Are you ever curious about how things work? We hear all the time to eat well and get our vitamins and minerals, but don't always know the underpinnings of why we need them.  

This post is for all the curious people out there. 

You've got this.

~Lindsey

How Does Hair Grow? The Science Behind Your Strands

Have you ever wondered about the magic behind your hair? It grows, falls out, and grows back in a seemingly endless cycle. One day you’re getting a trim, and a few months later, you need another one. But what’s really happening on your scalp to make this happen? The process is a fascinating blend of biology, genetics, and personal health.

Understanding the answer to "how does hair grow?" can empower you to take better care of your locks and recognize when something might be disrupting the process. This guide will break down the science behind your strands, from the hidden follicles beneath your skin to the three key phases that every single hair goes through.

The Foundation of Growth: The Hair Follicle

Before we can understand how hair grows, we need to look at where it comes from: the hair follicle. A hair follicle is a tiny, tunnel-like structure in the outer layer of your skin, the epidermis. You are born with all the hair follicles you will ever have—around 5 million on your body and about 100,000 on your scalp. You can't grow new ones later in life.

At the base of each follicle is the papilla, which contains tiny blood vessels. These vessels supply the blood that delivers the oxygen and nutrients necessary for hair growth. Within the follicle is the hair bulb, where living cells divide and grow to build the hair shaft. As these cells multiply, they push upward, die, and harden, forming the strand of hair that you see. This strand is primarily made of a tough protein called keratin.

Keratin is a fibrous structural protein that provides strength and resilience to each strand. Alongside keratin, hair contains various other chemical components, such as lipids, which contribute to the hair's natural shine and moisture. Melanin, a pigment molecule which determines the natural color of the hair. Trace amounts of elements like sulfur, iron, and zinc are also present in hair and play roles in its structure and vitality. This complex mix of proteins, lipids, and minerals ensures that hair remains durable and functional.

So, when we talk about hair growth, we're really talking about a complex activity happening inside these thousands of tiny follicles all over your scalp.

The Three Phases of the Hair Growth Cycle

The hair on your head isn't growing all at once. Each follicle operates on its own schedule, moving through a three-phase cycle. This is why you shed a small number of hairs every day instead of losing them all at the same time. Let's explore each phase.

1. The Anagen Phase (The Growing Phase)

The anagen phase is the active growth period for your hair. During this time, the cells in the hair bulb divide rapidly, creating new hair. The hair pushes upward from the follicle and grows longer. At any given moment, about 85-90% of the hairs on your head are in this phase.

The length of the anagen phase determines the maximum length of your hair. For scalp hair, this phase can last anywhere from two to seven years. This duration is largely determined by your genetics, which is why some people can grow their hair down to their waist while others find it difficult to grow it past their shoulders.

2. The Catagen Phase (The Transition Phase)

After the anagen phase ends, the hair follicle enters a short transitional period called the catagen phase. This phase lasts only about two to three weeks. During this time, hair growth stops, and the follicle detaches from the blood supply. The follicle itself shrinks, and the hair shaft gets pushed upward. Only about 1-2% of your hairs are in the catagen phase at any time.

3. The Telogen Phase (The Resting Phase)

The telogen phase is the final stage, also known as the resting phase. The hair strand is no longer growing but remains in the follicle for about three months. At the same time, a new hair often begins to grow in the follicle beneath the resting one. Around 10-15% of your scalp hairs are in the telogen phase.

This phase ends when the follicle re-enters the anagen phase. The new hair growing underneath pushes the old, resting hair out, and it sheds. It's completely normal to shed between 50 and 100 telogen hairs each day. This shedding is what makes way for new growth, completing the cycle.

How the Hair Bulb Manufactures Hair

The hair bulb, located at the base of the hair follicle, plays a critical role in the production of hair. It is within this bulb that hair cells are actively created through a process of rapid cell division. The hair bulb contains specialized cells called keratinocytes and melanocytes. The keratinocytes produce keratin that makes hair strong and flexible. The melanocytes generate pigment that gives hair its color.

In order to create the new cells that give hair it's strength and color, the hair bulb needs lots of nutrients as building blocks and fuel. The papilla is a small, capillary-rich structure that delivers oxygen and essential nutrients to the hair bulb from the blood.

Proteins & Amino Acids

• Keratin (and other structural proteins) make up the majority of the hair's shaft, giving it its strength and flexibility.
• Cysteine and methionine aren't building blocks of the keratin, but are necessary in order to make it.

