Why Is My Hair Thinning? The Nutrient Deficiencies Behind It (And What to Do)

Noticing more hair on your brush than usual? Finding strands on your pillow, in the shower drain, or just sensing that your hair feels thinner than it used to? First things first: take a breath. Hair thinning is incredibly common in women, and in many cases, it has a straightforward explanation rooted in what your body is (or isn't) getting nutritionally.

This isn't about vanity. Hair is one of the first visible signs that something is off internally, and understanding the connection between nutrition and hair health can be genuinely empowering. So let's get into what's actually going on.

The short version: Hair follicles are metabolically active and nutrient-hungry. When your body is running low on certain vitamins and minerals, it prioritises vital organs over hair growth. Your follicles get less of what they need, and shedding increases. The good news? Deficiencies are correctable.

Why Nutrition Affects Your Hair

Hair follicles are among the fastest-dividing cells in the human body, which means they have a high demand for energy and nutrients. When that supply drops, even slightly, the hair growth cycle is one of the first things to suffer.

There are three phases to the hair growth cycle: the growth phase (anagen), the transitional phase (catagen), and the resting phase (telogen), during which hairs naturally shed. Nutrient deficiencies can push follicles out of the growth phase prematurely and into the resting phase, causing what's known as telogen effluvium - a type of diffuse shedding that can affect the whole scalp rather than one specific area.

The key thing to understand is that this shedding often shows up weeks or even months after the deficiency begins. So if you're losing more hair now, the nutritional trigger may have started much earlier.

The Key Nutrient Deficiencies Linked to Hair Thinning

Most women are deficient in at least one of the following, often without knowing it. Here's what the evidence says about each.

Iron: The Most Common Culprit

Iron deficiency is the most frequently cited nutritional cause of hair thinning in women, and it's particularly prevalent among those with heavy periods, restrictive diets, or a history of pregnancy. Iron is essential for carrying oxygen to your hair follicles; without enough of it, follicles are starved of the oxygen they need to sustain growth.

What makes iron deficiency tricky is that your haemoglobin levels (the standard blood test marker) can appear normal while your ferritin levels (stored iron) are dangerously low. Research suggests that ferritin levels below 70 µg/L may be sufficient to trigger hair shedding, even when you're not technically anaemic. As Dr Melissa Piliang of the Cleveland Clinic notes, iron deficiency is often an early, overlooked sign of hair shedding in women precisely because it impairs oxygen delivery to follicles before other symptoms appear.

Vitamin D: The Sunshine Deficiency

Vitamin D plays a direct role in regulating the hair follicle cycle. Low levels have been consistently linked to conditions like alopecia areata and telogen effluvium, and deficiency is widespread in the UK given our limited sun exposure for much of the year.

The Cleveland Clinic recommends supplementing with 2,000 to 4,000 IU of vitamin D to support hair density improvement in those who are deficient. If you haven't had your vitamin D checked recently, it's worth asking your GP.

Zinc: Quietly Undermining Your Follicles

Zinc supports protein synthesis and helps hair follicles repair and recover. A deficiency leads to brittle, fragile hair and increased shedding, and it's particularly common in women who are pregnant, breastfeeding, or following plant-based diets. Unlike iron, zinc deficiency rarely shows up as an obvious symptom until hair changes are already noticeable.

B Vitamins (Including Biotin and B12)

B vitamins are essential for hair cell production and strength. Deficiencies disrupt the process at a cellular level, leading to thinning and breakage. B12 in particular is a concern for women who eat little or no animal protein, as it's found almost exclusively in meat, fish, eggs, and dairy.

Biotin gets a lot of attention in the hair supplement space, and while it does play a role, severe biotin deficiency is actually quite rare in women eating a varied diet. It's worth including, but it's not the magic bullet it's often marketed as.

It's Not Always Just Nutrition

Nutrient deficiencies are a major piece of the puzzle, but they're rarely the whole picture. A few other factors are worth being aware of.

• Stress can push up to 70% of your hairs into the resting (shedding) phase simultaneously, according to the Cleveland Clinic. This is why many women notice significant hair loss two to three months after a stressful period, illness, or major life event.

• Hormonal changes during pregnancy, postpartum recovery, perimenopause, or thyroid disruption can all disrupt the hair growth cycle independently of nutrition.

• Genetics play a role in female pattern hair loss, which tends to present as gradual, diffuse thinning rather than bald patches.

One important note from Harvard Health: over-supplementing certain vitamins, particularly vitamins A and E, can actually worsen hair loss rather than improve it. More is not always better. If you're considering supplementation, it's worth focusing on formulas designed specifically for hair health rather than taking high-dose individual vitamins without guidance.

What to Do Next

If you're concerned about hair thinning, the most useful first step is to get a blood test. Ask your GP to check your ferritin (not just haemoglobin), vitamin D, zinc, and B12 levels. These are the markers most commonly associated with hair shedding in women, and knowing your levels gives you something concrete to act on rather than guessing.

Beyond testing, there are a few practical things worth doing now:

1. Review your diet. Are you getting enough iron-rich foods (red meat, lentils, spinach), oily fish for vitamin D, and varied protein sources? Dietary gaps are often the easiest to address.

2. Be consistent with supplementation. Hair grows slowly; even if you correct a deficiency, you may not see visible results for three to six months. Consistency matters more than intensity.

3. Reduce where you can. Chronic stress and poor sleep both impair nutrient absorption and disrupt hormonal balance. Addressing those factors alongside nutrition gives your hair the best environment to recover.

If you're looking for a convenient way to cover the key bases, Nurtured Club's hair gummies are formulated with the nutrients most commonly linked to hair health, including biotin, zinc, and vitamins that support the hair growth cycle, in a daily format that's easy to stick to. No complicated regimens, just consistent nourishment.

The bottom line: Hair thinning is your body sending a signal. In many cases, that signal points to a nutrient gap that's entirely addressable. Get tested, eat well, supplement smartly, and give it time.