BPK 110 Module 5 & 6

The Structure and Properties of Water

• Water is a polar molecule

• Other polar molecules are attracted to water = hydrophilic

• Non polar molecules are not attracted to water = hydrophobic

Where will water move

If there is an area with more dissolved polar structures, water will move towards these

When blood pressure is higher

There is a greater chance the water will move from blood vessels to extracellular space

Water Content of Human Body

• Human body is 60-70% water by weight

• Cells have lipid walls, but are comprised mostly of cytoplasm, a gel like substance that is 80% water. In healthy people, water content of cells doesn’t change substantially, however the extracellular water content is constantly being used for the body’s needs and must be regularly replenished

Intracellular water

2/3 found within cells

Extracellular water

1/3 found outside of cells (found around joints, in lungs, lining certain tissues and in lymph)

Osmosis

• The movement of water towards charged particles. This is done in an effort to even out concentration differences

• Blood pressure involves a force that pushes water out of blood and into extracellular space

Water Structure

• Water helps structure maintain their form

• Water within cells gives them the 3D shape necessary for cellular organelle to function properly

• Ex: Water within synovial found in sacs b/w joints. Allow bones to glide by each other more fluidly

Solvent

• Allows them to move around watery environments

• Allows them to collide with other molecules that they might react with

• Important for moving things around the body via blood vessels or digestive tract

Hydrolysis

Use water to split larger molecules into smaller ones

Defence from infections

• Water provides an environment for immune cells to fight off infection

• Water is the main component of mucus, which helps remove infectious agents

What happens if a infectious agent enters the body

It can be moved to the lymph, where these immune cells can act it for removal

Protection from Injury

• Can reduce the friction and damage from movement or trauma that can negatively affect our tissues

• Synovial fluid help bone articulate to prevent bone from scrapping each other

• Water around brain and spinal cord helps protect them from various forces (cerebrospinal fluid)

Temperature Regulation

• Strictly controlled and uses water to regulate body temp through two main mechanisms

  • When sweat evaporates, it cools down our body

  • Blood is shunted to the skin’s surface to help promote sweating, lower internal temp

What happens if body is unable to regulate temp

Heat illness can occur

What temp is the body able to regulate

Maintained at 37 C to function properly. A 0.5 C change in body temp can negatively affect body physiology

How can Heat Stroke Occur

When Body temp rises above 40 C. Accompanied by neurological symptoms such as delirium, confusion and convulsions and can lead to coma or death

Sources of Water

Liquids, Foods, Metabolism

Maintaining water balance

• Maintain homeostasis

• Heavy emphasis on preserving body water levels through two main mechanisms

  • Thirst response

  • Kidneys

Thirst response

Due to several body sensors that indicate to the brain that the concentration of dissolved particles in the blood is high meaning concentration of water is low

Kidney

Decide what stays in the blood and what is excreted in urine. When blood is high, excess water is exerted into kidneys

Dehydration

• Either due to insufficient consumption or excessive loss

• Symptoms include thirst, dry mouth, fatigue, dizziness, irritability, dark urine

• Chronic dehydration can lead to kidney damage, seizures and hypovolemic shock

• Mild dehydration can be uncomfortable while extreme dehydration can be deadly

Kidney disease

Dehydration puts extra stress on the kidneys as they don’t have enough water to help secrete waste products. This increases the risk of urinary tract infection, kidney stones, can lead to chronic kidney disease even death

Seizures

Excessive sweating, electrolyte imbalance can compromise the body’s electrical activity

Water Intoxication

• AKA water poisoning

• When water levels decrease the concentration of dissolved particles in the blood

  • Ex: hyponatremia (low sodium in blood)

• Potentially fatal

• Symptoms include headache, confusion, personality changes, irritability, drowsiness

• Typically due to excessive sweating that is replaced by water alone

Diuretics

• Substances that promote water loss through urination

• Ex: Diuretic pills, aka water pills, promote sodium excretion at the kidney, which also promotes water excretion

• Alcohol and caffeine are also diuretics

  • They are not nutrients, they are psychoactive drugs

Caffiene

• Compound naturally found in certain seeds, nuts, leaves

• A diuretic, but mainly used for its stimulant effects

  • Promotes alertness, reduces tiredness

• May have beneficial roles in disease reduction when consumed in coffee (decrease in cardiovascular disease, Parkinson’s, type 2 diabetes + certain type of cancer)

