Vitamin D Deficiency and Hair Loss in Singapore: What the Science Says

Written by Dr Heng Jiacheng, MBBS, Diploma in Aesthetic Medicine (AAAM)Associate Member, International Society of Hair Restoration Surgery (ISHRS) · Member, Asian Association of Hair Restoration Surgeons (AAHRS) Insights from a Singapore-based hair-loss physician

Updated: 24 June 2026

When people think of Singapore, we think of a hot, sunny, tropical island. Vitamin D is mainly obtained through sunlight exposure on the skin, which contributes around 80–90% of our total daily vitamin D, while diet contributes only around 10–20%.

Fun fact: one egg yolk contains approximately 20 IU of vitamin D. To meet the recommended daily intake of 600–800 IU for adults aged 1–70 years, you would need to eat around 20 eggs a day. This would likely exceed your daily caloric limit and push up your cholesterol levels.

Ironically, although we live close to the equator and receive sunlight throughout the year, several local studies have found unexpectedly high rates of vitamin D deficiency in specific Singapore populations.

You may have noticed that some hair vitamins include vitamin D. I also routinely test vitamin D levels in my hair clinic, and some people may ask why. In this article, we explore the connection between vitamin D deficiency and hair loss in Singapore, including why low vitamin D levels may still be common despite our sunny climate.

Vitamin D Deficiency and Hair Loss in Singapore: What the Research Shows

Yes. Research has found lower average vitamin D levels in people with several forms of hair loss compared with control groups.

The association has been reported in:

• Androgenetic alopecia, also known as male or female pattern hair loss;

• Alopecia areata, an autoimmune form of hair loss; and

• Telogen effluvium, which causes increased diffuse hair shedding.

Vitamin D receptors are also present in the hair follicle and are involved in normal hair-cycle regulation.

Of course, lower vitamin D levels do not prove that vitamin D deficiency is the primary cause of every patient’s hair loss. I always tell my patients that hair loss is normally multifactorial, and vitamin D is just a small piece of the puzzle.

Genetics, hormones, illness, stress, thyroid dysfunction, iron deficiency, weight loss, pregnancy and autoimmune disease can all affect the hair cycle.

Why vitamin D matters to the hair follicle

Vitamin D is more than just a nutrient involved in bone health. Its active form interacts with the vitamin D receptor, commonly abbreviated as VDR.

Vitamin D receptors are expressed in several parts of the hair follicle. Normal VDR signalling appears to contribute to the regulation of follicular growth and cycling.

A 2024 laboratory and animal study examined the active form of vitamin D, known as 1,25-dihydroxyvitamin D3. Researchers reported that it:

• Promoted hair regeneration;

• Prolonged the anagen, or active growth, phase;

• Increased dermal papilla-cell activity;

• Influenced inflammatory signalling pathways involving NLRP3, IL-1β and HIF-1α; and

• Partially counteracted the inhibitory effects of dihydrotestosterone, or DHT, in the study models.

These results help explain why vitamin D is biologically relevant to hair growth. However, this was mechanistic and preclinical research. It should not be interpreted as evidence that taking an oral vitamin D supplement will reverse established pattern hair loss in humans.

Vitamin D and androgenetic alopecia

Androgenetic alopecia is the most common cause of progressive hair thinning. It occurs when genetically susceptible follicles gradually miniaturise under the influence of androgens, particularly DHT.

In a case-control study of 50 men with premature androgenetic alopecia and 50 controls, the mean serum vitamin D levels were:

• 20.10 ng/mL in men with androgenetic alopecia

• 29.34 ng/mL in the control group

The difference was statistically significant. The researchers also reported an association between lower vitamin D levels and greater hair-loss severity.

A 2024 systematic review of micronutrients in androgenetic alopecia similarly identified vitamin D, iron, zinc and several B vitamins as potentially relevant nutritional factors. The review concluded that deficiencies may represent modifiable contributors in some patients, while also noting that the evidence for supplementation remains inconsistent.

This means that vitamin D deficiency may coexist with androgenetic alopecia and could make the overall follicular environment less favourable. However, it does not replace the need to address the underlying androgen-driven miniaturisation.

