Which vitamin deficiency causes hair loss?

The science of hair 

Hair is more than just an aesthetic part of our bodies. Indeed, hair helps to transmit sensory information and plays a major role in people’s identities. Interestingly, all of our hair follicles are formed in the womb before we are born. In fact, by week 22 of pregnancy, a foetus already has all of its hair follicles. Many of us take our hair for granted until we experience hair loss, in fact there are numerous products and supplements advertised for hair growth. But what really causes hair loss, is there a vitamin deficiency that causes hair loss or something else? Let’s start by looking at the science of hair. 

Our scalp contains approximately one hundred thousand hair follicles which is the highest number of follicles a human can have throughout their lifetime. In fact, we cannot generate new hair follicles beyond those we are born with. If you’ve ever wondered why your hair density seems lower as an adult compared to when you were a child, this is because our scalps grow as we transition from childhood to adulthood. 

Moreover, hair contains two different structures: the follicle and the shaft. The former is located in the skin whereas the latter is externally visible on the scalp. Our hair grows at a rate of about 6 inches per year (about .3 to .4 mm/day). However, unlike other mammals whose hair growth is either cyclical or seasonal, ours is not. In fact, each phase or hair growth has its own timeline which can be impacted by a variety of factors. 

There are three main phases of hair growth: anagen, catagen and telogen. These include the growth and maturation of hair and hair follicle activity. Finally, during a phase called “exogen”, hair begins to shed and the growth cycle begins again.(1)

The phases of hair growth 

Firstly, hair begins to grow in the anagen phase. This is the longest phase of the hair cycle. In fact, it can last between 3 and 5 years for your scalp hair. However, the anagen phase differs between types of hairs. For example, the anagen phase for eyebrow hairs is much shorter than for scalp hair. Throughout the anagen phase, hair follicles produce hairs that will grow until they fall out at the end of their lifespan. Approximately 90% of your scalp hairs are in the anagen phase at any one time. 

Then, once the anagen phase is complete, the catagen phase begins. This second phase usually lasts around 10 days. During this time, hair follicles grow smaller and hair grows at a slower rate. Approximately 5% of the hair on our head is in the catagen phase at any given time. Finally, during the telogen phase, the hair enters a “resting” stage. This phase normally lasts for 3 months, during this time hair doesn’t grow but it also doesn’t fall out. In addition, new hairs start to form in follicles that have previously released hairs in the catagen phase. 

Finally, the exogen phase is when shedding starts to take place. During the exogen phase, we may lose between 50 and 100 hairs per day. Moreover, this shedding phase can last between 2 and 5 months, during which new hairs are growing in the follicles where old hairs are shedding.(2)

Hair loss and stress

While normal hair growth appears relatively structured and predictable, what about hair loss? Hair loss is a condition that can affect people of any gender and age throughout life. In fact, there are many causes of hair loss from stress to nutrient deficiencies. High stress-levels have been linked to premature hair-loss conditions. These include telogen effluvium, trichotillomania and alopecia areata. 

Individuals with telogen effluvium suffer from hair loss due to hair moving quickly from the anagen phase into telogen and exogen phases. Thus their daily hair loss can often double or triple. 

Moreover, trichotillomania is a psychological condition in which affected individuals have an urge to pull hair from their scalp or other areas like eyebrows. 

In addition, alopecia areata also leads to hair loss, where hair falls out in small patches. In fact, this condition occurs when the immune system attacks the hair follicles therefore resulting in accelerated and increased shedding. 

However, the good news is that if hair loss is stress-induced, managing stress can be a solution to regaining normal and healthy hair growth.(3) 

Related reading

• How to lower cortisol
• Olivia Crighton, founder of Glasshouse Salon, on organic haircare

Which vitamin deficiency causes hair loss?

