Collagen powders, creams and bone broth: what the science says about their benefits

Collagen is turning up in coffee, crisps and beauty creams, promising firmer skin and stronger joints. As someone who studies collagen, I find some of the claims rather optimistic. I even gave collagen supplements to guests at my wedding, accompanied by a disclaimer that this was no endorsement of their effectiveness. The science is considerably more interesting than the marketing. Collagen is a family of at least 28 proteins that help give the body its shape and strength. All share a distinctive structure: three chains twisted together, rather like strands of a rope. Some of these molecules assemble into larger fibres around cells that support skin, tendons and bones. Other types form thin supporting networks separating different body compartments. Collagen is part of the extracellular matrix, the mesh of proteins and other materials surrounding our cells. Cells make collagen using amino acids, the building blocks of all proteins, and release it outside themselves to build and maintain tissues. As we age, keeping this structure in good repair becomes harder. The amount of collagen produced can change, but existing collagen also becomes altered. Some fibres last extraordinarily long: carbon-dating research suggests the central part of the human Achilles tendon contains collagen laid down during the first 17 years of life, with very little replacement in adulthood. Over time, chemical bonds can form between collagen molecules making the tissue less flexible. So having more collagen does not necessarily mean having healthier collagen. How it is assembled, maintained and replaced also matters. Does eating collagen replenish it? Many supplements contain hydrolysed collagen: collagen that has already been broken into smaller pieces. Gelatine, familiar from gummy sweets, is another processed form of collagen. After you swallow collagen, digestion breaks it down further into amino acids and short chains called peptides. Some of these reach the bloodstream. But they do not arrive in your cheeks or knees as ready-made collagen fibres. Cells may reuse those building blocks to make proteins, or for other purposes. So is collagen powder any better than getting enough protein from ordinary food? It’s an important question, and one we cannot yet answer confidently. Human trials of oral collagen supplements have produced mixed results. A 2025 analysis of 23 trials found improvements in skin hydration and elasticity overall, but no statistically significant benefits when higher-quality studies were examined separately. A newer review of 35 trials reported improvements in hydration and some measures of elasticity, but found no reliable evidence of reduced wrinkles or increased skin density. These findings do not establish whether taking collagen offers any advantage over eating an adequate, balanced diet. Bone broth is another source of collagen-derived protein. I enjoy it as part of the diet I grew up eating, but swallowing broth does not specifically replace collagen in your joints, at least not evidenced by science. Its nutritional value depends on the ingredients and preparation. Can creams and treatments do more? Collagen creams face another obstacle: the skin is a protective barrier. Intact collagen molecules are generally too large to pass through it. A cream may make your skin feel smoother by helping it retain water without delivering new collagen to deeper layers. There is better evidence for protecting the collagen you already have. Ultraviolet radiation from sunlight can increase collagen breakdown, making sunscreen important. Studies also suggest that retinoids, ingredients related to vitamin A, can improve fine wrinkles and stimulate collagen production, although they can irritate skin. I’m also cautious about skincare containing PDRN, fragments of DNA often promoted as being derived from salmon sperm. A review of clinical trials suggests PDRN may help damaged skin heal, including by speeding up wound repair. But these findings don’t necessarily apply to ordinary face creams. Wounded skin has a damaged protective barrier, whereas healthy skin makes it much harder for large molecules such as PDRN to penetrate. Whether enough PDRN can reach the deeper layers of intact skin to produce meaningful benefits remains uncertain. Microneedling works differently. Tiny needles create controlled injuries, setting off repair processes that can stimulate collagen formation. Clinical studies suggest benefits for some acne scars, but the procedure can cause infection, pigmentation changes or further scarring, especially when hygiene and technique are poor. Home microneedling rollers – handheld devices covered in tiny needles that are rolled across the skin – also carry risks. Pressing too hard or repeatedly treating the same area can damage the skin, potentially causing lasting discolouration or scarring. Poorly cleaned devices can introduce bacteria, while rolling over infected areas can spread viruses such as herpes across the skin. The American Academy of Dermatology also warns that home devices generally produce less noticeable results than professional treatments, so the potential benefits may be limited. The surprising connection with sleep My research has found that collagen maintenance follows a daily rhythm in mouse tendons. The animals’ cells produced and assembled collagen at different times, and disrupting their internal body clocks affected the fibres they formed. Later work showed that cells can take up existing collagen and recycle it into new fibres. This recycling process was altered in cells associated with fibrosis, a condition in which excessive scar-like tissue builds up in an organ. In the lungs, this can make breathing difficult. These are early findings about how tissues maintain collagen, not proof that a particular bedtime will improve human skin, although it is clear that sleep disruption wreaks havoc on our body in general. Nor does eating collagen cause fibrosis. The point is that the body must regulate how much collagen it makes and how it organises and removes it. For now, I would prioritise a balanced diet, physical activity, consistent sleep and sun protection over expensive promises to “boost collagen”. Looking after the systems that maintain our tissues is more sensible than assuming a scoop of powder will rebuild them.