Losing Your Hair? Check Your Iron

This is the best-supported nutritional deficiency that can drive hair loss.

Deficiencies of ​riboflavin​, ​biotin​, ​zinc​, ​iron​, or ​iodine​; ​iron overload​, selenium toxicity,​ and ​vitamin A toxicity can all cause hair loss, or in medical jargon, alopecia, but none of these has as much evidence for being a very common cause of hair loss as iron deficiency.

As reviewed here:

• In women with alopecia areata (round patches of hair falling out), serum ferritin was less than half the values of controls, but this was not true for women with alopecia totalis (the whole head) or universalis (losing hair all over the body). There was no difference in hemoglobin levels, showing that low serum ferritin was a more useful marker in this case.
  

• In women with androgenetic alopecia, which is known colloquially as male pattern baldness, and causes a receding hairline in men but not in women (in women it causes universal thinning), ferritin was 38% lower than in controls. In women under 40, the difference was even larger, 62% lower in cases than controls. Again, no difference in hemoglobin.
  

• In 40 women with androgenetic alopecia, 20 were treated with an antiandrogen and estrogen, and improvement was limited to women with ferritin over 40.
  

• In 100 women with androgenetic alopecia, the first 50 were tested and 36 of them had ferritin concentrations below that of the lowest control (40 mg/mL).
  

• In 106 women with telogen effluvium (diffuse hair loss 2-3 months after premature shifting of the hair from the growth phase to the resting phase in response to some trigger), there was no difference in iron status with controls. However, when they limited the analysis to women under 40, the ones with hair loss had 76% lower ferritin and 13% lower hemoglobin.
  

• A small (n=12) double-blind, placebo-controlled study in women with telogen effluvium found 72 mg iron and 1.5 g lysine per day led to 31% reduction in hair shedding vs 9% increase in placebo. The same protocol in 22 women reduced the percentage of hair in the telogen (resting) phase.
  

• In a 1963 study, in 18 female patients with diffuse hair loss, no skin disease, and iron deficiency, 37-40 mg elemental iron 1 to 2 tablets 3 times daily caused hair loss to cease.
  

• Another study, not reviewed in the previous reference, found that 97 men with male pattern baldness had 47% lower ferritin than 97 healthy controls (similar results in women), though other markers were not different and none had diagnosable iron deficiency.

Taking the two randomized controlled trials, while small and both in women, the distinction between a 31% reduction in hair shedding and a complete abolition of hair shedding likely results from the fact that the latter study was in women who were clinically iron deficient.

Thus, if you know you qualify as deficient it’s a much surer bet that fixing the deficiency will get rid of the hair loss.

But if suboptimal iron status is a major but incomplete part of the suboptimal energy metabolism in your hair follicle, getting your iron levels up is likely to provide very large but incomplete benefits.

Now, we know that no one really knows what ferritin is doing in serum or how to interpret it, but as I pointed out in Understanding Iron, serum ferritin will often, but not always, capture a state of iron deficiency.

But with a couple of small randomized trials and some animal experiments covered below, optimizing iron status seems like a very promising way to help with hair loss.

How Does Iron Help Hair Loss?

Some potential mechanisms mentioned in human studies include these:

• Iron is a cofactor for ribonucleotide reductase, which is rate-limiting for DNA synthesis and thus needed for cellular proliferation, and hair follicle cells have high differentiation rate so will depend on this enzyme.

• Stearyl CoA desaturase is an iron-dependent enzyme needed for oleic acid production, and loss of this enzyme causes hair loss in mice.

One study found that in human keritinocytes, iron deficiency impaired keratin expression while cysteine abolished this effect. Keratin is an important component of hair. It appears that cysteine upregulated ferritin, which helped retain iron in the cell that would have otherwise been depleted by the chelator they were using to induce iron deficiency. However, as I covered in Understanding Iron, hydrogen sulfide releases iron from ferritin. Cysteine is the main source of hydrogen sulfide. So it is also possible cysteine would support the dynamic release of iron from ferritin, making it available for use in iron-dependent enzymes.

This study found that topical application of 5-aminolevulinic acid (5-ALA, a precursor to heme, which contains iron), was slightly better at stimulating hair growth in mice than iron alone, but that topical application of both together was much better and was as effective as minoxidil, which is used for androgenic alopecia.

Minoxidil is thought to work by increasing blood supply to the follicle. This mouse study suggests the effect of iron is mediated by heme synthesis.

There was no change in cellular proliferation in this study, suggesting that the effect of iron is not only heme-dependent but is independent of ribonucleotide reductase-dependent DNA synthesis.

When taken in the context of the comparison to minoxidil, the most surface-level obvious explanation is that minoxidil works by increasing the volume of blood delivered, while iron plus 5-ALA works by increasing the amount of hemoglobin in the blood, both of which would increase oxygen delivery to the follicle.

Notably, however, heme has many functions outside of hemoglobin, including the antioxidant enzyme catalase, and parts of the electron transport chain needed to make ATP.

Further, the systemic delivery of oxygen would be improved by increased heme synthesis in red blood cell precursors of the bone marrow, so topical application is probably increasing heme synthesis in the follicle itself, and that is probably working through improved mitochondrial energy metabolism.

After all, if delivering oxygen to the hair follicle works, then you can bet the farm that improving energy metabolism in the hair follicle by any other means will work, because the whole point of delivering oxygen to the hair follicle is to use in in the mitochondrial respiratory chain to make ATP.

Iron is also a cofactor for thyroid peroxidase, and is every single bit as essential to thyroid hormone production as iodine is. Hypothyroidism is famous for causing hair loss.

Of course, the whole point of thyroid hormone is to increase the metabolic rate in response to the brain’s perception that ATP extraction from food is efficient and that there is enough food, and thus food molecules should be burned in a big metabolic fire to make and use lots of ATP.

So, all roads that lead to increased energy metabolism in the hair follicle support hair growth.

The Bottom Line

A beautiful head of hair is biological peacocking, the original form of peacocking, bragging to everyone around you that you have extra ATP the way some people buy Lambos and boats to show off their extra cash. There is a small but compelling dataset suggesting iron is commonly the limiting nutritional factor for ATP production in the hair follicle and that optimizing iron status is often the lowest-hanging fruit to improve energy metabolism and reduce hair loss. Optimizing iron status should be done with the Cheat Sheet along with the new “Key Insights” bulleted out in the Understanding Iron article.