Hair Physiology

Hair Physiology

Protein synthesis of the hair takes place in the matrix cells of hair bulb at the base of hair follicle. The majority of hair protein is keratin. Keratin is aggregates of proteins that contain sulfur. These synthesized protein and keratin determine hair strength and durability. Hair consists of proteins (65 – 95 percent), lipids (1- 9 percent), trace elements, polysaccharides and water. Hair grows at different rates in different people. Hair color is created by pigment cells producing melanin in the hair follicle. With aging, pigment cells die, and hair turns gray.

In the scalp, each hair steadily grows, approximately 1⁄2 inch per month and continuously for 3–5 years then stops. Old hair is shed and new hair starts to grow from the same follicle. A typical scalp has about 120,000-150,000 strands

of hair, and sheds about 50 to 100 strands daily. Each hair follicle undergoes many cycles of degeneration and regrowth throughout one’s entire life. During the neonatal period and throughout adolescence, scalp hairs become progressively thicker because such follicles gradually enlarge with each new hair cycle.

Figure 1: Hair anatomy[Adapted from: http://www.hairtx.com/hair-growth-procedures-dallas/hair-anatomy/]

Nutrients for Healthy Hair

“Healthy hair” is strong and shiny hair that is appropriately growing out of every hair follicle in a healthy scalp. The best way to promote healthy hair is eating a healthy, balanced diet to maintain or improve overall health. The essential nutrients needed for healthy hair are protein, iron, zinc, vitamin D, and biotin. The requirements for these nutrients should follow Dietary Reference Intakes (DRIs) which is set for general population to have general good health.

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