For moderate or advanced pattern hair loss, evidence-based medical management may still be required. Nutritional support should be viewed as an adjunct rather than a substitute for appropriate treatment.

Read more about the science of androgenetic alopecia and the Roots² approach.

Vitamin D and alopecia areata

Alopecia areata is an autoimmune condition in which the immune system targets the hair follicle. It commonly presents as one or more clearly defined bald patches, although more extensive forms can also occur.

I also routinely test vitamin D levels in patients who present with alopecia areata.

A 2026 case-control study found median vitamin D levels of:

• 17.10 ng/mL in patients with alopecia areata

• 22.60 ng/mL in the control group

  
  

The researchers calculated that vitamin D deficiency was associated with approximately 3.22 times higher odds of alopecia areata in the study population.

Other studies have also reported lower vitamin D levels in patients with alopecia areata. Vitamin D’s role in immune regulation provides a plausible biological explanation for this association.

Nevertheless, vitamin D supplementation should not be regarded as a replacement for the medical treatment of alopecia areata. New bald patches, eyebrow loss, eyelash loss or rapidly progressive hair loss should be medically assessed.

Vitamin D and telogen effluvium

Telogen effluvium is a diffuse shedding condition that commonly appears two to four months after a physiological or emotional stressor.

Possible triggers include:

• Fever or significant illness;

• Surgery;

• Rapid weight loss or restrictive dieting;

• Major emotional stress;

• Thyroid dysfunction;

• Iron or other nutritional deficiencies;

• Pregnancy and childbirth; and

• Certain medications.

  
  

Several studies have reported lower vitamin D levels in patients with telogen effluvium, although the findings are not completely consistent.

A small prospective study involving 40 women reported improvement after oral vitamin D3 supplementation. At six months, 82.5% had an improved hair-pull test, and 85% reported satisfaction.

Learn more about telogen effluvium and the Roots² TE Protocol.

Is vitamin D deficiency common in sunny Singapore?

Yes, at least within several Singapore populations that have been studied. This is very ironic, given our climate.

However, there is a good explanation for this, at least in my opinion. It is simply too hot, so even I hide from the sun.

The results vary because the studies examined different groups and used different thresholds. They should not be interpreted as meaning that every Singapore resident has the same level of risk.

Singapore study population	Main finding
114 generally healthy adults	Approximately 42% had vitamin D levels below 20 ng/mL
213 indoor workers	32.9% had levels below 50 nmol/L
111 overweight or obese adults seeking weight management	75.7% were classified as vitamin D deficient
Women in the first trimester of pregnancy	Only 2.2% had levels of at least 30 ng/mL

These studies demonstrate an important point: living in a sunny country does not guarantee an adequate vitamin D level.

Taken together, the local data show that vitamin D deficiency is a genuine issue in Singapore.

So, why can Singaporeans still be vitamin D deficient?

1. Indoor working and studying

Many Singapore residents spend most daylight hours inside offices, schools, clinics, shopping centres or vehicles.

A Singapore study of indoor workers found that office workers, workshop workers and night-shift employees were among the groups at increased risk of deficiency.

2. Limited direct UVB exposure

Vitamin D production requires ultraviolet B exposure to the skin. Bright surroundings or sitting beside a closed window do not necessarily provide the same UVB exposure as being outdoors.

Sun exposure should still be balanced with concerns about skin cancer and pigmentation. Sunburn is not required and should not be encouraged to maintain vitamin D levels.

3. Sun-avoidance behaviour

Umbrellas, covered clothing, sunscreen and deliberately avoiding the midday heat can all reduce direct UVB exposure.

These behaviours are understandable in Singapore’s climate, but they help explain why abundant environmental sunlight does not always translate into adequate vitamin D production.

4. Skin pigmentation

Melanin reduces the rate at which the skin produces vitamin D in response to UVB exposure. Individuals with darker skin may require longer sun exposure to produce an equivalent amount of vitamin D.

5. Higher body-fat percentage

Vitamin D is fat soluble. Higher body-fat levels have been associated with lower circulating vitamin D concentrations.