  • Coffee is believed to have antioxidant and anti-inflammatory properties

• May increase the risk of miscarriage and kidney stones

Alcohol

• Psychoactive drug found in certain foods and beverages

• Provides 7 kcal/g

• Higher levels of consumption increase risk for cancers, liver cirrhosis, confusion, dementia, malnutrition, all-cause mortality …

• However, light to moderate amounts (1-2 servings a day) may provide a slightly lower risk of CVD

Factors that Affect Level of Intoxication

• How much is consumed

• How quickly alcohol is absorbed

• The size of the individual

• Gender

• Genetic factors

• Type of alcohol consumed

• Menstruation cycle

Alcohol Metabolism

• 90% of alcohol is metabolized and eliminated at the liver

• Alcohol dehydrogenase aldehyde dehydrogenase are the enzymes responsible for metabolizing alcohol

• Genetic changes can negatively impact the activity of these enzymes

  • May result in facial redness, nausea, sweating, dizziness and racing heart rate when alcohol is consumed (Asian Flush)

Hangovers

• Typically occur 6+ hours after drinking

• Symptoms include vomiting, tiredness, decreased attention, decreased concentration, stomach pain and disturbed sleep

• May be due to direct effect of alcohol, acetaldehyde buildup or congeners

• Best ways to avoid a hangover is to moderate or abstain from alcohol consumption

Views of Water

• Western Lens:

  • Important natural resource

  • Commodity

  • Used for industry, agriculture

  • Used by humans as a nutrient

• Indigenous Lens:

  • Tied to our existence

  • Part of who we are

  • Has a life of its own

  • “Mother Life’s blood”

Water Recommendations

• Look for signs of dehydration, including thirst and darkened urine colour. When they occur, drinking water can reduce symptoms and complications

• The AI or water is 2.7 L/day for women and 3.7 L/day for men

• When excessive water is lost due to sweating, vomiting or diarrhea, it is important to replenish both the lost water and electrolytes

• Consume alcohol in moderation as it has many negative mental, social and physical effects

• The best remedy for a hangover is time

Carbohydrates

• Denotes what their structure is composed of carbo (carbon) and hydrate (hydrogen and oxygen)

• Three main types: Sugars, Starch and Fibre

• All three made up of monosaccharides, or sugars

Sugars refers to what

Molecules that have a single (monosaccharide) or double (disaccharide) unit of sugar in their structure

Intrinsic sugars

Sugars that are found naturally in many foods including fruits and milk

Monosaccharides (Single Sugars)

• There are three main monosaccharides found in the food we eat

• Glucose is the most common monosaccharide

Glucose

• The building block of most other larger carbohydrates like starch and fibre. Can be found in the blood

• Can fuel the needs in the body, including brain cells & RBC as well as convert to ATP

Fructose

Fruit sugar - sweeter than glucose + many other sugars

Galactose

Milk sugar - similar sweetness of glucose

Disaccharides (Double Sugars)

The dietary monosaccharides that are used to make up the most common dietary disaccharides in sucrose, maltose and lactose

Sucrose

Table sugar (what we think of) - make up of a glucose molecule bound to a molecule of fructose

Sucrase

Breaks down sucrose into two sugars

Maltose

Malt, makes bread taste better - comprised of two glucose molecules

Lactose

Main sugar in milk, composed of glucose + galactose molecules

Brown vs White Sugar

• Both brown and white sugar are sucrose that originates from either sugar cane or beets

• Brown sugar is white sugar that is mixed with molasses

• They are very similar nutritionally

Extrinsic sugars

• AKA added sugars, are added into food by manufacturers to increase their sweetness

• Foods higher in this are more likely to be nutrient poor and energy dense and may increase risk of disease

Oligosaccharides (Few Sugars)

• Have between 3 and 10 monosaccharides in their chain

• Considered fibres, because humans lack the enzymes needed to digest them

• Most commons oligos = fructooligosaccharides (FOSs) and galactooligosaccharides (GOSs)

• Are prebiotics because digestive bacteria can use them for food

Polysaccharides (Many Sugars)

• Have more than 10 monosaccharides in their chain

• Typically composed of long glucose chains

• Two main types:

  • Starch (humans have the enzymes needed to break it down)

  • Fibre (humans do not have the enzymes needed to break it down)

Starch

• Long glucose chain that is either straight (amylose) or branched (amylopectin)

• Receives this from eating plants, potatoes, rice, corn, wheat, etc.

