Quickly and recently, amino acids have become big business. Whether you’re shopping for a collagen supplement, bone broth or even more meat and dairy foods, the different amino acids that make up these proteins are what you’re ultimately buying and ingesting, says Mark Moyad, M.D., director of preventive and alternative medicine at the University of Michigan.

Your body uses amino acids to build muscle, bone, cartilage, skin, hair, connective tissue and much more. There are many different types of amino acids, but the most abundant kind in your body make up collagen. Collagen is the main structural protein that forms your connective tissues and skin.

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Since your body’s collagen production declines as you age and you need adequate collagen for strong bones, joints and skin, adding more collagen to your diet sounds like a no-brainer. That’s why many supplement makers have started selling collagen powders and pills, which Dr. Moyad says are made mostly from animal parts, like fish scales or cow bones or skin. (Vegans, take note.)

But do these supplements really do anything? Here’s what you need to know.

What is collagen powder?

According to Rahul Shah, a board-certified orthopedic spine and neck surgeon at Premier Orthopaedic Spine Associates, there are many types of collagen, each composed of different “peptides” or amino acids. Different types form skin and tendons as opposed to cartilage. Figuring out which ones may help your health has proved tricky. (More on that in a minute.) Also: According to nutritionists from Harvard University, supplements containing collagen are not regulated by the Food and Drug Administration (FDA) and vary a ton.

Most collagen peptides powder on the market contain a “hydrolyzed” type-I collagen extracted from hides, bones, or fish scales. Hydrolyzed simply means that the amino acid chains have been broken down into smaller units, a process that allows the powder to dissolve in both hot and cold liquids.

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This type of collagen has become incredibly popular due to the fact you to add it to everything from hot coffee and soups to cold brew and smoothies. It also packs a protein punch, with a two-scoop serving of most collagen peptides delivering around 18 grams.

What are the benefits of collagen powder?

The research on the side effects and potential benefits of collagen supplements is ongoing, but here’s what we know right now about the potential upsides for different body parts.

Joints

Right now, the most-complete research focuses on joint health. Going back to at least the early ’90s, studies have linked collagen supplementation with reduced symptoms of arthritis. Four out of five osteoarthritis sufferers who took a daily 40 mg dose of undenatured type-II collagen saw their pain drop by an average of 26%, according to a 2009 study in the International Journal of Medical Sciences. (Type-II collagen is derived from chicken cartilage — not cow bones and hides or fish scales.)

What’s not clear is how the collagen in the supplement actually helped the OA sufferers’ joints. Rather than contributing to the body’s supply of collagen or cartilage, these supplements may reduce inflammation and consequently improve OA symptoms, the study authors write.

In other words, collagen supplements do not help you rebuild collagen after it’s been damage from injury and wear and tear, or even reverse it’s natural depletion as you age, says Dr. Shah.

“The science demonstrates that the collagen that is ingested orally is broken down into its building blocks in the digestive process and does not go directly to improving the joints. Injected collagen, on the other hand, seems to work by decreasing overall inflammation when it is injected into the joints but does not clearly rebuild depleted or damaged collagen in joints,” he says. But, “joint pain can be somewhat addressed by collagen” by reducing inflammation.

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You may want to skip out on those expensive collagen supplements, though since your classic OTC anti-inflammatories (like ibuprofen) are more likely to be effective, says Dr. Shah.

Bones

In one study of postmenopausal women, those who took a daily collagen supplement showed improvements in their bone mineral density a year later, especially when they took it in combination with Vitamin D and calcium. The researchers aren’t exactly sure why collagen seems to strengthen our skeleton, but they think it might trigger certain anabolic processes that promote the growth of bones.

Doctors at UPenn Medicine also believe that taking a collagen supplement may be able prevent bone loss. However, other M.D.’s think that supplementation not as effective as some might think.

“When ingested, collagen is broken down by our digestive system into its building blocks,” says Dr. Shah. “These building blocks then are used by our bodies in the form of energy [and] are not preferentially used by the body to form bone or any other musculoskeletal tissues.”

How to choose a collagen supplement:

1. Choose ones with as few simple ingredients as possible. Collagen protein powder should just be collagen protein isolate, a.k.a. collagen hydrolysate, hydrolyzed collagen, or collagen peptides.

2. Skip the flavored versions. These can contain added sugars, which could upset your GI tract or just add calories where you didn’t want ’em. Go for the plain version and add a sweetener to desserts yourself.

3. Look for a third-party certification. Given the lack of FDA regulation, any time you’re choosing a dietary supplement, check if a credible group like the NSF, UL, or USP has tested it for safety before.

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