Keratin is a protein made by cells in your skin that make up your hair and nails. As keratin cells naturally push upward through the skin, they die and then harden, turning into your hair or nails. Known as keratinization, this process is what makes hair and nails grow, and several factors contribute to its sustained momentum. Hair grows an average of 3 inches a year, whereas nails usually grow about 1 1/2 inches a year.
A doctor can tell a lot about a person’s overall health simply by looking at hair and nails. A healthy body will produce strong and smooth nails, whereas a diseased body will create dry, brittle, dotted, yellow, pink or otherwise irregular nails. A well-functioning kidney and thyroid, as well as balanced hormones, are especially essential for the healthy development of hair and nails.
Several types of nutrients support nail and hair growth. When you ingest protein in foods such as animal meat or leafy green vegetables, your body breaks it down into amino acids, then redistributes it as needed to build new proteins specific to its needs. Because the production of keratin depends on this process, proteins are essential for nail growth.
In addition, some of the amino acids necessary to produce keratin rely on having a sufficient amount of sulfur in the body. Vitamin A helps your body absorb protein correctly and is known to aid in the physical composition of hair and nails. Vitamin C works with zinc to create collagen, which helps develop healthy connective tissue to support other structures in your fingers and the rest of your body. Vitamin B2 helps develop new tissue, and Vitamin B7, also known as biotin, helps develop stronger, smoother nails. Vitamin E, Vitamin D, iron, calcium and iodine also aid in the healthy development of hair and nails.
Getting needed nutrients to your fingers and scalp through good blood flow is also necessary for your hair and nails to grow. Poor circulation generally results in thin, weak nails and brittle, stringy hair.
Because your hormones fluctuate at different stages of life and your body may change with age, your hair and nail quality and growth rate may decrease with age. Seasonal changes also affect growth; your nails and hair grow faster and stronger when they get plenty of Vitamin D and stay moist. Thus, during summer months, they grow more than in cold and dry winter months.
You may have heard that hair and nails continue growing after you die. This common misconception is created by an optical illusion. Bodies become increasingly dry and dehydrated after death, causing the skin covering the scalp and skeleton to shrink, which makes the hair and nails appear longer.
A healthy, normal nail is smooth, without ridges or grooves. These features can be normal variants, but ideally, all the nails are uniform in color and consistency and free of spots or discoloration.
- Journal of Investigative Dermatology: Human Hair Keratins
- “Formation and Structure of Human Hair”; P. Jollès, H. Zahn, H. Höcker; 1997
- Yale School of Medicine: Hair