Sudden, patchy or rapid hair loss is a medical matter, not a nutritional one. Alopecia areata, thyroid dysfunction, iron deficiency anaemia and several medications all cause it, and all are diagnosable. Ask for bloodwork before you change your diet.
This guide is about gradual thinning and reduced density — the version most people experience.
Hair is the slowest-reporting system you have, and that delay is why almost nobody works out what caused it.
What shows at your scalp today reflects what was happening in your body roughly three months ago.
A hair sits in a growth phase for years, then a resting phase, then it sheds. A stressor — illness, surgery, a crash diet, a genuinely awful few months, childbirth — pushes an unusual number of hairs into resting simultaneously. They shed together about three months later.
Which means the shedding you notice in September belongs to June. And you have almost certainly already blamed a shampoo you started in August.
Why hair goes first
Your body triages, and hair is at the bottom of the list. It is not required for survival.
Under stress, illness or insufficient food, resources go to organs, immune function and repair. Hair gets what's left. Which is unhelpful cosmetically and genuinely useful diagnostically: thinning hair is often the earliest visible signal that something upstream is short.
Most commonly, two things.
Zinc and protein
The two most common gaps
Oats · Lentils · Tofu · Quinoa · Pumpkin seeds · Cashew
Protein. Hair is made of keratin, which is protein. Insufficient protein means insufficient raw material, and hair is where the shortfall shows first because it's the least important place. This is a common finding in people eating well but not eating enough — a pattern that shows up frequently in under-fuelled training.
Zinc. Required for the protein synthesis and cell division that hair follicles depend on. Zinc deficiency is one of the better-documented nutritional causes of hair loss, and it's more common in plant-based diets because plant zinc is absorbed less efficiently.
Pumpkin seeds and lentils appear on that list twice over — both are zinc and protein, which makes them the two highest-value items. Pumpkin seeds also show up on the low mood and heavy period lists, which is worth noticing if more than one of those applies to you.
The other three worth checking
Zinc and protein are the common ones. Three more come up often enough to name:
Iron. Particularly relevant with heavy periods. Low ferritin is a well-established cause of diffuse thinning, and it's a blood test, not a guess.
Vitamin D. Involved in the follicle cycle. Frequently low, especially through winter.
Thyroid. Both under- and overactive thyroid cause hair changes. If thinning comes with fatigue, temperature sensitivity or weight change, this is the first thing to test.
All three are bloodwork. Get the bloodwork.
What the scalp itself needs
Nutrition is upstream. There's a smaller, real, downstream piece:
Circulation. Follicles are fed by blood supply. A few minutes of scalp massage genuinely increases local circulation — and it's free, which puts it above every product.
Not stripping the barrier. Your scalp is skin. Harsh detergents, very hot water and daily washing dry it out, and an irritated scalp is a worse growing environment.
Reducing traction. Tight styles, worn constantly, pull hair out mechanically. Nothing nutritional fixes that.
The hair shelf covers the products worth owning — there are four, and only two matter much.
The timeline, and why people quit
This is the part that defeats everyone.
- Months 0–3: you change things. Nothing happens. The shedding may even continue, because it's still reporting on the old period.
- Months 3–6: shedding slows. New growth begins — short fine hairs at the hairline, easy to miss.
- Months 6–12: density visibly improves.
Judge it at six months, in a photograph, in daylight. Not in a mirror on a bad morning. Take the photograph today so you have something to compare against, because your memory of your own hair is unreliable in both directions.
Where people go wrong
- Blaming the recent thing. The cause was about three months ago. Look back at that period instead.
- Buying a product before checking protein intake. Hair is made of protein. Start there.
- Not getting bloodwork. Ferritin, vitamin D and thyroid are three tests that answer most of this properly.
- Judging it at six weeks. You are looking at hair that formed before you changed anything.
- Eating well but not enough. Undereating is a stressor, and hair is the first thing deprioritised.
- Washing daily with something harsh and then treating the resulting irritation as a separate problem.
The one thing
Take a photograph of your hairline and your parting today, in daylight, and put it somewhere you won't look at it for six months.
Then add pumpkin seeds and lentils to the week. Zinc and protein in two foods — and in six months you'll have actual evidence rather than a feeling.