Amylopectin

Most common carbohydrate in the human diet. Most foods that contain starch have a greater degree of amylopectin than amylose

Starch digestion

Starch → oligosaccharides → disaccharides → monosaccharides glucose → absorbed

Fibre

• Many types including cellulose, dextrin and inulin which are dietary fibre

• Can be either insoluble or soluble

• Compared to starch, the bonds that hold adjacent glucose molecules together are different

  • We lack the enzymes to break these bonds

  • No chemical digestion of fibre in small intestine

• Vegetables, fruits, whole grains + legume are good sources

Soluble Fibre

• Dissolves in water (form a gelatinous solution, which adds bulk and viscosity to ingested food)

• Found in apples, beans, peas, citrus fruits…

• May help to regulate blood glucose and lower blood cholesterol (decrease in blood glucose)

• Bacteria in the large intestine can ferment soluble fibre to produce short chain fatty acids

  • Provide 2-3 kcal of energy per gram of soluble fibre

Insoluble fibre

• Does not dissolve readily in water

• Passes through digestive tract virtually unchanged

• Found in wheat, bran, beans, potatoes, cauliflower …

• May promote digestive health

• Not fermented by bacteria in the large intestine and passes through the digestive tract unchanged

Glycogen

• A large unbranched chain of glucose units. Found in negligible amounts in the human diet

• Storage form of carbohydrate (0.5-2 kg), quick source of glucose when needed

• Stored in muscles and around out liver (small pockets)

• Max storage capacity is 15 g/ kg body weight

• Fat is our main long-term energy source

Unrefined Carbohydrates

• Those consumed in their entire form i.e. the entire grain is used

  • Ex: Whole grain wheat + Whole grain oats

• Main edible parts of the plant have not been changed or removed

• More nutrient dense, higher in fibre, phytochemicals

Refined sources

• Have part of the grain removed, typically the bran and germ layer (lowers the nutrient density of that plant)

• Lower in fibre, phytochemical + lack their associated benefits

Bran Layer

Outer, waxy cover of the grain (fibre, B vitamins, calcuim)

Endosperm

Most of the grain. Composed of starch and tends to be lower in other nutrients (starch, protein, B vitamins)

Germ Layer

Or embryo, the smaller inner part of the grain, Has the highest protein content of the three (protein, lipid, vitamin E)

Carbohydrate Digestion

1. In the mouth, salivary amylase begins the digestion of starch

2. In the stomach, hydrochloric acid inactivates salivary amylase; no carbohydrate digestion occurs here

3. Pancreatic amylase is secreted into the small intestine to continue carbohydrate digestion

4. The microvilli of the small intestine also secrete various carbohydrate-digesting enzymes

5. Undigested carbohydrates pass on to the large intestine; some are further broken down by bacteria.

6. Any remaining undigested carbohydrate is excreted

Cholescystoskin (CCK)

A hormone that acts on receptors in the pancreas to promote the release of pancreatic juice into the small intestine

Digestion and Absorption of Carbohydrates at the Villi

• Brush border contains an essential set of carbohydrate-digesting enzymes that are released by intestinal cells to finish off the digesting job that the amylases started. Lactase, maltose + sucrose are all brush border enzymes

• These enzymes are located within the cells that line the villi, so once carbohydrates have been digested into monosaccharides they can be then absorbed immediately

• Glucose, fructose & galactose are absorbed across the walls of small intestine cells into blood capillaries. They then go to the liver, where fructose and galactose are metabolized. Some glucose are stored in liver as glycologen

Lactose Intolerance

• Caused by insufficient secretion of the enzyme lactase

  • Since lactose cannot be digested in small intestine, bacteria in the large intestine ferment it

    • Leads to the production of methane gas

• Symptoms include cramps, bloating, diarrhea, abdominal pain when lactose is consumed

Glycemic responnse

• Spike in blood glucose that follows a meal once glucose enters the general circulation

  • Diets that produce a lower GR associated with a lower risk of type 2 diabetes, CVD and obesity

  • Individuals with both type 1 and type 2 diabetes choose foods that produce a lower glycemic response to help control blood sugar levels

