By Jade
You catch a nail on a sleeve and a thin layer lifts away. The tip splits, a corner peels, and by Thursday you are filing down what is left. You have read that it is biotin, or collagen, or a deficiency of something, and every bottle in the pharmacy promises a stronger nail by the end of the month. This article covers what a nail is built from, how slowly it grows and what the research says about biotin. It is education only, and it cannot tell you why your nails are splitting. A clinician can.
Brittle, peeling nails have many possible causes, from repeated wetting and drying to iron status, and the evidence for biotin is limited outside specific cases, so the sensible response is to rule out a medical cause with a clinician, protect the nail from water and friction, and keep protein, iron and vitamin C coming in through food.
What is a nail actually made of?
Your nail plate is keratin. A 2010 review in Clinics in Dermatology by Cashman and Sloan describes the nail as a specialized keratinous skin appendage and reviews the chemical profile of the normal nail plate: its keratin content (hair-type keratin and epithelial-type keratin), its sulfur content, and its minerals, including magnesium, calcium, iron, zinc, sodium and copper. The same review states that virtually every nutritional deficiency can affect the growth of the nail in some manner.
Your body builds the plate from the inside, cell by cell, out of protein and a handful of minerals. Nothing you paint or rub onto the surface becomes part of that structure. Food supplies the raw material, and the body does the building.
The building is slow. Cashman and Sloan report that the nail grows approximately 2 to 3 mm per month, with complete replacement achieved in 6 to 9 months. They also note that nail disorders make up approximately 10% of all dermatologic conditions.
Slow growth changes how you should read every nail claim. The tip you see today reflects what the nail matrix produced months ago, and a change you make this week reaches the free edge months from now. A product promising a visible result in two weeks is promising something the biology does not run on.
Why do nails peel and split in layers?
A 2019 review in Dermatology and Therapy by Chessa and colleagues puts nail plate brittleness at up to 20% of the population, especially women over 50, with fingernails affected more often than toenails. The presentations they name include onychoschizia, the layered splitting at the free edge that most people mean when they say their nails peel, and onychorrhexis, the longitudinal ridging and splitting.
Chessa and colleagues separate a primary form, called idiopathic or brittle nail syndrome, from a secondary form tied to inflammatory nail disorders, infections, systemic diseases, trauma or altered nail hydration, and say the underlying cause needs to be addressed. A nail that changes suddenly, thickens, discolours or hurts belongs with a clinician, not a shopping basket.
Hydration is the part you can see in daily life. Chessa and colleagues list alteration of nail hydration among the secondary causes of fragility. In a 2025 study in Contact Dermatitis, Sashindran and colleagues examined 76 male parachute riggers. Loss of cuticle was present in 57 of them (75%), xeroderma in 30.2% and onychoschizia in 10 (13.1%). The authors attributed the changes to repeated friction, pressure and dryness of the hands, and recommended barrier creams, good gloves and education.
Does biotin actually work for nails?
A 2017 review in Skin Appendage Disorders by Patel and colleagues notes that biotin has gained commercial popularity for hair and nail claims, with limited research in healthy individuals. They found 18 reported cases of biotin use for hair and nail changes. In all of them, the patients had an underlying pathology for poor hair or nail growth, and all showed clinical improvement. The authors propose that such cases are uncommon and that there is a lack of sufficient evidence for supplementation in healthy individuals.
Here is the honest concession: the research is not empty. A 2017 review in the Journal of Dermatological Treatment by Lipner and Scher reports that clinical trials have shown an improvement in firmness, hardness and thickness of brittle nails with oral biotin, and that larger controlled trials are needed. A 2019 randomized, assessor-blinded trial in Dermatologic Therapy by Chiavetta and colleagues gave 50 people with brittle nail syndrome (mean age 64) a chitosan-based nail lacquer alone or with 10 mg of oral biotin daily for four months. A nail severity score fell by 57% with the lacquer and 62% with the lacquer plus biotin, and 53% versus 80% of people reached a reduction of 50% or more (p = .05).
A 2025 retrospective study in the Journal of Drugs in Dermatology by Shemer and colleagues is the most telling. Among 61 patients with onychoschizia given 1 mg a day of biotin, 100 mg a day of pyridoxine, or both, for three months, complete response was 10% with biotin alone and 11.1% with pyridoxine alone, against 69.6% with the combination. A retrospective study cannot say more than that.
First, regulation. A 2024 review in Skin Appendage Disorders by Zaraa and Richert lists biotin, collagen peptides, solubilized keratin MSM and choline-stabilized orthosilicic acid among ingredients that have been shown to improve the clinical appearance of nails, and states that manufacturers of dietary supplements are not required to carry out efficacy studies.
Second, blood tests. A 2020 survey in the Journal of Dermatological Treatment by Waqas and colleagues recalls a 2017 FDA safety alert warning that biotin can interfere with laboratory testing. Of 149 physicians surveyed, 43.9% prescribe biotin, primarily for hair and nail disorders. Most knew that it interferes with thyroid and troponin testing, almost half did not ask patients to discontinue biotin before laboratory testing. If you take a biotin product, tell whoever orders your bloodwork.
