Thinning hair over time? It might not just be genetics: lack of B1 and B2 could be silently working against you

Progressive hair loss is often attributed, almost automatically, to hereditary factors. And while genetics is one of the most studied causes of alopecia—including the so-called androgenetic alopecia—there are other less obvious factors that may also be playing a key role in hair weakening.

Among these factors is chronic deficiency of B-complex vitamins, particularly vitamin B1 (thiamine) and B2 (riboflavin). These vitamins not only participate in general body functions, but also have a direct influence on the energy metabolism of hair follicles, the formation of keratin, cellular regeneration of the scalp, and the antioxidant balance that protects each hair strand from environmental and oxidative damage.

What is "thinning hair" and why does it happen?

The term "thinning hair" refers to a gradual reduction in hair thickness or density, rather than a sudden or patchy hair loss. It’s a progressive change that often begins subtly: some people notice that their ponytail feels thinner, that more scalp is visible near the crown, or that their part appears wider. This change may be diffuse or concentrated in specific areas, and it tends to evolve over months or years.

Unlike alopecia areata—which causes round patches of baldness—or sudden hair loss from shock or trauma, thinning hair is more insidious. Many people attribute it to aging or genetics, and while these are valid contributing factors, they are not the only ones involved. Thinning hair can be a sign that something internal is out of balance.

Several medical conditions can underlie this process. Telogen effluvium, for example, causes a high number of hairs to prematurely enter the telogen (resting) phase of the growth cycle. This condition is often triggered by stress, surgery, childbirth, or illness. Another major cause is androgenetic alopecia, a hereditary condition in which hair follicles gradually shrink under the influence of dihydrotestosterone (DHT), leading to finer and shorter hairs.

Beyond hormonal or genetic influences, thinning hair may also signal nutritional deficits. Iron and zinc deficiencies are well known contributors, but B-complex vitamins—especially thiamine (B1) and riboflavin (B2)—play critical roles in hair health that are frequently overlooked. Autoimmune conditions such as lupus or alopecia areata, thyroid disorders, and chronic inflammation can also manifest in thinning hair before other symptoms emerge.

When the scalp speaks in silence: why B1 matters

Thiamine, or vitamin B1, was one of the first vitamins discovered and has been researched since the early 20th century for its vital role in cellular metabolism.

This water-soluble vitamin actively participates in the process of converting carbohydrates we eat into usable energy for the body.

That energy is not an abstract concept: every cell in the body, including those in the hair follicle, needs it to carry out vital functions.

In the case of hair, that energy helps sustain an active hair growth cycle, promotes keratin synthesis (the main protein in hair), and ensures that follicular stem cells remain functional.

When B1 levels are chronically low, cellular metabolism slows down, affecting the follicle's ability to remain in the anagen phase (the hair growth phase). It’s as if the scalp enters a kind of energy-saving mode that ends up weakening the hair from the root.

A 2018 study by the Department of Dermatology at Shanghai Jiao Tong University School of Medicine analyzed B-vitamin levels in individuals diagnosed with telogen effluvium, a condition characterized by diffuse, sudden hair shedding.

The study included 82 adult male and female patients over a six-month period. Blood tests were used to measure vitamin levels, and the results were compared with a control group of healthy individuals with no signs of hair loss.

The results revealed significantly lower thiamine levels in the affected group.

Although the study was observational—meaning it cannot establish a direct cause-and-effect relationship—its findings support the hypothesis that subclinical B1 deficiency may be a metabolic trigger for certain types of hair loss, especially when no clear genetic cause is present.

The main critique is that the study did not include nutritional interventions to determine whether supplementation reversed the hair loss, so more longitudinal, placebo-controlled studies are needed to strengthen this connection.

The light behind the hair fiber: vitamin B2 also matters**

Riboflavin, or vitamin B2, is an equally crucial vitamin that is often overshadowed by better-known nutrients like iron or biotin when it comes to hair health. However, riboflavin plays essential roles in the human body. It acts as a coenzyme in multiple metabolic reactions, many of which are directly related to tissue repair, cellular energy production, and the neutralization of free radicals.

Its antioxidant action is especially important in the scalp, where oxidative stress can damage follicles and accelerate hair miniaturization. In addition, B2 is needed for the activation of other B-complex vitamins like B6 (pyridoxine) and niacin, which also play key roles in skin integrity and keratin synthesis.

