DIET AND DISEASE IMAGES
Alanine
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.
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Leg of a child with
kwashiorkor
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.
High-protein foods
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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Children with
rickets
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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Dietary sources of vitamin
A
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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Citrus fruits rich in vitamin
C
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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Scurvy teeth and
gums
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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Hands of a person with
pellagra
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.
Credit: Wellcome Images.
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Cereal and
legumes
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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Starch grains
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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Glucose molecule
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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A cooked
breakfast
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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Body mass
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.
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