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Human Nutrition - Y2S1 > Energy + Nutrients > Flashcards

Energy + Nutrients Flashcards

1
Q

What are the 2 essential nutrients?

A

Macronutrients - fats, carbs, protein

Micronutrients - vitamins, minerals

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2
Q

What makes essential nutrients ‘essential’?

A

They cannot be produced by our body (not in an adequate amount) so must be provided in diet

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3
Q

What is ‘adequate nutrition’

A

All essential nutrients are consumed in adequate amounts + correct proportions for…

  • energy
  • regulate metabolism
  • growth + development
  • good health
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4
Q

Digestion + Absorption

Describe the Alimentary Canal of Gastrointestinal (GI) system

A
  1. Mouth - food is pushed into throat by tongue
  2. Oesophagus - peristalsis begins, moving food to stomach
  3. Stomach - food is mixed with digestive juices = chyme
  4. Small intestine - continued digestions (water + nutrients are reabsorbed)
  5. Large intestine - absorbs water, forms + moves stool to rectum
  6. Anus - remaining waste is expelled as stool
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5
Q

What are the accessory organs during digestion + absorption?

A
  1. Salivary glands - produce saliva to moisten food, aiding in easy movement to stomach
  2. Pancreas - produces enzymes that break down carbs, fats, lipids
  3. Liver - creates bile = breakdown of fats
  4. Gallbladder - stores bile from liver + releases into small intestine
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6
Q

Describe the 3 main processes that occur in GI tract

A

Digestion - large -> small molecules via mechanical and chemical breakdown

Absorption - transporting digested molecules across GI tract walls into blood

Elimination - removing undigested food + waste products from body

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7
Q

What does the cephalic phase of digestion refer to?

A

The stage in which the stomach responds to the mere sight, smell, taste, or thought of food.

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8
Q

What are the 3 responses of cephalic phase of digestion?

A
  1. Anticipatory physiological response - sensing or expecting food (uses senses)
  2. Preparations for food processing - activates GI tract (20% of acid produced before)
  3. Vagus nerve activation to increase production of… saliva, bile, stomach acids, enzymes, gastric + pancreatic hormones
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9
Q

Describe mechanical digestion (what are the 2 main processes that can occur?)

A

Involves the contraction of circular + longitudinal muscles = moves food through GI tract

  1. Peristalsis
  2. Segmentation
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10
Q

Explain peristalsis

A

Propels food via contracting longitudinal muscle

  • wave-like contractions push food in one direction along tract
  • includes oesophagus, stomach + intestines
  • when stomach rumbles = peristalsis is occurring
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11
Q

Explain segmentation

A

Mixing of chyme via contraction of circular muscle

  • Small intestine creates alternating forward + back contractions
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12
Q

Describe chemical digestion

A
  1. Dietary components - starches, sugars, fats + proteins must be broken down into smaller molecules for absorption + metabolism
  2. Ezymatic hydrolysis - enzymes break chemical bonds holding food molecules together, transforming them into constituent ‘building blocks’ = then absorbed + utilised by body
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13
Q

What are the constituent ‘building blocks’ of each macronutrient?

A

Carbs -> monosaccharides

Lipids -> fatty acids + monoglycerides

Protein -> amino acids

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14
Q

Where is the stomach located + explain key structures

A

Located between oesophagus + small intestine, essential for mechanical digestion

  1. Gastroesophageal sphincter (at top) - prevent backflow of contents to oesophagus
  2. Fundus = reservoir for food
  3. Antrum + pyloric gland area - mechanically breakdown’s semi-digested food into chyme
  4. Pyloric sphincter (bottom) - releases chyme into duodenum of SI
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15
Q

Small intestine digestion - what’s a key structure of SI and what are the 3 parts of SI?

A

Has villi that increases the SA of SI where absorption takes place

  1. Duodenum = C-shaped region extending on from stomach
  2. Jejunum
  3. Ileum - runs into cecum of LI
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16
Q

List the enzymes involved in digestion, where are they released + what do they breakdown?

A
  1. Salivary amylase - from mouth - carbs
  2. Pepsin - from stomach - proteins
  3. Pancreatic amylase - pancreas - carbs
  4. Bile salts - liver - lipids
  5. Lipase - pancreas - lipids
  6. Trypsin, chymotrypsin, carboxypeptidase - pancreas - proteins
  7. Disaccharidases - SI - carbs
  8. Peptidases - SI - proteins
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17
Q

What is gastric emptying + its importance?

A

The contents of stomach are transferred into the duodenum

  • important as nutrients passage + indigestible particles through GI tract needs to be regulated
18
Q

How is gastric emptying regulated?

A

Determined by coordinated motor activity of stomach + proximal intestine (involves smooth muscle + neural + hormonal factors)

19
Q

Where are the following hormones produced + what do they do?

  • Ghrelin
  • Gastric Inhibitory Polypeptide (GIP)
A

Ghrelin - produced in stomach to accelerate gastric emptying + stimulate appetite

GIP - Produced by intestinal K cells to delay gastric emptying + reduce appetite

20
Q

How is gastric emptying different for solid vs liquid meals?

A

Solids - 2 phase process

  1. Initial delay (lag period of roughly 30mins) before emptying begins (solids-> smaller particles)
  2. Linear pattern of emptying (30-120mins) - changes depending on volume of meal, consistency + fat content

Liquids - generally empty stomach in exponential matter (much faster process)

21
Q

What factors slow gastric emptying?

