Quick answer

Collagen is a structural protein found in skin, bone and tendon. Trials of 2.5 to 10 g of collagen peptides a day for 8 to 12 weeks found modest gains in skin hydration and elasticity, graded moderate, but a 2025 analysis saw them only in company-funded trials. Joint and tendon evidence is early.^1,2,3

Key facts

Your body needs vitamin C to make collagen.⁴
Collagen lacks the essential amino acid tryptophan, so it is not a complete protein.⁵
Of the 26 skin trials pooled in 2023, 14 used fish collagen and only one used bovine.²
Exercise trials reported no adverse effects, even at 60 g a day in short studies.⁶

What collagen is

Collagen is a structural protein: it gives skin its tensile strength and ligaments their resistance to pulling, and type I collagen runs through skin, bone and tendon.¹

About 28 types of collagen are known. Type I is the most common in skin, bone and tendon, type II is found in cartilage, and type III in skin, muscle and blood vessels.¹

Collagen peptides, also sold as hydrolyzed collagen or collagen hydrolysate, are collagen cut by enzymes into small pieces of about 3 to 6 kDa, against about 300 kDa for whole collagen. That makes them dissolve easily in water.¹

A 2019 review states that collagen loss starts in early adulthood and that after 40 the body loses around 1 percent of its collagen a year.¹

What the evidence shows

Each claim carries a grade for how much human research there is and how well it agrees, with the amounts studied beside it. Most trials used branded fish or pork peptides, not the bovine hide collagen in our product.^2,7

May support skin hydration and elasticity*^2,3

Moderate evidence

A 2023 meta-analysis of 26 randomized trials (1,721 people, mostly women) found better skin hydration and elasticity with hydrolyzed collagen, usually 2.5 to 10 g a day for 8 to 12 weeks, though only one trial used bovine collagen like this product. A 2025 meta-analysis of 23 trials (1,474 people) found the benefit only in company-funded trials; trials without company funding, and higher-quality trials, showed no effect.

Amount studied: 2.5 to 10 g a day for 8 to 12 weeks

A 2025 analysis of 23 skin trials found benefits only in trials funded by companies; trials without company funding, and higher-quality trials, showed no effect.³

May support joint comfort during physical activity*^6,7,8

Early evidence

In a 12-week trial of 180 active adults aged 18 to 30 with exercise-related knee discomfort and no diagnosed joint condition, 5 g a day of a pork-derived collagen peptide lowered discomfort during activity by about 22 points on a 100-point scale, against 16 with placebo; the trial was part-funded by the peptide's maker. A separate 12-week trial of 10 g a day in 167 active adults (median age 63) found no difference from placebo.

Amount studied: 5 to 10 g a day for 12 weeks

Alongside resistance training, may support tendon adaptation*^9,10

Early evidence

A 2024 meta-analysis of collagen peptides taken with training (19 trials, 768 healthy adults) pooled four small trials that measured tendons (114 people; 5, 15 or 30 g a day) and found larger gains in tendon size but no difference in tendon stiffness; the authors rated this evidence as very low certainty. In a 2025 study, 30 g of collagen after exercise did not speed up connective tissue protein building in muscle.

Amount studied: 5, 15 or 30 g a day with training; most training trials used 15 g

Hair and nails

No hair or nail claim is made here. The research is two small studies of branded ingredients, described below with their limits.

In one open-label study with no placebo group, 25 people with easily broken nails took 2.5 g of a branded collagen peptide daily for 24 weeks; nail growth rose 12 percent and broken nails fell 42 percent.¹¹

Hair research is thin. In one 24-week trial of 114 women, 1 g a day of a specialized low-molecular-weight fish collagen peptide increased hair diameter compared with placebo, and a 2026 review found most hair and nail studies short, mixed in design, often multi-ingredient and often industry funded.^12,13

Muscle and protein

No muscle claim is made for collagen: in a 2025 study, 30 g after exercise did not raise muscle protein building, and whey outperformed collagen in head-to-head tests.^6,10

Protein-quality calculations suggest collagen could make up as much as 36 percent of daily protein in a typical Western diet while essential amino acid needs are still met.⁵

How much people take

Skin trials mostly used 2.5 to 10 g a day, joint trials 5 to 10 g, and training trials 15 g. The dosage guide sets these out by goal, with trial lengths.^2,6,9

Food sources

Collagen comes from animals. The collagen in supplements and gelatin is taken from the hide and bones of cattle, the skin of pigs, the skin, scales and bones of fish, and from chicken.¹

Bone broth made to a standard recipe held much less glycine, proline and hydroxyproline than a 20 g dose of a collagen supplement, and broths made to other recipes varied widely, so it is not a reliable source.¹⁴

Your body needs vitamin C to make collagen. Red and green peppers, oranges and other citrus fruit, kiwifruit, broccoli, strawberries and Brussels sprouts are among the best sources.^4,15

What's in ours

What’s in ours

Collagen Peptides: Hydrolyzed Collagen Peptides, 20 g per serving, from the label
Collagen Peptides: Hydrolyzed Collagen Peptides, 20 g per serving, from the label

Both of our Collagen Peptides give 20 g of collagen per serving, more than most trials used. No trial reviewed here compared 20 g with a smaller amount, and 10 g sits at the top of the range studied for skin and joints.^2,6

Side effects and who should ask first

Across 25 randomized skin trials, hydrolyzed collagen was generally well tolerated with few adverse events, though the reviewers judged most of the trials likely to be biased.¹⁶

Collagen is rich in hydroxyproline, which the body partly turns into oxalate. In a feeding study, 30 g of gelatin raised urinary oxalate 43 percent compared with whey, and 5 to 10 g also changed it, which matters for people who form calcium oxalate kidney stones.¹⁷

Fish collagen is a concern for people allergic to fish, a major food allergen that labels must name. Some people with alpha-gal syndrome, a red meat allergy usually caused by tick bites, also react to gelatin and other products made from mammals.^18,19

No tolerable upper intake level has been set for collagen. Most trials used 2.5 to 15 g a day for up to 12 months, and a review of 15 trials found no adverse effects reported, including in short studies at 60 g a day.^6,20

Ask first if you are pregnant or nursing; the collagen trials reviewed here did not include pregnant or nursing women
Ask first if you have kidney disease or have had kidney stones
Ask first if you have been told to limit protein
Check the source animal on the label if you are allergic to fish, beef, pork or gelatin, or have alpha-gal syndrome
See a doctor about joint pain or swelling that has not been checked

The official sources we checked name no medicine that interacts with collagen. That is not proof of safety: if you take a regular medicine, ask your pharmacist.

Questions people ask

What does collagen do for your body?

Collagen gives skin, bone, tendons and cartilage their structure. Eaten as a supplement, it is digested into amino acids, especially glycine, and small peptides; whether these reach the tissues and change them is what the trials above test.^1,21

Is collagen worth taking for men too?

The skin trials were mostly in women, but the joint and training trials included men: the main joint trial enrolled 180 active men and women aged 18 to 30, and a 2025 muscle study had 21 men among 45 adults.^2,7,10

Is collagen safe to take every day?

Trials of up to 12 months reported no side effects linked to collagen, and no upper limit has been set. Ask your doctor first if you have kidney disease or have had kidney stones, are pregnant or nursing, or are allergic to the source animal.^6,17,20

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Sources

*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.