We've all heard the phrase 'you are what you eat', but what do we really need to achieve beauty from the inside out?

Just as certain foods can affect how we feel, what we eat can also influence how we look. Anyone who has binged on sugar and chocolate or greasy fish and chips, only to break out the next day in spots, knows this to be true. But food doesn't only have a negative effect on our appearance. 'A sufficient intake of nutrients from our diet can affect our internal health, which is in turn reflected on the outside through clear skin, strong nails and glossy hair,' says Dr Sarah Schenker, a nutrition scientist at the British Nutrition Foundation.

Certain vitamins and minerals are essential for maintaining healthy skin, hair and nails. Ensuring that sufficient quantities of these are in your diet can make a noticeable difference. So if you want to achieve supermodel skin and hair, a balanced diet is an essential starting point. Take a look at the following overview of what you need to keep you looking young and beautiful:

Vitamin A
Function: important for growth, development and maintenance of healthy skin and teeth, vision in dim light and effective functioning of the immune system.
Deficiency: a deficiency disturbs the delicate balance of the skin and results in the loss of the cells that produce lubricants to keep the skin soft and supple. This in turn leads to infection, irritation and flaky skin.
Source: retinol from animal products and carotenes - mainly Beta (b) carotene - from fruits and vegetables. Great sources of retinol are liver, fish liver oils, kidneys, dairy foods and eggs, while b carotene is found in carrots and dark or yellow vegetables (the darker the veg, the more carotene it contain).
How much: the daily recommended amount is 700 micrograms (ug) for an adult man and 600ug for an adult women. This can be achieved by eating either one medium boiled sweet potato, one large slice of mango or one medium chunk of cheese, a glass of semi-kimmed milk and a medium portion of boiled cabbage.

Niacin (a B vitamin)
Function: assists in the functioning of the digestive system, skin and nerves. It is also important in helping in the body's conversion of food to energy.
Deficiency: a deficiency has been shown to result in a disease called pellagra, the symptoms of which include skin inflammation, causing skin to become dark and scaly, especially when exposed to light. Although it is rare to develop a deficiency in the UK, it makes sense to ensure that you have an adequate amount.
Source: great sources of niacin include meat and meat products, potatoes, bread and fortified breakfast cereals.
How much: the daily recommended amount is 17 milligrams (mg) for an adult man and 13mg for an adult woman. This can be achieved by eating either one small roast chicken breast, one boiled egg and a medium serving of boiled peas or one small grilled pork chop, one medium portion of baked beans and two slices of wholemeal bread.

Riboflavin and pyridoxine (B vitamins)
Function: these vitamins are important for growth and help the body release energy from carbohydrates.Deficiency: a deficiency causes skin lesions or sores, especially at the corners of the mouth, eyelids and genitals.
Source: milk, meat, fortified cereal products and egg.
How much: the daily recommended amount of riboflavin is 1.3mg for an adult man and 1.1mg for an adult woman. This can be achieved by eating either one bowl of cornflakes, a thin scraping of marmite on toast, a medium serving of fried mushrooms, a medium serving of stewed beef and a small glass of milk or a small portion of fried lamb's liver. The recommended daily amount for pyridoxine is 1.4mg a day for an adult man and 1.2mg a day for an adult woman. This can be achieved by eating one medium baked potato, one large banana, one medium portion of boiled Brussels sprouts and one large orange.

Vitamin C
Function: this is needed to maintain healthy tissues.
Deficiency: a deficiency results in bleeding, especially from the gums and from blood vessels underneath the surface of the skin.
Source: great sources of this vitamin include fruit and fruit juices, potatoes, peppers, cabbage, courgettes and other vegetables.
How much: the daily recommended amount is 40mg for both adult men and women, this can be easily achieved by just eating one small orange or one medium portion of boiled cabbage and one tomato.

Iron
Function: this mineral is needed for the maintenance of healthy cells.
Deficiency: a long-term deficiency can cause nails to become spoon-shaped, brittle and thin, as well as hair loss and skin itchiness.
Source: there are two sources of iron - haem iron from animal and animal products and non-haem iron from vegetable sources. Haem iron is better absorbed in the body than non-haem iron. Good sources of haem iron include meat and offal such as liver and kidney, while non-haem iron is found in cereals, pulses, fruits, vegetables and eggs.
How much: the daily recommended amount is 8.7mg for an adult man and 14.8mg for an adult woman - double the amount, due to additional blood loss through menstruation. The required amount for an adult man can be achieved by eating one medium portion of stewing steak, two slices of wholemeal bread, one boiled egg and four dried apricots. An adult woman can achieve her higher requirement by having a bowl of fortified cornflakes, one small serving of canned sardines in tomato sauce and one small serving of boiled courgettes, in addition to the above.

Essential fatty acids
Function: fatty acids, which help make up the skin's structure, are needed to maintain skin surfaces, as well as other major bodily functions. Some types of polyunsaturated fat are termed essential because the body cannot make them so they must be derived from the diet. These essential fatty acids are called omega 3 or omega 6 fats.
Deficiency: a deficiency of these can result in a scaly rash all over the body, although this is very rare.
Source: good sources include oily fish, vegetables and red meat.
How much: the recommendation is to increase our intake of omega 3 fats to 0.2g a day. This can be achieved by eating one to two servings of oily fish - like sardines - a week.