BPK 110 Modules 7 & 8

Triglycerides

• The main dietary lipid

• Have a glycerol backbone with three fatty acids (fats) attached to it

• Fatty acids differ in their degree of saturation, length and/or their geometric organization

Saturated fatty acids

• no double bonds

• They are accordingly saturated with hydrogens

Unsaturated fatty acids

• One (mono) or more (poly) double bonds

Polyunsaturated fatty acids

• (PUFAs) are named according to where the double bone is when counting from the omega end

• Ends of both types of fats are the same

• Structure dictates function

Omega end

• Fatty acid’s methyl end

Essential Fatty Acids (PUFAs)

• PUFAs with the double bone before the 9th position

  • The body cannot make them itself, therefore they are essential

  • Two essential fatty acids: alpha-linoelic acid (omega-3) and linoleic acid (omega-6)

    • They can be used to synthesize other omega 3/6s

  • Form eicosanoids

Sources of omega 3

• Docosahexanenoic acid (DHA) and eicosapentanenoic (EPA) - Chia and flax sends contain high amount of alpha-linolenic acid while fish, fish oil, beef and lamb provide EPA and DHA

Eicosanoids

• Hormone-like molecules

• Derive from omega-3 fatty acids have anti-inflammatory properties, while those derived from omega-6 acids have pro-inflammatory properties

Sources of Omega-6

• Soybean, corn, vegetable oil

Length of Fatty Acids

• Long chain fatty acids are found in variety of animal products, some plants

• Medium-chain fatty acids are found in tropical oils

• Short-Chain fatty acids are made by bacteria when they ferment indigestible carbs - best source is fibre-rich foods

• Most fatty acids we consume have 18-22 carbon atoms

Long-chain fatty acids

• 14+ Carbon atoms

Medium-chain fatty acids

• 6-12 Carbon atoms

Short-chain fatty acids

• 2-4 Carbon atoms

Geometric Structure of Fatty Acids

• Unsaturated fatty acids can have a cis or trains configuration

  • This refers to the location of hydrogen atoms around the double bond

• Trans fatty acids can be artificially made through the process of hydrogeneration

  • These artificial/industrial trans fats significantly increase risk of CVD

• Main difference between cis and trans fatty acids is where the hydrogen lie in space around the double bond

Cis Configuration

• Hydrogens are on the same side of the double bond

Trans Configuration

• Hydrogens are on the opposite of the double bond

Sterols

• Have a hydrocarbon chain arranged in a ring formation

• Also hydrophobic

• Play a variety of structural and functional roles in the body

  • Ex: cell membrane structure, hormone formation

• Can be consumed from both plant and animal sources

Animal-Derived Sterols

• Most common = cholesterol (1/3 of human cell membrane)

• Has many important roles in the body

  • Cell membrane structure

  • Precursor for vitamin D

  • Precursor for estrogen, testosterone, cortisol

• Liver and other body structures can synthesize their own cholesterol, so it is not necessary from the diet

Plant-Derived Sterols

• AKA plant sterols, phytosterols

• Slightly different molecular structure than animal-derived sterols

• Found in unrefined vegetable oils, nuts seeds, fruits

• May limit the absorption of animal-derived sterols

• Vegetable oils are the richest source of plant sterols. However, when oils are refined, such as hydrogeneration, their relative composition of plant sterols is lowered

Phospholipids

• Their amphiphilic nature (having a hydrophilic and a hydrophobic end) gives them special properties and functions

  • They can form a bilayer when immersed in water

    • Ex: Phospholipid bilayer of the cell membrane

  • Act as emulsifiers

  • Carry other lipids around the body

Lipid Digestion

• Triglycerides must first be digested into glycerol and fatty acids

• Bile emulsifies lipids, lingual/gastric/pancreatic lipases digest them

• If lipids aren’t digested by lipase, they cannot be digested, nor absorbed

• This emulsification of lipids allow large lipids globules to be divided into smaller, more uniformly distributed droplets. This process increase the SA on which pancreatic lipase can act, making its work more efficient. Prepares for absorption

Micelle

• When bile salts emulsify a structure is formed that has lipids in the center and bile salts surrounding them.

