Many people perceive the quality of their hair and nails purely as an aesthetic matter. From the perspective of the body, however, they are sensitive indicators of internal balance and health. Since these tissues are not essential for survival, in the case of nutrient deficiency or stress, the body restricts them first in order to save energy for more important organs. Changes in their appearance can therefore be an early warning sign that something inside the body is not right.
What will you learn in this article?
- Nails: What do Shape and Color Reveal?
- Hair: What Does It Reveal About Hormones, Immunity, and Nutrition?
- Key Nutrients for Healthy Hair and Nails
- The Effect of Stress on the Health of Hair and Nails
- Hair Loss in Men
- Key Takeaways
Nails: What do Shape and Color Reveal?
Nails grow from the nail bed, which is richly supplied with blood vessels. Any long-term changes in metabolism, blood circulation, and nutrition of the organism can therefore be reflected in their appearance.
Pale or bluish nails
If the nail bed loses its natural pink color and shifts to a bluish tone, it may be related to poorer tissue oxygenation or anemia. Iron deficiency leads to reduced hemoglobin production, which transports oxygen to cells. [1]
Spoon-shaped nails (koilonychia)
A concave nail shape is a typical symptom of long-term iron deficiency and appears especially in chronic deficiencies or disorders of nutrient absorption. [2]
White spots
A widespread myth links white spots on nails with calcium deficiency. In reality, they are most often minor mechanical injuries of the nail matrix. In practice, zinc deficiency is also relatively common and may manifest as white spots on nails. [3]
Horizontal ridges (Beau’s lines)
Pronounced horizontal ridges may develop after high fever, severe infection, surgery, or significant psychological stress. These nail changes may also be associated with insufficient protein intake in the diet. [4]
Vertical ridges
Vertical ridges on nails are quite common, and their occurrence may increase with age. These lines may be related to poorer nutrient absorption and weakened digestion or protein deficiency. More pronounced vertical ridges may indicate long-term exhaustion of the organism, stress, or insufficient production of gastric acid (HCl), which is important for proper digestion and utilization of nutrients needed for healthy nail growth.
Brittle and weak nails
Brittleness is often contributed to by a combination of vitamin and mineral deficiencies, for example iron, zinc, biotin, calcium, magnesium, and silicon. Long-term dehydration and frequent contact with chemicals or aggressive cosmetics, especially nail polish, also play a role.
Hair: What Does It Reveal About Hormones, Immunity, and Nutrition?
The hair follicle is one of the most metabolically active tissues in the body. For this reason, it is highly sensitive to hormonal changes, nutrient deficiencies, and psychological stress.
Hormonal imbalance as a cause
Changes in estrogen levels may be reflected, for example, after childbirth, during perimenopause, or in polyendocrine metabolic syndrome of the ovaries (PMOS), formerly known as polycystic ovary syndrome (PCOS). Thyroid hormone fluctuations also play a significant role. Both reduced and increased thyroid function can disrupt the hair growth cycle and lead to increased shedding. [6]
Nutrient deficiency
Hair loss is also associated with iron deficiency, especially low ferritin levels, which represent the storage form of iron in the body. Hair follicles are among the fastest dividing tissues in the body, and therefore very sensitive to oxygen and nutrient deficiency. Optimal ferritin levels for supporting hair growth are often considered to be approximately above 50–80 µg/l, although laboratory reference ranges are usually broader. [7]
B vitamins—especially biotin, vitamin B12, and folic acid—also play an important role, supporting cell division, energy metabolism, and red blood cell formation. Their deficiency may therefore contribute to poorer hair quality, weakening, and increased shedding. [8]
Extreme diets, low-calorie intake, or insufficient protein intake (often in improperly designed vegan and vegetarian diets) expose the body to significant stress. In such cases, the body prefers to use amino acids for muscles and organs rather than for hair. It is therefore recommended to ensure sufficient protein intake. More about the importance of proteins and their inclusion in the diet can be found in the article What to eat for breakfast: and why you should focus on protein.
Dry and brittle hair
Brittle, dull hair is often associated with reduced thyroid function. Thyroid hormones influence metabolic rate and hair follicle renewal. [6] Hair quality is also influenced by sufficient intake of omega-3 fatty acids, which help maintain hydration, elasticity, and healthy hair structure. Dry and brittle hair can also be worsened by chronic stress, hormonal changes, insufficient energy intake, or impaired nutrient absorption.
