d1 human nutrition

Question 1

what are essential nutrients?

Answer 1

• biological molecules that cannot be synthesised directly and have to be consumed in that form
• essential nutrients cannot be synthesized by the body, therefore they have to be included in the diet
• many biological molecules in the human can be synthesised from other molecules
• e.g. testosterone is synthesised from cholesterol, and cholesterol can itself be synthesised carbohydrates

Question 2

what are the 4 main classes of essential nutrients?

Answer 2

• essential fatty acids
• essential amino acids
• essential vitamins
• essential minerals

Question 3

what are dietary minerals?

Answer 3

• essential chemical elements
• minerals: simple inorganic nutrients
• e.g.:
  • calcium required in large amounts for bone synthesis
  • phosphorous needed in large amounts (production of
  phosphates)
  • iodine required in making of thyroid hormones
• as minerals are elements, there are no ways to produce them, and hence they must be obtained externally from the diet
• some important functions played by minerals:
  • major constituents of structures such as teeth and bones (e.g. Ca, P, Mg)
  • important components of body fluids (e.g. Na, K, Cl)
  • cofactors for specific enzymes or components of proteins and hormones (e.g. Fe, P, I)

Question 4

what is the purpose of calcium in humans and where to obtain?

Answer 4

DIETARY SOURCES

• dairy products
• dark green vegetables
• legumes

FUNCTIONS IN THE BODY

• bone and tooth formation
• blood clotting
• nerve and muscle function

BONUS FUNCTION IN PLANTS
- important for plant root and shoot elongation

SYMPTOMS OF DEFICIENCY

• impaired growth
• loss of bone mass

Question 5

what is the purpose of phosphorus in humans and where to obtain?

Answer 5

DIETARY SOURCES

• dairy products
• meats
• grains

FUNCTIONS IN THE BODY

• bone and tooth formation
• acid-base balance
• nucleotide synthesis

SYMPTOMS OF DEFICIENCY

• weakness
• loss of minerals from bone
• calcium loss

Question 6

what is the purpose of sulfur in humans and where to obtain?

Answer 6

DIETARY SOURCEES
- proteins from many sources

FUNCTIONS IN THE BODY
- component of certain amino acids

SYMPTOMS OF DEFICIENCY

• impaired growth
• fatigue
• swelling

Question 7

what is the purpose of potassium in humans and where to obtain?

Answer 7

DIETARY SOURCES

• meats
• dairy products
• many fruits and vegetables
• grains

FUNCTIONS IN THE BODY

• acid-base balance
• water balance
• nerve function

BONUS FUNCTION IN PLANTS
- inorganic salt found within the sap of a plant (maintains water potential)

SYMPTOMS OF DEFICIENCY

• muscular weakness
• paralysis
• nausea
• heart failure

Question 8

what are vitamins?

Answer 8

• chemically diverse carbon compounds that cannot be synthesized by body
• vitamins are organic compounds (unlike minerals) needed in small quantities for efficient biological processes in human body
• essential vitamins refers to vitamins that cannot be naturally synthesised by human body, and needs to be absorbed from diet in their vitamin form
• some vitamins not technically essential, meaning that human body is capable of synthesising them (e.g. Vitamin D and Vitamin B7), but often not produced in sufficient amounts and hence need to be supplemented in diet
• vitamins are classified as fat soluble and water soluble vitamins

Question 9

why is vitamin c considered an essential nutrient for some but not for others?

Answer 9

• vitamin C can be produced by some mammals, and hence for these mammals Vitamin C is not considered an essential nutrient
• majority of mammals able to synthesise Vitamin C
• done through enzyme mediated steps to convert monosaccharides into ascorbic acid (Vitamin C)
• examples of mammals unable to synthesise include mammals from the primate suborder of Haplorrhini, which includes humans and tarsiers and many other monkeys and apes
• for these animals, a dietary supply of Vitamin C is needed

Question 10

what are the effects in lack of vitamin d and calcium?

Answer 10

• lack of Vitamin D or calcium can affect bone mineralization and cause rickets or osteomalacia
• in healthy production of bone tissues, osteocytes (bone cells) deposit calcium phosphate and calcium carbonate around them
• hence lack of calcium in diet will interfere with healthy production of bone tissues
• Vitamin D also needed to ensure efficient absorption of calcium in intestines
• deficiency in Vitamin D can also lead to a deficiency in calcium in the body

Question 11

what is rickets?

Answer 11

• disease that affects children, caused by low calcium levels in developing children (mainly due to low Vitamin D levels)
• results in bone tenderness (soft bones), and deformities as the bones develop
• main classic symptom is bow-leggedness, while irregular spine curvature may also develop
• other bones may also develop to be deformed as well

Question 12

what is osteomalacia?

