
(10) Taylor et al (2023) The effects of collagen peptides on exercise-induced gastrointestinal stress: a randomized, controlled trial. Eur J Nutr Mar;62(2):1027-1039. https://pubmed.ncbi.nlm.nih.gov/36370176/ 
(11) WebMD. Collagen Peptides Uses, Side Effects, and More. 2024. https://www.webmd.com/vitamins/ai/ingredientmono-1606/collagen-peptides