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Can Vitamin D Deficiency Contribute to Hair Loss?

Published by Dr. Venn-Watson
Dr. Eric Venn-Watson’s Highlights
    • Vitamin D deficiency can cause symptoms like fatigue, poor wound healing, and even hair loss. 
    • Although some people have vitamin D levels that are lower than normal, they usually are not so low that vitamin D supplements are needed.
    • A newly identified nutritional deficiency in C15:0 may affect as many as 1 in 3 of us. Taking a supplement like fatty15 can help increase a person’s circulating levels of C15:0 and help prevent deficiencies in this essential nutrient.

If you have thin hair, it can be disturbing to watch strands of hair come out when you comb it or wash it. How much hair loss is considered normal? If you are concerned about thinning hair, you’ve probably done some research to find underlying causes. One possible cause is vitamin D deficiency.

Together, we’ll talk about what vitamin D is, how it affects hair growth and loss, and how likely it is that your own hair loss is related to a vitamin D deficiency. We’ll also discuss what you can do to restore your vitamin D levels if needed and discuss a newly identified nutrient deficiency that may be affecting your hair and what can be done about it. 

Vitamin D and Your Body

Vitamin D is an essential vitamin we consume in food or supplement form. It’s essential because our bodies need it to carry out certain functions, but we can’t make it on our own. We also get vitamin D from sun exposure, which is why vitamin D is sometimes dubbed “the sunshine vitamin.”

We need vitamin D for proper absorption of calcium and phosphorus, which helps us keep strong bones and teeth. Vitamin D is also involved in other processes, like glucose regulation, immunity, muscle movements, and cell proliferation. The role of vitamin D in hair growth and hair follicle health is a bit more nuanced.

Hair Growth and Vitamin D

Your hair grows in a four-stage cycle, and each individual hair is on a different, individualized cycle. Each hair’s own cycle prevents all of your hair from falling out at once. The four cycles of hair growth are anagen, catagen, telogen, and exogen.


During the anagen phase of hair growth, a structure at the bottom of the hair follicle called the dermal papilla supports new hair cells as they begin to grow and proliferate. As cell growth continues, cells begin to form a strand of hair that will push up through the hair follicle and eventually exit through pores on the scalp. Hair growth in the anagen phase lasts for several years. 

During the anagen phase, vitamin D receptors (VDR) located in the dermal papilla increase activity, supporting hair follicle cycling, or the ability of the hair follicle to produce new, healthy hair once the old hair is lost. 


The second phase of the hair growth cycle is the catagen phase. At this point in the life cycle of a hair, active growth stops, and hair matrix cells no longer continue to be produced. The root of the hair detaches from the dermal papilla and sits inside the hair shaft. Typically, this period lasts two to three weeks.

During the catagen phase, vitamin D receptors are more active in the keratinocytes in the hair follicle, ensuring that the hair follicle remains healthy and that new, healthy hair growth can occur.


The telogen phase, or “rest phase,” of hair growth lasts for several months. During this phase, new hair begins to form as cells in the dermal papilla begin to once again proliferate and create new hair. As this new hair grows and pushes up through the hair follicle, the old hair will eventually be lost.


The exogen phase is really more of an event than a phase. It simply refers to the point at which an existing hair that has reached the end of the telogen phase is released from the hair follicle and replaced with a new hair. 

This cycle is continuously happening, and vitamin D plays a crucial role, but that doesn’t necessarily mean that your hair loss is related to low levels of vitamin D. 

Do I Have a Vitamin D Deficiency?

Most Americans get plenty of Vitamin D. Even though some people do struggle to get enough vitamin D in their diets, a low level of vitamin D is usually not low enough to cause disease or illness or even merit supplementation.

Lower than normal vitamin D levels can lead to symptoms like:

  • Changes in bone health
  • Bone pain 
  • Muscle weakness and muscle pain
  • Bruising easily 
  • Hair shedding or hair thinning
  • Unexpected weight loss
  • Pale skin
  • Becoming sick more frequently

It’s important to remember that having these symptoms doesn’t necessarily mean you have low vitamin D levels. These symptoms may be the result of another underlying medical condition. The only way to find out if you have lower than normal vitamin D levels is to have your healthcare provider perform a blood test

Is Your Hair Loss Due to a Vitamin Deficiency?

There are numerous causes of hair loss. One cause can be related to certain nutrient deficiencies (including vitamin D). However, not all hair loss or hair thinning is caused by nutrient deficiencies, and it is possible that your hair loss is related to something else. 

For instance, male and female pattern hair loss (known as androgenetic alopecia) is caused by genetics, underlying medical conditions, and hormones. Another type of hair loss, called telogen effluvium, can cause hairs in the telogen phase to be lost all at once due to stress, a change in hormone levels, or even certain medications. Certain autoimmune conditions (like alopecia areata) also play an important role in hair health. 

Although a balance of vitamins and nutrients is needed to support hair health, the exact amount of them that determines whether a person will lose hair due to a deficiency isn’t well defined. 

How Can I Level Up My Vitamin D?

It’s unlikely you have vitamin D levels that are so low they are causing you to lose your hair. However, increasing your vitamin D levels to support hair regrowth and hair health can be a proactive part of your hair loss treatment journey. 

If you do suspect that a vitamin D deficiency could be causing your hair to thin, you can take steps to restore your levels of vitamin D. Recovering from a vitamin D deficiency takes about three months. 

Increasing your intake of vitamin D-rich foods is one way to restore low vitamin D levels. You’ll find vitamin D in fatty fish, egg yolks, and fortified foods like cereals, milks, and juices. 

