NAKED Collagen Peptides Review: The Label, the Research, and the Honest Limits

Collagen is the supplement that has been sold as the answer to joints, skin, hair, nails, gut, and recovery, sometimes in the same paragraph. That breadth is a warning sign on its own, because a product that promises to fix everything has usually been tested for very little. At the same time, collagen peptides have attracted real research in the last decade, mostly from German and Australian groups, and some of it concerns lifters directly: tendon thickness, muscle mass in older men, and recovery from damaging exercise. A fair review has to hold both facts at once.

This article covers the label, the evidence for each use people claim, how a scoop compares with the doses in the trials, and the cost math. We link to our existing collagen guides instead of repeating them: Collagen Peptides: What They Actually Do and Collagen Supplements: Joint Health Claims vs. the Actual Research.

What You Are Buying

The details below come from the Amazon listing for NAKED Collagen Peptides (ASIN B07H5SLML1), Unflavored, 60 servings. The listing offers other flavors and sizes; this review covers the 60-serving unflavored tub.

The numbers are internally consistent. A 20 oz tub is about 567 g, and 567 g divided by 60 servings is about 9.45 g per scoop, which matches the 9.5 g of collagen peptides the listing states. The panel itself was not a text field we could read, so the per-scoop amino acid numbers come from the listing bullets and should be checked against the bag. Notice what the label says about protein: 9 g per scoop, of 9.5 g of powder. That is about 95 percent protein by weight, which is plausible for a hydrolyzed collagen and not unusual. It is also protein of a specific kind, which matters for how you use it.

The Listing's Health Claims, Read Honestly

Before the evidence, a note on the marketing, since the listing is long on it. The bullets state that collagen "helps repair a leaky gut," describe leaky gut as a leading cause of autoimmune diseases, call collagen an anti-inflammatory, say it "protects cartilage and bones," and promise youthful skin, stronger nails, healthier hair, and workout recovery. They also assert that after about age 30 the body produces less collagen and that health and sports research shows it can improve muscle recovery and digestion.

We cannot support most of that with research we have verified. We did not find a trial we could cite showing that oral collagen repairs the gut lining, and the statement that gut permeability is a leading cause of autoimmune disease is a contested hypothesis, not an established cause. The anti-inflammatory and "protects cartilage and bones" claims are not backed by anything in the trials we read below. The age-30 statement is a general physiology claim we have not checked for this review. The only claims in that list that line up with published trials are the tendon, muscle, and recovery claims, and even those come with qualifiers.

Collagen Is an Incomplete Protein

This is the point that most affects how a lifter should think about the tub. Paul and colleagues (2019) note that by the current protein quality method, the Protein Digestibility-Corrected Amino Acid Score, collagen protein lacks one indispensable amino acid, tryptophan, and is therefore categorized as an incomplete protein source, with a low indispensable amino acid profile overall. Their conclusion was constructive: iterative calculations showed that as much as 36 percent of the protein in a typical Western diet could be replaced by collagen peptides while still meeting indispensable amino acid requirements, and the effective amounts used in the literature, 2.5 to 15 g a day, are below that maximum. In other words, collagen is not harmful as part of an otherwise complete diet. It is just not a substitute for whey, eggs, meat, or other complete proteins.

The muscle-building data back this up. Impey and colleagues (2018) had eight men consume 22 g of a hydrolyzed collagen blend or whey three times around a cycling session done with low carbohydrate availability. Whey produced larger increases in plasma branched-chain amino acids and leucine than collagen, and a greater increase in p70S6K1 activity, a signaling marker linked to muscle protein synthesis, at 1.5 hours after exercise (180 versus 73 fmol per minute per mg). The authors attributed the difference to the greater leucine availability with whey. It is a small acute study measuring a signaling marker, not muscle growth. It still illustrates the practical point: the 9 g of "protein" in a scoop of collagen is not the same as 9 g of whey protein for the purposes of building muscle. If you count it toward your daily protein, count it as a partial credit. Our protein powder buyer's guide has a section on why collagen is not a muscle protein.

Collagen and Muscle: What the Trials Show

The best summary is the 2024 systematic review and meta-analysis by Bischof and colleagues, which pooled 19 randomized trials with 768 healthy adults who took collagen peptides daily for at least eight weeks, with or without exercise. The pooled results favored collagen for fat-free mass (standardized mean difference 0.48, p < 0.01), tendon morphology (0.67), muscle architecture (0.39), maximal strength (0.19), and 48-hour recovery of reactive strength after exercise-induced muscle damage (0.43, p = 0.045). The certainty of that evidence, graded with the GRADE approach, was moderate for body composition, very low for tendon morphology and mechanical properties, and low for the remaining outcomes.