In the Singapore weight-management study, vitamin D levels were negatively associated with body mass index, waist circumference and body-fat percentage.

6. Pregnancy and the postpartum period

Pregnancy increases nutritional demands, while some mothers spend much of the early postpartum period indoors, possibly because of the cultural practice of a confinement period.

Vitamin D deficiency may therefore coexist with other contributors to postpartum hair shedding, including hormonal changes, blood loss, iron deficiency, reduced dietary intake and sleep disruption. Explore how roots² incorporate vitamin D supplementation in our roots2 postpartum protocol.

Singapore is not the only sunny country with this problem

Vitamin D deficiency has also been documented across Asia and in other tropical or low-latitude regions.

A large Asian systematic review and meta-analysis involving 472 studies and 746,564 participants reported that:

• 57.69% had vitamin D levels below 50 nmol/L; and

• 76.85% had levels below 75 nmol/L.

High rates have also been reported in nationally representative research from Colombia, among women in southern Thailand, across Africa and in a Brazilian geospatial meta-analysis.

These percentages cannot be compared directly because the populations, laboratory methods and definitions differed. Nevertheless, they challenge the assumption that vitamin D deficiency occurs only in countries with cold climates or limited sunlight.

Can vitamin D supplements stop hair loss?

Not by themselves in most cases.

Vitamin D supplementation is most rational when a person has:

• A documented deficiency or insufficiency;

• A high risk of deficiency;

• Limited dietary intake or sunlight exposure; or

• A medical reason for supplementation identified by a healthcare professional.

If a person’s vitamin D level is already adequate, there is no strong clinical evidence that taking additional vitamin D will produce further hair regrowth.

The effect also depends on the diagnosis.

Should vitamin D be tested during a hair-loss assessment?

I routinely test vitamin D levels in my clinic patients, especially in women.

The standard test is serum 25-hydroxyvitamin D, written as 25(OH)D.

Of course, vitamin D is only one part of a hair-loss assessment.

How much vitamin D should you take?

Singapore’s Health Sciences Authority lists 25 mcg, equivalent to 1,000 IU, as the maximum daily amount of vitamin D in general-adult health supplements.

This is a regulatory limit for general health supplements, not a universal treatment dose for every patient.

For patients with a known deficiency and tested baseline levels, I may prescribe a higher dose of up to 2,000–3,000 IU per day.

One thing I would like to caution readers about is that anything taken in excess can become harmful, including vitamin D supplements.

Taking too much vitamin D can cause problems such as kidney stones, psychosis and various other side effects. Again, everything should be taken in moderation.

Individuals with kidney disease, abnormal calcium levels, certain granulomatous conditions or other medical concerns should seek professional advice before taking additional vitamin D.

Why vitamin D is included in Roots² formulations

Roots² does not approach every type of hair loss with the same formula.

Vitamin D3 is included in selected Roots² protocols because:

• Vitamin D receptors are involved in normal follicular biology;

• Lower vitamin D levels are repeatedly observed in several hair-loss populations;

• Deficiency remains common in Singapore despite abundant sunlight; and

• Vitamin D may be especially relevant when nutritional insufficiency contributes to diffuse shedding.

It is included as part of a broader, condition-specific nutritional strategy—not as a claim that vitamin D alone cures hair loss.

The appropriate formula depends on whether the main presentation is:

• Progressive androgenetic alopecia;

• Stress- or illness-related telogen effluvium; or

• Postpartum hair shedding.

You can also read the overview of hair supplements in Singapore and how the Roots² protocols differ, explore the Roots² science, or use the hair-loss protocol quiz.

Practical tip from a doctor

Vitamin D deficiency is very common, especially in my clinical practice.

I tell my patients to get at least 10–20 minutes of midday sunlight. The thing is, I do not always practise what I preach.

I also fear the sun because of my pursuit of beauty.

If you see me on the streets, I am usually dressed like a suspicious individual, wearing long sleeves, a hat, sunglasses and sunblock everywhere.

I take long-term vitamin D supplements.

