Vitamin B1 – also known as thiamin (or thiamine) – is part of the B-vitamin complex. Marketers claim that vitamin B1 can help support healthy hair growth, reduce hair shedding, and even prevent hair loss. Then again, marketers also make the same claims about B-vitamins like biotin, niacin, and vitamin B12. And typically, the claims are just plain wrong.

So, is vitamin B1 any different? In this article, we’ll dive into the evidence (and answers).

First, we’ll uncover why some people that vitamin B1 helps support hair growth. Then, we’ll dive into the evidence on the vitamin B1 / thiamin-hair loss connection. Finally, we’ll dive into evidence that might implicate vitamin B1 as an accelerator of hair loss… and steps to take if you suspect you’re deficient.

By the end, you’ll have a better idea of whether vitamin B1 is a worthy investment for your hair, or just another marketing gimmick. If you have any questions or comments, please post them below!

What is Vitamin B1?

Vitamin B1 (also thiamin or thiamine), is one of the many members of the B vitamin family.  

Vitamin B1/thiamine

Researchers first identified this essential micronutrient through the study of beri beri, a serious disease of the nervous system that was common in South East Asia prior to the 1900s.

Unlike most diseases in that time, beri beri was much more common among wealthy citizens than it was among poorer citizens. Upon further investigation, researchers found the reason for the perplexing discrepancy was actually attributed to the differences in rice consumption. 

While poorer individuals tended to consume brown rice, richer individuals tended to consume milled white rice — devoid of the husks, bran, and germ.

Through experimentation with this brown rice, a Polish biochemist, Casmir Funk, was able to isolate the compound that prevented beri beri. This compound? He termed it thiamine, meaning sulfur-containing amine — what we now know as vitamin B1.

Fast forward to today: we now know that vitamin B1 plays a crucial role in mitochondrial health, metabolism of macronutrients, and energy production — processes that are essential for the normal functioning of almost every cell in the body (1).

But, beyond the prevention of serious neurological conditions, does vitamin B1 have any benefit to our hair? 

Let’s explore the evidence.

Vitamin B1: might it help support hair growth?

There’s no doubt that vitamin B1 is critical for important processes, like (1):

• The production of ATP, the energy molecule that fuels cellular activity
• The synthesis of amino acids
• The creation of NADPH, a co-factor necessary for steroid hormone production, fatty acid synthesis, and more.

And similar to other B-complex vitamins, vitamin B1’s role in these processes often form the basis of the claim that vitamin B1 can influence hair loss. After all, if you can’t produce amino acids — the raw material our hair is actually made of — how can you grow hair?

But, is this actually true? Are there any other ways that B1 might influence our hair? And what does this mean in the context of diet in the developed world?

Let’s explore the evidence.

Does a thiamine / vitamin B1 deficiency cause hair loss?

Maybe. But this isn’t the right question to ask. Rather, we need to ask this question in two parts:

1. Does a vitamin B1 deficiency cause hair loss?
2. Does a vitamin B1 deficiency within realistic parameters cause hair loss?

Why would we do this? Because at the extremes, almost anything causes hair loss. For instance, a “water deficiency” can cause hair loss. If we don’t drink water, we die. If we’re dead, we can’t grow hair. But that doesn’t mean that drinking water will regrow our hair. It also doesn’t mean we should warn people that hair loss is a side effect of a water deficiency.

The truth is that these types of logic leaps are what marketers use to claim that deficiencies in selenium, vitamin E, and iodine can all cause hair loss. Yes, this is true – but only if our scope of deficiency includes the endpoints: malnourished poverty-stricken children, people with genetic disorders who can’t absorb these nutrients, and people with certain chronic conditions that make nutrient assimilation nearly impossible.

All this is to say that we should ask if a thiamine deficiency, in the absolutes, causes hair loss. But the better question is: does a thiamine / vitamin B1 deficiency within realistic parameters cause hair loss, too?

Let’s take these one-by-one.

1. Does a thiamine deficiency, at the extremes, cause hair loss?

Maybe (in rodent models).

This 1968 study (2) sought to determine what happens in mice fed a diet that rapidly induces a thiamine deficiency. After two and a half weeks, some mice began to experience rapid weight loss, followed by abnormal hair shedding. Soon thereafter, neurological function began to decline. After four weeks, the mice were confused and could barely walk – symptoms similar to those seen in humans with beri beri.

