Human hair grows at a fairly steady rate, about 1/2 inch per month, or 6 inches per year. Strangely, it tends to grow faster in summer and at night while you sleep, and good nutrition can play a part in how much and how fast hair grows. If you want waist-length hair, you need to wait about seven years. The growth cycle for most hair lasts between 3 to 7 years. If you have a long growth cycle, your hair can grow longer.
Hair Growth Cycles
According to the Proctor and Gamble website, there is an average of 100,000 hairs on the human head. They are always in one of three cycles: the anagen stage, where hair grows; the catagen stage, which is the intermediary stage; and the teleogen stage, the shedding stage. Babies' hair grow at a uniform rate, but as we age, each follicle grows and sheds at a different rate; if they didn't, we would go through periodic stages of uniform baldness. The anagen stage can last 3 to 7 years. As we age, this stage usually lasts a shorter and shorter amount of time, so someone who in her youth had waist-length hair may not be able to grow it to that length again as she ages.
The Guiness Book of World Records states that Xie Qiuping of China holds the record for the longest hair. In 2004, her hair measured more than 18 feet long. She had been growing it since 1973, when she was 13. Tran Van Hay, from Vietnam, has hair that measures more than 20 feet long. He stopped growing his hair when his first child was born. As of 2009, he had not yet been entered into the Guiness Book of World Records. If Qiuping started with hair that was 2 feet long in 1973, her hair grew at a rate of about 2 feet per year, or 4 times the average. Genetics, good nutrition and proper hair care all play a part in hair growth rates.
Nutrition is now being cited as an important part of hair growth. According to the Proctor and Gamble website, scientists are making the connection between hair growth and lack of zinc in the diet, for example. People who suffer from severe alcoholism also suffer from malnutrition and have unhealthy hair, which is very fine and does not grow fast. People who suffer from anemia also have hair that grows very slowly. These examples show that nutrition may play a part in hair growth rate.
Nutrients that may be important for faster hair growth include the vitamin B complex, vitamin E and minerals such as magnesium, zinc and sulfur. Eating a diet rich in green leafy vegetables, with lots of almonds and other nuts and seeds, can help. Red meat is a good source of vitamin B12, halibut is a good source of magnesium, and oysters are an excellent source of zinc.
Hormones and Hair Growth
Hormones also affect hair growth, according to the Proctor and Gamble website. The balance between male and female hormones determines the rate of hair growth as well as how long hair stays in the growing stage. Male hormone levels dictate the thickness of the hair as well as how fast it grows. Female hormones dictate how long hair lasts in the growing stage. The thyroid hormone can make hair grow faster, while taking oral steroids can make hair grow at a slower rate.