If you’ve ever experienced that twinge of envy at the sight of someone’s head of full, thick, healthy-looking hair, you’re not alone. The truth is that many of us struggle with thin, weak, or brittle hair—indeed, keeping your hair looking its best as you age can feel like an uphill battle. But, science shows that healthy hair growth and retention might have just as much do with your internal health as it does with your genetic predisposition.
On the surface, it seems straightforward: if you want to have strong, beautiful hair, you just have to wash your hair regularly, get haircuts when the split ends start to show, and add in the occasional deep conditioning treatment to keep things looking shiny, right?
Actually, what's going on inside your body is just as important when it comes to healthy, natural hair growth. Your nutrition, certain genetic conditions, and your stress levels can all play a role...and according to new research, so can your gut microbiome.
It might sound a little strange (after all, how can the bacteria in your gut affect the hair on your head?), but they're actually closely connected—so much so, in fact, that having an imbalance in your gut bacteria can lead to significant, highly visible hair loss!1
To understand this connection, it helps to know just how hair grows, and what factors can impede the process.
Hair Growth 101
You can think of hair growth kind of like plant growth: it all starts with a seed, or in the case of hair, a follicle. At the bottom of each of your follicles, there's a root that's made of protein cells. Each root is fed by blood containing the nutrients needed to create the structures that make up hair, and hormones that tell the follicle when to create more cells and when to take a rest.
When a follicle is in the growing phase (called anagen), it produces keratin and lipid cells, which make up the structure of each strand of hair.2 These cells grow out of the follicle, forming the strands of hair you can see, as long as the follicle is in its anagen phase.
After 3-5 years of being in anagen, the follicle will transition into catagen, or the transitional phase during which growth slows, and then telogen, when the follicle stops producing hair and that particular strand falls out. After a few weeks, if your hormones are working properly, it will transition back into anagen, producing a new hair.
However, the process isn’t always so smooth, and any disruption in the growth cycle can lead to hair thinning, hair growth problems, and hair loss.
The Gut Microbiome and Hair Growth Connection
Hair growth sounds like it only takes place in the scalp, but your gut has more to do with it than you'd think. Research shows that your gut microbiome not only supports the production of some of the nutrients needed for growing hair, it also supports the hormones that control the transition between the anagen, catagen, and telogen phases, and can even maintain conditions in your body that favor healthy hair growth. And, when it’s in balance, your microbiome can help to crowd out inhospitable bacteria that can lead to hair loss and thinning.
In one study on mice, supplementation with probiotic Lactobacillus reuteri not only increased anagen hair follicle counts by a whopping 106%, but when comparing mice in the control group to mice in the probiotic group, researchers determined that the probiotic-fed male mice had 74% of their hairs in the active, anagen phase, while the control group only had 36% (66% and 30%, respectively, for the female mice). In fact, a full 64% of hairs on the mice in the non-probiotic group were in the non-growth telogen phase!1
So, how exactly do beneficial bacteria in your gut microbiome support hair growth? Here’s a quick rundown of a few of the main mechanisms:
1. Provide Nutrients
Remember how the follicle creates the cells that make up hair using nutrients delivered by the bloodstream? Your gut microbiome actually synthesizes some of the key materials needed for hair growth. Perhaps the most important one is biotin (also called vitamin B7 or vitamin H), which your body uses to metabolize the amino acids needed to produce keratin, the cells that make up your hair. While it's possible to get biotin in your diet and in supplements for hair growth, some strains of beneficial gut bacteria actually produce it, too.3,4
If your gut gets out of balance though, and other undesirable species take over, biotin production reduces, which can contribute to hair loss. For instance, one study found that mice who had a course of strong antibiotics ended up with an overgrowth of L. murinus, a bacteria that eats biotin. As a result, the mice experienced hair loss––which was reversible with biotin supplementation.5
Your gut bacteria also produce vitamin K2, which regulates calcium in your body, helping to make sure that it ends up where it needs to be (your bones and teeth), and not in places it shouldn't, like the walls of your blood vessels. If the blood vessels in your scalp get too much calcium in their walls, this can compromise the blood flow to your follicles, making hair growth that much harder.6,7
Friendly gut bacteria also help your body make niacin, which relaxes the walls of your blood vessels, allowing for better blood flow and potentially helping with hair growth.8,9
2. Regulate Hormones
Beneficial bacteria help regulate the levels of various hormones in your body, including those related to hair growth, like testosterone, estrogen, and cortisol.12,13 If you have too much testosterone or too little estrogen, your hair can't move through its growth cycle appropriately, potentially leading to hair loss; but a healthy gut microbiome can work to keep your levels of each hormone normal. Similarly, abnormally high levels of cortisol (the stress hormone) can disrupt the levels of hyaluronic acid and proteoglycans in your skin, impairing the function of your hair follicles.14,15,16
But if your gut microbiome is in balance, it can help your body moderate its response to stress, reducing your cortisol levels so your follicles can remain healthy.17 Lower levels of stress can also help with behavioral issues that can lead to hair loss, like feeling the urge to repeatedly pull out individual hairs in response to stressful feelings.18
3. Optimize Immune Function
Some types of hair loss are related to an over-functioning immune system: much like how your immune system can overreact to non-harmful substances like pollen, it can also sometimes mistake its own cells as dangerous, attacking your hair follicles and making it difficult for them to function correctly. Not only does the microbiome help to regulate immune function so the immune system doesn’t overreact, but helpful bacteria can also increase anti-inflammatory cytokines, which are signaling proteins released by immune cells that tell tissues how to behave. L. reuteri in the gut, for instance, can increase the expression of a cytokine called IL-10 in the skin, which regulates sebum production and increases the numbers of hairs in the anagen phase.1
What's more, a balanced gut microbiome lowers your stress levels to give your immune system a break, and even helps your body learn how to respond to all sorts of stimuli appropriately––after all, 80% of your immune cells are in your gut!19
How to Nourish Your Hair From the Inside Out
Clearly, you've got to get your gut in on the game if you want to keep your hair thick and healthy. So what can you do to make sure that you're giving your body the building blocks it needs for spectacular hair? You’ll have to approach the issue from both sides, paying mind not only to what you put on your hair, but also to what you put in your body.