If you are going to rely on vitamin D supplements, such as 1,000 IU per day, please ensure that you take them after a meal containing some fat, as vitamin D is a fat-soluble vitamin. If you take it on an empty stomach, you may not absorb it as well, especially if the supplement is not in the form of an oil-based capsule.

Scientific References

Vitamin D and hair loss

1. Wang R, Lin J, Liu Q, et al. Micronutrients and Androgenetic Alopecia: A Systematic Review. Molecular Nutrition & Food Research. 2024.

2. Drake L, Reyes-Hadsall S, Martinez J, et al. Evaluation of the Safety and Effectiveness of Nutritional Supplements for Treating Hair Loss: A Systematic Review. JAMA Dermatology. 2023.

3. Sanke S, Samudrala S, Yadav A, Chander R, Goyal R. Study of Serum Vitamin D Levels in Men With Premature Androgenetic Alopecia. International Journal of Dermatology. 2020.

4. Garg S, Vardhan KH, Goel S, Rathi R. Assessment of Vitamin D Levels in Patients With Alopecia Areata: A Case-Control Study. Annals of Medicine. 2026.

5. Zong X, Yang S, Tang Z, et al. 1,25-(OH)2D3 Promotes Hair Growth by Inhibiting NLRP3/IL-1β and HIF-1α/IL-1β Signalling Pathways. Journal of Nutritional Biochemistry. 2024.

Singapore vitamin D research

6. Divakar U, Sathish T, Soljak M, et al. Prevalence of Vitamin D Deficiency and Its Associated Work-Related Factors Among Indoor Workers. International Journal of Environmental Research and Public Health. 2019.

7. Bi X, Tey SL, Leong C, Quek R, Henry CJ. Prevalence of Vitamin D Deficiency in Singapore: Its Implications to Cardiovascular Risk Factors. PLOS ONE. 2016.

8. Ong MW, Tan CH, Cheng AKS. Prevalence and Determinants of Vitamin D Deficiency Among Overweight and Obese Singaporeans. Obesity Surgery. 2018.

9. Amelia CZE, Gwan CH, Qi TS, Seng JTC. Prevalence of Vitamin D Insufficiency in Early Pregnancies—A Singapore Study. PLOS ONE. 2024.

Regional and tropical-country research

10. Jiang Z, Pu R, Li N, et al. High Prevalence of Vitamin D Deficiency in Asia: A Systematic Review and Meta-Analysis. Critical Reviews in Food Science and Nutrition. Published online 2021; journal issue 2023.

11. Beer RJ, Herrán OF, Villamor E. Prevalence and Correlates of Vitamin D Deficiency in a Tropical Setting. American Journal of Clinical Nutrition. 2020.

12. Mogire RM, Mutua A, Kimita W, et al. Prevalence of Vitamin D Deficiency in Africa: A Systematic Review and Meta-Analysis. The Lancet Global Health. 2020.

13. Jaruratanasirikul S, Boonrusmee S, Kasemsripitak S, et al. Vitamin D Status in Non-Pregnant Women of Reproductive Age in Southern Thailand. Scientific Reports. 2023.

14. Pereira-Santos M, Santos JYG, Carvalho GQ, et al. Epidemiology of Vitamin D Insufficiency and Deficiency in a Sunny Country: Geospatial Meta-Analysis in Brazil. Critical Reviews in Food Science and Nutrition. 2019.

15. Arabi A, El Rassi R, El-Hajj Fuleihan G. Hypovitaminosis D in Developing Countries—Prevalence, Risk Factors and Outcomes. Nature Reviews Endocrinology. 2010.

Singapore guidance and dosing references

16. Singapore Health Sciences Authority. Regulatory Overview of Health Supplements.

17. Singapore HealthHub. Vitamin D, Sunlight and Calcium Absorption.

18. National Institutes of Health Office of Dietary Supplements. Vitamin D Fact Sheet for Health Professionals.

Medical and product disclaimer:This article is provided for general educational purposes and does not constitute personal medical advice. Roots² is a nutritional supplement and is not intended to diagnose, treat, cure or prevent any disease or medical condition. Persistent, progressive, localised or otherwise unexplained hair loss should be assessed by a qualified healthcare professional.