However, it was unclear if the hair loss was caused by the vitamin B1 deficiency or the rapid weight loss.

2. Does a thiamine deficiency, within realistic parameters, cause hair loss?

Probably not.

For starters, people with beri beri rarely reported hair shedding (even despite their rapid weight loss). Moreover, when we expand our scope to human studies, we haven’t found any hard evidence that causally links a vitamin B1 deficiency to hair loss.

We could close the case right there, and say the article is done. At the same time, the absence of evidence doesn’t always imply evidence of absence.

For instance, there’s always the possibility that vitamin B1 might exacerbate certain chronic conditions linked to hair loss, or certain disease states associated with shedding disorders.

In fact, we could assert that since a vitamin B1 deficiency can lead to rapid neurological decline and thereby weight loss, and because rapid weight loss can trigger excessive (but temporary) hair shedding, then vitamin B1 deficiencies might be indirectly related to hair loss. The deficiency causes the weight loss; the weight loss causes the hair loss.

But again, if you’re so deficient in vitamin B1 that you start losing weight, you’ve got bigger things to worry about than your hair (like rapid impending neurological deterioration).

So, do we see any other circumstances where vitamin B1 is indirectly linked to hair shedding or hair loss?

Potentially. We can find them by look at the role of vitamin B1 in the body, and then comparing this to how different types of hair loss actually develop.

Vitamin B1 deficiency may exacerbate autoimmunity

At present time, there have been several animal studies conducted to investigate a link between vitamin B1 and autoimmunity. In general, these studies have suggested that vitamin B1 deficiencies may exacerbate autoimmunity in certain autoimmune disorders – specifically, multiple sclerosis (3, 4). It stands to reason that improving vitamin B1 deficiency may also improve these autoimmune conditions.

So, how could these effects translate to hair loss?

There are several forms of hair loss that seem to be mediated by autoimmune processes. These include alopecia areata as well as some forms of scarring alopecia.

If thiamine deficiencies happened to exacerbate the autoimmune processes involved in these hair loss disorders, it’s possible that restoring thiamine levels could improve these conditions.

Again, there’s no evidence that vitamin B1 deficiency is related to these hair-related autoimmune conditions. And while all autoimmune conditions involve autoimmune processes, not all autoimmune conditions develop in the same way. Thus, we can’t necessarily extrapolate the results from the animal studies, which primarily looked at multiple sclerosis, to the autoimmune conditions that lead to hair loss.

There’s also another point to consider: the effects of certain compounds reflected in animal studies are also traditionally very difficult to extrapolate to humans. Take our rodent study from earlier: thiamin-deficient rodents developed weight loss, neurological decline, and hair loss; whereas humans with beri beri – a sign of a thiamin deficiency – typically only develop weight loss and neurological decline.

That leaves us with one last piece of evidence to consider when it comes to linking autoimmune hair loss to vitamin B1: a case series on three human patients with autoimmune thyroid conditions (5).

Vitamin B1, autoimmune thyroid disorders, and hair shedding: a possible connection?

Autoimmune conditions that affect the thyroid – like Graves’ disease and Hashimoto’s thyroiditis – can have a domino effect on hair growth which is, in part, controlled by thyroid hormones. When these hormones get too high (i.e., Graves’ disease) or too low (i.e., Hashimoto’s thyroiditis), it can cause telogen effluvium – a form of diffuse hair shedding.

Interestingly, vitamin B1 might have relevance here, especially in the context of Hashimoto’s thyroiditis.

In one case series, doctors administered vitamin B1 to three patients with Hashimoto’s thyroiditis. They hypothesized that vitamin B1 could help relieve one of the hallmark symptoms of low thyroid hormone: fatigue. 

Amazingly, that’s exactly what vitamin B1 did. In just a few hours to a few days, administration of B1 drastically improved the patients’ fatigue. 

But, this wasn’t because of a subsequent improvement in the underlying autoimmune condition.

Instead, the authors hypothesized that the autoimmune processes involved in Hashimoto’s thyroiditis may have resulted in a vitamin B1 deficiency, subsequently leading to a reduction in energy production and, thus, fatigue.

In other words, the vitamin B1 deficiency likely isn’t a contributor to the development of Hashimoto’s thyroiditis. Instead, vitamin B1 deficiency, in this case, is a consequence of the condition.

