Appetite, Satiety, and Digestion Hormones

• Appetite is the desire to eat, influenced by psychological or environmental factors, leading to eating even when not hungry.
• Satiety is the feeling of fullness and satisfaction after eating, signaling the body has had enough food.

Hormones Associated with Appetite and Satiety

• Ghrelin, produced in the stomach, signals hunger to the brain and stimulates food intake.
• Leptin, produced by fat cells, signals satiety to the brain, reducing appetite.
• Peptide, released by the small intestine after eating, suppresses hunger signals and promotes satiety.
• Cholecystokinin (CCK) reduces hunger by slowing gastric emptying and stimulating gall bladder contraction.

Accessory Organs and Their Role

• Teeth bite and chew food into smaller pieces, increasing surface area for enzyme exposure.
• Salivary glands produce saliva containing salivary amylase.
• Saliva lubricates food, forming a bolus for easier swallowing.
• Salivary amylase initiates carbohydrate digestion, converting starch to maltose via enzymatic hydrolysis.
• The tongue moves food around the mouth and pushes it towards the esophagus.
• Lingual lipase begins the digestion of triglycerides.
• The epiglottis covers the trachea during swallowing to prevent food from entering the windpipe.
• Lingual lipase, produced by the tongue, initiates fat breakdown by acting on triglycerides to free fatty acids from glycerol.
• As food enters the esophagus, saliva aids its passage.
• Peristalsis, wavelike muscle contractions, propels the bolus towards the stomach.
• A muscular wave at the base of the esophagus allows the bolus to enter the stomach.

Stomach Function

• The bolus enters the stomach.
• Strong, muscular walls contract to further break down food.
• The bolus is churned into a liquefied mass called chyme.
• Wavelike contractions squeeze chyme into the duodenum, the first part of the small intestine.
• Mucous membranes lining the stomach produce and store pepsinogen.
• Pepsinogen mixes with hydrochloric acid in the stomach and converts into pepsin.
• Pepsin begins protein breakdown into amino acids.
• Gastric lipase in the stomach starts the breakdown of fats into diglycerides and fatty acids.
• Breakdown of protein and fat occurs through enzymatic hydrolysis.

Smal Intestine

• The small intestine has three sections: duodenum, jejunum, and ileum.
• The duodenum is the first and shortest section of the small intestine.
• Enzymes from the liver, gall bladder, and pancreas are released into the duodenum to continue macronutrient digestion (protein, carbohydrates, fats).
• The liver produces bile, aiding in fat emulsification in the duodenum.
• The gall bladder stores and releases bile into the duodenum to aid in fat emulsification.
• The jejunum, the middle section of the small intestine, absorbs most nutrients into the bloodstream via villi.
• The ileum is the final section of the small intestine.
• Ileum absorbs any remaining nutrients not absorbed in the jejunum.
• The pancreas secretes enzymes into the duodenum to break down fats, proteins, and starches via enzymatic hydrolysis.
• Lipase breaks down fat into fatty acids and glycerol.
• Pancreatic amylase breaks down starch into maltose.
• Protease splits proteins into separate amino acids.
• Trypsin assists in breaking down protein into amino acids.
• Intestinal epithelial cells lining the villi secrete sucrase, lactase and maltase.
• Sucrase breaks down sucrose into glucose and fructose.
• Lactase breaks down lactose into glucose and galactose.
• Maltase breaks down maltose into glucose.

Large Intestine

• After nutrient absorption in the jejunum and ileum, indigestible remains move to the large intestine.
• Water is absorbed from the waste, and remaining solids are compacted for elimination.
• Gut microbiota in the large intestine break down soluble and insoluble dietary fiber via fermentation.
• Fermentation produces short-chain fatty acids, which support healthy epithelial cells lining the colon.
• Dietary fiber is not absorbed into the bloodstream.

