Introduction

Have you ever considered the potential impact of a micronutrient as potent as vitamin D on the health of your hair? While commonly recognised for its significance in bone health, Vitamin D also emerges as a crucial factor in promoting the well-being of your hair. This article delves into the noteworthy correlation between insufficient vitamin D levels and the occurrence of hair loss.

Overview of vitamin D

Vitamin D, also known as Calciferol, is a type of fat-soluble vitamin that occurs naturally in a limited number of foods ( oily fish, red meat, liver, egg yolks) while some other foods ( cereals, juices, dairy products and margarine) are  fortified with vitamin D. Additionally, it is available as a dietary supplement. When our skin is exposed to ultraviolet (UV) rays from the sun, it is capable of producing vitamin D within the human body by triggering its synthesis from a precursor molecule.

Synthesis of vitamin D in the body

There are two forms of vitamin D: vitamin D2 (ergocalciferol) obtained from dietary sources, and vitamin D3 (cholecalciferol) synthesised naturally in the body. Vitamin D acquired from food, supplements, or sunlight is inactive and needs two chemical modifications to become active. The first modification occurs in the liver, which turns vitamin D into calcidiol (25-hydroxyvitamin D). The second modification takes place mainly in the kidney and generates the active form of vitamin D, calcitriol (1,25-dihydroxy vitamin D).

Role of vitamin D in the human body

• Vitamin D is important for keeping our bones healthy. It helps our body absorb calcium, which is needed for strong bones. 
• Vitamin D is also important for bone growth and repair. 
• Besides that, it helps to reduce inflammation in the body and regulates important processes like our immune system, how our muscles work, and how our body uses sugar.

It is worth noting that having adequate levels of vitamin D can prevent rickets in children and osteomalacia in adults. Furthermore,when taken in conjunction with calcium, vitamin D can help safeguard older adults against osteoporosis. 

Levels of vitamin D

Greater than 75nmol/L of vitamin D present in the blood is considered to be optimum, However, levels less than 75 nmol/L are considered insufficient. Deficiency of vitamin D occurs at levels below 50nmol/L.^1,2 

Causes of vitamin D deficiency³

• Not getting enough vitamin D in your diet or through sunlight.
• Your body is not absorbing or using vitamin D properly.
• Certain medical conditions.
• Weight loss surgeries.
• Certain medications.

Moreover, different biological and environmental factors can also put someone at a greater risk of developing vitamin D deficiency. For example, getting old and having darker skin can put you at a higher risk of vitamin D deficiency.

Vitamin D deficiency and association with different disorders

A deficiency of vitamin D is associated with an increased risk of:^2,4 

• Rickets
• Growth retardation
• Fractures
• Colon, breast, and prostate cancer
• Chronic inflammatory and autoimmune diseases
• Metabolic disorders
• Infectious diseases

Hair growth cycle

Hair grows out of the hair follicles (The cavity from which the hair grows out) in cycles. This cycle has three phases:⁵

1. Anagen (growth) phase. In this phase, the hair begins to grow from the root. It usually lasts for several years. 
2. Catagen (transitional) phase.  In this phase, the growth slows down and the follicle shrinks. This phase lasts for a few weeks and during this time, the hair follicle loses about one-sixth of its width. 
3. Telogen (resting) phase. In this, hair doesn't grow. Around 10 to 15% of all the hairs on our body are in this phase at any given time, and the time it takes for the hair to grow again depends on where it is located in our body. For example, eyelashes take a few weeks to grow back, while scalp hair can take almost a year.

Overview of hair fall

Hair fall is a common complaint that can affect all ages and genders. Due to cosmetic concerns, women usually visit dermatologists. Therefore, hair loss seems to be more common in women than in men. Daily loss of 50–150 scalp hairs in the telogen phase is regarded as normal. However, Hair loss in the anagen stage is considered abnormal since active hair follicle growth is interrupted.⁶ Many people assigned female at birth(PAFAB) are nowadays presenting with complaints of diffuse hair loss (DHL) at a relatively younger age with the majority of consultations.⁷

Hair loss is known as -alopecia. Alopecia is a disease that causes non-scarring and scarring hair loss due to autoimmune diseases, hormonal imbalance, nutritional deficiency, and other systemic diseases affecting the scalp/any hair-bearing area causing generalised (overall) hair loss, and localised (patchy) hair loss. 