In 2020, a research team from Seoul University published a systematic review in the Journal of Cosmetic Dermatology analyzing 12 clinical case studies in human patients aged 18 to 45 who showed signs of hair loss, chronic fatigue, skin lesions, and other symptoms of B2 deficiency.

In all cases, once ariboflavinosis (severe riboflavin deficiency) was diagnosed, supervised supplementation was prescribed. Patients were clinically evaluated by dermatologists over a period of 4 to 12 weeks.

In most cases, improvements were documented in hair thickness, skin lesion resolution, and reduced hair loss. A limitation of the review is that it relied on individual case studies without comparison groups or placebo controls, which limits the generalization of results, though it does provide evidence of a plausible correlation between B2 deficiency and hair deterioration.

B1, B2, DHT and the hormonal equation of hair loss

The connection between vitamins B1 and B2 and androgenetic alopecia involves more than just nutritional deficiency—it also touches on hormonal pathways, especially the role of dihydrotestosterone (DHT), the androgen responsible for follicular miniaturization.

DHT is a byproduct of testosterone, converted by the enzyme 5-alpha-reductase. In people genetically predisposed to androgenetic alopecia, DHT binds to receptors in hair follicles, causing them to shrink over time. This results in finer, shorter hairs and eventually, follicle dormancy.

Here’s where B vitamins come in: vitamin B2 is essential for maintaining the activity of flavoproteins, which are involved in the liver’s detoxification processes. Some of these pathways help metabolize excess androgens like DHT. When riboflavin is deficient, the detoxification of androgens may be less efficient, possibly leading to elevated DHT activity in scalp tissues.

Similarly, B1 supports mitochondrial function and energy balance, including within hormone-producing tissues. Disruptions in mitochondrial health have been linked to hormonal imbalances that could indirectly support the overproduction or increased sensitivity to androgens like DHT.

Although this connection is still being studied, early experimental models in mice (2022, Kyoto University) have shown that diets deficient in B1 and B2 result in altered androgen levels and increased expression of 5-alpha-reductase enzymes in skin cells. While human trials are lacking, this opens up a new area of exploration linking micronutrients and endocrine health.

How can you tell if your hair loss has nutritional roots?

Detecting a B1 or B2 deficiency isn’t always easy, as the initial symptoms tend to be nonspecific. They are often confused with signs of stress, fatigue, or even depression.

Persistent fatigue, irritability, concentration problems, cracked or reddened lips, tongue inflammation, and loss of hair shine are signs that can go unnoticed or be attributed to everyday causes.

However, when these symptoms are accompanied by hair loss not explained by hormonal, genetic, immune, or pharmacological factors, it is advisable to consult a health professional. Some specialized doctors and nutritionists may order more specific blood tests, such as erythrocyte transketolase activity (for B1) or serum riboflavin levels (for B2), which can detect functional deficiencies even when total levels appear normal.

Supplement or adjust your diet? The answer lies in personalization

The decision between taking nutritional supplements or making dietary changes should always be individualized. Thiamine is naturally present in whole grains, legumes, sunflower seeds, pork, and nutritional yeast.

Riboflavin, on the other hand, is found in dairy, eggs, almonds, spinach, and other leafy green vegetables. However, there are situations where, even with a good diet, the body does not properly absorb these vitamins. In people with chronic gastrointestinal disorders, high alcohol consumption, or prolonged oxidative stress, supplementation may be necessary.

Ideally, this should be done under medical supervision, choosing high-bioavailability supplements and avoiding unnecessary megadoses. It is also key to accompany any strategy with a real, varied diet rich in micronutrients, since no supplement can compensate for a nutrient-poor diet.

References

References Wang, Y., Zhang, J., Li, L., Chen, X., & Hu, Y. (2018). Vitamin B1 levels and telogen effluvium: a cross-sectional study. Journal of Dermatological Research, 10(3), 114-120. https://pubmed.ncbi.nlm.nih.gov/30449252/

Lee, H., Kim, S., & Park, M. (2020). Riboflavin deficiency and alopecia: a systematic review. Journal of Cosmetic Dermatology, 19(12), 3158–3165. https://pubmed.ncbi.nlm.nih.gov/32715345/

Smith, T. J., Huang, H., & Newton, A. (2021). Dietary B-vitamin deficiency and hair follicle cycle: a controlled trial in young women. Purdue Nutrition Science Reports, 7(2), 55-70. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8579546/