Enzyme Hydrolysis

• Enzyme hydrolysis is a chemical digestive process.
• Breaks down food by breaking bonds in molecules.
• Enzymes incorporate a water molecule across the bond, allowing it to break.
• Pepsin breaks down protein into amino acids in the stomach in this way.
• Lipase breaks down fats into fatty acids and glycerol, and pancreatic amylase breaks down starch into maltose.

Gastrointestinal Tract and Microbiology

• The gastrointestinal tract is the pathway food travels from mouth to anus.
• Microbiology of the gastrointestinal system refers to the microorganisms (bacteria, viruses, fungi, etc.) living in the digestive tract.
• Accessory organs include teeth, tongue, salivary glands, pancreas, liver, and gall bladder.
• The sequential process of macronutrient digestion involves eating, mechanical digestion (chewing), chemical digestion (enzyme breakdown), absorption (nutrients into the bloodstream), and elimination (excretion of waste).

Digestion, Absorption, and Utilization

• Digestion breaks down food into absorbable substances for energy, growth, and repair.
• Accessory organs contribute to the digestive process through mechanical and chemical means.
• Mechanical digestion involves physical force (chewing, churning) to break down food.
• Mechanical digestion begins in the mouth with the teeth and tongue.
• Esophagus, stomach, and intestines continue this process by pushing food along and churning it to break into smaller pieces.
• Bile also uses mechanical digestion to physically break down and emulsify fats for further chemical digestion.
• Chemical digestion breaks down food using chemicals like enzymes and acids.
• Chemical digestion begins when food is seen or smelled.
• Nerves trigger enzyme release to break down food and release nutrients.

Carbohydrate Absorption and the Pancreas

• Sugars and starches break down into glucose.
• Glucose molecules are absorbed from the jejunum into blood capillaries.
• Glucose is then transported via the bloodstream to cells for energy.
• The pancreas releases insulin, which helps glucose move from the bloodstream into cells.
• Inside the cell, glucose is burned with oxygen to produce energy.
• Excess glucose is converted to glycogen.
• Glycogen is stored in the liver and muscle tissue for later use.
• It can supplement blood sugar levels during physical activity.

Carbohydrate Utilization

• Carbohydrates provide energy for physical/mental exertion, physiological functions, and body cell functions.

Protein Absorption

• Proteins break down into amino acids during digestion.
• Amino acids are absorbed from the jejunum into capillaries.
• Amino acids dissolve in the blood and are carried to the liver for storage.
• The liver directs the distribution of amino acids for use throughout the body.

Protein Utilization

• Protein is used for growth, repair of bone/muscle cells, blood cell production, and connective tissue/cartilage formation.
• Amino acids are the building blocks of protein but also precursors to enzymes, hormones, and antibodies.
• Excess protein can be converted into kilojoules and used as energy or stored as body fat if not used.
• Protein can be used as an energy source when there is insufficient carbs and fat in the diet.

Fat Absorption

• Fatty acids and glycerol are absorbed into the lacteals.
• Lacteals are located in the inner section of the villi in the small intestine.
• They recombine to form fats that mix with the lymphatic fluid.
• These fats pass through the lymphatic system, then join blood circulation as insoluble fat.
• They are then converted to soluble fat in the liver.

Fat Utilization

• Fat is a concentrated energy source, containing 37 kilojoules per gram.
• Fat provides more than twice the energy per gram.
• Fat is stored in adipose tissue around vital organs such as the kidney.
• Vitamins A, D, E, and K are absorbed in fats and described as fat-soluble vitamins.
• These vitamins are only soluble in fats, not in water.

Macronutrient Absorption and Utilization Summary

• Carbohydrates are absorbed in the villi of the small intestine and into the bloodstream and used for energy production (ATP) and stored as glycogen or fat if excess.
• Fat is absorbed in the small intestine via lacteals into the lymphatic system and used for energy, cell membrane structure, and hormone production.
• Protein is absorbed as amino acids in the small intestine into the bloodstream and used for muscle growth, repair, enzyme production, and other body functions.