• Avoid external stressors. Many common hair products are actually not good for your body. Artificial chemicals and synthetic materials can disrupt your skin microbiome, which is crucial for keeping your skin (hair follicles included) healthy and your gut microbiome balanced. Chemicals on your skin can affect your gut via the gut-skin axis, so be mindful of the things you're using on your skin and hair, opt for natural products without harmful chemicals, and avoid overbathing in general. There's nothing wrong with being clean, but the way we approach it in our modern Western society, with very hot water and regular exposure to chemical-laden products, is often over-the-top, disrupting the skin microbiome and even immune function!
While you're at it, make sure that you avoid putting structural stress on your hair: one other potential cause of hair loss and thinning is regularly wearing your hair in styles that pull on it, like a tight ponytail. Doing this over and over again can damage your follicles, causing patterns of hair loss around the edges of your scalp.
• Replace your old hair products with natural, plant-based alternatives. Once you've cleaned out your harsh, synthetic cleansers, replace them with natural products that can give your skin and hair a little extra moisturization and protection. You've got so many options for promoting healthy, supple skin and shiny hair, including argan oil and castor oil, both of which are rich in vitamins and fatty acids that keep your skin healthy and your hair lush. For cleansing, try natural options like Carina Organics...or just make it yourself with castile soap!
• Eat foods that nourish your microbiome and promote healthy hair. Your body can't grow healthy hair without the right building blocks, so make sure that you're eating foods that support your gut microbiome and contain biotin, vitamin K2, and the amino acids used to produce healthy hair, like hyaluronic acid. Generally speaking, look for lots of vitamin-rich seasonal, organic produce; high quality meat, dairy, and eggs (great sources of biotin and vitamin K2); and fermented foods like natto, kimchi, and sauerkraut, which are rich in probiotics that can help produce essential vitamins.
• Replenish your microbiome with probiotics and prebiotics. Of course, your body can only make the most of those nutrients for healthy hair if you have a good balance of beneficial bacteria in your gut, and given all the things that can disrupt your bacterial balance, that's often very difficult to achieve without supplementation. So consider adding a premium probiotic like PRO-15 to your daily routine. Made with fifteen carefully-curated strains of bacteria, it's a good way to give your gut and your hair some serious love.20
And if you want to make the most of your new bacterial balance, try adding prebiotic powder to the mix as well––it's made with the three types of fiber that your beneficial bacteria most need to thrive and crowd out the bad guys.
• Bonus tip: don't forget about your mindset! One of the most amazing characteristics of the gut microbiome is its two-way connection to the brain via the gut-brain axis. Rebalancing your gut microbiome can lower your stress levels, but making a conscious effort to improve your mindset can also help your gut balance. Gratitude practices, meditation, and spending time with people who make you happy can all lower your stress levels, creating conditions that allow beneficial bacteria to thrive. And since your stress and microbiome are crucial for the health of your hair, it's well worth paying some attention to your mindset as part of a holistic approach to your health and appearance.
When it comes down to it, your hair isn't just a cosmetic concern. Its appearance has such a big impact on your confidence and how you move through the world, so make sure you’re giving your body the support it needs to create thick, luscious hair. By paying as much attention to what you put in your body as what you put on it, you’ll be able to get right to the root of the issue––literally!
References:
1. Levkovich, T., Poutahidis, T., Smillie, C., Varian, B. J., Ibrahim, Y. M., Lakritz, J. R., Alm, E. J., Erdman, S. E., (2013). Probiotic Bacteria Induce a ‘Glow of Health’. PLoS ONE, 8(1): e53867. https://doi.org/10.1371/journal.pone.0053867
2. Yang, F., Zhang, Y., Rheinstädter, M. C., (2014). The structure of people’s hair. PeerJ, 2: e619. doi: 10.7717/peerj.619
3. Said, H. M., (2009). Cell and Molecular Aspects of Human Intestinal Biotin Absorption. The Journal of Nutrition, 139(1): 158–162. doi: 10.3945/jn.108.092023
4. Magnúsdóttir, S., Ravcheev, D., de Crécy-Lagard, V., Thiele, I., (2015). Systematic genome assessment of B-vitamin biosynthesis suggests co-operation among gut microbes. Frontiers in Genetics, 6:148. doi: 10.3389/fgene.2015.00148. eCollection 2015.
