Human health and diseases – Diet

A balanced diet

• A balanced diet is one which contains adequate amounts of all the necessary energy and nutrients required for healthy growth and activity.
• This includes both macro nutrients (carbohydrates, fats and proteins) and micro nutrients (vitamins and minerals).
• Sometimes cells can convert one compound to another, but this is not the case with a few things, and these are known as essential since we must intake them in our food to survive.
• They include essential amino acids, essential fatty acids and most minerals.

 

Energy and nutrient requirements of people

Gender

• Males require more protein because their growth is greater than females during adolescence, and after that stage they have a greater mass of tissue to repair and replace.
• Males require more of the vitamin B complexes that are needed for respiration and metabolism.
• Males require more calcium and phosphorus in adolescence because they develop larger bones than females during this stage of growth.

 

Age

• Energy requirements increase with age, up to and including adolescence, as growth is rapid during these years and physical activity is generally at high level.
• These energy requirements remain almost constant up to the age of 60 years, after which they decrease as physical activity diminishes and body mass often decreases.
• Protein requirements increase with age, especially around puberty. This is because additional protein is needed for the rapid growth around adolescence and thereafter, to repair and replace cells.
• Calcium and phosphorus requirements are greater in the first year of life as they are laid down in the bones of infants.
• The rate again increases in adolescence when the second growth spurt involves relatively rapid elongation of the bones.
• After adolescence, the requirements remain constant.
• Requirements for other minerals and vitamins increases up to the age 20 years, but thereafter remains relatively constant

 

 Activity

• The more physically active a person is, the greater their energy requirement.
• It follows that, compared to an office worker; a manual labourer requires a greater energy intake, especially of carbohydrate food.

 

Discuss with reasons why the diets of women should be modified during pregnancy and lactation

Pregnancy

• Energy requirements increase more during the last three months
• For growth of the baby
• To build store fat ready for lactation
• Not first six months because extra energy needed is compensated for by reductions in physical activity/metabolic rate
• increased need for proteins for growth of foetus
• extra protein for tissue in mother
• g. uterus/placenta/blood/breasts
• extra calcium for growth of bones/skeleton
• increased iron for haemoglobin/blood formation
• increased folic acid for protection against neural defects/spina bifida/improved absorption of iron
• increased vitamins (not Vitamins D or B6) for foetus
• increased Vitamin A for foetal growth and development of immune system/epithelia
• Vitamin A, C and D, although too much vitamin A can be harmful to the fetus in the early stages of pregnancy.
• For this reason pregnant women are recommended to avoid liver, which is very rich in vitamin A.

 

Lactation

• extra energy for growth and activity of the baby
• extra protein for growth of the baby
• extra calcium for growth of bones/skeleton/teeth
• extra zinc for bones/some enzymes of the baby
• extra vitamins (as for pregnancy)

 

Dietary Reference Values (DRVs)

• This is sets of figures relating to the requirements for energy and nutrient intake of all healthy individuals in the UK, this is sat by the department of Health in 1991.
• Dietary reference values are just that – they are values that can help you plan your diet and ensure you are receiving everything you need in the right proportions.  There are three types of Dietary reference values
  • Estimated average requirement (energy/nutrients) – this is an estimate of the average requirements of a population
  • Reference nutrient intake – enough or more for nearly all the population

(iii)Low reference nutrient intake – sufficient for those with low needs (this is at the bottom of the range and is enough for only about 2% of the population).

 

Uses of DRVs

• Chefs (most professional cook) and caterers to design appropriate menus for groups of people living in communities such as schools, old people’s home and prisons.
• Managers to plan food supplies for large groups of people.
• Dieticians and others to assess the dietary needs of individuals, e.g. the elderly and pregnant women.
• Individuals to calculate their own dietary requirements and to maintain or improve health.
• Food manufacturers to provide appropriate nutritional information on food labels.

 

Food Labels

• Dietary reference values are also used on food labels to allow customers to make the choice that they want.
• Manufacturers may publish Recommended daily allowance information, and this must be accurate by law – for a food to be a source of a nutrient it must have at least 17% of the recommended daily allowance for that nutrient, and if it is ‘rich in’ a nutrient, it must contain over 50% of the recommended daily allowance for that nutrient.

