The 6 key biomarkers for your hair health

This listicle is inspired by our 2-part series on hair loss:

• Hair loss 1/2: what your body is trying to tell you

• Hair loss 2/2: practical steps you can take

Hair loss is multifactorial. But among the most underestimated levers, nutritional deficiencies rank high. Certain nutrients play a direct role in the hair cycle, and a simple blood test can reveal imbalances that are easy to correct. Here are the 6 biomarkers to watch to understand what your body is trying to tell you.

1. Iron and ferritin: the fundamental duo of the hair cycle

The link between iron status and hair loss is one of the most documented in dermatology.

Why it matters: Iron deficiency or low ferritin may be associated with certain forms of diffuse hair loss, especially in women, even without frank anemia. Hair, as a metabolically active tissue, depends directly on adequate iron supply to maintain its growth cycle.

Warning signs:

• Diffuse, progressive hair loss

• Context of dietary restriction or rapid weight loss

• Low ferritin even without anemia

• Diet low in heme iron sources

Key takeaway: Plant-based iron absorption is improved by vitamin C. Combine legumes with citrus fruits, spinach with peppers. Have your ferritin checked if hair loss persists.

2. Zinc: the cofactor of hair protein synthesis

Zinc is involved in many cellular mechanisms, including the synthesis of keratin that makes up hair.

Why it matters: A zinc deficiency can contribute to disrupting the hair cycle, particularly in contexts of malabsorption, insufficient intake, or restrictive diets.

Warning signs:

• Known or suspected malabsorption

• Restrictive or unsupplemented vegan diet

• Insufficient intake of animal protein sources

• Hair loss combined with other deficiency signs

Key takeaway: The best dietary sources of zinc are oysters, beef, pumpkin seeds, cashews, and eggs.

3. Vitamins B12 and B9: the cellular metabolism engine

These two vitamins actively participate in cell renewal, including that of the hair follicle.

Why it matters: B12 and B9 deficiencies can be found in some people experiencing hair loss, particularly in the context of unsupplemented vegan diets, digestive issues, or prolonged medication use.

Warning signs:

• Vegan diet without B12 supplementation

• Chronic digestive disorders

• Prolonged use of certain medications

• Diffuse hair loss in these contexts

Key takeaway: B12 is mainly provided by animal products. B9 is found in leafy greens, legumes, and nutritional yeast. Blood testing is recommended if you are in a risk context.

4. Vitamin D: a marker not to overlook

Low vitamin D levels have been associated with certain forms of alopecia in several studies.

Why it matters: A vitamin D deficiency may be part of the terrain to correct when documented, even if it does not alone explain hair loss. It often fits into a broader picture of imbalances.

Warning signs:

• Insufficient sun exposure

• Persistent hair loss with no identified cause

• Documented deficiency on blood testing

Key takeaway: Vitamin D is mainly synthesized through sun exposure. When a deficiency is documented, adapted supplementation can be considered under medical advice.

5. Vitamin C: the antioxidant protector of the follicle

Vitamin C is involved in collagen synthesis and protects the hair follicle through its antioxidant properties.

Why it matters: Beyond its direct role, vitamin C improves plant-based iron absorption, creating an essential synergy for hair health.

Warning signs:

• Low intake of fresh fruits and vegetables

• Diet poor in citrus, peppers, kiwi, broccoli

• Hair loss combined with low ferritin

Key takeaway: Prioritize dietary sources: citrus fruits, kiwi, peppers, broccoli, strawberries, parsley, cabbage. The iron + vitamin C combination is a simple and effective reflex.

6. Omega-3: the inflammation modulator

Omega-3s play a plausible role in a global approach to hair health, primarily through inflammation modulation.

Why it matters: Chronic low-grade inflammation may be part of an unfavorable terrain for hair health, by altering the local follicle environment. Omega-3s can contribute to a more favorable terrain.

Warning signs:

• Diet low in fatty fish and nuts

• Global inflammatory terrain

• Imbalanced omega-6/omega-3 ratio

Key takeaway: Their specific effect on hair regrowth is less firmly established than their overall anti-inflammatory benefits. Diet (fatty fish, nuts) remains the preferred approach.

These 6 biomarkers form an essential nutritional foundation for hair health. But hair loss is multifactorial: lifestyle (stress, sleep, inflammation) also plays a fundamental role. A single lever is rarely sufficient. The most coherent approach combines several interventions and always begins by understanding what is happening in your body.

At Lucis, we analyze these biomarkers in their global context: ferritin, iron, zinc, B vitamins, vitamin D, and many other markers related to thyroid, sex hormones, inflammation, and metabolism. The goal: to help you understand your biological terrain, identify imbalances, and guide your actions in a targeted way.

The information in this article is provided for educational purposes only and does not constitute medical advice or a medical recommendation. In case of significant, sudden, localized, or persistent hair loss, medical or dermatological advice is recommended. Please consult a healthcare professional before modifying your diet or supplementation.