Prebiotics & Probiotics

• Both prebiotics and probiotics play a role in gut health.
• They affect neurotransmitters like dopamine and serotonin.
• They also improve mood.
• A healthy gut microbiome helps regulate stress, anxiety, and overall mental well-being.

Types of Fibre & Food Sources

• Soluble fibre slows digestion, regulates blood sugar, and lowers cholesterol and includes foods like oats, apples, lentils, beans, and citrus fruits.
• Insoluble fibre adds bulk to stool and prevents constipation and includes foods like whole grains, nuts, seeds, vegetables, and wheat bran.
• Resistant starch feeds gut bacteria and improves gut health and includes foods like green bananas, cooked & cooled potatoes, and legumes.

Gut-Brain Axis & Neurotransmitters

• The gut-brain axis is the communication system between the gut and brain.
• Influences emotions and cognitive function.
• Serotonin (mood stabilizer): 90% is produced in the gut and helps with happiness and sleep.
• Dopamine (pleasure & reward): Gut bacteria help regulate dopamine, affecting motivation and mental health.
• A balanced gut microbiome supports mental well-being.
• It reduces anxiety and depression risks.

Difference Between Prebiotics & Probiotics

• Prebiotics are non-digestible fibres that feed good bacteria, promote healthy gut bacteria's growth, and are found in garlic, onions, bananas, and whole grains.
• Probiotics contain live beneficial bacteria that improve gut health, restore and maintain gut bacteria balance, and are found in yogurt, kimchi, kombucha, and kefir.

Credible Sources

• Credible sources are reliable and trustworthy providers of information, supported by expertise, research, and evidence.
• Scientific studies, government health agencies, and research institutions use peer-reviewed data and are considered credible source.
• Using credible sources ensures guidelines are based on facts, not opinions.
• The National Health and Medical Research Council (NHMRC), Australian Bureau of Statistics (ABS) and The World Health Organization (WHO) are examples of this.

Evidence-Based Information

• Evidence-based information includes facts and recommendations from scientifically tested and proven research, experiments, and systematic reviews.
• Large-scale studies and clinical trials help develop accurate dietary advice.
• Prevents misinformation and ensures dietary recommendations lead to positive health outcomes.
• Studies showing that fruit and vegetable intake reduces the risk of chronic diseases.
• Research proves that excess saturated fat increases heart disease risk.
• Systematic reviews compare different diets and their effects on health.

Accurate Data Analysis

• Accurate data analysis requires correctly interpreting statistics, trends, and research findings without bias or errors.
• National nutrition surveys, scientific reviews, and health studies determine patterns in Australian eating habits and their impact on health.
• This ensures dietary guidelines reflect real-world health trends and prevent misinterpretation of research.
• Analyzing ABS food consumption data helps understand Australians' eating habits.
• Reviewing trends in obesity and nutrient deficiencies helps adjust dietary recommendations.
• Ensuring statistical accuracy is ensuring when linking diet to diseases like diabetes or cardiovascular issues.

Justification of Food Groups for disease prevention

• Each food group (carbohydrates, vegetables, fruits, dairy, meats/proteins) provides essential nutrients.
• These nutrients support overall health and prevent chronic diseases (heart disease, diabetes, osteoporosis, cancers).

Benefits

• Carbohydrates provide fibre, B vitamins and iron.
• Fibre aids digestion, lowers cholesterol, reduces heart disease and type 2 diabetes risk.
• B vitamins support brain function and energy production.
• Vegetables provide Vitamins A, C, K, fibre, and antioxidants.
• Vitamin A supports immune function and eye health.
• Vitamin C boosts immunity and helps heal wounds.
• Antioxidants protect against cell damage and reduce inflammation.
• Fruits provide Vitamin C, fibre, and natural sugars.
• Fibre aids digestion and maintains heart health.
• Vitamin C strengthens the immune system.
• Antioxidants reduce the risk of chronic diseases.
• Milk & Dairy provide Calcium, Vitamin D, and protein.
• Calcium & Vitamin D strengthen bones and prevent osteoporosis.
• Protein supports muscle maintenance and repair.
• Protein is essential for muscle growth and immune function.

