Course 1 Flashcards
Why study feeding & drinking? (9)
• Eating and drinking are essential to survival
• Consequently, much of our behaviour, physiology and anatomy has been shaped by evolutionary forces related to ingestion
• Colour vision (from primates and ripe fruit)
• Liking for junk food (hard wired for sugar and fat)
• Disposition to gain weight not lose it (saving fat to survive famines)
• Bipedalism for predator detection and hunting (running)
• Gut and teeth design, and face structure (chewing)
• This is important because malnourishment kills, lowers IQ, cuts earnings and entrenches poverty; Obesity shortens lifespan, induces chronic diseases and is very costly
• Eating disorders seem to be coming more common, and they are also involved in obesity, notably binge eating disorder
What is energy metabolism? (7)
• The basic purpose of food is to provide energy
• Food provides chemical energy which the body
converts into
– Mechanical energy (muscles)
– Electrical energy (nerves)
– Heat (maintaining optimal temperature)
– Other forms of chemical energy (fat; proteins)
• The key food constituents that provide energy are
carbohydrates, proteins and fats (macronutrients)
What are the 3 main metabolic pathways?
- Three principal methods of generating energy – metabolic pathways
a (Glycolysis (primary in brain)), b (Kreb’s cycle, aerobic), c (Lactic acid cycle, anaerobic)
Fitness determined by capacity to get oxygen to muscle (VO2 max) - Two principal methods of energy storage = glycogen (ST) and fat (LT)
- Note that all energy sources can be converted to fat
How do we measure the energy in food? (4)
• One Kcal is the energy needed to raise 1L of water by 1 degree centigrade
• This is measured using a bomb calorimeter
• The amount of energy contained per gram, differs for fats, carbohydrates and proteins
– Proteins & Carbohydrate yield 4 Kcal/g
– Fats yield 9 Kcal/g
– (Alcohol yields 7 Kcal/g)
• This is why fats are called energy dense foods
What are the body’s energy needs? (6)
At rest, the body expends considerable energy - termed the basal metabolic rate (BMR)
• Most of the food (i.e., energy) you consume goes to maintaining your BMR – about 70-80%
• BMR includes energy for cellular physiology (pumps), breathing and blood flow, muscle tone and protein synthesis (e.g., immune system)
• Women need about 0.9 Kcal per kg/hour of bodyweight to maintain BMR and men around 1.0 Kcal per Kg/hour
• Over 24 hours, a 70 kg man would need around 1680 Kcal just to maintain BMR (i.e., 24x70x1.0)
• BMR varies a lot dependent upon lactation, pregnancy, muscle/fat bulk, physical fitness, illness and age
How do we calculate our energy needs?
• Most tables that report the caloric intake that you need are based upon calculating your BMR and then estimating a light to moderate level of activity
– Very light (BMR x 1.3)
– Light (men x 1.6, women x 1.5)
– Moderate (men x 1.7, women x 1.6)
– Heavy (men x 2.1, women x 1.9)
• Most westerners have activity levels that are typically in the very light to light range
What are carbs? (3 types + function)
• Types
- Simple
- Monosaccharides
- Glucose – corn, grapes
- Fructose – honey, many fruits
- Galactose – avocados
- Discaccharides (2 monosaccs together)
- Sucrose – ‘sugar’ (glucose + fructose)
- Lactose - milk sugar (glucose + galactose)
- Maltose - beer (2 glucose)
- Complex
- Polysaccharides (starch, cellulose; long chains of glucose)
• Function
– Primarily to provide energy
Total amount of added sugar is increasing and sucrose is decreasing but is compensated for by high fructose corn syrup (derived from corn and used to sweeten soft drink)
What are fats? (4 types + 5 functions)
• Or more properly Triglycerides a glycerol with three fatty acid tails
• Types (These are the different types of tail the glycerol can have)
- Saturated (animal, coconut, palm) – some may increase LDL (bad cholesterol)
- Monounsaturated (olive oil, canola) – some may increase HDL (good cholesterol)
- Polyunsaturated
- Omega 6 (vegetable)
- Omega 3 (deep sea fish) – may increase HDL and lower LDL
- Trans-saturated
- Artificially produced from Mono or Polyunsaturated fats
- Have significant commercial benefit/use (storage/non-animal)
- Have negative health consequences (CHD, Diabetes, Obesity)
- Health controversies – fats and heart disease
• Function
– Structural (nerves), Hormone synthesis, Fat soluble vitamins, Insulation & Padding, Energy storage
What are proteins? (+ 4 functions)
Types
– All proteins built from Amino acids
– Some are essential and some can be synthesised by the body (meat provides all essentials, but combinations of vegetables and legumes can do so as well)
• Function
– Tissue maintenance & growth, Hormone, Enzyme and Protein synthesis, Fluid balance, Energy
What are vitamins? (5)
Micronutrients
• Deficiencies relatively rare in Western nations, yet almost a third of the US population consume them
• Fat soluble vitamins (A, D, E & K)
• Vulnerabilities after obesity surgery & lipase inhibitors
• Water soluble vitamins (C, B1, 2, Niacin, 6, Folate,12, Pantothenic acid, Biotin)
What are minerals? (7 and 5)
Micronutrients
• Most Westerner’s have too much sodium (as Salt
[consume 10+g/day, RDA 3-6g/day]) and too little calcium
• Macrominerals (100mg/day+)
– Calcium (osteoporosis affects 25M in USA - bones,
clotting, cellular function)
– Phosphorus (1% of Body Weight - metabolism)
– Sodium (water balance, nerves)
– Potassium (water balance, nerves)
– Magnesium, Chloride & Sulphur
• Microminerals (100mg/day-)
– Iron (5g in total - hemoglobin)
– Iodine (thyroid function)
– Fluoride, Selenium & Zinc (and several others…)
What is the human digestive system? (7)
• The basic function of the digestive system is to efficiently extract nutrients from food
• We can characterise the digestive system as having two major parts
– Main organs (stomach, intestines)
– Accessory organs (liver, pancreas, gallbladder)
• Food is broken down mechanically, chemically (acid) and by enzymes
• Mouth – saliva, amylase and mechanical action
• Stomach
• Small intestine; Duodenum, jejunum, ileum
• Accessory organs
• Large intestine; Colon, rectum - Water re/absorption & compaction
What does the stomach do? (3)
• Food is received in the upper part of the stomach (fundus) where it is mechanically ground into particles 1-2mm in diameter
• It is then mixed with stomach acid and enzymes to form a semi-liquid fluid called chyme, collecting in the lower part of the stomach (antrum)
• After the stomach discharges its content into the gut, it starts to make rhythmic contractions that you may associate with hunger
What does the small intestine do? (5)
• It is about 2.5-3 cm in diameter and 6-7 M long (ranges from 4-10 M) and 90% of chemical absorption from food into the body happens here
• Food in the SI triggers CCK release and the accessory organs release bile (500ml/day) and pancreatic juices
• Bile breaks down fat
• Pancreatic juice breaks down protein and carbohydrates (gut secretions assist too)
• The products of digestion move through the SI wall (up to 60M2 surface area) into the HPV (hepatic portal vein) and travel to the liver and thence to the body’s cells
What does the large intestine do? (4)
• It is about 1-2m long
• It consists of four parts
– Cecum: Receives digested matter from small intestine (appendix)
– Colon: Removes remaining water and bacterial action results in the formation of B & K vitamins which are absorbed
– Rectum: Temporary storage
– Anal canal: As one would imagine
