Vitamin A is considered essential for eye, skin, bone, dental, and intestinal health. It’s also one of the most commonly found vitamins inside hair loss supplements. But is there any evidence that vitamin A supplementation can help improve hair health… or even reverse hair loss?
The answers might surprise you. Here’s where the research currently stands:
- For people who can afford to buy supplements, vitamin A deficiencies are incredibly rare. This means for most people, vitamin A supplementation is unnecessary.
- There are a few case reports of people with widespread nutrient deficiencies – including vitamin A – and hair loss. However, these case reports are mostly from the developing world. They can’t be applied to people in the developed world, and even if they could, the studies don’t definitively show that vitamin A deficiencies were the main cause of thinning hair.
- In the amounts found in supplements, long-term vitamin A supplementation (as beta carotene or retinol) has actually been linked to an increased risk of hair loss, mortality, and certain cancers.
As someone who used to take a multivitamin for years, I was shocked to learn just how little evidence there was to support vitamin A supplementation. I was particularly disappointed to find out that, contrary to the marketing claims I’d fallen victim to, vitamin A supplements may be more likely to hurt our hair than they are to help it.
If you’re curious about the real science behind vitamin A – its different forms, health benefits, and its connection to hair loss and hair growth – this article is here to set the record straight… so you can stop buying into misinformation, and start making more informed treatment choices for your hair.
What is vitamin A?
Vitamin A is a fat-soluble vitamin. It’s involved in a variety of bodily functions – from skin health to immune support to reproductive health (1).
In the skin, one of vitamin A’s main functions is to encourage cell turnover, which is why so many cosmetic products contain vitamin A derivatives (as they can make the skin look more flush, plump, and firm – at least in the short-term).
There are two forms of vitamin A: beta carotene and retinol. Distinguishing between the two is important.
Beta-carotene versus retinol
Beta-carotene and retinol are the two main forms of vitamin A.
Beta-carotene is the precursor to retinol. It’s considered an antioxidant, and is somewhat of an “inactive” form of vitamin A.
On the other hand, retinol is considered the “active” form of vitamin A. And retinol can be further divided into two forms: all-trans retinoic acid and 9-cis retinoic acid. Just how much beta-carotene is converted into these two forms of retinol depends on our genetics.
The sources of beta-carotene versus retinol are also very different. While beta-carotene is found in both plant and animal-based foods, retinol is only found in animal-based foods.
This means that if you’re supplementing with vitamin A, your supplement can contain any one of these three vitamin A forms: beta-carotene, all-trans retinoic acid, or 9-cis retinoic acid. This is important, because each type of vitamin A is connected to a different set of risks, benefits, and therapeutic functions.
Summary: Vitamin A comes in two forms: beta-carotene and retinol. Inside the body, beta-carotene (vitamin A’s precursor) will convert into retinol, which is the active form of vitamin A. Technically speaking, beta-carotene can convert into either all-trans retinoic acid or 9-cis retinoic acid. This leaves you with (at least) three types of vitamin A that you might find inside a supplement: beta-carotene (precursor), all-trans retinoic acid (active), or 9-cis retinoic acid (active).
Why is the distinction between beta-carotene and retinol important?
Beta-carotene and retinol have distinct and different roles in the body. Think of it this way: beta-carotene is what’s known as a carotenoid antioxidant (i.e., an antioxidant in the form of vitamin A). After ingesting it, some beta-carotene will remain as this antioxidant, and some will become retinol.
In contrast, retinol acts more like a hormone. Our cells even have receptors for retinol – called RAR and RXR – much like our cells have receptors for sex hormones like estrogen and testosterone.
Cell receptors are sort of like landing pads for a cell. When substances attach to a cell receptor, those substances can begin to change that cell’s behavior. This is as true for testosterone as it is for retinol. And more specifically, when retinol bind to these receptors, the retinol can actually change the way our DNA is expressed. As a result, the presence or absence of retinol will dramatically alter the way our cells function and, by extension, the tissues that make up bodily function.
Summary: once ingested, beta-carotene acts more like an antioxidant, whereas retinol acts more like a hormone. Whereas beta-carotene helps to fight off free radicals (i.e., inflammation), retinol helps to change cell behavior, and by extension, the functionality of our organs and tissues.
Vitamin A: how might it help improve hair health?
Before we dive into (1) the percentage of people with a vitamin A deficiency, or (2) the or clinical evidence between vitamin A and hair health – we first wanted to discuss some hypothetical scenarios whereby vitamin A might improve hair loss.
Why are we doing this? Because the studies we’re about to cite are the ones that marketers will show you when trying to convince you that vitamin A supplements are important for hair growth.