As such, we can’t expect vitamin B1 to actually improve Hashimoto’s thyroiditis or the hair loss that occurs as a result. Instead, vitamin B1 can only improve symptoms related to a vitamin B1 deficiency that may occur alongside the condition.

So, we’ve established that vitamin B1 may or may not improve autoimmune forms of hair loss. We’ve also ruled out vitamin B1 as a means to improve Hashimoto’s thyroiditis and the hair shedding that ensues as a result.

But, are there any other pathways by which B1 might influence hair loss? Maybe… and that leads us to point number two.

Vitamin B1 deficiency may impair glutathione synthesis

Glutathione is a sulfur-containing compound with powerful antioxidant activity. Unlike antioxidants we consume in our diet (like polyphenols in green tea, berries, and other health-promoting foods), glutathione is manufactured by our own cells from amino acids like cysteine, glycine, and glutamic acid. This process requires NADPH, which requires vitamin B1 (along with various other B vitamins) (6).

So, how does this relate to hair loss?

Glutathione deficiency is associated with many conditions including diabetes, cardiovascular disease, as well as autoimmune diseases (7). Some studies also show low glutathione is associated with androgenic alopecia (AGA) (8).

As an anti-inflammatory agent, it’s possible that glutathione deficiency could exacerbate the microinflammation in AGA follicles — a process that drives the hair loss observed in AGA (7, 9). 

In this context, it’s possible that through a possible increase in glutathione, vitamin B1 could reduce inflammation in AGA and, thus, improve AGA.

But there’s a difference between possible and plausible. Yes, if we stretch our imagination, it’s possible that a vitamin B1 deficiency might decrease glutathione production, and that if enough of this occurs in balding hair follicle sites, this decrease might exacerbate inflammation in AGA.

Possible, yes. But plausible?

Probably not.

While B1 deficiency seems to be related to low glutathione levels, vitamin B1 deficiency is extremely rare amongst most of the population. So, in this context, vitamin B1 is probably not something that most AGA patients need to worry about.

In these cases, glutathione deficiency is more likely to be related to co-morbidities seen in AGA: conditions like diabetes, obesity, and cardiovascular disease (all of which we know can deplete glutathione) (10).

So, while vitamin B1 deficiency could, technically, lead to or exacerbate a glutathione deficiency, it’s safe to say this is probably not the case for most AGA patients with low glutathione.

A quick recap

So far, we’ve established that B1 is an essential micronutrient. We’ve also established that in its complete absence, it can cause hair loss in rodents. Aside from that, it doesn’t appear that a vitamin B1 deficiency is a major driver of hair loss in humans.

The reason for this is three-fold: 

• Vitamin B1 deficiency is extremely uncommon in the general hair loss population.
• In the rare cases where vitamin B1 levels are depleted and associated with hair loss, improving vitamin B1 levels only improves symptoms associated with vitamin B1 depletion. In other words, vitamin B1 improves nervous system abnormalities like fatigue but not the underlying conditions that lead to hair loss.
• When looking at the relationship between vitamin B1, glutathione, and AGA, it’s unlikely that vitamin B1 deficiency contributes to low glutathione levels that may exacerbate hair loss. Rather, low glutathione levels observed in some patients appear to be a consequence of some common co-morbidities associated with AGA. 

So, that leads us to this conclusion: in the overwhelming majority of cases, vitamin B1 is not likely to confer any benefit in hair loss.

This leaves us with one last question worth asking before we close the books on the vitamin B1-hair health connection…

Could increasing vitamin B1 levels beyond normal levels have any negative effect on hair loss?

Maybe, maybe not. Let’s look at the research.

Why vitamin B1 might be bad for hair: the NADPH-DHT connection

Vitamin B1 is an essential cofactor in the production of the molecule, NADPH.

NADPH – or nicotinamide adenine dinucleotide phosphate – is a cofactor for enzymatic reactions. In other words, it’s a molecule that helps kickstart processes in the body. Earlier we established that NADPH was crucial for glutathione production. But that’s not all that NADPH does. NADPH is also essential for the production of steroid hormones.

Specifically, NADPH is a key molecule of the enzymatic process that converts testosterone into dihydrotestosterone, or DHT. Without NADPH, the enzyme that performs this conversion cannot function (11).

