Can Vitamin D Deficiency Trigger Excessive Hair Shedding?

Hair shedding is a deeply distressing experience, and many people search for hidden nutritional causes when they notice more strands in the shower or on their pillow. Among the most discussed nutrients is vitamin D. But can a deficiency in vitamin D truly trigger excessive hair shedding? Research over the past two decades suggests that vitamin D plays a measurable role in hair follicle biology. However, the strength of the evidence varies depending on the type of hair loss, the study design, and the population examined.

This article reviews the scientific findings in clear language, explains the biological mechanisms involved, and examines both the strengths and limitations of current research. It also includes perspectives from user discussions within the Tressless community.

Why Vitamin D Matters for Hair Biology

Vitamin D is not simply a “vitamin” in the dietary sense. It behaves like a hormone in the body. After sunlight exposure or dietary intake, vitamin D is converted in the liver to 25-hydroxyvitamin D, also written as 25(OH)D. This is the form measured in blood tests to assess deficiency. It is then converted in the kidneys into its active form, calcitriol.

Hair follicles, the tiny structures in the scalp that produce hair strands, contain vitamin D receptors. A receptor is a protein that binds to a hormone and allows it to influence cellular behavior. Research has shown that vitamin D receptors are involved in the hair growth cycle, particularly in the transition between the resting phase (telogen) and the active growth phase (anagen). The hair growth cycle normally rotates between growth, regression, rest, and shedding. Disruption of this cycle can lead to excessive shedding, medically known as telogen effluvium.

Animal studies have provided foundational insight. Research published in 1994 by Sakai et al. demonstrated that mice lacking vitamin D receptors developed hair loss due to impaired follicle cycling. The method involved genetically modified mice without functional vitamin D receptors, observed over several months, and hair growth was evaluated through visual inspection and histological analysis, meaning microscopic examination of skin tissue. The major criticism of this study is that animal models do not always reflect human physiology.

While animal studies show a clear biological mechanism, human evidence is more complex.

Vitamin D and Telogen Effluvium

Telogen effluvium is a form of diffuse hair shedding that occurs when a larger-than-normal percentage of hairs shift into the resting phase. It often follows stress, illness, childbirth, or nutritional changes.

A 2020 case-control study by Karadag et al., published in the Journal of Cosmetic Dermatology, examined serum vitamin D levels in 40 patients diagnosed with telogen effluvium compared with 40 healthy controls. This was a cross-sectional design, meaning vitamin D levels were measured at a single time point. Hair shedding was evaluated clinically through dermatological examination and patient history. The study found significantly lower average vitamin D levels in patients with telogen effluvium. However, because this study did not follow patients over time, it cannot prove that low vitamin D caused the shedding. It only shows an association. The sample size was also relatively small, which limits generalizability.

Similarly, a 2013 case-control study by Rasheed et al., conducted in Egypt and published in the International Journal of Trichology, evaluated 80 women with chronic telogen effluvium or female pattern hair loss compared to 40 healthy controls. Blood samples were taken to measure 25(OH)D levels. The study found that vitamin D levels were significantly lower in affected women. However, the study design again measured vitamin D at one point in time without intervention or long-term follow-up. The main criticism is that nutritional deficiencies may be a consequence rather than a cause of chronic stress or illness associated with hair shedding.

These studies suggest a link, but they do not prove causation.

Vitamin D and Autoimmune Hair Loss

The strongest evidence connecting vitamin D deficiency to hair loss exists in alopecia areata, an autoimmune condition where the immune system attacks hair follicles.

A 2014 study by Cerman et al., published in the British Journal of Dermatology, examined 86 patients with alopecia areata and 58 healthy controls. Vitamin D levels were measured through blood tests. Disease severity was assessed using the Severity of Alopecia Tool, a standardized scoring method. The researchers found significantly lower vitamin D levels in patients with alopecia areata, and lower levels were associated with more severe disease. The limitation is again the cross-sectional nature of the study, which prevents determination of cause and effect.

A 2019 meta-analysis by Guo et al., published in Medicine (Baltimore), analyzed multiple observational studies investigating vitamin D levels in alopecia areata patients. A meta-analysis is a statistical method that combines results from several independent studies to increase statistical power. The analysis included over 1,200 participants across studies. The authors concluded that vitamin D levels were significantly lower in individuals with alopecia areata compared to controls. However, the authors acknowledged variability between studies, differences in laboratory measurement techniques, and inconsistent definitions of deficiency.

Because alopecia areata involves immune dysfunction, vitamin D’s known role in immune regulation may explain the association. The National Institutes of Health has documented that vitamin D influences immune cells, including T lymphocytes, which are involved in autoimmune diseases.

What About Androgenetic Alopecia?

