One of the more common questions we tend to get is what supplement ingredients play well together. Well, that comes down to two additional questions. The second is do they work toward a common health support goal or even synergistically to help each other be more effective and bioavailable? Well, certain actives tend to be common supplement duos, as is the case with collagen and biotin. So let’s get into how and why they’re formulated together. Because it has several roles all throughout the body, taking a collagen peptide supplement can provide several all-over benefits from your hair to your bones.* We go into collagen supplements in pretty impressive detail in our guide (if we do say so), but a quick rundown can help: Collagen supplements also provide many of the amino acids and nutrients needed for hair growth: “Amino acids are the building blocks for keratin, the material that hair is made of,” according to board-certified dermatologist Joshua Zeichner, M.D. Yes, for the body to build keratin, it needs several types of amino acids, many of which are found in collagen peptides2. In fact, the main amino acid in keratin is proline—which is readily found in many collagen supplements.* The beauty supplement can also help nail strength; one study found that when patients took collagen daily for 24 weeks, it helped support their nail health3, including better growth rates, reduced breakage, and improved appearance.* Ashley Jordan Ferira, Ph.D., RDN, vice president of scientific affairs at mindbodygreen, further explains that “in addition to providing key amino acids to fuel the gut, collagen peptides are also thought to support tight junctions5 in the GI tract, in other words, preserving the integrity of the gut lining.”* Collagen is found in all connective tissues that make up our joints (including ligaments and tendons), and collagen supplements provide almost 20 unique essential and nonessential amino acids to support natural levels throughout the body.* Healthy connective tissue structure helps support joint health and function. Another found that supplements can support skeletal muscle mass and strength8.* In fact, according to Nour Zibdeh, M.S., RDN, CLT, “Collagen can also support lean muscle and help improve body composition."* While this is an emerging area of research, the science has shown that collagen can help support bone density9.* Of course, given bone growth and development—and the lengthy timeline associated with it—it’s a harder area to study, but it seems promising. Biotin is critical for the daily utilization of fats, carbs, and amino acids (ahem, like those found in collagen supplements) for energy (ATP).* And while biotin has earned its place in a B-complex, most people supplement with biotin with beauty in mind.* Most products with biotin are cosmeceutical in nature, and thus that’s what we’ll focus on here. Now, before we dive into the benefits of biotin, it’s important to note a few things. The first is that cases of biotin insufficiency and frank deficiency are quite rare in our modern world. The second is that the research about this supplement’s benefits isn’t as robust as that for collagen. “The biotin and hair, skin, and nails association and evidence candidly carries more anecdotal clout than published science as a stand-alone nutrient, but the biological mechanism of its support is enough evidence for most people,”* says mbg’s Ferira. “Then when their hair and nails improve, that’s additional proof.”* Biotin is thought to support healthy hair growth because it is involved in the production of keratin11, the main component of hair.* In one small study, women reported hair growth when supplementing with biotin (as part of a multi-ingredient supplement) when compared to those given a placebo.* Biotin has been shown to support thickness and firmness of nails12 in several human studies.* “Collagen and biotin are both safe, well-tolerated cosmeceutical bioactives, supporting hair, skin, and nail health,”* says Ferira. “But they have their own unique and individual mechanisms for structurally and functionally doing that, hence the reasonable potential for synergy in combining them. Both collagen- and biotin-containing foods and supplements provide key nutrients or building blocks for our body. Collagen provides macronutrient—protein—nourishment and critical amino acid building blocks. Biotin provides an essential water-soluble B vitamin (B7), which acts as a versatile cofactor in a variety of bodily functions.”* Research shows this too. While biotin hasn’t been as well studied on its own, there’s a decent amount of clinical research studying the two ingredients together. For example, this study demonstrates that taking both has a positive impact on skin hydration, elasticity, smoothness, and density13.* Another clinical intervention found improved collagen structure of facial skin14 via objective microscopy results, plus positive subjective results for skin’s appearance (e.g., elasticity, wrinkles, and texture) on hands, neck, legs, belly, and décolletage.* Not only that, but research suggests they may help each other out too. Now, after reading all this, you likely are in the market for a new supplement, so check out our list of the best collagen supplements around.