What do iron and protein have to do with brittle nails?
Iron is the clearest nutritional link in the literature. A 2018 report in Clinical Case Reports by Moiz describes koilonychia, thin, brittle, spoon-shaped nails, as frequently observed in chronic iron deficiency secondary to malnutrition, chronic blood loss or malabsorption. It may also be idiopathic or related to occupation. Moiz concludes that the presence of koilonychia should prompt investigations for iron deficiency. The nail is a reason to test, not a reason to start taking iron on a hunch. Our piece on iron, vitamin C and whole-food nutrition covers the food side of that conversation.
Protein is the other obvious raw material, because the plate is keratin. Chessa and colleagues note that amino acids, especially cysteine, have been reported to be useful in idiopathic nail fragility. Cysteine is a sulfur-containing amino acid, which fits Cashman and Sloan's description of a sulfur-rich plate.
A 2022 review in ACS Omega by Piskin and colleagues explains that the average dietary intake of 10 to 15 mg a day yields only 1 to 2 mg absorbed. Ascorbic acid and proteins enhance iron bioavailability, while calcium, phytates and polyphenols inhibit it. In practice: pair lentils or spinach with peppers or citrus, and keep tea, coffee and other polyphenol-rich drinks away from your main iron-rich meal.
| What the nail draws on | What the research says | Foods to lean on |
|---|---|---|
| Protein and cysteine | The plate is keratin, and sulfur is part of its chemistry | Eggs, fish, poultry, lentils, tofu |
| Iron | Spoon nails are common in chronic iron deficiency | Red meat, lentils, spinach, pumpkin seeds |
| Zinc and other minerals | Zinc, copper and magnesium are in the plate | Shellfish, beef, chickpeas, cashews |
| Vitamin C | Needed for collagen, and it lifts iron absorption | Peppers, citrus, kiwi, berries |
| Biotin | Evidence is limited outside specific cases | Eggs, nuts, fish |
What does vitamin C do for the tissue around the nail?
Be precise here, because this is where nail marketing gets loose. The nail plate is keratin, not collagen, and vitamin C does not build the plate. But the nail sits inside living tissue: under the cuticle, the nail matrix makes the plate, and the body maintains that tissue every day, collagen included.
A 2022 scoping review in Nutrients by Noriega-González and colleagues, written about tendons, notes that vitamin C deficiency is associated with a decrease in procollagen synthesis and reduced hydroxylation of proline and lysine residues. A 2024 review in Postepy Biochemii by Goik says the same about skin: vitamin C participates in the hydroxylation of proline and lysine during collagen biosynthesis, and its deficiency causes irregularities in the epidermis and dermis. Humans cannot make vitamin C, which is why it has to arrive through food every day. For the wider skin picture, see our piece on skin, collagen and nutrition.
What does your body actually need?
Put the research together and the list is short. A clinician to rule out a medical cause. Protein at every meal. Iron it can absorb, eaten with a vitamin C food. Vitamin C every day, because the body cannot make its own. And protection: gloves for wet work, a plain moisturizer and fewer cycles of soaking and drying.
Where does sea buckthorn fit?
Human Renaissance sea buckthorn purée is not a nail product, and we make no claim that it affects your nails. What it is, in plain terms: Human Renaissance sea buckthorn purée contains 190+ naturally occurring compounds, omega 3, 6, 7 and 9, 201 mg of vitamin C per pouch, 0 g sugar and 5,640 hand-picked berries per box.
It is a whole berry, wild on the Tibetan Plateau, above 3,000 metres (about 10,000 feet), and in Inner Mongolia, pressed whole into a 30 mL pouch with 201 mg of vitamin C, 223% NRV. Because the berry arrives with its own matrix, your body handles it the way it handles any food. Human Renaissance is the only sea buckthorn purée in the world sold in a single-serve pouch.
Mind the polyphenol note from the iron section. Berries are polyphenol-rich foods, and Piskin and colleagues list polyphenols among the inhibitors of iron absorption, so berries carry both vitamin C, which aids iron absorption, and polyphenols, which can reduce it. No study has tested the pouch with an iron-rich meal. And be ready for the taste. It is intensely tart, and the first pouch brings a Tabasco-sharp warmth at the back of the throat, because it is the whole berry, unblended. Here is what to expect.
How do you put this into practice this week?
A routine, not a promise of a result.
Day 1. Photograph your nails in daylight and write down how many times a day your hands get wet.
Day 1 or 2. If your nails are thin, spoon-shaped, ridged or changing fast, book a visit and ask whether bloodwork for iron status makes sense. If you take biotin, say so.
Every meal. Put protein on the plate first: eggs, fish, poultry, lentils, tofu.
Iron meals. Pair them with a vitamin C food, such as peppers, citrus or kiwi, and have your tea or coffee an hour or two later.
Every wet job. Wear gloves for washing up and cleaning. At night, press a plain moisturizer into the nails and cuticles.
Every morning. Eat one vitamin C food. If you take a pouch, it is a food habit, not a nail step. Keep water nearby, because the first pouch is sharp.