Answer 12

• also results in bone softening due to a lack of calcium and/or Vitamin D in the diet
• technically rickets is a form of osteomalacia that occurs in children
• in adults, this can result in joint and bone pain, difficulty in walking, soft bones leading to easy fracturing and bending of bones

Question 13

what are the effects in lack of vitamin d and calcium?

Answer 13

• lack of Vitamin D or calcium can affect bone mineralization and cause rickets or osteomalacia
• in healthy production of bone tissues, osteocytes (bone cells) deposit calcium phosphate and calcium carbonate around them
• hence lack of calcium in diet will interfere with healthy production of bone tissues
• Vitamin D also needed to ensure efficient absorption of calcium in intestines
• deficiency in Vitamin D can also lead to a deficiency in calcium in the body

Question 14

how may cholesterol lead to coronary heart disease?

Answer 14

• cholesterol: organic molecule needed in body for formation of many other compounds (like steroid hormones) and in cell membrane
• hydrophobic, hence transported in form of lipoproteins in bloodstream
• 2 forms of lipoproteins: high density lipoproteins (HDL) and low density lipoproteins (LDL)
• HDL: in general removes fat molecules from cells back to liver for destruction or metabolism
• LDL: in general delivers fat molecules to cells, linked to atherosclerosis
• LDL: known as “bad cholesterol”, high levels of LDL leads to increased risks of atherosclerosis, where cholesterol and other fatty compounds deposited as plaque in arteries, and leads to hypertension
• when atherosclerosis occurs in the coronary arteries, they become blocked, leading to greatly reduced blood flow to heart muscles and hence coronary heart disease

Question 15

what is osteomalacia?

Answer 15

• also results in bone softening due to a lack of calcium and/or Vitamin D in the diet
• technically rickets is a form of osteomalacia that occurs in children
• in adults, this can result in joint and bone pain, difficulty in walking, soft bones leading to easy fracturing and bending of bones

Question 16

what is the cause of phenylketonuria? (pku)

how is phenylketonuria (pku) managed / treated?

Answer 16

• phenylketonuria (PKU): inherited disorder resulting in reduced capacity to metabolise phenylalanine
• gene responsible for creating enzymes involved in breaking down phenylalanine is such that metabolisation becomes very ineffective -> cannot break down to urea
• autosomal recessive disease
• caused by reduced production of enzyme
  phenylalanine hydroxylase
• end result is toxic buildup of phenylalanine in body, which can lead to intellectual disability, seizures, behavioural problems and other mental disorders in young children (during development)
• adults may also suffer from other similar neurological symptoms

TREATMENT / MANAGEMENT

• not a curable disease
• proper management to live normal life
• main form of management is great reduction in the amount of proteins consumed, especially in foods containing higher levels of phenylalanine
• individuals may end up with insufficient proteins in diet, may be supplemented with specially formulated supplements that have less phenylalanine

Question 17

how is malnutrition caused?

Answer 17

• caused by deficiency, imbalance or excess of nutrients in diet
• in absence of particular nutrient in diet will lead to deficiency diseases as body unable to function properly
• imbalances may also occur when regulatory systems (e.g. hormonal systems) are also malfunctioning
• 1 example would be diabetes where production or receptivity of insulin is affected, can lead to imbalance in glucose levels in bloodstream
• other hormonal problems may lead to imbalance in storage and utilising of fats and cholesterol (deposition)
• excess nutrients can also lead to diseases, especially those associated with obesity

Question 18

how is appetite controlled?

Answer 18

• appetite is controlled by centre in hypothalamus
• hypothalamus contains receptors that can be stimulated by particular hormones, and can also release hormones of their own, to control appetite
• hypothalamus can release hormones like neuropeptide Y that causes feeling of hunger, and hypothalamus can also release hormones that inhibit hunger
• other hormones stimulate hypothalamus to release necessary hormones to stimulate or suppress appetite
• stretch receptors in stomach send nerve impulses to brain when stomach is stretched (after feeding) to stimulate hypothalamus to suppress appetite
• adipose tissues release hormones (like leptin) that can lead to appetite suppression
• pancreas release hormones that respond to blood glucose levels (insulin and glucagon) that will stimulate the hypothalamus accordingly to modify appetite levels of a person

Question 19

what is the cause of phenylketonuria? (pku)

how is phenylketonuria (pku) managed / treated?