Hair loss is relatively common, with the condition affecting almost 50% of men and women by age 50. Moreover, people with hair loss are often curious to know which nutrients they need to prevent hair loss or to restore lost hair. In fact, many people self-administer supplements in the hope that they will help their condition. However, while hair growth may be influenced by calorie and protein malnutrition and micronutrient deficiencies, the relationship between diet and hair is a complex one. So which vitamin deficiency causes hair loss?(4)

The role of B vitamins

There is some evidence linking hair loss to biotin deficiency. In fact, biotin deficiency can manifest as skin rashes, conjunctivitis and alopecia. Although biotin deficiency is quite rare, it can occur with excess antibiotic use, anti-epileptic drug use and congenital enzyme deficiencies. However, in the absence of a diagnosed biotin deficiency, there is no evidence that supplementation is helpful. Nonetheless, biotin supplements are heavily marketed to consumers for hair loss. Overall, unless you have a diagnosed deficiency, these are unlikely to provide any benefit. 

Moreover, niacin (vitamin B3) deficiency has been associated with hair loss. Niacin deficiency can lead to a condition called pellagra. This condition displays symptoms such as diarrhoea, dementia and dermatitis. Moreover, alopecia is also a common occurrence in individuals with pellagra. Fortunately, this condition is rare in many countries where niacin fortification of foods became compulsory. In fact, in developed countries, alcoholism is the leading cause of this disease. However, there is limited data available on the impact of niacin supplementation on hair growth in the absence of a clinical deficiency.(5)

The sunshine vitamin and hair loss

We know that vitamin D is essential for various functions in the body, from maintaining healthy bones to supporting our immune system. Vitamin D deficiency can occur with inadequate sun exposure, obesity and fat malabsorption. Moreover, a study of women with telogen effluvium or female pattern hair loss found that their vitamin D levels were significantly lower compared to a control group. Furthermore, the lower the vitamin D levels, the more severe the alopecia. Nonetheless, there is insufficient data to support vitamin D supplementation for hair loss. However it is important to ensure that your vitamin D intakes are adequate, which we will discuss later.(6)

Vitamin C to support iron absorption

In addition to being a potent antioxidant preventing free radical damage, vitamin C plays an essential role in our body’s absorption of iron. Therefore vitamin C intake is crucial in individuals whose hair loss is caused by iron deficiency. In fact, iron deficiency is the most common nutritional deficiency globally and it contributes to telogen effluvium. Thus, not only should we be ensuring an adequate iron intake in our diet, we should also consume enough vitamin C through foods to ensure proper iron absorption. 

More than just vitamin deficiencies

Although vitamin deficiencies can contribute to hair loss, overall diet patterns seem to play a major role in hair growth. The question is not as simple as “Which vitamin deficiency causes hair loss?”. In fact, restrictive diets which are either low in calories, proteins or micronutrients can lead to hair loss. Although the exact mechanisms are not clear, it seems that adequate caloric intake along with protein, vitamins, minerals and essential fatty acids all play a role in nourishing the hair follicle, subsequently encouraging healthy growth. A study found that following a few months of severe caloric restriction through a crash diet weight loss program, some people developed telogen effluvium. It may be that extreme dietary calorie restriction impacts the energy supply to the hair matrix.(7)

Meeting your micronutrient requirements

In addition to vitamins, minerals are also involved in the maintenance of healthy hair and support of hair growth. In fact, iron and zinc deficiencies are linked with hair loss. The first step in ensuring you are meeting all of your vitamin and mineral requirements is to start from your diet. Eating a wide variety of fruits, vegetables, nuts, seeds, healthy fats and protein will decrease your risk of developing nutritional deficiencies. 

If you are struggling with getting enough of a specific nutrient in your diet, sometimes a small change is all you need to rectify the situation. For example, many people may struggle to get enough vitamin D in the winter months and vitamin D from food alone is not always enough to meet requirements. However, a great natural food source of vitamin D is hemp. In fact, hemp seed oil and hemp protein powder are rich in naturally occurring vitamin D which is required to support your immune system, strong bones and normal hair growth. 

Furthermore, sweet potato is one of the best vegetable sources of biotin. Our organic rosemary sweet potato crackers contain biotin-rich sweet potato to help you meet your daily biotin requirements. Another B vitamin involved in hair growth, niacin, is found in foods such as chia seeds and almonds. These are easy to incorporate into your diet as a snack or in your morning porridge/cereal to get your daily dose of niacin without the need for supplements. 

Variety is key