Lipid Absorption

1. The micelle breaks down, Its lipid contents are absorbed into the small intestine cells through passive diffusion

2. Lipids get wrapped in phospholipids as they exit the small intestine cell and enter the centre of the villus. The resulting structure is called a chylomicron

3. Chylomicrons are too large to enter the blood. Instead, they enter lacteals

Lipid Transport

• Since most lipids are hydrophobic, the hydrophilic shell provides a structure that allows them to dissolve and more readily through watery environments such as the blood and lymph

• They accordingly need lipoproteins, lipid transporters, to carry them around the body

Lipoproteins

• Lipid transporters

Types of Lipoproteins

• Chylomicron

• VLDL - very low density lipoprotein

• LDL - low density lipoprotein

• HDL - high density lipoprotein

Chylomicron

• From small intestine villus → lymph → blood → body cells → liver

• Mainly delivers triglycerides

VLDL

• Made in liver → body cells → becomes LDL as it losses triglycerides

• Mainly delivers tryglycerides

LDL

• From VLDL → delivers cholesterol to body cells OR returns to the liver OR gets deposited in artery walls

• Mainly delivers cholesterol; AKA “bad cholesterol” because it can build up in artery walls

HDL

• Made in liver → picks up cholesterol from body cells → returns it to the liver

• Mainly removes cholesterol from blood, body cells; AKA “good cholesterol” because it lowers the build up of cholesterol in artery walls

Lipoproteins Transport and Deliver Lipids

1. Chylomicrons (CM) are the largest lipoproteins. They deliver triglycerides (TGs) from the small intestine to body cells

2. At the tissues, the enzyme lipoprotein lipase (LPL) breaks down triglycerides into fatty acids (FAs) and glycerol so they can be absorbed out of the CM and into the tissue. The CM becomes smaller

3. The remaining CM returns to the liver where it breaks down into its components

4. The liver reassembles TGs, cholesterol (chol), protein (pro) and phopholipids (PPL) into VLDL. VLDL is the main TG delivery system from the liver to tissues

5. At the tissues, LPL breaks down the TGs, allowing its components to enter cells

6. As it loses TGs, VLDL becomes smaller and more dense to eventually form LDL: the main chol delivery system

7. There are three potential fates of LDL:

   a. Cells with LDL-receptors can take up entire LDL structures, where chol and its other content is broken down

   b. LDL returns to the liver to be broken down

   c. If LDL levels are high, it is more likely to become oxidized. These highly reactive structures can stick to artery walls, narrowing them and increasing risk for atherosclerosis. Atherosclerosis is the main heart cause of heart attacks and strokes

8. The liver also makes high-density lipoprotein (HDL). HDL is high in pro and low in TG. HDL picks up chol from body cells and lipoproteins and returns it to the liver

Energy Provision

• Lipids provide 9 kcal/gram

• If carbohydrates are adequate in the diet, triglycerides are metabolized and their products enter the citric acid cycle and the electron transport chain to yield ATP

• If carbohydrates are inadequate in the diet, ketones are formed

Lipid Storage vs Lipid Metabolism

• At an energy surplus, extra energy is stored as lipid in adipose tissue (fat tissue)

• At an energy deficit, lipids are retrieved from adipose tissue

Membranes

• The membranes of cells and the membranes of cellular organelle are composed of phospholipids

• Regulates what goes in or out of the cell

Transport and Storage of Fat Soluble Vitamins

• Vitamins A, D, E and K are fat-soluble vitamins (packaged, absorbed and transported along with other dietary lipids within the micelles and lipoproteins

