Nutrients and Supplements for Hair Cycle Support and Hair Loss Management
Hair loss is a prevalent condition and poses serious negative impacts on the self-esteem and quality of life of those affected.
Currently, there is an expanding market of nutraceutical and herbal supplements formulated to support the hair cycle and increase hair growth.
To best support our patients in alternative and complementary treatment approaches, it is necessary to understand the physiology of hair growth, the role of nutrient deficiencies, and the evidence around associated nutraceutical and herbal ingredients.
The Hair Cycle
Hair grows at a rate of 1-1.3cm/month and does so through a cycle of three distinct phases.1 There are approximately 100,000 hair follicles on the scalp, and each undergoes 10-20 cycles over its lifetime.2 Changes in the normal cycle of hair growth can result in hair disorders, and thus, are important to understand.
The three phases of the hair cycle are:
Anagen (the growth phase)
Catagen (the involution phase)
Telogen (the rest phase)
Anagen
Anagen is a period of active growth that can last for 2-7 years.3 It is where pigmented hair shafts are produced, and where the maximal length and thickness of a hair shaft are determined. At a given time, approximately 84% of the scalp hair follicles are in the anagen phase.
Catagen
Catagen can be thought of as the transition between growth and rest. Here, cell division and pigmentary activity cease, and instead, apoptotic activity in the lower component of the hair follicle causes it to shorten.4 This phase lasts 2-4 weeks, and affects 1-2% of scalp hair follicles at a given time.
Telogen
Telogen is the resting, or dormant phase of the hair cycle and affects 10-15% of scalp follicles at a given time.3 This phase lasts approximately 3 months and is followed by exogen, where the telogen hairs are shed; approximately 100 telogen hairs are shed per day.4
Common Hair Loss Pathologies
Different conditions that affect the hair cycle present with distinct patterns of hair loss and have a distinct pathophysiology. In order to make the appropriate treatment recommendations, it is important to assess the patient’s presentation and potential diagnosis. Some of the common hair loss conditions addressed in nutrition and supplement research include telogen effluvium, alopecia areata, and androgenic alopecia.
The Impact of Nutrition on the Hair Cycle
Caloric restriction and weight loss diets
The matrix cells of the hair follicle have a high turnover rate during the hair cycle, and thus, require adequate energy sources.10 With this in mind, an association between caloric restriction and hair loss is not surprising. Some studies suggest telogen effluvium can be secondary to weight reduction programs;11 it is thought that a daily intake of less than 1000 kcal can lead to hair loss.12 In a case report of 9 patients who underwent drastic weight reduction, there was an increased proportion of follicles in the telogen phase (25-50%), and diagnoses of TE.
Vitamin D
Vitamin D has been found to play a role in the hair cycle through the binding of vitamin D receptors (VDRs), found in the epidermal keratinocytes and mesodermal dermal papilla cells of the hair follicle.13 In murine hair follicles, the VDRs have been shown to have the highest activity in the anagen phase,14 and are thought to be required for the initiation of anagen.15 Furthermore, vitamin D is also thought to affect the hair cycle, specifically in conditions of alopecia areata, due to its immunomodulating effects.13
Vitamin C
Hair is composed of keratin proteins, and vitamin C is considered to be essential for the cross-linking of keratin fibers.12,16 For this reason, it is thought to play a role in the strength and growth of hair.3 Although there are no clinical studies of the role of vitamin C on hair health, vitamin C may play an important role in iron absorption, which may impact the hair cycle.10
Iron
Iron plays a role in the hair cycle through acting as a cofactor for the rate-limiting enzyme in DNA synthesis.17 This is especially important for cells with high turnover rates, such as hair follicles. Additionally, its role is implicated in the hair cycle through its ability to regulate the expression of 6 different genes of the hair follicle: CDC2, NDRG1, ALAD, RRM2, Decorin, and DCT.10
Zinc
The role of zinc in the hair cycle is not fully established, but it is known to be important for the keratinization of hair.18 In humans, there are proteins called metallothioneins that bind zinc and have been found to be active in proliferating keratinocytes, such as those of the hair matrix.19 Further, in mouse models, zinc transporters have been found on the progenitor cells of the outer root sheath of hair follicles, and the depletion of these transporters has led to inadequate development of the hair follicles.19 In addition, zinc may potentially play a role in the hair cycle through its anti-oxidant effects when bound to the enzyme, copper/zinc superoxide dismutase.17
Copper
Like zinc, copper may potentially affect the hair cycle through its antioxidant activity in the copper/zinc superoxide dismutase.17 This trace element also assists with cross-linking keratin fibers, and thus, contributing to hair strength.12
Assessing for Nutritional Deficiencies
Iron
Iron deficiency is associated with hair loss, thinner anagen hairs, and in African hair, has been associated with band-like colour changes.12 Though there is some discrepancy in the literature, a 2005 review has highlighted the role of low ferritin levels in AA, TE, AGA, and diffuse hair loss.20 In addition, iron supplementation has been found to decrease the percentage of hairs in telogen relative to baseline, and has been found to decrease hair shedding relative to placebo.21
Serum ferritin levels are considered to be a good indicator of iron stores in the body. Some sources suggest that a level of 40 mg/L should be maintained, while others suggest a level of 70 mg/L.12 Furthermore, it is suggested that amino acids may enhance the uptake of iron. For example, one study has found that concurrent supplementation with 1.5 g of L-lysine significantly increased serum ferritin concentrations when added to 100 mg/day of elemental iron.21 As previously mentioned, the use of vitamin C can also help increase the absorption of iron.10
Overall, the current evidence suggests deficiency in iron can contribute to hair loss and suggests that restoring iron levels can confer benefit. However, at this time there are no clear guidelines and criteria for assessing serum ferritin in patients with hair loss, indicating the need for further research.