The three most common types of non-scarring alopecia are Androgenetic alopecia (AGA), telogen effluvium (TE), and alopecia areata (AA).⁹

Role of vitamin D in the hair growth cycle

The progression of the hair cycle is thought to be associated with vitamin D receptors.⁶ The receptors of Vitamin D can control the genes that are needed for the normal growth cycle of hair follicles.⁷ The growth and differentiation of keratin-producing cells are influenced by vitamin D, which binds to the vitamin D receptors.⁹  It has been suggested that vitamin D3 deficiency may be a potential factor in hair fall. The status of blood vitamin D3 levels of patients with hair fall significantly differs from that of healthy people.⁶ 

Influence of vitamin D deficiency on various types of hair falls

Telogen effluvium (diffuse hair loss)

• It is a type of temporary hair loss characterised by diffuse loss of telogen hair in response to metabolic, physical, or psychological stressors.
• It affects hair when it’s in the telogen stage.¹

Research studies have found that low levels of vitamin D3 in women can be associated with hair loss. Therefore, it is suggested to check the vitamin D levels in women experiencing hair loss and supplement with vitamin D if there is a deficiency. Doctors often recommend a weekly dose of 50,000 IU of cholecalciferol for 1-3 months, followed by a daily dose of 800-2000 IU to prevent further hair loss. In a study, patients with hair loss were given oral vitamin D3- 200,000 IU fortnightly for 3 months, which resulted in significant improvement in hair regrowth.¹

Androgenetic alopecia (pattern hair loss)

• It is characterised by hair loss in a specific pattern on the top and front of the head 
• It occurs in both People assigned male at birth (PAMAB) and People assigned Female at birth (PAFAB).¹

As mentioned earlier, vitamin D can help with hair growth and start the hair growth cycle. If there is a problem with vitamin D or its function, it can lead to hair loss. Having low vitamin D levels is linked to hair loss, so it's important to check for vitamin D deficiency.^1,8,10 

Alopecia areata

• Alopecia areata occurs when the immune system attacks the hair follicle. 
• It is characterised by sharply demarcated, round to oval, skin-coloured patches.¹⁰ 

Studies have found a connection between low levels of vitamin D and a condition called alopecia areata. Many patients with alopecia areata were also found to have low levels of vitamin D. This suggests that doctors should measure vitamin D levels in alopecia areata patients and consider giving vitamin D supplements or topical treatments to those who are deficient.^9,11,12

Summary

Vitamin D is essential for various bodily functions and is linked to disorders when deficient. In the context of hair growth, studies suggest that low vitamin D levels are associated with different types of hair loss, including telogen effluvium, androgenetic alopecia, and alopecia areata. Supplementation with vitamin D has shown improvements in hair regrowth for individuals experiencing hair loss, emphasising the importance of maintaining optimal vitamin D levels for overall health and hair health. Regular monitoring and appropriate interventions are recommended for those with vitamin D deficiency and associated hair concerns.

Frequently asked questions

1. How does vitamin D influence hair growth cycles?

Our hair growth is impacted by a protein called Vitamin D receptors. These proteins control the behaviour of genes in hair follicles, which play a role in hair growth and development.

2. Is there a connection between vitamin D and autoimmune-related hair loss?

Yes, low vitamin D levels have been correlated with conditions like alopecia areata, an autoimmune disorder where the immune system attacks hair follicles. Monitoring and supplementing vitamin D may be beneficial for affected individuals.

3. What are the recommended vitamin D levels in the blood?

Levels greater than 75 nmol/L are considered optimum, while levels below 50 nmol/L indicate a deficiency. Regular monitoring can help maintain appropriate levels.