So, what does this mean for hair?

If you’ve done any research into androgenic alopecia (AGA), you probably already know that DHT is a significant contributor to the development of pattern hair loss (12). As such, any increase in DHT conversion could potentially worsen or speed up the balding process.

But, this would require NADPH to increase beyond what’s considered “physiological” — or what’s considered normal. So, does vitamin B1 do this?

Probably not. But we just don’t know.

What we do know is that, oftentimes, enzymes that produce molecules like NADPH have negative feedback mechanisms in place. This means that when their end-products increase, the body automatically reduces the activity of the enzymes that produce them. The net product is no increase in production.

However, this isn’t always the case. In some cases, these negative feedback loops are dysfunctional.

So, it’s possible that vitamin B1 doesn’t increase NADPH beyond what’s considered normal. As such, it’s also possible that vitamin B1 has no impact on DHT levels. At the same time, it’s also possible that it could.

In either case, the solution is the same: leverage diet to ensure vitamin B1 sufficiency and address a vitamin B1 deficiency if it’s present — but don’t go overboard.

If we’re deficient in B1, what should we do?

It’s important to note that an overwhelming majority of individuals likely aren’t deficient in vitamin B1. But, that doesn’t mean it’s impossible. Of the small pool of individuals B1 deficiency seems to affect in the modern world, risk factors appear to be:

• Hashimoto’s thyroiditis (5)
• Gastric bypass surgery (13)
• Anorexia (13)
• Severe crash dieting (13)
• Marked impairments in nutrient absorption, as in severe inflammatory bowel disease (13)
• Alcoholism (13)
• Septic shock (14)

But, again, it’s important to underscore that, even in these cases, we shouldn’t expect vitamin B1 to regrow our hair. This is because a vitamin B1 insufficiency is highly likely to present alongside other contributors to hair loss – like low thyroid hormone, zinc deficiency, iron deficiency, and severe calorie deficit. So, an improvement in B1 levels alone isn’t going to override these other factors. If anything, the thiamine deficiency-hair loss connection is more association than it is causation.

In any case, maintaining sufficient vitamin B1 levels is essential for overall health. So, you should aim to hit the recommended daily intake (RDI) everyday.

The good news is that you’re probably already doing this without even thinking about it – especially with all of the B-complex fortified foods out there. And if you find yourself falling into any of the risk categories, it’s not hard to find a supplement containing thiamine; nearly every multivitamin includes it as an ingredient.

At the same time, there could be a small minority of B1 deficiencies that go undetected, as was the case with the case series of Hashimoto’s thyroiditis patients. So, if you find yourself with fatigue that isn’t responding to standard treatment for Hashimoto’s thyroiditis, it may be worth discussing the possibility of vitamin B1 supplementation with your doctor.

Summary 

Vitamin B1 is an essential vitamin. It ensures our body can effectively produce amino acids, glutathione, and other cofactors that are crucial for cellular function.

Deficiencies in vitamin B1 have been linked to weight loss, neurological decline, and hair loss in rodents. In humans, the evidence points more so toward neurological decline and weight loss than it does hair shedding. Having said that, a vitamin B1 deficiency might indirectly exacerbate hair loss through:

1. Rapid weight loss
2. Autoimmunity
3. Glutathione impairment

But the bottom line is this: if your thiamine / vitamin B1 levels are low enough to associate with hair loss, you’ve got bigger problems than hair… like mental debilitation, neurological deterioration, and impending death.

Needless to say, 99.9% of us probably don’t need to be supplementing with vitamin B1 as a hair loss preventive. In fact, given vitamin B1’s relationship to NADPH production, and NADPH’s relationship to DHT, we could make a similar logic-leap argument that too much vitamin B1 may exacerbate hair loss.

This leaves us with one firm conclusion: maintain sufficient vitamin B1 levels by consuming the recommended daily intake. In the developed world, nearly every single diet will do this for you… provided you don’t have any of the hallmarks that increase your risk of a B1 deficiency (i.e., alcoholism, gastric bypass surgery, anorexia, etc.).

In the rare case that you are deficient, work with a doctor to address why your levels might be decreased in the first place and, if needed, to increase your levels with supplementation.

Have any questions about Vitamin B1 and hair health? Please leave them below in the comments!