A
  1. Solids vs liquids
  2. Fats vs carbs + protein
  3. Increased energy density - indigestible foods stay in stomach for longer (high fibre, veg)
  4. acidity
  5. Larger volume
22
Q

How can nutrients influence gastric emptying?

A

ST nutrient exposure - increased exposure to specific nutrients can alter GE

e.g. dietary supplementation with 400g of glucose per day for 3 days can sig. increase GE compared to normal diet

The SI can rapidly adapt with specific adaptations in regulatory mechanisms for GE in response to increase dietary load

23
Q

What is the importance of gastric emptying in metabolic health?

A
  1. Slower GE rate leads to rise in macronutrients postprandially (after eating)
    - this can reduce burden of clearing substances from circulation
  2. Postprandial triacylglycerol conc - if not cleared it is an independent risk factor for CVD
  3. Impact of glycaemic control - small differences in GE can sig. affect postprandial glycaemia (blood sugar) in healthy + type 2 diabetes people
  4. Has a role in appetite - GE is associated with satiety + hunger = influences food intake
  5. Energy homeostasis - crucial role in maintaining chronic food intake + energy balance in body
24
Q

How is gastric emptying important during exercise performance?

A

GI tract has role in delivering carbs + fluid during prolonged exercise (not always optimal in endurance conditions)

  • Body loses fluid via sweat, so any fluid taken on needs to be efficiently emptied into small intestine to be absorbed into bloodstream (avoid dehydration + impaired thermoregulation)
  • Carbs are usually consumed during prolonged exercise - they need to reach small intestine, absorbed + utilised to ensure maintenance of blood sugar levels, delaying onset of fatigue

GE can be influenced by nutritional factors (type of nutrients consumed + previous dietary history)

25
Q

What are the recommendations of % of energy from macronutrients intake for a balanced diet?

A

50% from carbs

35% from fats

15% from protein

26
Q

How do requirements of macronutrients change throughout life?

A

Young - more energy to grow + be active

Decreases in adulthood - needs depend on activity levels

Older adults - energy requirements decreases as less active + reduction in basal metabolic rate

  • pregnant women require can extra 200kcal/day during 3rd trimester
27
Q

What is energy intake defined as?

A

The energy content of food + drink ingested as provided by major sources of dietary energy

  • different food = different energy for a given weight
28
Q

How is the energy contribution (calorie density) of foods measured?

A

Via Atwater General Factor System

  • uses single energy value for each macronutrient

Basis of system - avg heats of combustion of each food group

  • then adjustments are made for losses during digestion, absorption + urinary excretion of urea
29
Q

What are the energy contributions of each macronutrients + alcohol?

A

Carbohydrates = 4kcal/g

Proteins = 4kcal/g

Fat = 9kcal/g

Alcohol = 7kcal/g

30
Q

What makes up an individuals total energy expenditure?

A
  1. Resting / basal metabolic rate
  2. Activity energy
  3. Thermic effect of food
31
Q

Basal metabolic rate

What is it, how much of total EE, factors influencing, differences between young vs old and male vs female

A

The rate of EE at rest, necessary for bodily functions (70% of total EE)

  • determined by fat-free mass, fat mass, sex, age, genetics

Infants - higher due to rapid growth (proportionally) and elderly - lower as decreased muscle mass

Males have higher RMR than females (more muscle mass)

32
Q

Activity expenditure

How much of total EE, factors influencing

A

Most variable component (depends on activity levels) - ranges from 15% (highly sedentary) to 50% (highly active)

  • Energy cost is determined by activity levels + efficiency
  • Muscular work - comprises of spontaneous + voluntary exercise (e.g. sitting upright + running)
33
Q

Thermic effect of food

What is it, how much of total EE, factors influencing + impacted by

A

Refers to energy required to digest, absorb + metabolise + store nutrients (approx 10% of EE)

  • influenced by - type of nutrients (+ amount) + diet composition
  • impacted by - sedentary lifestyle (lower), ageing (lower), activity (enhanced), obesity (altered), insulin resistance (independently impact TEF regardless of food intake)
34
Q

What is energy balance? If there is energy balance, what would this mean?

A

Between energy intake + expenditure

  • state of energy balance = maintained body weight over a period of time
35
Q

What occurs if there’s a positive energy imbalance compared to a negative energy imbalance?

A

Positive…
Energy consumed > energy expended = weight gain

Negative…
Energy consumed < energy expended = weight loss

36
Q

What is obesity?

A

An excess accumulation of body energy, in form of fat (adipose tissue)

37
Q

What are the types of adipose tissue?

A
  1. Visceral adipose tissue
  • accumulation = risk factor for CMD
  • located in abdominal cavity
  1. Subcutaneous adipose tissue
  • just below skin
  • considered neutral / protective
38
Q

What is the body mass index + equation?

A

A surrogate measure of body fatness - but measures excess weight (not fat)

BMI = Weight / Height (m2)

39
Q

What are positive of BMI?

A

+ Simple, inexpensive + non-invasive

+ High BMI is important risk factor for CVD and T2D

+ Good tool for tracking + identifying pop. trends - comparisons across time, countries, pop subgroups etc

40
Q

What are negatives of BMI?

A
  • surrogate measure of body fatness
  • age, sex, ethnicity + muscle mass can influence interpretation
  • does not distinguish between excess fat, muscle or bone mass
  • does not provide indication of fat distribution

Human Nutrition - Y2S1 (8 decks)

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