Hold the two halves of that sentence together. Statistically significant effects, yes. High confidence in them, no, apart from a moderate grade for body composition. The maximal strength effect of 0.19 is small. And those numbers pool studies of different populations, doses, and products.

The individual trial most often cited for muscle is Zdzieblik and colleagues (2015). Fifty-three men with sarcopenia, average age 72, completed a 12-week guided resistance training program three times a week and took 15 g a day of collagen peptides or a silica placebo. Everyone improved, and the collagen group improved more: fat-free mass rose 4.2 kg versus 2.9 kg in the placebo group (p < 0.05), isokinetic quadriceps strength rose 16.5 Nm versus 7.3 Nm, and fat mass fell 5.4 kg versus 3.5 kg. This is a trial in older sarcopenic men taking 15 g a day, which is about one and a half scoops, and its relevance to a healthy younger lifter eating adequate protein is limited. Our existing coverage of the product category is in the collagen peptides guide.

Collagen, Tendon, and Connective Tissue

Tendon is where the mechanism story is most appealing and the evidence most preliminary. Shaw and colleagues (2017) ran a small crossover study in eight healthy men. Participants consumed 5 or 15 g of vitamin C-enriched gelatin or a placebo, and one hour later did six minutes of rope skipping, repeated three times a day for three days. Gelatin raised circulating glycine, proline, hydroxyproline, and hydroxylysine. Engineered ligaments treated with serum taken after the 15 g dose showed more collagen and better mechanics, and the men who took 15 g one hour before exercise had double the blood level of the amino-terminal propeptide of collagen I, a marker of collagen synthesis. The authors concluded that adding gelatin to an intermittent exercise program could improve collagen synthesis. It is a clever design with a tiny sample, a biomarker outcome, and gelatin enriched with vitamin C, and the abstract does not tell us whether vitamin C or the gelatin did the work.

The clinical-style trials are small too. Praet and colleagues (2019) gave 20 people with chronic mid-portion Achilles tendinopathy either a branded specific collagen peptide product or placebo alongside a six-month calf-strengthening program, with a crossover at three months. After three months, the Victorian Institute of Sports Assessment-Achilles score rose by 12.6 points in the group that received collagen first, compared with 5.3 in the placebo-first group. That is a pilot study, and the authors called it one. Jerger and colleagues (2023) randomized 50 healthy, moderately active men to 14 weeks of high-load knee extensor training with 5 g a day of specific collagen peptides or placebo. The collagen group showed a greater increase in patellar tendon cross-sectional area at some points along the tendon. Both groups increased tendon stiffness, muscle size, and strength, with no significant differences between groups. So the supplement changed one structural measure and none of the performance ones. A thicker tendon is not proven to be a better or safer tendon.

Collagen and Joint Pain

The joint pain claim is the oldest one, and the evidence is stronger in people with osteoarthritis than in healthy lifters. Liu and colleagues (2018) reviewed 69 trials of 20 dietary supplements for hand, hip, or knee osteoarthritis and found that collagen hydrolysate was one of seven supplements with a large short-term effect on pain, but they graded the overall quality of evidence as very low, and no supplement showed clinically important effects on pain at the long term. They also found no differences from placebo in safety outcomes except for one drug. That is a result for a clinical population, and it does not tell a healthy 28-year-old that collagen will protect his knees. We cover the osteoarthritis literature, the athlete trials, and the funding question in more depth in our joint health claims article.

Why These Trials Do Not Transfer Cleanly to This Tub

This is the honest limit. Several of the trials we describe used branded, characterized collagen peptide products, which the authors call "specific collagen peptides," or a trademarked tendon-targeted product in the Praet pilot. The NAKED listing describes plain bovine hide collagen peptides with no brand name for the peptide, no stated molecular weight range, and no published peptide profile in the text we retrieved. Collagen peptides are made by enzymatic hydrolysis, and different sources and processes give different mixes of peptide sizes. The research does not tell us that every collagen powder behaves like the ones in the trials. It is quite possible that they are similar. It is also not demonstrated.

We have not assessed the funding behind each trial for this review, which is one reason we lean on the pooled, graded analysis from Bischof and colleagues and on the fact that its certainty ratings were low or very low for the tendon outcomes. Our joint claims article discusses the funding question.