Answer 19

• phenylketonuria (PKU): inherited disorder resulting in reduced capacity to metabolise phenylalanine
• gene responsible for creating enzymes involved in breaking down phenylalanine is such that metabolisation becomes very ineffective -> cannot break down to urea
• autosomal recessive disease
• caused by reduced production of enzyme
  phenylalanine hydroxylase
• end result is toxic buildup of phenylalanine in body, which can lead to intellectual disability, seizures, behavioural problems and other mental disorders in young children (during development)
• adults may also suffer from other similar neurological symptoms

TREATMENT / MANAGEMENT

• not a curable disease
• proper management to live normal life
• main form of management is great reduction in the amount of proteins consumed, especially in foods containing higher levels of phenylalanine
• individuals may end up with insufficient proteins in diet, may be supplemented with specially formulated supplements that have less phenylalanine

Question 20

how is malnutrition caused?

Answer 20

• caused by deficiency, imbalance or excess of nutrients in diet
• in absence of particular nutrient in diet will lead to deficiency diseases as body unable to function properly
• imbalances may also occur when regulatory systems (e.g. hormonal systems) are also malfunctioning
• 1 example would be diabetes where production or receptivity of insulin is affected, can lead to imbalance in glucose levels in bloodstream
• other hormonal problems may lead to imbalance in storage and utilising of fats and cholesterol (deposition)
• excess nutrients can also lead to diseases, especially those associated with obesity

Question 21

how is appetite controlled?

Answer 21

• appetite is controlled by centre in hypothalamus
• hypothalamus contains receptors that can be stimulated by particular hormones, and can also release hormones of their own, to control appetite
• hypothalamus can release hormones like neuropeptide Y that causes feeling of hunger, and hypothalamus can also release hormones that inhibit hunger
• other hormones stimulate hypothalamus to release necessary hormones to stimulate or suppress appetite
• stretch receptors in stomach send nerve impulses to brain when stomach is stretched (after feeding) to stimulate hypothalamus to suppress appetite
• adipose tissues release hormones (like leptin) that can lead to appetite suppression
• pancreas release hormones that respond to blood glucose levels (insulin and glucagon) that will stimulate the hypothalamus accordingly to modify appetite levels of a person

Question 22

what are overweight individuals more likely to suffer from?

Answer 22

• hypertension and type II diabetes
• individuals can become overweight when over-nourished with excessive diet
• main cause for weight gain is storage of fats in adipose tissues in body
• many ways to determine if an individual is overweight, but 1 common method is to calculate the Body Mass Index (BMI), with individuals with a BMI of above 30 considered to be overweight
• hence, person who is overweight tends to have increased energy intake (big diet) and/or a reduced
  energy expenditure (lack of exercise or sedentary lifestyle)

HYPERTENSION
- refers to symptom where a person has a much higher blood pressure than a normal person
- atherosclerosis, leading to narrowing of the blood vessels, is a leading cause of hypertension
• cholesterol and other fatty substances can form plaque on walls of arteries
• can be caused by a high cholesterol diet or genes
- usually 1st symptom of coronary heart
disease
- overweight individuals tend to have a high sugar, high fat diet that can lead to atherosclerosis
- lack of exercise in overweight individuals also may mean a weaker heart and circulatory system, and the heart might have to compensate by beating faster/harder

DIABETES MELLITUS TYPE II

• arises when cells in body no longer respond effectively to secretion of insulin, and this is known as “insulin resistance”
• e.g. liver normally stores excess glucose in form of glycogen, but as liver cells becomes desensitized to insulin, it no longer stores glucose and may instead release stored glucose
• usually consequence of high sugar diet, and cells become overstimulated by insulin and gradually becomes desensitized
• overweight individuals tend to have a high sugar diet, and hence are more likely to suffer from diabetes type II

Question 23

what is the impact of starvation on body tissue?

Answer 23

• starvation can lead to breakdown of body tissue
• arises when there is insufficient intake of nutrients into body
• to sustain life, body will start to breakdown tissues to obtain molecules to sustain life
• e.g. when starvation occurs, body will first break down storage tissues (mainly adipose tissues) to release energy
• when body runs out of fat reserves (adipose tissues), body will start to break down proteins in muscles for metabolism to release energy
• subsequently, other organs will be broken down for the same reasons, and this can lead or organ damage and ultimately loss of life

Question 24

what is the impact of anorexia on heart muscle?

Answer 24

• breakdown of heart muscle due to anorexia
• eating disorder, where individual greatly reduces food intake to point of self detriment or to obsessive level
• bodies may start to breakdown muscle tissue in order to release sufficient energy to support life
• may lead to decreased thickness of muscle walls in heart, leading to reduced blood pressure and insufficient flow of blood in the body
• heart may also suffer from arrhythmia, where the heartbeat becomes irregular

Question 25

how can energy content of food be determined?

Answer 25

• energy content of different foods can be estimated via combustion, and using the heat energy released to heat up water
• as specific heat capacity of water is known (4.18J per degree Celsius per gram of water), it is possible to calculate the amount of energy released