DIET AND DISEASE IMAGES. The building blocks of all proteins are amino acids. There are 20 amino acids required for human life, although others do exist.

DIET AND DISEASE IMAGES

The building blocks of all proteins are amino acids. There are 20 amino acids required for human life, although others do exist in nature. Twelve of these can be synthesised within the body, but we need to eat foods containing the other eight to get them into our bodies. These eight are known as essential amino acids.

Each amino acid has the same molecular backbone, but each has a different chemical group attached to its central carbon atom. These are known as ‘R groups’. The above example shows the amino acid alanine, which has a CH3 R group.

Credit: Maurizio De Angelis, Wellcome Images.BIGPICTUREEDUCATION.COM

Alanine

Proteins have a huge array of vital functions within the human body. Inadequate dietary protein can lead to a number of diseases, particularly in children. The child in the picture above is suffering from kwashiorkor, a disease rare in developed countries but more common in those that experience famine. Its symptoms include oedema

(fluid accumulation beneath the skin), decreased muscle mass, failure to grow and a large belly that sticks out. This condition is fatal if untreated.Credit: Wellcome Images.

Leg of a child with kwashiorkor

This image shows a plate of lean meat, liver and kidneys. Meat is an example of a food that contains ‘complete protein’, which contains all of the essential amino acids. Vegetarians and vegans need to gain their essential amino acids from plant sources such as soy or chickpeas. Meat contains haem iron, zinc, preformed

vitamin A, and B complex vitamins. It provides energy from the protein and fat. Liver is exceptionally rich in these, as well as vitamins C and D.Credit: Wellcome Library, London.

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High-protein foods

This image dates from 1920-1930 and shows three children with rickets, a disease of childhood in which the long bones soften and bend. It is most commonly caused by a deficiency of vitamin D, which is needed in the body for the absorption of calcium and the mineralisation of bone. Rickets is now rare in the UK. Vitamin D is a

fat-soluble vitamin that is produced in human skin in response to exposure to sunlight. Dietary sources include oily fish.Credit: Wellcome Library, London.

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Children with rickets

This image shows foods rich in vitamin A. This fat-soluble vitamin is needed to produce retinal, a light-absorbing chemical found within the eye, involved with low light and colour vision. Vitamin A can be found in two dietary forms: retinol, from animal food sources and some carotenes from vegetables. Deficiency in this vitamin in children can

lead to blindness or even death. The condition ‘night-blindness’ can also result from a lack of vitamin A - leading to a poor ability to see in low light conditions.Credit: Wellcome Library, London.

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Dietary sources of vitamin A

Vitamin C, also known as ascorbic acid, is essential for humans, who are unable to synthesise it. It is found naturally in a wide range of fruits and vegetables. Vitamin C has a number of important uses in the body, including acting as an antioxidant and being involved in the synthesis of several molecules such as

collagen. Some people believe that vitamin C can be used to treat the common cold, but research into this has produced different results.Credit: Wellcome Library, London.

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Citrus fruits rich in vitamin C

Scurvy is a disease caused by a lack of vitamin C. This vitamin is required for the formation of collagen, and a deficiency leads to capillary bleeding and defective repair of skin and bones. The classic symptom of the disease is bleeding from the gums, as can be seen in the image above. The disease ultimately ends in death. Scurvy was once common in sailors

as fresh fruits and vegetables would not survive long sea voyages. In the 19th century, British sailors were given a daily allowance of limes in order to prevent scurvy. This led to British people being described as ‘limeys’ by the Americans, a slang term still in existence today.

Credit: Wellcome Images.

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Scurvy teeth and gums

Pellagra is a disease caused by a lack of vitamin B3, which is also known as niacin. This vitamin is essential for humans and must be gained through the diet, although the body produces a small amount. There are eight B vitamins in total, and are needed to assist in the conversion of carbohydrates into glucose. The also help to metabolise proteins

and fats, and keep the nervous system functioning correctly. Pellagra has a number of symptoms including the dermatological conditions that can be seen in the picture above. Ultimately a lack of vitamin B3 leads to death. It is a now a rare disease in developed nations.

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Hands of a person with pellagra

This image shows various types of cereals and legumes, the two most important plant food groups. Cereals are the seeds of plants belonging to the grass family. Rice, wheat and corn are major staple foods for many people. The grains are high in carbohydrate and protein, and contain vitamins and minerals in their outer layer. Legumes (chickpeas, peas, beans, peanuts, lentils) are also high in carbohydrate

and protein, and in the case of soya beans and peanuts, high in oil. They are good sources of micronutrients, and usually contain significant amounts of thiamin, niacin, riboflavin, phosphorus, non-haem iron and calcium. In vegetarians, legumes are important in improving iron intake. Legumes also increase the nutritional value of the meal by providing amino acids that are deficient in the cereals.

Credit: Wellcome Library London.

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Cereal and legumes

Light micrograph of starch grains viewed with polarised light. Starch is a polysaccharide - a carbohydrate molecule made of multiple glucose subunits. Starch is made by plants so they can store the glucose they need for energy. It is the largest source of carbohydrate in the human diet, and is found in foods such as rice and potatoes. The

enzyme amylase breaks down starch into its glucose subunits. Human saliva has high levels of amylase, which is also released by the pancreas into the small intestine.Credit: Spike Walker, Wellcome Images.

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Starch grains

Glucose is a monosaccharide used by cells as an energy source. Glucose from the bloodstream is transported into the cells and broken down to make the energy molecule adenosine triphosphate (ATP). Glucose is stored in the liver and muscles as glycogen in a process known as glycogenesis. This molecule can be quickly broken when energy is required. This is known as glycogenolysis. When glucose levels are very low, it can be made from non-carbohydrate molecules such as certain amino acids, known as gluconeogenesis. The primary

source of energy for the brain is glucose. This organ uses 20 per cent of the body’s energy, more than any other.Credit: Anna Tanczos.

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Glucose molecule

Saturated fat molecules contain no double bonds between their carbon atoms. They are found in large amounts in foods like butter or lard. A diet high in saturated fats, including those found in some of the foods in the picture above, can increase the risk of cardiovascular disease.

Credit: Wellcome Library, London.

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A cooked breakfast

A computer graphic showing the contours of the body of an overweight man. Obesity is defined as having an excessive level of body fat that can cause a risk to health. Levels of obesity worldwide have doubled since 1980, with the WHO estimating that in 2008 over 200 million men and 300 million women were obese. Obesity is the leading

preventable cause of disease worldwide. The condition is a major risk factor in a number of diseases including cardiovascular disease, diabetes and cancer. The WHO definition of overweight is having a body mass index (BMI) of between 25 and 29.9. Obesity is defined by a BMI above 30.

Credit: Jurgen Ziewe, Wellcome Images.BIGPICTUREEDUCATION.COM

Body mass

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