• Since they are hydrophobic, they require a lipoprotein for their transport

• They are also stored in adipose tissue

Synthesis of Other Key Molecules

• Cholesterol-derived molecules

• Essential fatty acid-derived molecules

Cholesterol-derived molecules include

• Steroid hormones, bile salts, vitamin D, estrogen, testosterone

Essential fatty acid-derived molecules include:

• Eicosanoids, endocannabinoids

• Omega-3 and omega-6 fatty acids can be used to be synthesize a wide range of eicosanoids. These signalling molecules have diverse roles in the body, including effects on blood vessels, blood clotting and inflammation. Can be used to synthesize endocannabinoids. Have potential effects on cognitive function, appetite, mood and memory

Lipids and CVD

• CVD compromises the cardiovascular system’s ability to deliver cellular needs (ex. oxygen, nutrients) and remove wastes (ex. CO2)

• Atherosclerosis

• Certain lipids can increase of decrease the risk of developing atherosclerosis

Atherosclerosis

• The build=up of fatty materials in artery walls, is a type of CVD that causes heart attacks and strokes

• Blood clot that gets stuck in narrow artery, stopping blood flow together

Ways to decrease CVD

• No smoking, consistent exercise, maintaining a healthy weight, managing stress levels and consuming a diet rich in whole foods with lots of vegetation and fruits

Trans Fatty Acids and CVD

• On a per-calorie basis, trans fats appear to increase the risk of heart disease more than any other macronutrient - 1-3% of total energy uptake

• Are known to increase:

  • Ratio of LDL to HDL

  • Risk of CVD

  • Risk of CVD mortality

• To reduce/avoid trans fats, minimize the consumption of processed and ultra-processed foods, especially those that are hydrogenated

Saturated Fatty Acids

• Diets high in saturated fat:

  • Increase LDL → which increases risk of CVD = lipid hypothesis

  • However, a direct link between saturated fat and CVD has not been established

• Replacing saturated fats (mainly found in animal products) with unsaturated fats (mainly found in plant products) may lower potential risk

Polyunsaturated Fatty Acids

• When PUFAs replace saturated fat, LDL levels decrease

• PUFAs that are essential amino acids have also been studied for their roles in CVD

Essential Fatty Acids

• Omega-3 fatty acids

  • Have several cardioprotective effects including decreasing inflammation, blood cholesterol, vasoconstriction and blood clotting

    • However, supplementation of omega-3 has not been shown to decrease cardiovascular events

• Omega-6 fatty acids

  • Though to increase risk of CVD because they increase inflammation and blood clotting

    • However, results of RCTs have been mixed

• Both omega-3 and omega-6 fatty acids have protective effects on the brain

Cholesterol

• For most people, dietary cholesterol has a minimal effect on increasing LDL and cardiovascular risk

  • The body makes less cholesterol when more is consumed, LDL levels don’t rise

• However, 25-30% of people are believed to be cholesterol hyper-responders

  • Their LDL does go up when more cholesterol is consumed

Eggs and Cardiovascular Health

• Eggs are extremely nutrient dense

  • Each 75 kcal egg is high in protein, fat, vitamins, minerals

  • May also be high in omega-3 fatty acids if chickens are fed flaxseeds

    • Chicken converts alpha-linoleic acid to DHA

• Eggs are also high in cholesterol (225 mg/egg)

  • Higher cholesterol consumption does not increase LDL

  • In moderation (1-3 eggs per day), they do not seem to increase risk of CVD

Plant Sterols

• Reduce LDL levels by competing with cholesterol for absorption and altering cholesterol metabolism

  • Whether this leads to a reduction in CVD risk/mortality has not been established

Indigenous Lens : Nuts are like the panfish of the forest

• The word pecan is derived from the word Pigan, which in certain Indigenous languages refers to all nuts

  • Indigenous peoples have long known their highly-nutritious nature

Lipids and Obesity

• No single nutrient causes obesity

• It is the total energy that is consumed which affects likelihood for fat gain (energy surplus) or fat loss (energy deficit) from body

