Vitamin D and hair loss


Vitamin D (also known as calciferol) is a fat soluble vitamin produced endogenously in the skin from ultraviolet rays from the sun, it is also present in certain foods.  Vitamin D obtained from food and exposure to the sun just undergo a series of changes (hydroxylations) in the body for it to become active.  The first change occurs in the liver, here vitamin D is converted to 25-hydroxyvitamin D (also known as calcidiol).  The second change occurs in the kidneys, at this point vitamin D is converted into the physiologically active 1,25-dihydroxyvitamin D (also known as calcitrol).

Vitamin D promotes the absorption of calcium in the gut and maintains bone health.  Without vitamin D bones can become misshapen and lead to a condition known as rickets.

Vitamin D is also involved in cell growth, the reduction of inflammation, glucose metabolism and immune function.  Vitamin D levels are generally tightly regulated and deficiency will only occur when the need for vitamin D is outweighed by intake.

Vitamin D is associated with hair loss at levels below 75 mol/L (30 ng/mL).

nmol/L ng/mL
Less than 30 Less than 12 Vitamin D deficient.
30-50 12-20 Considered to be inadequate for overall health.
50-75 20-30 Considered to be adequate for bone health and overall health.
75-125 30-50 Optimal levels for healthy hair growth.
more than 125 more than 50 Linked to potential adverse health effects, particularly at levels that exceed 150 nmol/L / 60 ng/mL.


At the start of a normal hair growth cycle, stem cells migrate from the hair follicle bulge and are stimulated to grow and differentiate in the germinal matrix forming the seven inner layers of the hair fibre.  Differentiation is a process by which multipotent stem cells change and grow into a more specialised cell type through a succession of alterations in cell morphology, metabolic activity and responsiveness to signals.

Vitamin D mediates the differentiation of epidermal cells and a lack of vitamin D leads to decreased interfollicular cell differentiation [1].  Cells that are not able to develop as normal, are not able to become part of the hair fibre matrix and lie dormant in the epidermal layer of the skin. Whilst the exact mechanisms that control the stem cell response to low levels of vitamin D are unclear, low levels of vitamin D are linked to non-scarring alopecia, alopecia areata and androgenic alopecia in women.


  1. Food– Few foods contain vitamin D naturally, the flesh of fatty fish such as tuna, salmon, trout and mackerel are the best sources in the diet.  Other dietary sources of vitamin D are cheese and egg yolks.  Mushrooms can provide a small amount of vitamin D2.  The vitamin D content of animal tissue is affected by the animal’s diet, mushrooms can be treated with UV light to increase the content of vitamin D2.  Some cereals are fortified with vitamin D and can provide around 10% of the estimated required daily value.
  2. Sun exposure – UVB radiation with an approximate wavelength of 290-320nm can penetrate exposed skin and convert 7-dehydrocholesterol in the skin to provitamin D3, this can then be converted into vitamin D3.  The season, cloud cover and melanin content of the skin affect vitamin D synthesis.  The factors that affect vitamin D synthesis in an individual make it difficult to estimate a definitive amount if sun exposure required for adequate vitamin D synthesis.  Experts estimate as little as 5-30 minutes of sun exposure to the face, arms, legs and hands, between the hours of 10 am and 4 pm at least twice a week, should be enough for adequate vitamin D synthesis.
  3. Vitamin D supplements – Supplements containing vitamin D3 are shown to increase serum levels of 25-hydroxyvitamin D more effectively than vitamin D2.


  1. Xie, Z., Komuves, L., Yu, Q.C., Elalieh, H., Ng, D.C., Leary, C., Chang, S., Crumrine, D., Bikle, D.D., Yoshizawa, T. and Kato, S., 2002. Lack of the vitamin D receptor is associated with reduced epidermal differentiation and hair follicle growth. Journal of investigative dermatology, 118(1), pp.11-16.