Protein, iron and zinc: what hair needs

Hair needs many nutrients, but three stand out for the evidence linking them to hair loss: protein, which the strand is made of; iron, whose lack is associated with hair loss in women even without anaemia; and zinc, which appears lower in several types of hair loss.

The golden rule is simple: get these nutrients mainly from food, and turn to supplements only when blood tests confirm a deficiency. Excess does not make hair grow more and can have adverse effects, especially with zinc and iron.

In this guide we explain how much each person needs according to the official European references, which foods contain them, how to improve absorption, who is at higher risk of deficiency and when supplements help or harm.

Protein: the raw material of the hair strand

Why it matters

A hair strand is made mostly of keratin, a protein. The follicle, which produces the strand, is one of the structures in the body where cells divide fastest. When protein is lacking, the body uses it first for the vital organs and muscle, and hair suffers: it becomes thinner, grows more slowly and sheds more.

How much you need

• Healthy adults: the European Food Safety Authority (EFSA) sets the reference at 0.83 g of protein per kg of body weight per day. For a person weighing 70 kg, that is about 58 g a day.
• During weight loss: an expert review suggests about 1.2 to 1.6 g per kg per day, with 25 to 30 g at each main meal (Leidy et al., 2015). We explain this in Losing weight without losing hair.
• Pregnancy, breastfeeding and older age: needs increase.
• Kidney disease: the amount should be set with your doctor.

Spreading it through the day

More important than a large plate at dinner is having a source of protein at every main meal. Breakfast is where it most often falls short: an egg, plain or Greek yoghurt, fresh cheese or turkey ham will do.

Animal and plant sources

• Animal: fish, meat, eggs, dairy. They contain all the essential amino acids in good proportion.
• Plant: pulses (beans, chickpeas, lentils, peas), soy and its derivatives (tofu, tempeh), nuts and seeds. Combining pulses with cereals over the day provides all the amino acids.

Signs of too little protein

Thinner, more fragile hair, diffuse shedding, nails that break, loss of muscle mass, slow wound healing and, in severe cases, swollen legs.

Iron: the most studied in female hair loss

What the evidence says

A meta-analysis of 36 studies, with more than 10,000 participants, found that women with non-scarring hair loss have significantly lower ferritin than women without hair loss, on average 18.5 ng/mL lower. The difference was greater before menopause. Interestingly, anaemia was not more common: what was low were the iron stores (Treister-Goltzman et al., 2022).

It has not yet been shown that correcting ferritin increases hair density in every case. But correcting an iron deficiency is always good for health, and many specialists regard it as part of treating hair loss.

How much you need

According to the European EFSA references:

Women of childbearing age need more because of menstrual losses. Pregnancy and the postpartum period further increase the risk of deficiency.

Haem and non-haem iron

• Haem iron, from foods of animal origin (meat, fish, shellfish): well absorbed.
• Non-haem iron, mainly from plant sources (pulses, green vegetables, cereals, nuts, seeds): less well absorbed.

How to absorb more iron

Source: EUFIC, based on EFSA references.

The "normal" ferritin

Laboratories often consider a ferritin above 10 to 15 ng/mL normal. But in hair loss, values below 30 to 40 ng/mL may already reflect insufficient stores. Interpretation should be medical, because ferritin rises with inflammation. Learn more in Blood tests for hair loss: what to ask for.

Zinc: important, but at the right dose

What the evidence says

Zinc takes part in hundreds of reactions in the body, including cell division and protein synthesis, both essential to the follicle. In a study of 312 patients with different types of hair loss, blood zinc was lower than in people without hair loss, in every group: alopecia areata, male pattern baldness, female hair loss and telogen effluvium. Values below 70 µg/dL were more frequent in alopecia areata and in effluvium (Kil et al., 2013). After bariatric surgery, zinc was also lower in those with hair loss.

Severe zinc deficiency causes hair loss, skin problems and poor wound healing. But it is uncommon in people who eat a varied diet, and there is no good evidence that supplementing without a deficiency helps the hair.

How much you need

The 2023 Nordic recommendations, which follow the EFSA approach, give the following for a diet with an average phytate content:

People who eat a lot of wholegrain cereals and pulses, which are rich in phytates, need a little more, because phytates reduce absorption.

Where to find it

Meat, shellfish (especially oysters and cockles), dairy, eggs, pulses, seeds (pumpkin, sesame), nuts and wholegrain cereals.

Beware of excess

The tolerable upper intake level of zinc for adults is 25 mg a day, including food and supplements (Nordic Nutrition Recommendations, 2023). High, prolonged doses can cause nausea and vomiting and, above all, reduce the absorption of copper and iron, leading to copper deficiency, which can cause anaemia and neurological problems. Many "hair" supplements contain doses close to or above this limit.

Foods that combine all three

Approximate values per usual portion. They vary with the species, the brand and the way it is prepared.

Meal ideas that add up

• Black-eyed bean stew with a little meat and pepper salad: protein, haem and non-haem iron, vitamin C.
• Chickpea curry with spinach and an orange for dessert.
• Grilled sardines with tomato salad and mixed-grain bread.
• Seafood rice or clams Bulhão Pato style with salad.
• Spinach omelette with pumpkin seeds on top of the salad.
• Vegetarian bowl: tofu, lentils, quinoa, roasted pepper and seeds.

Leave coffee and tea until one to two hours after the main meals.

Who is at higher risk of deficiency

If you belong to one of these groups and have hair loss, it is worth talking to your doctor about blood tests. See also Very restrictive diets and hair loss and Iron and vitamins after childbirth.

Supplements: when they help and when they harm

When they make sense

• Iron: when blood tests show low ferritin. The dose, form and duration are set by the doctor. One study showed that taking iron on alternate days may increase absorption (Stoffel et al., 2020). Replenishing the stores usually takes 3 months or more.
• Zinc: when there is a confirmed deficiency or a high risk, such as after bariatric surgery, always with a set dose and duration.
• Protein powder: only when diet is not enough, for example with a poor appetite; it should not replace meals on an ongoing basis.

When they do harm

• Iron without a deficiency: it does not help the hair, causes constipation and nausea and, in people prone to accumulating iron (haemochromatosis), can be dangerous.
• High, prolonged doses of zinc: can cause copper deficiency, with anaemia and neurological problems. Respect the limit of 25 mg a day in total.
• Adding up several supplements: it is easy to exceed the limits without realising, because many multivitamins and "hair" products already contain iron and zinc.
• "Hair" supplements with biotin: biotin can distort thyroid and other tests. Stop it before having tests and tell your doctor.

The practical rule

Blood tests first, then supplements. And bring every pack you take to the appointment.

When to seek a medical assessment

At Luxmed, the Hair Medicine consultation assesses the cause of hair loss with trichoscopy and, when indicated, blood tests, and determines whether any deficiency needs correcting.

This article is for information only and does not replace a medical consultation.

Frequently asked questions