Premature graying
In addition to genetic predisposition, long-term oxidative stress or deficiency of vitamin B12, folic acid, or iron may play a role. Some studies suggest that stress may affect melanocyte stem cells responsible for hair pigmentation. [9]
Key nutrients for healthy hair and nails
For strong structure of hair and nails, the body needs specific building blocks that must be obtained through diet or nutritional supplements.
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Proteins: Hair is composed of approximately 90% of a protein called keratin, which is also the main structural component of nails. Nails contain keratin in about 80–90%, in a harder and more rigid form. It is found mainly in animal foods such as eggs, meat, and fish. Precursors for keratin formation (not to be confused with creatine) are the amino acids methionine and cysteine. Low protein intake can therefore lead to slower hair growth, brittleness, and increased hair loss. When amino acids are lacking, the body prioritizes more essential tissues first.
- Zinc: Zinc is involved in cell regeneration, keratin synthesis, and protection of cells against oxidative stress; therefore, its deficiency may lead to deterioration of hair and nail quality. [11]
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Iron: Iron is essential for oxygen delivery to cells and proper cell division in hair roots. Low ferritin levels are associated with increased hair shedding, especially in women. [7]
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Biotin (vitamin B7): It is essential for nail strength and healthy hair growth. Its deficiency leads to splitting and brittleness. It supports amino acid metabolism important for keratin formation. True deficiency is rare, but when present, it may manifest as brittle nails, hair loss, or dermatitis. [8]
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Omega-3: These essential fatty acids help regulate inflammatory processes, support skin hydration, and may influence the quality of the scalp and hair follicle. [12]
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Vitamin D: This “sun” vitamin plays an important role in the hair growth cycle and proper hair follicle function. Low levels are more often associated with certain types of hair loss, such as androgenetic alopecia in men. [18] Vitamin D is involved in regulating cell growth, immune processes, and hair follicle regeneration. However, its deficiency is usually not the sole cause of hair loss but rather one of the contributing factors.
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Collagen: Collagen contains amino acids important for skin structure and the surrounding hair environment. Some studies suggest that hydrolyzed collagen may support skin quality and indirectly also hair and nails. [13]
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Antioxidants: Oxidative stress can damage hair follicles and nail-forming cells. Antioxidants such as vitamin C, vitamin E, selenium, polyphenols, or carotenoids help protect cells from free radicals and support tissue regeneration. They are also important for collagen protection and scalp health.
The Effect of Stress on the Health of Hair and Nails
Modern science and the study Role of stress in skin diseases in the journal Brain, Behavior and Immunity confirm a direct connection between the brain, gut, and skin. Long-term stress increases cortisol levels, which reduces blood circulation in the skin and limits nutrient supply to hair and nails. In addition, stress impairs absorption of important minerals from the diet, which affects these tissues with a delay of several weeks. [14]
Stress also changes the composition of the gut microbiome and can negatively influence the absorption of iron, zinc, or B vitamins. The result is impaired regeneration of hair and nails, appearing after several weeks to months. More about the impact of stress on the microbiome and skin health is discussed in the article The Gut-Skin Axis.
Hair Loss in Men
The most common cause of hair loss in men is androgenetic alopecia, a hereditary type of baldness influenced by hormones and genetic predisposition. A key role is played by the male hormone dihydrotestosterone (DHT), which gradually shortens the hair growth phase and leads to shrinking hair follicles. However, hair loss can also be worsened by chronic stress, lack of sleep, smoking, inflammation, or deficiencies in iron, zinc, protein, or vitamin D. Overall metabolic health and scalp condition also play an important role. [15]
Key Takeaways
- Hair and nails reflect the state of the body: Changes in their quality may be one of the first signs of nutrient deficiency, hormonal imbalance, or long-term stress.
- The body limits hair and nail regeneration first when it is lacking nutrients: The organism prioritizes essential organs over less important tissues.
- Nail changes may indicate a health problem: Pale, brittle, or deformed nails may be associated with anemia, iron deficiency, or past stress.
- Hair loss often reflects events in the body months earlier: Increased shedding is a response to infection, psychological stress, hormonal changes, or restrictive diets.
