Great news: If you’re already using collagen peptides for your hair, skin, and nails, you’re likely getting a bunch of other whole-body benefits.
Clearly we humans are meant to consume a good amount of collagen. Our ancestors ate nose-to-tail , consuming skin and connective tissue, and boiling down bones to make broth. Gelatin and collagen would have been abundant in the human diet. They provide amino acids needed for a dizzying array of metabolic functions. The amino acids also serve as blocks for collagen in the body.
Collagen is the most abundant protein in the human body, providing structure and support for the musculoskeletal and cardiovascular systems. Crucially, we need glycine from collagen to balance the lifespan-shortening effects of methionine in meat.1 
Today I’m going to highlight some potential benefits that have nothing to do with skin, nails, or hair . I’ll say up front that I’m firmly on the pro-collagen train. I’ve noticed great results personally from taking it. That said, I’m not trying to make wild claims about collagen as a miracle supplement. These are areas of research I’m watching with interest. I hope to see more studies that help us understand when, why, and how collagen is most useful.
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A Quick Primer on Collagen
When you purchase collagen, you’ll get either collagen peptides  or collagen hydrolysate. These terms are interchangeable. Gelatin and collagen peptides have the same amino acid profile, and they should confer the same benefits. The difference is the proteins in collagen have been broken down into smaller chains (peptides), so they are more easily absorbed.
There are at least 28 types of collagen. The collagen peptides you buy at the store are mostly types I and III unless they specify otherwise. I’m not going to talk about studies that focus on types you can’t readily get in supplement form (like type IV, which is potentially relevant for Alzheimer’s disease).
Okay, now that that’s out of the way, let’s look at some potential benefits.
Sleep Better with Collagen
Collagen has a different amino acid profile than meat, and that’s important here. Specifically, collagen is rich in the amino acid glycine. Among its many functions in the body, glycine is known to improve sleep.2 
Human studies show that just 3 grams of glycine taken before bed improves sleep quality and daytime alertness for individuals with chronic sleep issues,3  insomnia,4  and sleep restriction.5  It might work by enhancing serotonin production, which is needed to produce melatonin.6  Glycine also facilitates the drop in core body temperature that promotes a healthy sleep cycle.7  8 
Sleep experts generally recommend taking 3 to 5 grams of glycine before bedtime. You can buy glycine supplements, but collagen is about one-third glycine. A heaping scoop of collagen peptides will net you those 3 grams of glycine, plus other important amino acids.
Collagen Benefits Your Muscles, Tendons, and Bones
When talking about body composition, we usually mean the amount of body fat and muscle mass an individual carries. What about the other stuff—the bones and connective tissue that give our body structure and allow us to move around? In fact, the entire musculoskeletal system benefits from the amino acids in collagen.
Collagen to Build Strength
Lots of people use whey or soy protein supplements to enhance the effects of resistance training and build muscle.  Collagen, on the other hand, has been largely overlooked because it’s not a complete protein. In particular, it doesn’t contain the levels of BCAAs  found in whey protein.
I think collagen deserves a second look, though. For one thing, the high amount of glycine plus alanine in collagen provide building blocks for creatine . Creatine boosts energy production in muscle cells, and it’s probably the most widely used supplement for increasing muscle mass.
Also, in a series of studies, elderly men with sarcopenia,9  healthy young men,10  and premenopausal women11  undertook 12 weeks of resistance training. Half the participants in each study supplemented with 15 grams of collagen post-workout. Across the board, the collagen + training groups gained more fat-free mass and strength compared to training alone. The older men and the women also lost more body fat.
However, when the researchers measured the young men’s type II muscle fibers, they found no differences between the collagen and no-collagen groups. That said, in an interesting follow-up using the same protocol, researchers also performed muscle biopsies. The collagen + training group saw upregulation of proteins and pathways associated with positive training adaptations in contractile muscle fibers.12 
What does this mean? Collagen ups the effectiveness of resistance training. More research is needed to understand precisely how—whether it increases muscle synthesis, tendon integrity, both, and/or other. In any case, though, adding a couple scoops of collagen to your post-workout routine seems a worthy experiment.
Collagen for Your Connective Tissues and Joints
Speaking of tendons, there’s evidence that collagen supplementation helps strengthen and maintain connective tissue . Connective tissue is made up of collagen, so it’s not really a big surprise. I first become enamored with collagen after rehabbing a serious Achilles tendon injury. I’m convinced that my recovery was accelerated thanks to loading up on collagen peptides.