 

Describe the role of DRVs in estimating the diet of people in Britain

• DRVs are not recommended quantities for individuals
• based on normal distribution curve of requirements
• Mean requirement (EAR)– this is an estimate of the average requirements of a population. 50% of the population will need more than the EAR for the energy or for nutrient and 50% will need less.
• Reference nutrient intake (RNI) –this represents enough or more than enough to meet the energy or nutrient needs of almost all the population, even those with high needs.
• Low reference nutrient intake (LNRI) – is almost sufficient for those with low needs (this is at the bottom of the range and is enough for only about 2% of the population).
• Tables produced which show differing DRVs for different groups of people depending on age/sex/pregnancy/lactation (any of these)
• tables are for energy or nutrients
• there are no LRNI or RNI for energy but they apply to nutrients
• but there are only EARs for energy
• because individual requirements within each category vary so much
• if RNIs for energy were published, some people might eat more than individual requirements –
• leading to obesity/ other harmful-to-health consequences
• safe intakes are a second group of DRVs
• for nutrients for which there are insufficient data to construct graphs/normal distribution curves
• g. Vitamin E/K/F and minerals such as fluoride in children
• an intake below the Safe intake would risk deficiency
• so one should aim for an intake just above

 

Describe the roles of essential fatty acids in the body

• an essential fatty acid is linoleic/linolenic acid
• liver converts EFAs into arachidonic acid/prostaglandins/thromboxanes
• blood clotting
• linoleic acid reduce risk of heart diseases
• regulating blood pressure vasodilation
• immune response
• renal functions
• contraction of uterus
• needed for lipoproteins
• transport of fat/breakdown of cholesterol
• needed for phospholipids in cell membranes
• reduce risk of heart disease

 

Describe the roles of essential amino acids in the body

• increase muscle mass and helps muscle recover after exercise e.g. leucine
• It also regulates blood sugar and supplies the body with energy. These functions make it invaluable when the body is stressed.
• Leucine is used clinically to help the body heal, and it also affects brain function and can be used in place of glucose in ‗fasting‘ states.
• isoleucine is important for the regulation of blood sugar.
•  important for antibody production e.g. threonine and is also needed to create other amino acids that aid in production of collagen
• phenylalanine acts as a precursor to chemicals that regulate the central and peripheral nervous system
• valine is necessary for muscle metabolism and the repair of tissues and can be useful in the treatment of liver and gallbladder disorders.
• lysine enables the synthesis of carnitine, which converts fatty acids into energy and also plays an important role in the production of hormones, antibodies and enzymes. Having a deficiency in lysine can lead to niacin deficiency and cause a health condition called pellagra.
• this amino acid aids in the production of sulphur, which is necessary for normal metabolism and it is also essential for the synthesis of haemoglobin and glutathione that fights against free radicals

 

 

Describe the roles of Vitamin A in the body

• vitamin A is converted into rhodopsin which is bleached when light enters the eye
• needed for vision
• healthy skin
• formation of mucous membranes
• bone and tooth growth
• immune system health
• epithelial cells use retinol from vitamin A to make retinoic acid, a chemical that aids cell growth and differentiation, and without it the epithelia are not maintained properly
• and the body becomes susceptible to infections in the gut or gaseous exchange system, where epithelia cells protects it.

 

Describe the roles of Vitamin D in the body

• Needed for proper absorption of calcium and phosphate
• Vitamin D (converted to an active form) promotes calcium and phosphate absorption from intestines
• Strengthening of bones and teeth
• Acts on bone cells to regulate the deposition of calcium

 Malnutrition

Explain what is meant by the term malnutrition.

• Malnutrition is the general term for a medical condition caused by an improper or insufficient diet.
• it is usually caused by inadequate consumption, but as with obesity can be caused by overconsumption.
• not a balanced diet
• one or more nutrients absent
• or not present in correct proportions
• e.g. obesity-too much anorexia nervosa- too little

 

Starvation

• This is both a lack of energy and nutrients,
• the body can last a rather large amount of time without food (as opposed to without water), since it will drop its metabolic rate and utilise its reserves of carbohydrates, fats and proteins.
• The body uses glycogen stores in the liver (for less than a day), then fat stores (for 4-6 weeks, depending on the person) and finally protein in muscles and other tissues.
• However, as long as people are well fed before the starvation, they are usually ok for a while – but this is not true of those with previous deficiency, especially vitamin A deficiency.