How a Scoop Compares With the Studied Doses

One scoop sits inside the studied range, above the 5 g that gave a tendon change in healthy men and below the 15 g used in older sarcopenic men. One scoop a day is therefore a defensible dose, and two scoops is toward the high end. Nothing in the research tells us that taking more than the studied doses helps. And if you want to follow the Shaw protocol of taking the collagen about an hour before activity, the NAKED product has no vitamin C in it, so you would need to supply that yourself, although the study as we read it did not test whether the vitamin C was necessary.

What It Costs Per Dose

At $41.99 for 60 scoops, one scoop costs about 70 cents. By the gram, that is about 7.4 cents per gram of collagen peptides (570 g in 60 servings of 9.5 g) and about 7.8 cents per gram of protein.

As protein, it is not a bargain, because it is not complete protein: the cost per gram of protein is only meaningful if the protein does the job you are buying it for. Our buyer's guide explains the cost-per-gram method, and a complete protein does more for muscle. As a collagen product, 70 cents a day for something with moderate-to-low certainty evidence is a judgment call. At a daily scoop, a year costs about $255, which is a number worth looking at before you commit. We have not fetched prices of other collagen products, so we do not make comparisons with them.

Safety and Sourcing

Collagen peptides are a food-derived protein and, in the trials we read, were not associated with notable adverse effects, though the abstracts we read do not focus on safety and we cannot give you a rate. The listing states a single bovine-derived ingredient and no other additives, no sugar, and none of the common allergens it names (gluten, soy). The product is bovine, so it is not suitable for vegetarians or vegans, and anyone with a beef allergy should avoid it. The listing says the cows are pasture-raised and European. We cannot verify origin from a listing. People with kidney disease or on protein restriction should discuss any added protein with their physician.

If you take collagen for connective tissue goals, remember that it does not replace the things that load tendons: progressive training, adequate total protein, enough calories, and sleep. See our training injuries guide.

Quality and Third-Party Testing

This product's listing makes a product-level testing claim: the title says NSF Certified, and the bullets say it is verified for purity and safety and independently tested. That is a stronger statement than a facility claim, and it matters in a category where heavy metals and label accuracy are fair questions. We did not look the product up in NSF's public database for this review, so we are reporting what the listing says, not confirming it. If the certification matters to you, confirm it on NSF's site, check which program the mark refers to, and ask the company for a certificate of analysis for your lot. The listing's comparative claims, such as that other brands use a cheaper source that does not mix as well, are marketing and we have not verified them.

Who Should Buy It and Who Should Skip It

It makes sense if you want a flavorless, single-ingredient collagen powder to stir into coffee or a smoothie, you are interested in the modest evidence for tendon and body composition effects when paired with resistance training, you tolerate beef-derived products, and you accept that this is a low-certainty, small-effect supplement. A single scoop is within the studied range, and the testing claim is a point in its favor.

Skip it if you want it as a primary protein source, you expect it to fix joint pain or repair your gut, you are on a tight budget and your training, protein, and sleep are not yet in order, or you avoid animal products. For muscle, a complete protein is the better use of the money. And if you have tendon pain that does not settle, see a clinician or physical therapist and do not buy your way out of it. Remember the hierarchy: loading, total protein, and recovery do more than any peptide.

What Buyers Report

Buyers of the unflavored collagen powder, mostly on retailer pages, focus on how it mixes and tastes.

• Mixing and taste: Most positive reviews say it dissolves fully in hot coffee, tea, juice or smoothies and has no noticeable taste or aftertaste. Several say they cannot tell it is there.
• Ingredients: Buyers appreciate the short ingredient list and the clean sourcing claims.
• Complaints: The negative reviews are fewer but consistent: some buyers call the taste bad or the texture gritty, and one says the tub looked only about half full when it arrived.
• Tolerability: A few buyers say it felt gentle on the stomach, and others say it did not suit them.

Takeaway: most buyers treat it as an easy-to-hide, flavorless add-in, and the minority who dislike it mostly object to taste or texture. Buyer reports are anecdotal and are not the same as the research above; they are not evidence about what a supplement does and not advice.

How HonestLifter Is Reviewing This Product

HonestLifter's editorial model is longitudinal. A one-time first-impressions post tells you very little about a supplement, so the plan for each product is a written research review at the start, followed by dated checkpoint updates at 30 days, 60 days, 90 days, 6 months, and 12 months of use. The checkpoint updates are meant to report real use, real notes, and, where available, real data exports, not recycled research. You can read more in our longitudinal review program article.

The checkpoint schedule is below.