Glycemic Index

• Help manage blood sugar levels, relative ranking of a food’s potential to spike blood sugar on a 100-point scale

  • Glucose scores 100

• Glycemic Load may be more accurate then glycemic index because it also takes into account how many carbohydrate is actually in the food

  • Low GI (<55)

  • Medium GI (56-69)

  • High GI (>70)

Blood Sugar Regulation

• Our bodies try to establish glucose homeostasis (there is neither too much nor too little glucose in the blood)

  • Insulin and glucagon are blood-regulating hormones - secreted in the pancreas

• When blood is not in balance, it can have negative effects

  • Hypogloycemia

  • Hyperglycemia

Hypoglycemia

Low blood glucose, can affect energy levels, tiredness, lethargy and irritability, extreme hunger, and mental confusion

Hyperglycaemia

High blood glucose, if chronic, can lead to diabetes and can damage blood vessels and the kidney

Endocrine Pancreas

Pancreas secretes insulin and glucagon into the blood in order to regulate blood glucose

Exocrine Pancreas

Pancreas secretes pancreatic juice into the digestive tract to facilitate digestion

Insulin and Blood Glucose

1. Normal blood glucose

2. Following a meal, blood glucose concentration increases

3. In response to the increase in blood glucose, the pancreas secretes insulin into the blood

4. Insulin binds to its receptor on cells

5. The binding of insulin to its receptor brings glucose channels to the cells surface

6. Glucose leaves the blood and enters the cells through glucose channels

7. Blood glucose returns to normal

Glucagon and Blood Glucose

• When blood glucose drop, the pancreas releases glucagon (can occur during times of fasting)

• Glucagon increases blood glucose through three main processes:

  • Glycogenolysis

  • Gluconeogenesis

  • Lipolysis

Glycogenolysis

The conversion of glycogen to glucose

Gluconeogenesis

The conversion of certain amino acids into glucose

Lipolysis

The breakdown of stored lipids. The glycerol from triglycerides can then be used to make glucose

Energy Provision

• The main role of carbohydrates is to provide energy

• Recall that cells metabolize glucose to capture its energy as ATP

Carbohydrates Spare Proteins

• If the body does not consume enough carbohydrates, certain amino acids will used to make glucose through process of gluconeogenesis

  • This leads to the breakdown of body proteins - can occur during periods of carbohydrate and/or caloric restriction

• Getting enough carbohydrate in the diet minimizes the breakdown of body proteins

Fat Burns in Carbohydrate Flame

• Metabolism of glycerol + fatty acids make up triglyceride → acetyl CoA. Can enter the citric acid cycle if oxaloacetate present.

• Sufficient dietary carbohydrate are needed in order to maintain oxaloacetate levels (citric acid cycle)

• If the diet is very low in carbohydrates, the products of lipid metabolism cannot enter the citric acid cycle and will instead form ketones

Diabetes

• Chronically elevated blood glucose levels

• Has both acute and chronic symptoms

  • Acute: Increased thirst, tiredness/lack of energy, slow healing infections, frequent urinations, weight loss

  • Chronic: neuropathy/numbness, cardiovascular disease, blindness, kidney disease, amputation

An Indigenous Lens on Diabetes

• In Canada, Type 2 diabetes is 2-3 times more common in Indigenous populations

• This is believed to be due, in part, to colonization and cultural loss

• Indigenous individuals who retain their culture through language are less likely to develop diabetes

Type 1 Diabetes

• Approx 10% of cases

• AKA juvenile or insulin-dependent diabetes

• The immune system attacks the insulin-secreting cells of the pancreas

  • The immune system attacks the insulin-secreting cells of the pancreas and no insulin to promote glucose’s uptake into and out of the blood, blood glucose remains high

Type 2 Diabetes

• Approx 90% of cases

• Mainly evidenced by insulin resistance

  • Cells lose their sensitivity to insulin, don’t respond to it

  • Initial stages: levels tend to be very high, as the body produces more of it to get the excess glucose into the cells

  • Later stages: Insulin secretions by the pancreas may decrease and an individual may also require insulin injections

Gestational Disease

• Elevated blood glucose and impaired glucose management that first occurs during pregnancy

• Approx 5% of pregnant women develop it (more common in older women)

• Increases future risk for type 2 diabetes in mother

• To reduce risk, a moderate diet and activity patterns that promote healthy weight is recommended. It is also important that mothers are screened for this so it can detected early and properly managed

Risk factors in Diabetes

• Type 1

  • Unknown

  • Genetics? Infections?

