Eat all the protein you want (but without the right tools to convert it into hair)you're just spinning your wheels. Patients load up on biotin gummies for months, and then ferritin, that's stored iron, comes back at 15 ng/mL. Look, lab reference range says 15-150 is normal. For hair growth, ferritin needs to be above 70. Below 70, follicles literally shut down non-essential production.
Iron: The Most Common Deficiency I See
Iron deficiency is the single biggest nutritional cause of hair loss in premenopausal women. Truth is, around 30% of women aged 20-49 have low ferritin. Lose blood every cycle, and don't eat enough red meat. Or you're vegetarian. All adds up to hair loss. In reality, hair sheds diffusely. All over the scalp, not in patches. Ferritin test, about $35 without insurance. Honestly, under 40? Ask your doctor about ferrous bisglycinate instead of sulfate. Around 1 in 4 get constipation from ferrous sulfate.
Vitamin D: The Surprise Culprit
Vitamin D receptors are right on the hair follicle cells. Not activated?
The follicle can't cycle right.
65% of alopecia areata patients had low vitamin D, according to a 2021 International Journal of Dermatology study. Even without alopecia, levels below 20 ng/mL mean more shedding. Sunlight in Boston from November to March? Zero UVB. So vitamin D from sunlight? Not happening. Test first, then supplement 600-800 IU daily. Toxicity above 4000 IU? Rare but real.
Brittle hair breaking off mid-shaft-that's zinc deficiency, and not just shedding. High risk: vegans and Crohn's patients. Truth is, rDA sits at 8-11 mg. But I've seen patients pop 50 mg zinc lozenges for colds. Long-term? That much can cause copper deficiency-which also triggers hair loss. B12 deficiency? Diffuse shedding, just like iron deficiency. Over 50? Less stomach acid to extract B12 from food. In reality, mcg methylcobalamin sublingual tablet daily. Bypasses the whole problem.