Chapter 5: Energy, Protein, Water

Nutrition balances

1) Energy balance

• Energy flows (measurements)

• Energy value vs requirements

2) Nitrogen balance

• Nitrogen flows (measurements)

• Protein value vs requirements

3) Water balance

• Urine production

• Essential vs metabolic water

Energy balance

Energy intake (food) = energy consumption (heat, work) + energy stored

• in equilibrium when energy content of food = total amount energy used by the body

• Energy intake > energy consumption → excess energy is stored

• Energy intake < energy consumption for a long period → undernutrition

Energy balance: requirement of energy

ingesta = egesta

• ingesta = food, water, air

• egesta =

  • breading

  • urine, faeces, gasses

  • sweat, hair, nails

  • milk, growth, pregnancy

• Balance technique

  • shortage, equilibrium, excess

Balance technique (different types of energy)

Gross energy (GE) = heat released during complete combustion of a food to CO2 and H2O

Digestible energy (DE) = ingested GE that is not completely retained in the feces and the gasses

Metabolisable energy (ME) = ingested DE that is not retained in intestinal gasses, and in excreted hair, skin, respired air and urine

Net energy (NE) = ingested ME that is not removed as heat

In short time-intervals (e.g. hours), energy-intake does not correspond to energy consumption

Intake of energy is not continuous → storage of energy

1) Free glucose

2) Glycogen

3) Proteins

4) Adipose tissue

Circadian rythm

= biological rythms

• Hypothalamus: SCN: sensitive to light/dark cycles crossing the eyes

• periodic synchronizers that

  • involve schedule of ingestion and fasting, activity and rest

  • influence other clocks in organs and tissues like adipose tissue, liver and gut

Chronodisruption (chronic extension, how to lose weight, how obesity is formed)

• related to chronic diseases (e.g. metabolic syndrome and CVD)

Chronic extension of appropriate meal (e.g. late night eating)

• cause metabolic dysregulation due to circadian disruption

How to benefit weight loss?

• TRE = time restricted eating = control of meal time

  • decrease in calorie intake

• keeping energy intake constant (large breakfast vs small dinner)

• meal composition

Example: night shifts, jet lags

Determination of energy value: caloric bomb and tables

Energy value

• determined from chemical composition of food + atwater factors

• is variable

  • energy value phospholipids < energy value fat

  • chain length for carbohydrates

  • contribution of alcohol

  • overestimation for vegetable products

• Influenced by turnover

Caloric bomb

• = closed recipient container heated up in water container

• measures GE

• measures energy available in the body for ATP-formation

• combustion value of N corrected for excretion of N as urea in urine

• Carbohydrate and fat show ATP yield higher than that of volatile FA and protein

Determination of energy value: Weende analysis

• Water vs DM

• Ash vs OM

• Crude fat: Soxhlet

• Crude protein: Kjeldahl

• Total Dietary Fibre

• Remaining carbohydrates = 100 -%H2O - %ASH - %fibre - %CP - %CF

Determination of energy value: Total dietary fibre

= edible carbohydrate polymers with 3 or more monomeric units, which are not digested or absorbed in the small intestine of humans

• determination by the Prosky method

  • alfa-amylase, protease, amyloglucosidase

  • EtOH (precipitation TDF)

  • Correction protein and ash

• Additional separation by

  • Insoluble in water (e.g. cellulose)

  • Soluble in water (e.g. pectin, beta-glucan)

Determination of energy value: Atwater coefficients

= a set of values that estimate the metabolizable energy provided per gram of carbohydrate, protein, fat, and alcohol in the human diet.

Energy consumption: Flow of energy - BMR

What

= Basal Metabolic Rate

• minimum heat production at

  • rest (lying)

  • post-absorptive

  • fastened

  • thermoneutrality

• Problems to measure in animals → resting metabolism or fasting metabolism

Formula

BMR\left(\frac{kJ}{d}\right)=293\cdot G^{\left(\frac34\right)} (with G in kg)

Energy consumption: Flow of energy - DIT

= Diet-Induced thermogenesis

• When a person at BMR receives food → heat production increases ( mechanical work for chewing…)

• Determined by composition of food

• Thermal effect for protein is higher than for carbohydrate and fat

Energy consumption: Flow of energy - Thermal effect of physical exercise

caused by use of skeletal muscle for any type of physical movement

Energy consumption: Flow of energy - thermogenesis by stimulans

• energy cost for growth

• adaptive thermogenesis during exposure to reduced or increased T

• thermogenesis can be increased by nicotin, caffein and spicy peppers

Energy consumption: Flow of energy - energy requirement at maintenance (MR)

