Hair is around 91% protein. Protein is made up of long amino acid chains, which are found in the cortex, or middle, part of the hair. The amino acids consist of carbon, hydrogen, oxygen, nitrogen and sulfur and are also the building blocks of nails and skin.

Can my diet affect my hair?

Not much is known about the connection between nutrition and healthy hair. The idea that damaged hair can be 'restored' to health is perhaps a beauty industry myth. However, there is evidence to suggest that diet can strengthen new hair and help prevent hair loss and weakness. The little scientific evidence there is regarding the effect of diet on hair, comes from studies into protein-energy malnutrition, eating disorders and starvation. Often, hair loss happens as a result of genetic conditions such as pattern baldness, or conditions such as alopecia and thyroid disease.In these cases, there is very little diet can do. However, if hair loss and damage occurs as a result of a nutritional deficiency, then a nutritionist may be able to construct a healthy diet to encourage stronger regrowth.
Protein deficiency

The hair is made mostly of protein. It makes sense, then, that a diet lacking in protein would affect the look, growth and strength of your hair. Protein deficiencies are thought to contribute to hair loss. The top recommended protein-packed foods for healthy hair include:

* Salmon - a favourite with nutritionists, salmon is packed with protein and good fats (omega-3 fatty acids) that contribute towards hair shine and strength, and help to prevent breakage. Oily fish should be eaten at least once a week.

* Nuts - nuts are often overlooked for their great range of nutritional benefits. They offer a rich source zinc as well as protein, and are thought to improve the overall look of hair (especially Brazil nuts, almonds and walnuts).

* Eggs - body-builders often drink them raw to build muscle strength, but eggs can also boost the vibrancy, growth rate and strength of hair. Eggs also contain B-vitamins which can contribute towards shine.

Iron deficiency

Iron helps make red blood cells, which carry oxygen around the body. Without sufficient oxygen, the hair bulb may not be able to create new hair cells, therefore slowing the hair growth. Iron rich foods that may in some cases help with the prevention of hair loss or thinning include:

* red meat
* liver
* nuts
* beans
* dried fruit
* wholegrains
* dark leafy vegetables such as watercress and kale.

Vitamin C (otherwise known as ascorbic acid) is thought to help with the absorption of iron, so eating foods rich in vitamin C could help boost the body's iron intake. Foods rich in vitamin C include:

* citrus fruits (oranges, limes, lemons, grapefruit)
* peppers
* broccoli
* sweet potatoes
* kiwi
* brussels sprouts.

Take care not to eat too much vitamin C. The daily recommendation for adults is 40mg. Taking too much may cause stomach pain, flatulence and diarrhoea.
Hair loss and weight loss

Some fad crash diets have been known to cause hair loss. This is because some of them, such as non-carb or fat-free diets, deprive the hair of the vital nutrients it needs to grow healthily. When calorie intake is too low, the body is forced to use any remaining protein for energy. Because hair growth is one of the least important processes in the body, this will be the first source to go.