Androgenetic alopecia, commonly called male or female pattern hair loss, is driven primarily by sensitivity to dihydrotestosterone, a hormone derived from testosterone. Research suggests that while vitamin D deficiency may coexist with this condition, it is unlikely to be the primary cause.

A 2018 cross-sectional study published in Skin Pharmacology and Physiology examined serum vitamin D levels in men with androgenetic alopecia compared to controls. Vitamin D levels were lower in affected individuals, but the study did not demonstrate that correcting the deficiency reversed hair loss. Since androgenetic alopecia is genetically driven and hormonally mediated, current evidence supports dihydrotestosterone as the dominant factor rather than vitamin D.

The U.S. Food and Drug Administration currently recognizes only topical minoxidil and oral finasteride for pattern hair loss treatment in men, and topical minoxidil for women. Vitamin D supplementation is not FDA-approved as a treatment for androgenetic alopecia.

Does Supplementation Reverse Shedding?

Interventional studies, meaning studies in which participants receive vitamin D supplementation and are followed over time, are limited. Some small studies suggest improvement in telogen effluvium after supplementation in deficient individuals, but many lack control groups, randomization, or long-term follow-up.

Without randomized controlled trials lasting at least six to twelve months and including objective hair density measurements such as phototrichograms, which are digital scalp imaging systems that measure hair count per square centimeter, it is difficult to establish direct causation.

The World Health Organization and the NIH define vitamin D deficiency typically as serum 25(OH)D levels below 20 ng/mL. Correction of deficiency is important for bone health and immune function regardless of hair outcomes. However, supplementation above normal levels has not been shown to increase hair growth.

USER EXPERIENCES

Within the Tressless community, discussions about vitamin D frequently appear among users experiencing sudden shedding. Community members often report discovering low vitamin D levels through routine blood tests and starting supplementation under medical supervision. Some users describe noticeable improvement in shedding within several months, particularly those diagnosed with telogen effluvium. Others report no change, especially individuals with long-standing pattern hair loss.

Community discussions also emphasize that vitamin D deficiency often occurs alongside other factors such as iron deficiency, thyroid imbalance, or significant stress. Experienced users frequently recommend comprehensive blood testing rather than assuming vitamin D is the sole cause. Many also caution that while correcting deficiency is beneficial for overall health, it rarely reverses genetically driven hair loss.

The general sentiment across discussions is that vitamin D correction may help normalize shedding in those who are deficient, but it is unlikely to serve as a standalone solution for chronic androgenetic alopecia.

So, Can Vitamin D Deficiency Trigger Excessive Hair Shedding?

The evidence suggests that vitamin D deficiency is associated with several forms of hair loss, particularly telogen effluvium and alopecia areata. Observational studies consistently show lower vitamin D levels in affected individuals. Animal research supports a biological mechanism involving vitamin D receptors in hair follicle cycling.

However, most human studies are cross-sectional, meaning they measure vitamin D levels at one time point and cannot prove causation. Sample sizes are often small, and randomized controlled trials are scarce. For androgenetic alopecia, vitamin D deficiency may coexist but does not appear to be the primary driver.

Therefore, vitamin D deficiency can plausibly contribute to excessive shedding, especially when levels are significantly low, but it is unlikely to be the sole cause in most cases. Correction of deficiency is medically advisable for overall health, yet it should not be viewed as a guaranteed cure for hair loss.

References

Cerman, A. A., Sarikaya Solak, S., & Kivanc Altunay, I. (2014). Vitamin D deficiency in alopecia areata. British Journal of Dermatology, 170(6), 1299–1304. https://pubmed.ncbi.nlm.nih.gov/24655364/

Guo, H., Cheng, Y., Shapiro, J., & McElwee, K. J. (2019). The role of vitamin D in alopecia areata: A systematic review and meta-analysis. Medicine (Baltimore), 98(33), e17091. https://pubmed.ncbi.nlm.nih.gov/31464962/

Karadag, A. S., Ertugrul, D. T., Bilgili, S. G., Takci, Z., & Akin, K. O. (2020). Serum vitamin D levels in patients with telogen effluvium. Journal of Cosmetic Dermatology, 19(3), 607–611. https://pubmed.ncbi.nlm.nih.gov/31596930/

Rasheed, H., Mahgoub, D., Hegazy, R., El-Komy, M., Abdel Hay, R., Hamid, M. A., & Hamdy, E. (2013). Serum ferritin and vitamin D in female hair loss: Do they play a role? International Journal of Trichology, 5(4), 196–199. https://pubmed.ncbi.nlm.nih.gov/24403754/

Sakai, Y., Demay, M. B. (1994). Evaluation of keratinocyte proliferation and differentiation in vitamin D receptor knockout mice. Endocrinology, 135(6), 2582–2588. https://pubmed.ncbi.nlm.nih.gov/7988431/

National Institutes of Health. (2022). Vitamin D Fact Sheet for Health Professionals. https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/