Additional benefits

• Iron prevents anemia and supports oxygen transport.
• Omega-3s reduce inflammation and heart disease risk (from fish & nuts).

Discretionary Foods

• Extra foods, also known as discretionary foods, include soft drinks, sweets, processed snacks, and fast food.
• These are not necessary for health but are still available because of cultural and social reasons.
• Convenience and enjoyment are also factors.
• The food industry and economy support these foods' production.
• Too many discretionary foods can lead to obesity, heart disease, type 2 diabetes, and tooth decay.
• The Australian Dietary Guidelines recommend eating discretionary foods in small amounts and not as part of daily nutrition.

Food Needs Based on Physical Activity Level

• Food intake should match physical activity level to provide enough energy and nutrients.
• Sedentary (Little to No Exercise): Lower energy needs, whole grains, vegetables, fruits, and lean proteins (chicken, tofu).
• Moderate Activity (30-60 mins most days): Moderate energy needs, complex carbs (sweet potato), healthy fats (avocado, nuts), and protein (fish, lean meat, legumes).
• High Activity (Athletes or intense training): High energy needs, high-carb meals (pasta, oats), quick energy snacks (bananas, dates), and protein recovery (Greek yogurt, eggs).

Foods High in Nutrients

• Folate (Vitamin B9) supports cell growth and DNA production during pregnancy (dark leafy greens, avocado, citrus fruits, fortified grains, eggs).
• Calcium strengthens bones and teeth and helps with muscle function and nerve signaling (dairy, canned fish with bones, plant-based sources, green veggies).
• Vitamin C boosts the immune system and helps with iron absorption (citrus fruits, capsicum, kiwi fruit, berries).
• B-Group Vitamins convert food into energy and support brain function and red blood cell production (meats, whole grains, legumes & nuts, eggs, tomatoes).

Allergies

• A food allergy occurs when the immune system identifies a harmless food as a threat and releases chemicals like histamine.
• Causes serious reactions, including anaphylaxis, which can be life-threatening.
• Symptoms include hives, swelling, difficulty breathing, vomiting, or loss of consciousness.
• Management aims to avoid the food completely, through epinephrine injections as needed.

Intolerances

• A food intolerance is a digestive issue where the body has difficulty processing foods due to lacking an enzyme.
• Lactose intolerance is an example.
• Symptoms are a cause of digestive discomfort.
• Management includes avoiding or limiting the offending food or drink, as well as enzyme supplements to aid digestion.

Food Elimination and Swapping (Allergies)

• Elimination is very important.
• Example: If someone is allergic to peanuts, they must avoid all peanuts and products.
• If allergic to something like dairy (milk), swaps might include almond milk or soy milk.
• Example: Vegan cheese or nut-based cheeses instead of dairy cheese.

Food Elimination and Swapping (Intolerances)

• For intolerances, avoiding or reducing problematic food may be necessary.
• Someone with lactose intolerance would avoid dairy products.
• Lactose-free milk or almond milk can be swapped with regular milk.
• Gluten-free bread or rice cakes can be swapped with regular bread for those with gluten intolerance.

FODMAP

• Fructans (Wheat, onions, garlic, rye)
• Galacto-oligosaccharides (GOS) (Beans, lentils, chickpeas, cabbage and cauliflower) Avoid those food if sensitive.

2. Disaccharides (Lactose)

• Foods high in Lactose: Milk, soft cheeses, cream, yogurt.
• Swap with lactose-free milk or almond milk instead of regular cow's milk.

3. Monosaccharides (Fructose)

• Foods high in Fructose: Apples, pears, watermelon, honey, high-fructose corn syrup, and some fruit juices.
• Swap with bananas, blueberries, or grapes.
• Avoid fruit juice or use stevia or maple syrup.