• Type 2

  • Obesity

  • Physical activity

  • Diets high in processed foods, sugar fat

  • Genetics

  • Family history

  • Gestational diabetes

Prevention of Diabetes

• Type 1

  • No preventative measure has been measured

• Type 2

  • Lifestyle changes

    • Weight balance, loss

    • Reduction in caloric intake, fat

    • Physical activity

  • Medication

Diabetes Management

• No cure for type 1 or type 2 diabetes

• Type 1 diabetes can be managed through:

  • Insulin injections (2-4 throughout the day)

  • Lifestyle

• Type 2 diabetes can be managed through:

  • Lifestyle

  • Blood sugar monitoring

  • Medication (metformin)

  • Bariatric surgery

  • Insulin injections

Fredrick Banting

Discovered insulin while working at UofT. Before this, people died with type 1 diabetes at a young age. Sold the patent for $1

Reactive hypoglycemia

Due to excessively high dose of insulin (occurs 2-5 hours after meal)

Non reactive hypoglycemia

May be due to fasting. medications, pregnancy, alcohol abuse and liver, heart, kidney disorders

Sugar and Health

• Sugar is not inherently bad or good

• However, foods high in extrinsic sugars are often energy dense and nutrient poor

• Diets high in extrinsic sugars are associated with higher risk of CVD diabetes, obesity

• In particular, high intake of sugar-sweetened beverages is associated with higher risk of obesity and CVD

• Food guide recommends replacing sugary drinks with water

Non- nutritive Sweeteners

• AKA sugar substitutes, artificial sweeteners

• Have negligible calories and a sweet-tasting flavour

  • 30-1300x sweeter than sugar

• Bind to sweet-detecting receptors on the tongue, allowing the brain to sense sweetness without the calories that come with sugary substances

Is Aspartame Safe?

• One of the most rigoursly studied food additives

• Large-scale systematic reviews have found no link between aspartame and cancer, neurological symptoms

Carbohydrates and Weight Management

• If carbohydrate intake does not increase caloric intake, weight will not be gained

• However, liquid sources of carbohydrates (i.e. sugar-sweetened beverages may promote a decrease in fullness)

  • Which may increase caloric consumption

• Conversely, fibre is associated with lower BMI

  • Perhaps due to its ability to increase fullness

Carbohydrates and Dental Caries

• Cavities = holes that develop in teeth

  • Can promote pain, tooth loss

• Sugars provide food for bacteria to grow and thrive

  • Bacteria release acid when they act on sugars

    • This damages tooth enamel (eats away at the surface of the tooth)

Carbohydrates and CVD

• A high GI diet has been associated with an increase cardiovascular risk factors such as high blood triglyceride levels and lower levels of good cholesterol, high density lipoprotein

• Diets high in fibre associated with lower CVD risk

  • Soluble fibres decreases LDL (“bad”) + total cholesterol levels in the blood

  • Blood glucose regulation is important for decreasing the risk of as well as managing type 2 diabetes. Soluble fibres has been shown to decrease glucose spikes. It can slow glycemic response by adding bulk to the diet, leading glucose to be more absorbed more slowly

Irritable Bowel Syndrome (IBS)

• Chronic condition that promotes symptoms such as abdominal pain, diarrhea, constipation, gas and bloating

• Physical, mental + social challenges

• Associated with poor interactions b/w digestive tract and brain but its full mechanism remains unclear

FODMAPs

• Short-chain carbohydrates are not fully absorbed in the small intestine and are fermented by bacteria in the large intestine, producing gas

  • May promote IBS symptoms

• Reducing these FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides and polyols) may improve IBS symptoms

Fibre and Colon Cancer

• Dietary fibre intake may reduce the risk of developing cancers of the large intestine

• Individuals who consumed the most fibre had the lowest risk of developing cancers in different parts of the colon

• Fibre may dilute the concentrations of cancer-causing agents, promote their removal and/or minimize the damage they can cause

• Since fibre improves transit time through the large intestine, this potentially reduces the negative impact carcinogens can have on our colon cells