We’ll build the the strongest argument for vitamin A helping with hair health. We’ll go through the hypothetical evidence supporting both beta-carotene and retinol as potential therapeutic agents for hair growth.
Then, we’ll tear these arguments to the ground.
Beta-carotene protects the skin against UV radiation
As mentioned earlier, beta-carotene is an antioxidant carotenoid. This means it helps to scavenge free radicals and help reduce inflammation. So, does its antioxidant effects have any impact on overall health – specifically for the skin, scalp, or hair?
Potentially. It seems beta-carotene might help the health of our hair in at least one way: it protects against UV radiation.
Fat-soluble vitamins tend to accumulate in skin tissues where fat stores reside. Because of this, antioxidant carotenoids (like beta-carotene) have an affinity for the skin, which means their antioxidant effects tend to favor these tissues.
If it’s not already obvious, our hair follicles reside in the skin.
It’s well-known that UV radiation – i.e., sunlight exposure – can increase free radical activity in skin tissues, and thereby elicit inflammation. This may occur in the scalp and in the hair follicles. In high quantities, UV radiation might elicit enough free radical activity to actually impede hair growth (2). Therefore, protecting against UV radiation may also protect against free radical-induced hair loss.
Antioxidant carotenoids are known to build resistance to UV radiation in the skin (3). Thus, beta-carotene consumption may protect against UV radiation-induced hair loss.
At the same time, beta-carotene isn’t the only carotenoid that does this. As such, if you’re lacking beta-carotene, your body will likely just find a different carotenoid or fat-soluble antioxidant to protect against UV radiation. After all, there are dozens of different antioxidants consumed from foods and stored within our body; it’s very rare to find yourself in a deficit.
Summary: In high quantities, UV radiation may impede hair growth. Interestingly, beta-carotene is an antioxidant; it can protect against UV radiation, and thereby might be useful against UV radiation-induced hair loss.
Retinol supports the immune system, fortifies gut health, and may help with metabolism
Retinol has very specific and essential functions that only retinol can fulfill. Specifically:
- Retinol supports the immune system (4). Retinol has been shown to enhance immune function while simultaneously blunting excessive inflammatory responses. This makes it easier for the body to resolve inflammation and prevent its chronicity. Additionally, retinol supports the production of endogenous antimicrobial proteins (5), which may help regulate bacterial overgrowth.
- Retinol fortifies gut health. Retinol plays a critical role in both maintaining the gut’s ability to regulate pathogenic bacterial overgrowth (6) and the integrity of the gut lining (7), preventing the induction of a condition called “leaky gut”.
- Retinol may play a role in maintaining metabolic health (8). Retinol is considered necessary for pancreatic homeostasis and, thus, helpful in maintaining blood sugar balance.
But, how do these functions relate to hair loss? And can an impairment of these functions, subsequent to retinol deficiency, lead to hair loss? Moreover, are there any specific effects of retinol on the hair follicle itself?
Can a retinol deficiency cause hair loss?
There is a myriad of ways that a retinol deficiency might hurt our hair health.
- Leaky gut and adipose tissue inflammation. Since retinol plays a critical role in preventing leaky gut, it also prevents the transmission of a highly inflammatory bacterial toxin called lipopolysaccharide (LPS). LPS can bind to receptors in the adipose tissue (9) that cushions the scalp and contributes to hair follicle homeostasis. This leads to adipose tissue inflammation and impairment of hormonal activity (10) that helps blunt chronic inflammation in scalp tissues. In other words, leaky gut impairs the scalp’s defense against inflammation.
- Impaired immune function. Given the impact retinol has on chronic inflammation, retinol deficiency may predispose to more intense inflammatory events in the skin.
- Suboptimal metabolic health. Metabolic dysfunction (11) has been linked to AGA. Whether metabolic dysfunction plays any role in its development, however, remains to be confirmed. Nonetheless, suboptimal metabolic function may lead to hormonal imbalances in adipose tissue under the scalp, potentially priming the scalp for inflammation.
But, the most important effects that retinol deficiency might have on hair growth is actually at the superficial level, meaning its effects on the scalp and the hair follicle itself:
- Potential stem cell dysfunction. Retinol is important for the activation of stem cells (12), a process that is necessary for hair growth. If retinol depletion is enough to induce stem cell dysfunction on its own, this may lead to impaired hair growth.
- Overproduction of sebum. Retinol plays a role in regulating sebum production in the sebaceous gland. In fact, one study (13) demonstrated that retinol dose-dependently reduced sebum production. Thus, adequate retinol may normalize sebum production, abrogating one of the factors that can lead to microbial overgrowth implicated in AGA.