Vitamin D
Several studies have correlated low levels of vitamin D with hair loss. A 2018 systematic review and meta-analysis has found serum 25-hydroxyvitamin D levels to be significantly lower in AA patients, relative to control.22 The authors of this paper suggest it is appropriate to measure vitamin D levels in patients with AA. Further studies have also demonstrated a negative correlation between vitamin D serum levels and AA severity,23 and AA duration.24
Though there are some inconsistent findings, some research suggests that women with androgenic hair loss and women with TE have lower serum vitamin D levels relative to control groups.13
A 2019 review article states that vitamin D should be supplemented in these cases if found to be low.10 However, there is currently a lack of clinical trials on vitamin D supplementation in cases of hair loss, and so, further research will be needed to determine both the criteria of deficiency, and appropriate dosages for supplementation.
Zinc
Low serum levels of zinc have been associated with hair loss, and thin, brittle hair.17 In one paper, 4 out of 6 case-control studies found a relationship between low serum zinc and AA.17 In one of these studies, an inverse correlation between serum zinc levels and AA severity was demonstrated.25 Interestingly, the addition of 1.5-2 g of L-lysine supplementation was shown to improve mean zinc concentrations.21 The mechanisms for this are unclear although one hypothesis is that L-lysine may enhance zinc absorption.
Another study also found a relationship between low serum zinc levels and TE, and AGA in males and females.26 Here, the authors concluded that zinc supplementation should be considered when levels are below 70 μg/dL.26 However, further research has not been able to consistently establish the connection between low zinc levels, TE, and AGA.10 In addition, the effects of zinc supplementation in cases of hair loss have also been inconsistent.10 A recent review paper concludes that assessing serum levels of zinc is currently not recommended.10
Further considerations with zinc supplementation
If a patient is supplementing with zinc, or is considering supplementation, it is important to keep the following in mind:
High levels of zinc intake can lead to copper deficiency, and can lower serum ferritin.12 A daily 50 mg zinc supplement over a 10 week period was associated with a decrease in copper levels and in serum ferritin levels in adult females.27
Multivitamin formulations with a 1:1 iron to zinc ratio should be avoided as these two minerals can compete and decrease the uptake of iron.21 Instead, a ratio of 3:1 (iron to zinc) is recommended.21
Copper
Currently, there is limited evidence for a relationship between low serum copper and hair loss.17 According to one study, patients with AA have lower hair and serum copper levels relative to control.28 However, all other studies have not found a difference in serum copper between AA patients and control patients.17 Assessing for and supplementing with copper for cases of hair loss is not recommended at this point in time.
Additional Supplements Considered for Hair Support
Biotin
Biotin, also referred to as vitamin H or B7, is a nutrient commonly marketed for hair support. This comes from evidence demonstrating a link between biotin deficiency and hair loss.29 However, the reference daily intake is 30 μg for adults, and is easily met in those who consume a normal diet; biotin deficiency is very rare.12 Currently, one study has demonstrated a benefit in hair growth when using biotin in combination with zinc and topical clobetasol,30 but overall, there is insufficient research demonstrating the singular role of biotin as an intervention for conditions of hair loss. Furthermore, in patients who are supplementing with biotin, it is important to note that this vitamin can interfere with lab test results such as cardiac troponin, parathyroid hormone, thyroid hormone, and follicle stimulating hormone, among several others.31,32
Probiotics
In studies on mice, the consumption of Lactobacillus reuteri was associated with increased hair growth.33 L. reuteri was also found to upregulate the anti-inflammatory cytokine, IL-10, and downregulate the inflammatory cytokine, IL-17, and which in turn, has been associated with increased hair follicles and anagen phase predominance.33 In another study, mice supplemented with Lactococcus lactis subsp. cremoris were found to have reduced hair loss relative to controls.34 The gut microbiome and its relation to hair, as well as all aspects of health, is an area of emerging and promising research. However, there are no clinical studies looking at the use of oral probiotics for hair growth. Further research and clinical trials will be needed to better assess the mechanism and efficacy of probiotics for hair support.
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Reference: Learnskin