This is a research review built on the product's listing and published studies. Our own notes will be added as dated updates later.

Checkpoint Update: 30-Day, 60-Day, 90-Day and 6-Month Notes (October 2026)

HonestLifter's owner reports the following from regular use. These are personal notes, not measurements.

• Use: Daily and regular, after training alongside whey.
• Taste: Unflavored, so none to report.
• Effect: The owner thinks it helps and does what it should, but is not certain. With nothing measured behind that, treat it as an impression, not a result.
• Verdict: Would buy again.

Several supplements are taken together, so none of these notes isolates the effect of this product. The 12-month update will be added when it is written.

The Bottom Line

NAKED Collagen Peptides is a clean, single-ingredient product with a credible testing claim and a scoop size that falls in the range used in published trials. The science behind collagen peptides is real but modest: a pooled analysis found small to moderate effects on fat-free mass and tendon structure when combined with training, with the grading of that evidence ranging from moderate down to very low, and a trial of 5 g a day found a thicker tendon but no better strength. Collagen is an incomplete protein and does not stimulate muscle protein synthesis like whey, and the listing's gut and autoimmune claims go well beyond anything we could verify.

Buy it if you want to try it as a modest, low-risk add-on to training and you can accept the evidence as it is. Do not buy it as your protein source or as a joint cure. Check the testing claim if it matters to you, and watch this page for our dated checkpoint updates.

References

1. Bischof, K., Moitzi, A.M., Stafilidis, S., & Konig, D. (2024). Impact of collagen peptide supplementation in combination with long-term physical training on strength, musculotendinous remodeling, functional recovery, and body composition in healthy adults: a systematic review with meta-analysis. Sports Medicine, 54(11), 2865-2888. doi:10.1007/s40279-024-02079-0. PMID 39060741.
2. Zdzieblik, D., Oesser, S., Baumstark, M.W., Gollhofer, A., & Konig, D. (2015). Collagen peptide supplementation in combination with resistance training improves body composition and increases muscle strength in elderly sarcopenic men: a randomised controlled trial. British Journal of Nutrition, 114(8), 1237-1245. doi:10.1017/S0007114515002810. PMID 26353786.
3. Shaw, G., Lee-Barthel, A., Ross, M.L., Wang, B., & Baar, K. (2017). Vitamin C-enriched gelatin supplementation before intermittent activity augments collagen synthesis. American Journal of Clinical Nutrition, 105(1), 136-143. doi:10.3945/ajcn.116.138594. PMID 27852613.
4. Praet, S.F.E., Purdam, C.R., Welvaert, M., Vlahovich, N., Lovell, G., Burke, L.M., et al. (2019). Oral supplementation of specific collagen peptides combined with calf-strengthening exercises enhances function and reduces pain in Achilles tendinopathy patients. Nutrients, 11(1), 76. doi:10.3390/nu11010076. PMID 30609761.
5. Jerger, S., Centner, C., Lauber, B., Seynnes, O., Friedrich, T., Lolli, D., et al. (2023). Specific collagen peptides increase adaptions of patellar tendon morphology following 14-weeks of high-load resistance training: a randomized-controlled trial. European Journal of Sport Science, 23(12), 2329-2339. doi:10.1080/17461391.2023.2232758. PMID 37424319.
6. Liu, X., Machado, G.C., Eyles, J.P., Ravi, V., & Hunter, D.J. (2018). Dietary supplements for treating osteoarthritis: a systematic review and meta-analysis. British Journal of Sports Medicine, 52(3), 167-175. doi:10.1136/bjsports-2016-097333. PMID 29018060.
7. Paul, C., Leser, S., & Oesser, S. (2019). Significant amounts of functional collagen peptides can be incorporated in the diet while maintaining indispensable amino acid balance. Nutrients, 11(5), 1079. doi:10.3390/nu11051079. PMID 31096622.
8. Impey, S.G., Hammond, K.M., Naughton, R., Langan-Evans, C., Shepherd, S.O., Sharples, A.P., et al. (2018). Whey protein augments leucinemia and postexercise p70S6K1 activity compared with a hydrolyzed collagen blend when in recovery from training with low carbohydrate availability. International Journal of Sport Nutrition and Exercise Metabolism, 28(6), 651-659. doi:10.1123/ijsnem.2018-0054. PMID 29757056.

Product details were taken from the Amazon listing for NAKED Collagen Peptides (Unflavored, 60 servings) and may change. HonestLifter carries no affiliate links. This article is educational and is not medical advice.