- Hyperkeratosis. Excessive skin cell proliferation (hyperkeratosis) can lead to dead skin cell buildup at the follicular opening and, thereby, poor oxygenation of the follicle. This can also facilitate the overgrowth of microbes implicated in AGA (14). Retinol deficiency can potentiate this excess skin cell proliferation.
- A potential increased risk of fibrosis. While high doses of retinol have been shown to exacerbate fibrosis (15), lower doses actually appear to inhibit TGF-B1, a protein that seems to cause fibrosis (and is also implicated in androgenic alopecia).
- Suboptimal antimicrobial action on the skin. Because retinol plays a crucial role in the production of antimicrobial peptides, it may also impair the body’s natural defense against microbial overgrowth at the follicular opening — which we know is connected to AGA.
At face-value, this all sounds encouraging. And in general, the evidence we’ve cited above is the evidence marketers use to convince us we need to supplement with vitamin A for hair growth.
Unfortunately, the studies above were conducted using petri dishes and mice. And unfortunately, neither petri dishes nor lab rat represent humans with scalp hair loss. So, we can’t just start supplementing with retinol and expect to see amazing hair benefits.
Rather, we need to look at epidemiological evidence. Specifically, we have to look at groups of people who are deficient in vitamin A / retinol. Then we have to see if these people have a higher incidence of hair loss, and if supplementation with retinol and/or vitamin A derivates actually helps them regrow hair.
In doing this exercise, it’ll become clear just how useless vitamin A supplements are for most hair loss sufferers… and how they may even do more harm than good. On a personal note, the evidence we’re about to present below is why I’ve chosen to cut out any supplements containing vitamin A in perpetuity.
Summary: In petri dishes and mouse models, retinol may help improve metabolic health and immune functionality, as well as reduce inflammation and the epithelial cells of our gut lining. Moreover, retinol deficiencies seem to be associated with stem cell dysfunctionality, an increased risk of fibrosis, and hyperkaratosis. All of this indirectly implies that retinol is important for hair health. At the same time, these studies don’t actually measure retinol’s effects on hair loss in humans. And if we want to know if vitamin A is important for human hair growth, we need to look at studies measuring vitamin A levels for humans with hair loss, and whether vitamin A supplementation actually helped them.
Vitamin A, hair loss, and hair growth: evidence in humans
Most researchers believe that some amount of vitamin A – as beta-carotene and/or retinol – is necessary for optimal health. This is most evident in children with vitamin A deficiencies, as many of them develop a condition called xerophthalmia (16) (eye dryness that, if left untreated, leads to blindness).
This is why the FDA has established a minimum daily intake of vitamin A – which varies by age, gender, and if someone is present. We’ll get into these thresholds later; for now, we need to ask ourselves:
What percent of people are actually vitamin A deficient?
The answer varies depending on where you live.
In developing parts of the world – i.e., Africa and East Asia – roughly 30-50% of children are vitamin A deficient. That’s a scary number. In fact, the World Health Organization (WHO) has considered this such a problem that they’ve begun administering high-dose vitamin A to as many children in these countries as possible (see the chart below):
But what about in the developed world? What about in places like North American, Europe, and Oceania (i.e., Australia and New Zealand)? In these countries, the average consumer can afford to buy a hair loss supplement. Therefore, these are countries supplement makers target when trying to sell hair loss supplements containing vitamin A.
So, how many people in the developed world are vitamin A deficient?
As of right now, the consensus is very few people. In fact, one study found that less than 1% of Americans were deficient in retinol (17) (i.e., vitamin A).
That means that vitamin A supplementation is not necessary for 99%+ of Americans.
Do the 1% of people with a vitamin A deficiency suffer from more hair loss?
The short-answer is no, with caveats.
There are two types of people who are at a heightened risk of a vitamin A deficiency: (1) someone who doesn’t eat vitamin A-containing foods, and (2) someone with a BCMO1 mutation (18).
A BCMO1 mutation is a genetic mutation that puts someone at a higher risk for a retinol deficiency. The mutation impairs the conversion of beta-carotene into retinol. As such, the portion of beta-carotene that would otherwise be converted into retinol remains as beta-carotene – potentially leading to a retinol deficiency, that is unless retinol (from animal products) is consumed.
BCMO1 mutations are actually very common; they predominantly affect Caucasian, Chinese, and Japanese individuals (but very few Africans). Interestingly, some studies have shown that up to 60% of Caucasians have a BCMO1 mutation.
This begs the question: if 60% of people have a mutation that impairs the conversion of beta-carotene to retinol, how come less than 1% of Americans (many of whom are Caucasian) have a retinol deficiency?
