The Science of Healthy Hair, Hair Loss and How to Regrow Hair

KEYPOINTS

• 01

  Hair loss starts long before people notice it

  By about age 50, roughly half of men and women have noticed significant hair loss, and up to 85% of them feel anxious enough to seek treatment. Huberman stresses that the loss is gradual from about 30 to 50 and is usually noticed only under bright bathroom light. Psychological state can affect hair color and growth, and hair changes in turn affect mood.

• 02

  Each hair comes from a stem cell niche that needs blood flow

  Below the skin, a bulb holds stem cells that build the hair's keratin from the bottom up, melanocytes that pigment it, a sebaceous gland whose sebum seals and protects the follicle, and capillaries supplying oxygen and nutrients. Growth is metabolically active, which is why so many folk remedies — scalp massage, tingling oils, avoiding hats, light devices — aim to raise blood flow. None of these alone robustly regrows hair.

• 03

  Three phases: anagen, catagen, telogen

  Anagen is the growth phase; catagen is when the hair recedes from the bulb outward; telogen is rest, when the bulb pinches off. Scalp follicles can re-enter anagen if stem cells, blood supply and the right hormonal signals remain. Because anagen is long, treatments take many months to show results.

• 04

  Hormones are the accelerators and brakes

  IGF-1 extends anagen, and cAMP signaling also supports growth. PDE (a phosphodiesterase) and TGF-beta 2 act as brakes. DHT, made from testosterone by 5-alpha reductase, shortens anagen and promotes catagen and telogen, so most treatments target DHT or the enzyme. Pattern hair loss reflects where androgen receptors sit on your scalp.

• 05

  The 'mother's father' rule is a myth

  You can't predict your hair loss from a photo of your maternal grandfather. Huberman says the androgen-receptor pattern is inherited through the mother's side, so logically you'd look to your mother's mother, but women's hair loss is usually less visible or hidden by longer hair.

• 06

  Minoxidil works through blood flow, with real side effects

  Oral doses range 20-fold, from 0.25 to 5 mg a day; topical is typically 5% once daily and can still reach the bloodstream through the follicle. Side effects can include fluid retention and raised prolactin (lower libido, lethargy). Huberman advises starting at the lowest dose, 0.25 mg orally. Like low-dose tadalafil (2.5–5 mg, which some doctors prescribe), it mainly preserves hair rather than reversing loss.

• 07

  Topical caffeine may rival minoxidil for slowing loss

  Caffeine inhibits PDE, indirectly boosting IGF-1, and appears to reduce stem cell death. Huberman cites head-to-head data showing topical caffeine about as effective as minoxidil for preventing loss, without the blood pressure or prolactin issues. He notes that much of the evidence is from cell studies and concentrations haven't been systematically tested. Use about three times a week. Drinking coffee won't help, since adenosine receptors elsewhere soak up most of it.

• 08

  Finasteride is the most potent mainstream option, but dose carefully

  Huberman says it can increase hair count by up to 20%, reduce loss in about 90% of users, and thicken hair 20–30%. DHT suppression is logarithmic: very low doses already cut blood DHT by about 50%, with diminishing returns up to 5 mg. His suggested starting points, ideally with a doctor and hormone monitoring: 0.5–1 mg oral daily, or 1 mL of 0.25% topical once a week. Wait up to about 25 weeks before raising the dose.

• 09

  Post-finasteride syndrome is a serious, poorly understood risk

  Mostly in men in their 20s and 30s, stopping finasteride has been followed by severely reduced libido and erectile function and depression, sometimes suicidal. Older men taking about 5 mg for the prostate rarely report it. Huberman suggests DHT may keep shaping the hypothalamus and the brain-genital axis into the 20s and 30s. Topical finasteride is reported to cause 30–50% fewer or milder side effects.