Week 8. Look at the base of the nail, not the tip. At 2 to 3 mm a month, two months gives about 4 to 6 mm of new nail, while the tip still shows the old plate. Compare against your Day 1 photograph and share what you see with your clinician.
Frequently asked
Does biotin work for brittle nails? The evidence is narrow. Patel and colleagues found 18 reported cases of biotin use for hair and nail changes in 2017, all with an underlying cause. Trials in brittle nail syndrome report improvement, and larger controlled trials are still needed.
Can a vitamin deficiency cause brittle nails? Sometimes. A 2018 report in Clinical Case Reports describes koilonychia, thin, brittle, spoon-shaped nails, as frequently seen in chronic iron deficiency, and says it should prompt investigation for iron deficiency. Only a clinician can tell you whether that is your case.
What should I eat for peeling nails? Nothing in food is a nail remedy. What the research supports is covering the raw materials: protein at each meal, iron eaten with a vitamin C food, a varied plate for minerals, and protection from repeated wetting and drying.
Will sea buckthorn make my nails stronger? No. Human Renaissance sea buckthorn purée is a food, not a nail product, and we make no claim that it affects your nails. It is a daily whole-food source of vitamin C, omega 3, 6, 7 and 9 and other naturally occurring compounds.
Does biotin affect blood tests? It can. A 2017 FDA safety alert warned that biotin can interfere with laboratory testing, and a 2020 survey of 149 physicians found that most knew it interferes with thyroid and troponin testing. Tell whoever orders your bloodwork if you take it.
When should I see a doctor about my nails? When a change is sudden, painful, discoloured or spoon-shaped, or does not settle.
Human Renaissance sea buckthorn purée
Human Renaissance is the only sea buckthorn purée in the world sold in a single-serve pouch. 190+ naturally occurring compounds, omega 3, 6, 7 and 9, 201 mg of vitamin C per pouch, 223% NRV, 0 g sugar, 60 pouches to a box, one a day.
Read the label and decide whether one small, dense food belongs in your morning. See the sea buckthorn purée.
Related reading
- Tired All the Time? Iron, Vitamin C and Whole-Food Nutrition
- Vitamin C Your Body Cannot Make: Why Humans Need It Daily
- Skin, Collagen and Nutrition: What Sea Buckthorn Actually Provides
- Why Your Body Absorbs Food Better Than Pills: The Food Matrix, Explained
Sources
- Cashman MW, Sloan SB. Nutrition and nail disease. Clinics in Dermatology, 2010. PMID 20620759. doi:10.1016/j.clindermatol.2010.03.037
- Chessa MA et al. Pathogenesis, Clinical Signs and Treatment Recommendations in Brittle Nails: A Review. Dermatology and Therapy, 2019. PMID 31749091. doi:10.1007/s13555-019-00338-x
- Patel DP, Swink SM, Castelo-Soccio L. A Review of the Use of Biotin for Hair Loss. Skin Appendage Disorders, 2017. PMID 28879195. doi:10.1159/000462981
- Lipner SR, Scher RK. Biotin for the treatment of nail disease: what is the evidence? Journal of Dermatological Treatment, 2017. PMID 29057689. doi:10.1080/09546634.2017.1395799
- Chiavetta A et al. Treatment of brittle nail with a hydroxypropyl chitosan-based lacquer, alone or in combination with oral biotin: a randomized, assessor-blinded trial. Dermatologic Therapy, 2019. PMID 31344296. doi:10.1111/dth.13028
- Shemer A et al. Biotin or Pyridoxine Versus Combined Regimen in the Treatment of Onychoschizia. Journal of Drugs in Dermatology, 2025. PMID 39913222. doi:10.36849/JDD.7687
- Zaraa I, Richert B. Nail Supplements: When, How, and Why? Skin Appendage Disorders, 2024. PMID 40176998. doi:10.1159/000541048
- Waqas B et al. A survey-based study of physician practices regarding biotin supplementation. Journal of Dermatological Treatment, 2020. PMID 32419559. doi:10.1080/09546634.2020.1770178
- Sashindran VK et al. Occupational Dermatoses in Parachute Riggers. Contact Dermatitis, 2025. PMID 39916500. doi:10.1111/cod.14763
- Moiz B. Spoon nails: still seen in today's world. Clinical Case Reports, 2018. PMID 29531740. doi:10.1002/ccr3.1404
- Piskin E et al. Iron Absorption: Factors, Limitations, and Improvement Methods. ACS Omega, 2022. PMID 35755397. doi:10.1021/acsomega.2c01833
- Noriega-González DC et al. Effect of Vitamin C on Tendinopathy Recovery: A Scoping Review. Nutrients, 2022. PMID 35807843. doi:10.3390/nu14132663
- Goik U. Vitamin C and its derivatives in maintaining the good skin condition. Postepy Biochemii, 2024. PMID 39365570. doi:10.18388/pb.2021_554
Specialists share education, not medical advice. This article is for informational purposes and does not diagnose, treat, cure or prevent any disease. Always consult your physician about changes in your nails.