Because most people with a BMCO1 mutation will eat animal foods containing retinol, thereby nearly eliminating their risk of a vitamin A deficiency.
This is why most people with a BMCO1 mutation don’t even know they have it.
Now, there are cases of people with a severe BMCO1 mutation – whereby both retinol conversion and absorption becomes problematic (19). And yes, these cases are associated with congenital hair loss (i.e., hair loss associated with birth defects). But these cases are few and far between, and usually, they’re accompanied by significant health concerns (mental impairment, etc.) as a result of a near-complete lack of vitamin A exposure in the womb.
For the people with common BMCO1 mutations, we have not found any evidence that these groups of people suffer from more hair loss than those without the mutations.
Summary: Less than 1% of Americans are deficient in serum retinol. This suggests that the overwhelming majority of people in the developed world are getting enough vitamin A through dietary means – even despite a high percentage of people with BMCO1 genetic mutations that make the conversion of beta-carotene to retinol more difficult. Moreover, there’s currently no evidence that people with a BMCO1 mutation suffer disproportionately from hair loss. With severe BMCO1 mutations, hair loss presents congenitally and is accompanied by metal impairment. But these cases are incredibly rare and do not justify vitamin A supplementation for the general population.
What about people who stop eating any vitamin A-containing foods? Is there evidence that they experience more hair loss?
The only evidence we could find linking hair loss to a dietary-driven vitamin A deficiency in humans came from a 2010 case report about two men from Italy who had undergone rapid weight loss (20). But these were unusual cases.
One man underwent bypass surgery to make his stomach smaller; the other lost 60 pounds in a year on a starvation-based diet.
In both cases, these men essentially stopped absorbing and/or eating foods with vitamin A. Subsequently, they developed a condition called phrynoderma, a rare disorder that leads to skin bumps and, in rare circumstances, hair shedding in the affected area (usually body hair). Technically, slight body hair loss was observed in both men.
Aside from these rare reports about a rare condition, we couldn’t find any evidence that dietary-driven vitamin A deficiencies in humans caused hair loss.
Surprisingly, we found evidence showing the opposite: that high-vitamin A diets might actually accelerate hair loss, and that low-vitamin A diets might actually prevent hair loss.
High-dose vitamin A is linked to hair loss in humans
Studies have demonstrated that excess retinol (through supplementation or drugs) may trigger a type of hair loss known as telogen effluvium (21). This is where a large number of hairs enter their “shedding” state prematurely, taking months (and sometimes years) to grow back.
If you’re looking for real-world examples of this, look no further than the side effects reported from the acne drug Accutane®, an isotretinion-based drug (22). For what it’s worth, isotretinoin drugs are nearly molecularly identical to retinol (i.e., vitamin A).
Low-vitamin A diets may delay hair loss in humans
In one study, a low-vitamin A diet delayed the onset of hair loss in mice (23). Of course, when it comes to hair health, mouse models rarely translate to humans. So we were surprised to discover that someone with male pattern hair loss had actually decided to put this mouse model to the test.
His name is Grant Genereux, and after years of suffering from brain fog, hair loss, and physical / cognitive decline, he decided to develop a vitamin A-deplete diet and test whether removing this vitamin entirely from his system would help improve his symptoms.
Over five years later, he’s still on the diet. His lab tests put him at barely-registering levels for serum retinol, and all of his physical and cognitive symptoms have vanished. Fascinatingly, his hair has also darkened, and he’s seen considerable regrowth and thickening from his male pattern hair loss. He’s since conducted tests on gerbils – putting them on the same diet as he is currently undertaking – and without any negative repercussions.
Note: we don’t endorse Grant Genereux’s diet, but for anyone interested in learning more, you can check out his site using the link above. Last we checked, he’d written three books on the topic.
Summary: The only cases that link dietary-driven vitamin A deficiencies to hair loss are from case reports of men who’ve undergone extreme weight loss. This wasn’t scalp hair loss; it was body hair loss. On the contrary, low-vitamin A diets have delayed the onset of hair loss in mice, and partially reversed male pattern hair loss according to the anecdotes of one self-experimenter. Moreover, high-dose vitamin A (as Accutane) is directly linked to a hair loss disorder known as telogen effluvium. For these reasons, vitamin A supplementation seems to carry a higher risk of hair loss than it does of hair regrowth.
Any other concerns with vitamin A?
Yes. Some of this research is already published; some is still ongoing.
Risks of all-cause mortality and cancers
Supplementation with beta-carotene and retinol – in the amounts commonly found in hair loss supplements – has been linked to an increased risk of all-cause mortality and certain cancers, respectively (24).