Proteins are Folded Amino Acid Chains

• Amino acids have three main groups:

  • A nitrogen-containing amine group on one side

  • A carboxylic acids on other side

  • A side chain (Rx)

• There are 21 amino acids

  • Structurally, they differ only in their side chain

Essential vs Non-Essential Amino Acids

• Nine amino acids are essential (absolutely required from the diet because the body cannot make them itself)

• The non-essential amino acids can be made by modifying other amino acids

  • Through process of transamination

• Conditionally essential amino acids are non-essential amino acids that become essential when the body cannot synthesize enough of them

Complete vs Incomplete

• Complete proteins are foods that have all nine essential amino acids

  • All animal sources are complete, as are soy, quinoa, buckwheat

• Incomplete proteins are foods that are missing one or more essential amino acids

  • Plant sources are typically incomplete

  • limiting amino acid

Limiting amino acid

• The amino acid that is lacking

Complementing proteins/ Mutual Complementation

• By eating lots of plant sources of protein, all essential amino acids can be consumed

  • (NB. doesn’t have to be eaten at same meal)

Protein Synthesis

• To become part of a fully functional protein, amino acids must bind together in a specific order

  • Our DNA holds the instructions for the sequence of amino acids needed in order to build specific proteins

    • We draw on the amino acids pool to make these chains

Primary Structure of a Protein

• The first level of protein structures arises from adjacent amino acids bonding to each other (occurs through a condensation reaction and leads to the formation of a peptide bond)

  • Peptide bonds lead to the formation of a polypeptide

• This polypeptide is not yet a protein

  • Must fold into secondary, tertiary, perhaps quaternary structure

Secondary structure of a Protein

• Hydrogen bonds between non-adjacent amino acids lead to the formation of

  • Alpha helices

  • Beta-pleated sheets

• These folds occur when non-adjacent amino acids form hydrogen bonds with each other

Tertiary Structure of a Protein

• Interactions between amino acids side chains leads to further folding of the polypeptide chain

• This may result in a functional protein

• There are several bonds that can occur between these side chains, including salt bridges and disulfide bonds. This allows the polypeptide to fold even further and may result in the formation of a fully functioning protein

Quaternary Structure of Protein

• Some proteins have a quaternary structure of protein

  • Several proteins with a tertiary structure bind together to form the final protein

    • Each of these is called a protein subunit

• Most quaternary structures are made up of eight or less protein subunits, each contributing a specific structure and function to that protein

Denaturation of a Protein

• A protein is denatured when it loses its folded three-dimensional structure

  • Also loses its function

• Acids, heat, agitation can all denature proteins

  • This is sometimes desirable

    • Ex: Food preparation

• In our bodies, the digestion of protein begins with denaturation. The acid in our stomachs unfold protein subunits, allowing enzymes to work on the primary structure of a protein, separating off amino acids for absorption

Protein Digestion

• Mechanical digestion of protein begins in the mouth as the teeth rip apart protein-containing structures from the rest of food.

  1. Mouth and saliva don’t contain any protein-digesting enzymes, so chemical digestion doesn’t begin until food reaches the stomach

  2. HCl acid releases into lumen that unravels protein & activates pepsin. Pepsin helps break the bonds between specific amino acids, further breaking down the unraveled polypeptide chain

  3. In Small Intestine, proteases (protein-digesting enzymes), trypsin, and chymotrypsin, which are secreted by the pancreas, act on the remaining polypeptide structures. Proteases act on different amino acids sites to further break polypeptide into single, double (dipeptides), or triple (tripeptides) amino acids. All three absorbed by active transport into villi. Body can’t absorb poly. 3 AA

  4. Once AA enters villi, they pass into bloodstream via capillaries and then proceed to the liver. AA that aren’t metabolized at liver are released into general circulation. Our tissues can then pick up AA from blood & use them for various functions