Some of the amino acids required for hair production and growth come from essential amino acids such as Leucine and Threonine. Essential amino acids cannot be created by the body (whereas other nonessential amino acids can be). This means, if you want your hair to grow, you must feed your body the right nutrients to do so.

Vitamins

Vitamins also play a key role:

• Biotin (Vitamin B7) is essential for strengthening hair strands and promoting growth.
• Vitamin C supports collagen production, which fortifies the hair structure.
• Vitamin E provides antioxidant properties that protect hair cells from damage.

Minerals

Minerals such as iron, zinc, and magnesium are indispensable:

• Iron plays a critical role in promoting healthy hair growth by supporting oxygen transport and enhancing cell repair.
• Zinc helps regulate the production of sebum, the natural oil that keeps the scalp hydrated and prevents dryness which can lead to hair breakage. Zinc also supports the repair of damaged hair follicles and promotes the formation of new cells.
• Magnesium plays a crucial role in promoting hair growth by improving scalp circulation and supporting the delivery of essential nutrients to hair follicles.

Fatty Acids

Fatty acids, particularly omega-3 and omega-6, are essential for maintaining healthy hair growth. These fatty acids help nourish the hair follicles, ensuring they remain strong and capable of producing healthy strands.

• Omega-3 fatty acids are known to boost moisture in the scalp, reducing dryness and flakiness that can inhibit hair growth. Additionally, they can improve hair elasticity and luster, preventing breakage.
• Omega-6 fatty acids contribute to healthy cell function and support the scalp’s structural integrity, creating an optimal environment for hair growth.

Consuming foods rich in fatty acids or using topical treatments infused with these nutrients can significantly enhance hair health over time.

What Influences How Hair Grows?

The hair growth cycle is a well-oiled machine, but several factors can influence its speed, efficiency, and overall health. If you've ever asked, "how does hair grow faster or thicker?" the answer lies in managing these key influences.

1. Genetics

Your genes are the primary blueprint for your hair. They dictate your hair's color, texture, and how long its anagen phase lasts. Genetic conditions, like androgenetic alopecia (male or female pattern baldness), can cause hair follicles to shrink over time, producing finer, shorter hairs until they eventually stop growing altogether.

2. Hormones

Hormones play a significant role in regulating hair growth. Hormonal shifts can disrupt the hair cycle and are a common cause of hair changes. For example:

• Pregnancy: High estrogen levels can prolong the anagen phase, leading to thicker-feeling hair. After childbirth, estrogen levels drop, causing many hairs to enter the telogen phase at once, resulting in postpartum shedding.
• Menopause: A decrease in estrogen and progesterone can lead to follicle miniaturization and slower growth, resulting in thinning hair.
• Stress: High levels of the stress hormone cortisol can push a large number of hairs into the telogen phase prematurely, leading to a condition called telogen effluvium, or stress-induced shedding.

3. Nutrition

Your hair follicles need a steady supply of nutrients to build strong hair. A diet lacking in essential vitamins and minerals can impair hair growth. Key nutrients for healthy hair include:

• Protein: Since hair is made of protein, an adequate supply is essential.
• Iron: Iron deficiency (anemia) is a well-known cause of hair loss.
• Biotin: A B-vitamin that helps produce keratin.
• Vitamins C, D, and E: Antioxidants that support scalp health and protect follicles.
• Zinc: Plays an important role in hair tissue growth and repair.

4. Age

As we age, the rate of hair growth slows down. The anagen phase naturally becomes shorter, and follicles may gradually stop producing new hairs. This leads to thinner hair and a gradual decrease in overall hair density, which is a normal part of the aging process.

5. Health and Lifestyle

Your overall health is reflected in your hair. Certain medical conditions, like thyroid disorders, can disrupt the hair cycle. Medications, major surgeries, and high fevers can also trigger temporary hair shedding. Lifestyle factors like smoking can restrict blood flow to the scalp, depriving follicles of the oxygen and nutrients they need.

Nurturing Your Hair's Natural Cycle

While you can't change your genetics, you can support your hair's natural growth cycle through positive lifestyle choices. A balanced diet, effective stress management, and gentle hair care can create the best possible environment for your follicles to thrive. By understanding the intricate science of how your hair grows, you can better appreciate the journey each strand takes and provide it with the care it needs to look its best.