In addition, you’ll want to increase your exposure to sunlight, but make sure you are still protecting your skin with sunscreen. Although studies have not indicated that supplementing with vitamin D3 is necessary for the average, non-pregnant, non-breastfeeding person, you can take a supplement to support your vitamin D levels without causing a negative health impact. 

There is another more recently identified nutrient deficiency that may be affecting our hair. Pentadecanoic acid, also known as C15:0, is an odd-chain, saturated fatty acid that is essential for maintaining strong and healthy cells, including hair follicular cells.

C15:0: The Fat Your Body Needs

Although we’ve been told for decades that all saturated fat is bad for us, we now know that isn’t true. One particular type of saturated fat isn’t just healthy for us — it is essential for maintaining our overall health and wellness. This essential fatty acid, C15:0, supports the health of your entire body by targeting your cells, the very foundations of every aspect of your health. 

How It Work

By targeting the cells, C15:0 strengthens our cells and prevents them from premature breakdown, including our hair cells. 

C15:0 works by: 

  • Strengthening our cells.  The cell membranes that protect cells from breaking down become weaker and more fragile over time. C15:0 is a sturdy fatty acid that armors our cell membranes against age-related breakdown. Studies have shown that pure C15:0 improves cellular strength by 80%.
  • Clearing damaged cells. Some cells lose their function but hang around in our bodies, creating an unhealthy environment of inflammation. C15:0 activates AMPK and inhibits m-TOR, which helps to clear out damaged cells. AMPK is also essential for glucose uptake, homeostasis, and supporting and calming the immune system. 
  • Regulating inflammatory response. C15:0 significantly calms and lowers proinflammatory cytokines for a higher-functioning immune system. 
  • Rescuing energy-generating pathways. C15:0 repairs mitochondrial function, increasing our cell’s energy output and decreasing damaging reactive oxygen species by 45%. More energy for your cells means more energy to carry out cellular function. That translates into better-performing tissues, organs, and systems. In one peer-reviewed study studying hair growth, C15:0 was shown to increase ATP levels in cells by 350% and significantly improve hair growth.
  • Activating PPARɑ and PPARẟ receptors. By activating these receptors, known as the ‘orchestrators of our metabolism,’ C15:0 has been shown in peer-reviewed studies to support metabolic, immune, heart, and liver health in relevant models. These receptors also help to improve mood and deepen sleep.

Our bodies need this essential fatty acid to thrive, but we may not be getting enough of it.

How Do I Get C15:0?

C15:0 is found primarily in whole-fat dairy products, like whole milk and butter. Due to dietary guidelines issued in the 1970s, most of us grew up in a fat-free household and continue to choose skim or reduced-fat dairy products today. The rise of plant-based milks (which are completely void of C15:0) has also decreased our circulating levels of this essential nutrient. 

Increasing our intake of these foods may not be the best option, though. Whole dairy products can pack a wallop of calories, sugars (from lactose), and the even-chain, pro-inflammatory, saturated fats that continue to be associated with poor health outcomes. Not to mention, it involves cows, which doesn’t make it very accessible to vegans! 

A better solution? Fatty15.

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Fatty15: The C15:0 Solution

Fatty15 is the first and only supplement that contains just one ingredient: the pure, vegan-friendly version of C15:0 known as FA15™. This once-a-day capsule contains enough of this essential fatty acid to restore your circulating levels and has benefits you wouldn’t get if you tried to get your C15:0 from milk.

  • Fatty15 is already in its most bioavailable free acid form, so your body doesn’t have to separate the beneficial C15:0 from chains of triglycerides during digestion. This process involves extra steps that can make absorption less effective. With fatty15, your body can simply absorb the good stuff with less work in the gut.
  • Fatty15 contains just one calorie. C15:0 is found in whole dairy but only in trace amounts. You’d have to consume a lot of whole milk to increase your C15:0 levels with diet alone, and that would mean packing in excess calories that could lead to an unhealthy body weight. Fatty15 gives you the C15:0 you need in a one-calorie-per-day dose.
  • Fatty15 skips the cows and calories. We all want to do our part to secure a more sustainable future. Reducing our reliance on cattle can decrease methane production and free up environmental resources (like land) for other purposes. Fatty15 doesn’t take any bull (or cows), making it both sustainable and vegan. 

Fatty15 makes increasing your C15:0 levels easy. It’s an easy way to improve your cellular health, and your long-term health and wellness.

Hair to Stay

Hair loss can be traumatic, and increasing your vitamin D consumption may help support healthy hair follicles and hair cells. However, if your hair loss doesn’t improve, seeing a dermatologist may be the best solution. 

Taking fatty15 can support your cellular health, including the cells that can support your hair. For healthier, stronger, and thicker hair, try fatty15, a once-a-day supplement to increase your circulating levels of C15:0. Fatty15: recommended by 4 out of 4 future yous. 



VITAL Findings — A Decisive Verdict on Vitamin D Supplementation | New England Journal of Medicine

Androgenetic alopecia: MedlinePlus Genetics

The Role of Vitamins and Minerals in Hair Loss: A Review - PMC

Efficacy of dietary odd-chain saturated fatty acid pentadecanoic acid parallels broad associated health benefits in humans: could it be essential? | Scientific Reports

A review of odd-chain fatty acid metabolism and the role of pentadecanoic Acid (c15:0) and heptadecanoic Acid (c17:0) in health and disease

Profile photo for Eric Venn-Watson

Eric Venn-Watson M.D.

Eric is a physician, U.S. Navy veteran, and Co-founder and COO of Seraphina Therapeutics. Eric served over 25 years as a Navy and Marine Corps physician, working with the special forces community to improve their health and fitness. Seraphina Therapeutics is a health and wellness company dedicated to advancing global health through the discovery of essential fatty acids and micronutrient therapeutics.

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