 

Protein energy deficiencies

Discuss the consequences of a child of a diet which is deficient in protein

• two possible conditions =
• kwashiorkor and marasmus (both referred to as protein energy malnutrition)
• stunted growth/underweight
• small muscles
• limited production of antibodies
• reduced resistance to infectious diseases
• degree of deficiency will determine severity

 

Kwashiorkor

• thin hair/easily removed/loses pigment
• moon faced appearance
• swollen abdomen
• oedema, particularly in feet/legs
• characteristic skin lesions/flaky paint (crazy paving) appearance of skin/rough skin irritability/constant crying/little interest in surroundings fatty liver/permanent liver damage

• underweight
• delayed wound healing

 

Marasmus

• wizened/shrunken features
• old man‘s face

 

Anorexia

• Anorexia nervosa, a self-inflicted psychological disease with physical consequences, and in extreme cases it can be fatal.
• Anorexia develops from extreme dieting, causing a weight well below normal, but the anorexic will continue to diet, sometimes until death.

 

Discuss the possible consequences if a person suffers from anorexia nervosa

• muscle wasting
• loss of weight/very thin/emaciated
• loss of body fat
• body returns to pre-adolescent stage
• menstruation may cease
• infertility
• soft (downy) hair may grow on face and shoulders
• thin sparse hair
• symptoms of marasmus/reduced resistance to infection
• low blood pressure/cold hands and feet
• muscle waste away because proteins are used as a source of energy
• constipation/increased tooth decay vitamin/mineral deficiency may die of starvation
• may need to be hospitalised
• social problems (lying to friends/relationships with family)
• cause anxiety over self image/growing up psychological distress/obsessive about avoiding food/overeating
• There is increased susceptibility to infection
• There are personality changes

 

Describe the consequences of a person being obese.

• a condition of malnutrition (over-eating)
• obesity is defined in two ways.

1. 20% or more above the recommended weight for heights; or
2. A body mass index of greater than 30 – The body mass index is calculated as

Body mass index =      body mass(kg)/ height (in meters)²

 

• is caused by eating more energy than used.
• the energy is stored as fat, and as weight increases.
• increases risk of diabetes, hypertension, CHDs
• arthritis/prostate/cervical/breast cancer (from increased strain on the skeleton)
• increased likelihood of developing hernia/gall stones/varicose veins and stroke
• high cholesterol levels
• risk of surgical operations
• body mass index (BMI) above 20%
• more above recommended weight
• awkward posture

 

Vitamin A deficiency

• dry rough skin
• inflammation of eyes
• drying or scarring of the cornea (xerophthalmia)
• night blindness
• malfunctioning of the rod cells
• poor maintenance of epithelia
• body become susceptible to infections, particularly measles and infections of the respiratory system and gut.
• Vitamin A is found in some animal foods such as milk, eggs and fish-liver oils, and some fruits.

 

Vitamin D deficiency (Describe how Vitamin D deficiency may affect the health of an individual)

• Vitamin D (converted to an active form) promotes calcium and phosphate absorption from intestines.
• affect deposition of calcium in bones
• and removal of phosphate from bone
• deficiency particularly damaging in childhood because skeleton is still growing.
• deficiency disease in children = rickets
• too little calcium and phosphate results in bones being too weak/soft to support weight of the body and bowing of legs occur.
• and bending of spine
• in adults leads to osteoma Lacia
• bones weak/soft and susceptible to fracture
• poor orientation of the pelvic girdles

 

Describe the consequences for children and adults of a deficiency of Vitamin D

• vitamin D is a precursor of active hormone that stimulates the absorption and deposition of calcium.
• from sunlight

 

Children

• reduced calcification of bones/bones lack calcium.
• for strengthening.
• long bones of legs bow outwards.
• reduced bone growth.
• bone pain/pain in shoulders/spine/ribs/pelvis
• muscle weakness
• late eruption of teeth

 

Adults

• osteoma Lacia
• loss of calcium/softening of bones
• bones susceptible to fracture