- Hormones and the thyroid gland have a major impact on hair quality: Hormonal imbalance can disrupt the hair growth cycle and increase shedding.
- Iron and B vitamin deficiencies are common causes of weakened hair: Low ferritin, vitamin B12, or biotin levels can negatively affect hair growth and strength.
- Proteins are a basic building block of hair and nails: Without sufficient amino acid intake, the body cannot effectively produce keratin.
- Long-term stress affects hair and nail quality: Elevated cortisol levels can impair blood circulation, increase oxidative stress, and disrupt nutrient absorption.
Sources:
[1] Cleveland Clinic. What Your Nails Say About Your Health. Cleveland Clinic. https://health.clevelandclinic.org/nails-and-your-health
[2] StatPearls Publishing. Koilonychia. In: Stat Pearls. Treasure Island (FL): StatPearls Publishing; 2023. https://www.ncbi.nlm.nih.gov/books/NBK559311/
[3] American Academy of Dermatology Association. Common nail problems. https://www.aad.org/public/everyday-care/nail-care-secrets/basics/nail-changes-dermatologist-should-examine
[4] Cleveland Clinic. Beau’s Lines. https://my.clevelandclinic.org/health/symptoms/22906-beaus-lines
[5] Harvard Health Publishing. Hair Loss. Harvard Medical School. https://www.health.harvard.edu/a_to_z/hair-loss-a-to-z
[6] British Thyroid Foundation. Hair loss and thyroid disorders. https://www.btf-thyroid.org/hair-loss-and-thyroid-disorders
[7] Zhang B, Ma S, Rachmin I, He M, Baral P, Choi S, Gonçalves WA, Shwartz Y, Fast EM, Su Y, Zon LI, Regev A, Buenrostro JD, Cunha TM, Chiu IM, Fisher DE, Hsu YC. Hyperactivation of sympathetic nerves drives depletion of melanocyte stem cells. Nature. 2020 Jan;577(7792):676-681. doi: 10.1038/s41586-020-1935-3. PMID: 31969699; PMCID: PMC7184936. https://www.nature.com/articles/s41586-020-1935-3
[8] Dermatology and Therapy. The Role of Vitamins and Minerals in Hair Loss: A Review. https://link.springer.com/article/10.1007/s13555-018-0278-6
[9] Trost LB, Bergfeld WF, Calogeras E. The diagnosis and treatment of iron deficiency and its potential relationship to hair loss. Dermatol Pract Concept. 2021;11(2):e2021063. https://dpcj.org/index.php/dpc/article/view/dermatol-pract-concept-articleid-dp1102a33
[10] National Institutes of Health Office of Dietary Supplements. Zinc Fact Sheet for Health Professionals. https://ods.od.nih.gov/factsheets/Zinc-HealthProfessional/
[11] National Institutes of Health Office of Dietary Supplements. Biotin Fact Sheet for Health Professionals. https://ods.od.nih.gov/factsheets/Biotin-HealthProfessional/
[12] Le Floc’h C, Cheniti A, Connétable S, Piccardi N, Vincenzi C, Tosti A. Effect of a nutritional supplement on hair loss in women. J Cosmet Dermatol. 2015 Mar;14(1):76-82. doi: 10.1111/jocd.12127. PMID: 25573272. https://doi.org/10.1111/jocd.12127
[13] Choi FD, Sung CT, Juhasz MLW, Mesinkovska NA. Oral collagen supplementation: A systematic review of dermatological applications. J Drugs Dermatol. 2019 Jan 1;18(1):9-16. PMID: 30681787. https://jddonline.com/articles/oral-collagen-supplementation-a-systematic-review-of-dermatological-applications-S1545961619P0009X
[14] Jafferany M, Huynh TV, Silverman MA, Zaidi Z. The skin and psychological stress: A review of the neurocutaneous connection. Front Endocrinol (Lausanne). 2020 Dec 23;11:607076. doi: 10.3389/fendo.2020.607076. PMCID: PMC7889604. https://www.frontiersin.org/articles/10.3389/fendo.2020.607076/full
[15] Sinclair R. Male pattern androgenetic alopecia. BMJ. 1998 Sep 26;317(7162):865-869. doi: 10.1136/bmj.317.7162.865. https://www.bmj.com/content/317/7162/865