Of course, correlation doesn’t necessarily equal causation. But given that more than 99% of Americans have adequate levels of serum retinol, there’s really no reason for most Americans (and likely, most others in the developed world) to even consider vitamin A supplementation.
In fact, there’s preliminary evidence that the increased risks of mortality and certain cancers is presenting disproportionately in third-world countries where the WHO has been providing mega-doses of vitamin A to treat deficient children (25). I personally know someone investigating this alongside an entire research team – to determine, in part, if the efforts made by the WHO to address third-world vitamin A deficiencies may be doing more harm than good.
How to get enough vitamin A (without supplementing)
A balanced diet filled with high-quality plant and animal products should provide more than enough vitamin A to maintain healthy beta-carotene levels.
If you’re concerned you’re not eating enough vitamin A, you may want to consider adding these foods into your diet.
Whole food sources of retinol
(RDA for retinol = 900 mcg retinoic acid equivalent (RAE) for males, 700 mcg RAE for females (ages 14-51+))
|Serving Size = mcg RAE, % RDA
|1 large egg = 80 mcg RAE, 9% for men, 11% for women
|2.3 oz = 6,421 mcg RAE, 713% for males, 917% for females
|1 tbsp = 43.2 mcg RAE, 5% for males, 6% for females
|1 oz = 75.6 mcg RAE, 8% for men, 10% for women
|1 tbsp = 95 mcg RAE, 10% for men, 13% for women
|1 cup = 110 mcg RAE, 12% for men, 15% for women
|Cod liver oil
|1 tsp = 1,350 mcg RAE, 150% for males, 192% for females
Beyond that, here are a few eating tips to help with assimilation and conversion:
- Avocados increase the activity of the enzyme that converts beta-carotene into retinol. So, eat avocados alongside your beta-carotene-rich foods like carrots, mangos, and sweet potato.
- Liver (and cod liver oil), eggs, and full-fat grass-fed dairy all provide significant amounts of retinol (among other health-promoting nutrients). Try to make these foods a regular part of your diet. However, make sure you can tolerate eggs and/or dairy before you consume these foods – as consumption in the presence of an allergy/intolerance may actually be sabotaging your efforts for hair regrowth.
- Cooking beta-carotene-rich foods in fats prior to eating makes the beta-carotene more bioavailable and, thus, increases the pool of beta-carotene that can be converted to retinol. So, try to cook your carrots and sweet potatoes in high-quality virgin avocado, olive, or coconut oil or grass-fed butter, ghee, or tallow.
Generally, you’ll want to stay at or under the RDA for retinol to keep your risk of adverse effects to a minimum.
I’m currently supplementing with desiccated liver or cod liver oil. Am I increasing the risk of my hair loss?
Desiccated liver and cod liver oil are natural, non-synthetic sources of retinol. This is much better than synthetic retinol – like retinyl palmitate (which is found in many supplements).
At the same time, the popularity of these supplements seems is derived more so from clever marketing than it is of necessity.
If you’re truly concerned, we recommend using a resource like Cronometer to track your food intake and retinol cosumption throughout the week. If the numbers look high, adjust accordingly. And if the numbers look low, consider making different food choices, or consider supplementation.
Vitamin A is an ingredient found inside many hair loss supplements. But it’s unnecessary for most people, and maybe even dangerous to supplement with long-term.
Evidence shows that less than 1% of Americans are vitamin A deficient. In the developed world, a normal diet provides more than enough vitamin A for the overwhelming majority of people.
Vitamin A deficiency-related hair loss has occurred, but it’s rare. We’ve seen it in humans with BMCO1 genetic mutations that are so severe, they causes congenital defects including hair loss. We’ve also seen it in humans who lose a massive amount of weight in a very short period of time – from gastric bypass surgery or crash dieting. But that’s it.
Paradoxically, the opposite seems more true – that vitamin A supplementation may actually increase our risk of hair loss. This is why hair loss is a common side effect reported by people taking synthetic vitamin A drugs, like Accutane®. On top of that, long-term supplementation with beta-carotene or retinol is linked with an increased risk of all-cause mortality and certain cancers, respectively.
The bottom line: save your money on supplements containing vitamin A. When it comes to hair health, they might be more likely to do more harm than good.
Questions? Comments? You can reach us any time in the comments section below.
Rob English is a researcher, medical editor, and the founder of perfecthairhealth.com. He acts as a peer reviewer for scholarly journals and has published five peer-reviewed papers on androgenic alopecia. He writes regularly about the science behind hair loss (and hair growth). Feel free to browse his long-form articles and publications throughout this site.