MR = BM + heat production for maintenance

Measurement of energy flow

Direct calorimetry	Indirect calorimetry
measurement heat production and heat of evaporation of water	determination O2 and CO2 by oxidation of fat, protein, carbohydrate
Expensive equipment and difficult to handle	Correction for methane production and urea excretion methane production: 1 L of CH4 == 2 L of O2-consumption urea excretion: combustion of protein is incomplete
Short measuring period	fixed period of time

Respiration coefficient

Method measuring CO2-production

Place

1) Respiration room

2) ventilated hood

3) mouthpiece

Method

DLW method = Double Labelled Water method

1) Organism ingests water with stable isotopes (2H and 18O)

2) 2H is removed by water loss and 18O is removed by water loss or CO2-production

Disadvantage

you need mass spectroscopy meter

Energy requirements

MR (= maintenance requirements) + extra amount of ME (= metabolic energy) necessary for production

• ME = NE for production from composition of final product *kp (= yield factor for energy utilisation)

Pregnancy

• NE = combustion value of gestation products (fetus, placenta, weight increase of the mother due to fat deposition

• kp = NE/ME = 20 to 30% = low = high cost for protein synthesis and turnover

Growth

• Composition tissues changes with age

• 18% protein (lower yield) vs 16% fat (higher yield)

• kp = NE/ME = 50%

• TEE + energy deposit of growing tissues

Lactation

• kp = NE/ME = 60 to 80%

physical activity

• Derived from indirect calorimetry

• Expressed as multiple of BMR

• Use of metabolic coefficients

  • Maintenance: 1 - 4

  • Light activity: 1-3

  • Heavy activity: 3-6

• Low yield

Regulation energy balance

1) Signals sent to central nervous system

• afferent signals: periferic signals from energy reserves (adipose tissue, muscles, liver)

• hormonal and gastro-intestinal signals: gastro-intestinal system, pancreas

2) Central nervous system gets information from signals about

• internal conditions: eg. nutritional status

• external conditions: eg. sensorial perception of food

3) Signals are translated into efferent signals → lead to changes in energy intake, energy consumption and distribution of energy throughout the body

Regulation energy balance: Satiation

= processes that bring the meal to an end

Regulation energy balance: Satiety

= cognitive, post-ingestive and post-absorptive processes that occur after a meal to inhibit further eating

= suppression of hunger and a feeling of fullness during the intermeal period

Regulation energy balance: brain

LHA

• = Lateral Hypothalamus

• Central hunger zone in the brain

• When stimulated: start hunger feeling

VMH

• = Ventral Medium Hypothalamus

• Central satiety or satiation zone

• When stimulated: stop eating food

Other parts of CZS

• NTS (= nucleus tractus solitarius) in DVC (= dorsal vagal complex)

External signals of food (appearance, smell…) → secretion of hormones, saliva and gastric juice → stimulation of food uptake → internal signals of food (digestion, metabolism) → peptides originate in digestive tract

• cholecystokinin

• CKK

• ghrelin

• GIP

• insulin (pancreas)

• leptin (fat tissue)

→ reach hypothalamus via blood stream → inhibition of food intake

Regulation energy balance: role endogenous peptides

GLP-1 = Glucagon Like Peptide-1

• °GI-system

• incretin activity → pancreas produces insulin → insulin binds to insulin receptor in the brain → reduce feeling of hunger

• satiating peptide

• Active via: GLP-1 receptor in the brains (DVC)

OXM = OxynthoModuline

• °GI-system

• incretin activity → pancreas produces insulin → insulin binds to insulin receptor in the brain → reduce feeling of hunger

• satiating peptides

• Active via: GLP-1 receptor in the brains (hypothalamus)

GIP = Gastric Inhibitory Peptide

• ° GI-system

• incretin activity → pancreas produces insulin → insulin binds to insulin receptor in the brain → reduce feeling of hunger

CCK = Cholecystokinin

• Reduces food intake by slowing down stomach emptying

• Active via: CCK1 receptor in the pancreas, pyloris sfyncter, hypothalamus and NTS

NPY = Neuropeptide Y

• stimulates appetite

• being activated by ghrelin produced in the stomach

• neuropeptide

PP = Pancreatic Polypeptide

• lowers appetite and food intake without influencing stomach emptying

• neuropeptide

PYY = Peptide YY

• °ileum and colon

• stimulates ileal break

• neuropeptide

Leptin

• °adipose tissue

• formed after increase in adipose tissue by stimulation of obesity-gen

• reduction of appetite and energy intake

• increase of sympathic activity and fat combustion

• endogenous peptide

obese people (environment vs genes)

“leptin resistance”