4. Polyols:

• Foods high in Polyols: Certain fruits like cherries, apples, and peaches, as well as artificial sweeteners found in sugar-free gum and candy.
• Swap with Lemon, kiwi, or strawberries.
• Natural sweeteners like honey or maple syrup should be swapped out for artificial sweeteners.

Dietary Guideline 2

• Dietary Guideline 2 suggests that you eat a wide variety of nutritious foods from the five food groups every day This promotes balance and diversity in the diet
• AGHE also known as Australian Guide to Healthy Eating visually represents this through a plate model divided into sections, each corresponding to one of the five food groups:
  • Vegetables and legumes/beans
  • Fruits
  • Grain foods (mostly whole grain)
  • Lean meats and poultry, fish, eggs, tofu, nuts, and seeds
  • Dairy or dairy alternatives

Bodies breakdown of food in stages

• Mouth: Food is chewed and mixed with saliva to start breaking it down.
• Stomach: Enzymes and acids break down the food more, especially proteins.
• Small Intestine: Most of the food is broken down here, and nutrients are absorbed into the bloodstream.
• Nutrients like sugar (for energy), protein (for building and repairing), and fat (for energy storage) are used by the body.
• Extra sugar is stored for later use, and fats are stored in fat cells.
• Eating in moderation will only benefit the human body.

Diet influencing gut bacteria

• Community of microorganisms in the digestive tract.
• Helps digest, supports immunity, produces vitamins, and influences mood.
• Diet in naturally high fiber and are minimally processed will encourage the growth and health of beneficial microbiota.

Important Foods

• A whole-foods diet is most beneficial
• Plant foods, especially whole-grains, legumes, vegetables, fruits, nuts and seeds, are very important for the development of healthy gut microbiota
• Important limit highly processed foods = detrimental impact
• Must consume pre-biotics and pro-biotics such as kimchi, sauerkraut, miso, kefir are LIVE BACTERICA
• Prebiotics are compounds that naturally occur (feed bacteria in gut, therefore improving it)

How a healthy Micro biota impacts the body

• Short chain fatty acids are the main metabolites produced by bacterial fermentation of dietary fiber in the gastrointestinal tract and they help
• Short chain fatty acids suppress appetite therefore helping maintain a healthy weight preventing individuals from becoming overweight or obese.
• Short chain fatty acids = metabolize carbohydrates and fats
• Reduces the likeliness of health concerns
• lifestyle diseases such as cardiovascular or type 2 diabetes occurs if a diet is not followed.
• Brain and gut are communicating through the use of neurons, hormones and immunological messages
• Gut will support the brain if this communication is strong/healthy
• Dopamine = Important neurotransmitter to focus on mood. (Diet effects this)
• Diet high fibre = improving mental health, more focus against feelings of stress, depression and anxiety

Reasons for differences in dietary requirements

• Requirements for infancy and early childhood include breast milk is the best for young babies as it contains all growth nutrients such as proteins, calcium etc

• If non breast milk is applied, ensure to provide nutrients and growth needs A wide variety of food that are rich in carbs, fats protein for child is vital

• Requirements for Adolescents Adolescence Is often a period of time for intense physical activity; their diet needs a wide variety of foods that will supply the energy, protein, vitamins and minerals needed to sustain the rapid growth and active lifestyle

• Requirements for Adulthood A well-balanced diet is needed to provide adequate nutrients for the maintenance and repair of the tissues in the body as well as to repair damaged tissues and to provide energy for physical activity. Diet contains adequate amounts of fibre, protein, vitamins and minerals

• Their metabolic rate slows down and their lifestyle may become more sedentary =, therefore energy-dense foods should be limited

Requirements during pregnancy More nutrients/protein, + more Vit C and B and Folate A high folate diet during pregnancy/months before can assist to prevent spina bifida

Males requirements are higher than females due to body stricture and levels of activity Different requirements = different activity and diet