Body Structure

• Bones, muscles, skin and every body organ contain protein

• Collagen is the main structural protein

• Elastin is another key structural protein

Collagen

• A protein found in bone, skin and connective tissue

• Organizes itself into a rigid matrix that calcium and phosphate harden

• Promotes firmness and strength and allows the outer earn to maintain its shape

Elastin

• Permits Elasticity & allow a structure to be slightly deformed and them resumes its shape

Transport

• Protein tracks in cells allow substances to walk along them, permitting transport around the cell

• Protein channels regulate movement into and out of the cell

• The blood hemoglobin transport oxygen around the body

Enzymes

• Most are proteins

• Speed up rate of reactions

• Ex: Lipases, amylases, proteases

Movement

• Myosin and actin are proteins found in muscle

• When myosin proteins attach to actin proteins and kink their heads, muscle contraction occurs (shorten muscle length)

  • Allows our bodies to produce movement

• When many actin and myosin containing muscle cells shorten in a coordinated way, the body can produce complex movements like walking or picking something from the ground

Fluid Balance

• Water is attracted to the positive and negative charges of the amino acids found in blood proteins

  • This draw water into the blood and out of the extracellular space

  • If blood proteins are low, fluid can build up in the extracellular space, leading to edema

Protection from disease

• Collagen in skin helps to restrict what can enter the body

• If infectious agents enter, proteins called antibodies stick to these agents, promoting their removal and limiting the harm they can cause

Antibodies

• Are Y-Shaped protein that stick to the outside of pathogens, labelling them for removal and restricting the harm they can cause the body

Energy

• While proteins provide 4 kcal/gram, they are a minor source of energy to the body

• It is wasteful to deaminate an amino acid so it can be metabolized to generate ATP

  • The body prefers to use protein for all its various functions

Deamination

• Removes the nitrogen-containing amine group so that the remaining structure can be used to pyruvate, acetyl CoA or citric cycle immediates.

• Which reactant of cellular respiration is formed depends on the side chain of the original amino acid before it was deaminated

Marasmus

• Wasting syndrome

  • Occurs when energy and protein are deficient

  • Promotes anemia, dehydration, heart irregularities, body temperature dysregulation

Kwashiorkor

• A form of protein malnutrition that occurs in young children but energy is sufficient

• Evidenced by a distended, swollen abdomen and an otherwise slim apperance

Protein and Body Weight

• The primary dietary factor that promotes weight gain is a caloric intake that is consistently above the body’s needs

  • Whether a high/low-protein diet leads to weight gain depends on the total calories consumed

• However, protein may promote a caloric deficit:

  • Promoting fullness

  • Contributing to carbohydrate and lipid metabolism

  • Requiring more energy to digest and absorb it

    • Has a higher thermic effect

Protein and Muscle Growth

• Protein is important for the repair and growth of muscle

• Protein muscle synthesis increases in the 24 hours following weight training

  • 10g of essential amino acids in the first 2 hours following exercise encourages muscle growth

  • Milk-based proteins, for instance, increases muscle strength and improves body composition

• Athletes have a higher overall protein requirement

  • ACSM recommends increasing intake from 0.8g/kg body weight to 1.2-2g/kg body weight, depending on the intensity and load of training

Protein and Bone Health

• In bone, collagen forms a matrix that mineral (ex. Calcium) harden

• However, high protein diets can promote calcium excretion

• Overall, high protein diets do not seem to negatively affect bone health

• About half of the volume of bone and a third of its mass is composed of protein. While protein is essential for bone structure, a high-protein diet has been associated with calcium excretion

Protein and Kidney Health

• High protein diets tax the kidneys because they have more waste products to excrete

• For those with reduced kidney function, consuming protein at the recommended intake level (0.8 g/kg) and not beyond it, is recommended

Protein Quality

• Typically refers to two factors:

  • How well a protein is digested

  • How the types and quantities of amino acids in that protein source match the body’s requirements

Ways to Assess Protein Quality

• Protein digestibility corrected amino acid score (PDCAAS)

• Digestible indispensable amino acid score (DIAAS)

• Protein efficiency ratio (PER)

PDCAAS

• Compares the amino acid content of a food against a standard amino acid profile. The highest score that can be achieved is 1.0. - means that, following digestion, each unit of protein meets or exceeds the human requirement for essential amino acids

• Industry standard

DIAAS

• Measures how well amino acids are digested in the ileum and more closely estimates the amount of amino acids absorbed by the body

• Database is still being built

PER

• How much weight an animal gains when consuming a specific amount of protein, divided by the amount of food it consumed

• Used in Canada

Protein Supplements

• Can be from whole sources and from protein supplements (ex. protein powders, shakes)

• Strength and muscle size increases with protein supplementation, especially in younger people who train regularly

  • However, excessive supplementation (>1.62 g/kg body weight) does not promote further gains

Branched-Chain Amino Acids

• Essential amino acids that have a branched side chain

• They account for 35-40% of the dietary essential amino acids found in body protein

• Have been shown to reduce muscle damage associated with weight training

  • Especially if consumed before exercise

• Can be consumed from whole sources, do not have to come from supplements!

• Metabolized in the muscle instead of liver

Animal sources of protein

• Have more total protein, a higher PDCAAS and are complete proteins

• Have vitamin B12 and are higher in vitamin D, iron, zinc and omega-3 fatty acids

• Also high in saturated fats and are absent in fibre, phytochemicals

• Also, processed animal products (ex. Deli meats, bacon) increase CVD risk/mortality

An Indigenous Lens: Protein Quality of Game Meats vs Processed Meats

• Traditional Indigenous diets were very high in protein due hunting and fishing practices

  • However, with colonization came limitations on these practices

  • With this, there has also been a shift towards processed meats

    • Believed to negatively affect protein quality of modern Indigenous diets

• Game meats have more total protein and tryptophan than processed meats

• Shifting to a traditional Indigenous diet may help correct potential deficiencies

Tryptophan

• Is an essential amino acid involved in many processed including mood regulation and sleep

Consuming Animal Products has a Significant Environment Impact

• Diets high in animal protein promotes a larger environmental impact than those high in plant protein

• More water is used to raise animals than to grow plants

• More land is required to raise animals than to grow plants

• Animals, especially larger ones, emit the greenhouse gas methane through their burps and flatulence

Health Benefits of Vegetarian diets

• Diets are high in fibre and phytochemical and low in saturated fats

• Vegetarians are more likely to have lower BMIs, total cholesterol and LDL

• They are also at lower risk for heart disease, cancer and CVD mortality

Risks of Vegetarian Diets

• They are lower in vitamin D, omega-3 fatty acids, calcium, iron and zinc

• Vitamin B12 is only found in animal products (with the exception of nutritional yeast) - more likely to be inadequate in a vegan diet

• Supplements is recommended if these are not sufficient in diet

Omnivore diet

• A person who consumes a variety of both animal and plant products

Semi-vegetarian

• A person who restricts one ore more type of animal product. For instance, a semi-vegetarian might avoid all red meat

Pescatarian diet

• A person who restricts most or all animal products except fish

Plant-based diet

• A diet that is mostly or entirely based on plant-derived foods and ingredients, However, there is no clear definition of this term. Vegetarian and vegan diets are plant based.

Vegetarian diet

• A person who avoids some or all animal-related food and ingredients

Lacto-ovo vegetarian diet

• A person who avoids animal flesh, but consumes milk products (lacto) and eggs (ovo)

Lacto-vegetarian diet

• A person who avoids animal flesh and eggs, but consume milk products

Vegan diet

• A person who excludes all animal products, including eggs and milk. This may also include any animal-involved products, such as honey