Studies back up my experience:
- Animal studies using rats13  and rabbits14  show that feeding the animals glycine and collagen peptides, respectively, strengthens their Achilles tendons.
- In humans, taking 15 grams of gelatin plus 50 mg of vitamin C before working out improves tendons’ performance by increasing collagen deposition and remodeling.15 
Collagen likewise shores up your joints and reduces joint pain:
- Men and women with chronic ankle instability took 5 grams of collagen or a placebo for six months. Those in the collagen group reported greater subjective stability and had fewer ankle injuries during the follow-up period.16 
- Male and female college athletes who supplemented with 10 grams of collagen hydrolysate for 24 weeks reported significantly less joint pain across various activities. The effects were particularly strong among participants with pre-existing knee arthralgia (pain).17 
- For osteoarthritis patients, a collagen supplement reduced pain scores and improved walking ability.18 
- In another study, adults over 50 with joint pain took a modest dose—1.2 g/day—of collagen for 6 months and reported less pain in the shoulder, arm, hand, and lumbar spine. There were no differences for knee or hip pain, though.19 
- Supplementing with collagen also shows promise for helping to regrow cartilage for folks with osteoarthritis.20 
Collagen Builds Strong Bones
More than 90 percent of the organic matrix of bone is collagen, mostly type I.21  Scientists believe that collagen plays a central role in regulating the growth and maintenance of strong, healthy bones.22 
It should come as no surprise, then, that collagen supplementation seems to improve bone health. This has been demonstrated repeatedly with rats.23  24  In humans, adding 5 grams of collagen peptides per day for 12 months increased bone mineral density in postmenopausal women at risk of osteoporosis.25 
Another cool study compared female identical twins. In each pair, one sister’s typical diet contained significantly more of the amino acids alanine and glycine. The high-intake twins had better bone mineral density in their spines and forearms.26 
Collagen for Heart Health
Many animal studies suggest that supplementing with collagen can improve cardiovascular health. Glycine, specifically, may be cardioprotective thanks to its known anti-inflammatory and anti-oxidative properties.
- In rats, administering glycine reduces blood triglycerides and blood pressure.27  28 
- Collagen tripeptides reduce the size of atherosclerotic plaques and improve cholesterol markers in rabbits with hypercholesterolemia.29 
- Collagen hydrolysate reduces blood pressure and reverses arterial damage in rats.30 
- In mice, it lowers total cholesterol, triglycerides, and pro-inflammatory cytokines. 31 
All promising stuff, but what about for us?
- In humans, low circulating glycine levels are associated with a greater risk of acute myocardial infarction.32 
- One study showed that healthy adults who took 16 grams of collagen daily for six months lowered their LDL-C/HDL-C ratio. They also had significantly fewer toxic advanced glycation end-products, a marker of atherosclerosis risk, in their bloodstreams at the end of the study.33 
- In another small study, 15 adults with mild hypertension lowered their blood pressure by taking 5.2 grams of collagen daily for 4 weeks.34  A follow-up found similar effects using a smaller dose of 2.9 grams per day.35 
- In contrast, a study of older adults did not find any effects for blood pressure, but taking 2.5 grams of collagen per day for 12 weeks did reduce arterial stiffness.36 
Collagen for Diabetes?
It might sound like a stretch at first, but individuals with low glycine are at greater risk for developing diabetes,37  38  while high glycine is associated with normal blood sugar control.39  Glycine supplementation may improve insulin sensitivity.40  A handful of studies further show that glycine can reduce certain diabetic complications in rats and humans.41 
I’ve yet to see good evidence that collagen can reverse the course of prediabetes or diabetes in humans, though. Something to watch for.
How to Incorporate More Collagen in Your Diet
First things first, if you’re only eating muscle meat and avoiding the rest of the animal—skin, organs, bones—you need to diversify. Turn those bones into collagen-rich broth . Throw in some chicken feet while you’re at it. Make chicken skin chips . And yes, you do get some collagen from meat, too, as well as eggs.
Collagen peptides can be derived from cows (bovine), chickens, or pigs (porcine). Marine peptides come from fish parts such as bones and scales. There’s really no such thing as vegetarian collagen , although researchers are working on engineering collagen from algae.
I usually use one or two scoops per day of collagen peptides or Collagen Fue l per day. That’s enough to cover my bases. If I’m healing from an injury, I’ll increase it and throw in some extra vitamin C for good measure. Vitamin C is needed for collagen synthesis, and I figure it can’t hurt.42 
I’m interested in your experience. Did you start incorporating bone broth or collagen peptides in your routine and notice any unexpected benefits? What’s your favorite way to get collagen in your diet?