5. Hayashi, A., Mikami, Y., Miyamoto, K., Kamada, N., Sato, T., . . . Kanai, T., (2017). Intestinal Dysbiosis and Biotin Deprivation Induce Alopecia through Overgrowth of Lactobacillus murinus in Mice. Cell Reports 20: 1513–1524. https://dx.doi.org/10.1016/j.celrep.2017.07.057
6. Conly, J. M., Stein, K., (1992). The production of menaquinones (vitamin K2) by intestinal bacteria and their role in maintaining coagulation homeostasis. Progress in Food & Nutrition Science, 16(4):307-43.
7. El Asmar, M. S., Naoum, J. J., Arbid, E. J., (2014). Vitamin K Dependent Proteins and the Role of Vitamin K2 in the Modulation of Vascular Calcification: A Review. Oman Medical Journal, 29(3): 172–177. doi: 10.5001/omj.2014.44
8. Kamanna, V. S., Ganji, S. H., Kashyap, M. L., (2009). The mechanism and mitigation of niacin‐induced flushing. IJCP, 63(9):1369-1377. https://doi.org/10.1111/j.1742-1241.2009.02099.x
9. Draelos, Z. D., Jacobson, E. L., Kim, H., Kim, M., Jacobson, M. K., (2005). A pilot study evaluating the efficacy of topically applied niacin derivatives for treatment of female pattern alopecia. Journal of Cosmetic Dermatology, 4(4):258-261. https://doi.org/10.1111/j.1473-2165.2005.00201.x
10. Jones, M. L., Martoni, C. J., & Prakash, S., (2012). Cholesterol lowering and inhibition of sterol absorption by Lactobacillus reuteri. NCIMB 30242: a randomized controlled trial. European Journal of Clinical Nutrition, 66(11):1234-1241.
11. Wilson Tang, W. H., Hazen, S. L., (2017). The Gut Microbiome and Its Role in Cardiovascular Diseases. Circulation, 135:1008-1010. https://doi.org/10.1161/circulationaha.116.024251
12. Kondo, S., Hozumi, Y., Aso, K., (1990). Organ culture of human scalp hair follicles: effect of testosterone and oestrogen on hair growth. Archives of Dermatological Research, 282(7):442–445. https://doi.org/10.1007/BF00402619
13. Riedel-Baima, B., Riedel, A., (2008). Female pattern hair loss may be triggered by low oestrogen to androgen ratio. Endocrine Regulations, 42(1):13-16.
14. Thom, E., (2016). Stress and the Hair Growth Cycle: Cortisol-Induced Hair Growth Disruption. Journal of Drugs in Dermatology, 15(8):1001-4.
15. Yagoda, M.R., Gans, E.H., (2012). A Nutritional Supplement Formulated with Peptides, Lipids, Collagen and Hyaluronic Acid Optimizes Key Aspects of Physical Appearance in Nails, Hair and Skin. Journal of Nutrition and Food Science, S5:002. doi: 10.4172/2155-9600.S5-002
16. Malgouries, S.,Thibaut, S., Bernard, B. A., (2008). Proteoglycan expression patterns in human hair follicle. British Journal of Dermatology, 158(2):234-42. doi:10.1111/j.1365-2133.2007.08339.x
17. Kato-Kataoka, A., Nishida, K., Takada, M., Kawai, M., Kikuchi-Hayakawa, H., Suda, K., . . . Rokutan, K. (2016). Fermented milk containing Lactobacillus casei strain Shirota preserves the diversity of the gut microbiota and relieves abdominal dysfunction in healthy medical students exposed to academic stress. Applied and Environmental Microbiology, 82(12):3649-3658. doi:10.1128/aem.04134-15
18. Rothbaum, B. O., (1992). The Behavioral Treatment of Trichotillomania. Behavioural and Cognitive Psychotherapy, 20(1):85-90. doi: 10.1017/S0141347300016372
19. Panda, S., Guarner, F., Manichanh, C., (2014). Structure and functions of the gut microbiome. Endocrine, Metabolic & Immune Disorders Drug Targets, 4, 290–299.
20. Noda, H., Akasaka, N., Ohsugi, M., (1994). Biotin production by bifidobacteria. Journal of Nutritional Science and Vitaminology (Tokyo), 40(2):181-8.
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Rachel Allen is a writer at Hyperbiotics who's absolutely obsessed with learning about how our bodies work. She's fascinated by the latest research on bacteria and the role they play in health, and loves to help others learn about how probiotics can help the body get back in balance. For more ideas on how you can benefit from the power of probiotics and live healthier days, be sure to subscribe to our newsletter. To learn more about how a healthy microbiome can enrich your life, subscribe to our newsletter.