Even if you are not having a bad hair day, the quality and quantity of your hair is a major component of self-confidence for men and women. Your hair grows about 1/4 to 1/2 inch every month if you have an adequate diet with healthy nutrients. Hair-care products often advertise the use of protein for increased hair strength, but it is difficult to know if these claims are accurate.

Protein and Hair

Protein is essential for every organ in your body. It is particularly involved in healthy hair. Keratinocytes are responsible for making keratin, a type of protein essential to hair growth. If you do not take in enough in your diet, hair loss can occur or hair can become dull and brittle. Loss of protein due to various hair-care products or even medical conditions will lead to damaged hair. Protein also affects hair texture. According to a study published in the "Journal of Investigative Dermatology" in February 2011, IGF-binding protein 5 affects whether hair is curly or straight, so even the shape of your hair is protein-based.

External Use of Protein

Many hair-care products have added protein. The use of protein in the products is for strengthening the hair shaft, adding shine and even for antistatic purposes. If your hair is fine, protein-based products will not thicken the hair shaft but they can make it healthier. Also, some products with protein will coat the surface of the hair but not penetrate the hair shaft. For true hair health, the shaft must take in the protein. Using heat in combination with the protein-based products will help with penetration, according to T.J. Kittelson, a hair-care professional who operates a salon in Colorado.

Internal Use of Protein

There is some evidence that ingesting certain types of whey protein can be beneficial for hair. Dr. Lawrence Shapiro, a hair transplant surgeon based in Florida, conducted a study in March of 2010 on the effects of ingesting a whey protein beverage made from concentrated whey protein and other nutrients. His website, Shapiros's Hair Institute, lists the results of this study. One hundred individuals participated in the study, and 94 percent noted improved hair condition. Those who participated also noted that use of whey isolate -- a more processed type of whey protein that has little fat -- caused damage to their hair.

Protein-Rich Foods for Hair Growth

According to Andrea Giancoli, a dietitian and spokesperson for the American Dietetic Association, you need enough omega-3 fatty acids for a scalp that will support healthy hair growth. Fish such as salmon are rich in this nutrient. If you do not like fish or are a vegetarian, supplementing with flaxseed oil will provide the protein you need. Eat lots of legumes such as kidney and navy beans to get complete proteins. Other good sources of protein in the diet are lean chicken and eggs.