Relationship between risk-alleles and BMI, but life style and environmental conditions will determine the seriousness of his disease

• Obese resistant + Restrictive environment: small BMI

• Obese resistant + Obesigenic environment (nutrition, physical activity): slightly higher BMI

• Obese prone + Restrictive environment: small BMI

• Obese prone + Obesigenic environment (nutrition, physical activity): way higher

Obesigenic environment

Regulation energy balance: leptin deficiency

If percentage of fat increase normally the leptin concentration would decrease, but in this graph it is the other way around

Nitrogen (protein) balance

Measure for synthesis of

• Protein

• Bile acids (taurine, glycine)

• Creatine, glutathion

• Porfyrines, choline, nucleic acids

Nitrogen balance

N_{balance}=N_{^{"ingesta"}}-N_{egesta}

• N_ingesta = nitrogen content of food consumed

• N_egesta = nitrogen losses via urinary nitrogen, fecal nitrogen and remaining losses

Nitrogen (protein) balance: requirements

• deduced from the N intake necessary to obtain a N balance = 0

• Inclination = quality of protein → more steeper curve, higher quality, less intake needed

Nitrogen (protein) balance: limitations

• miscellanous N-losses not know

• Small differences between large values for N intake and N losses

• Difficult determination of

  • N gas

  • Urea losses by the skin, ammonia by breath

• Nitrate in food and urine not measured by Kjeldahl

Nitrogen (protein) balance: Leucine kinetics in function of protein intake

Nitrogen (protein) balance: nitrogen and protein requirements

• essential AA

  • infants up to 6 months: lowest intake of AA from breastmilk

  • older infants and shildren: factorial approach based on maintenance and growth → validated for total branched-chain AA requirements by the IAAO method using stable isotopes

  • Adults: 13C-balance study

• total nitrogen (protein) = requirements neccessary for synthesis of non-essential and conditionally indispensible (semi-essential) AA + N-containing compounds

  • Infants, children, adolescents → same factorial approach based on N balance at maintenance

  • Adults → factorial method based on N balance at maintenance which is taken as estimate for the population average N requirement

    • extra corrections for pregnancy and lactation

  • Average requirement of N intake goes down when you get older

Nitrogen (protein) balance: 13C-balance study

General

• Amino acids that are not used for protein synthesis kan be oxidised

• When requirement is reached → no protein synthesis anymore, but oxidation

DAAO = Direct Amino Acid Oxidation

• = measure oxidation of AA that is added

  • labelled (13C) + non-labelled (12C)

• Oxidation measured by

  • 13CO2 + 12CO2 in breathing air

  • indirect precursor = KIC → determine which part of 12CO2 is from non-labelled AA

• C-balans = intake - oxidation

• Under requirement

  • AA is fully used

  • low oxidation → low respons

• Above requirement

  • extra AA can not be builded in → linear increase of oxidation

IAAO = indicator amino acid oxidation

• = measure oxidation of indicator-AA (eg. Trp)

  • labelled (13C) + non-labelled (12C)

• Under requirement

  • Leucine is limiting → protein synthesis is low

  • indicator-AA is oxidised

• At requirement

  • Leucine is no longer limiting

  • Tryptophane does not get longer used or oxidised

  • respons = constant

Nitrogen (protein) balance: Protein digestibility

NPU = Net Protein Utilization = nutritional value of protein

• digestibility

• biological value = cellular bioavailability of absorbed AA in relation to their demand

apparent fecal nitrogen digestibility	apparent ileal nitrogen digestibility	true ileal nitrogen digestibility
VC_{fecal}=\frac{\left(N_{^{"ingesta"}}-N_{"feces"}\right)}{N_{"ingesta"}}	VC_{ileal}=\frac{\left(N_{^{"ingesta"}}-N_{"ileum"}\right)}{N_{"ingesta"}}	VC_{ileal}=\frac{\left(N_{^{"ingesta"}}-\left(N_{"ileum"}-EAAL\right)\right)}{N_{"ingesta"}}
not accurate because: 50% of the fecal nitrogen is derived from the body rather than from undigested protein	influence of microbial flora is assumed to be minimal or negligible	EAAL: compromise nitrogen loss due to intestinal desquamation and excretion of digestive enzymes and bile dependent of dietary protein, fibre and ANF

Nitrogen (protein) balance: PDCAAS-score

= Protein Digestibility Corrected Amino Acid Score

• points of discussion

  • uncertainty about reference protein

  • use of true fecal instead of ileal DC

  • Adjusting values above 100%

Nitrogen (protein) balance: Protein quality

• related to amount of essential AA (EAA) in a protein

  • limiting AA: EAA giving the lowest proportion → when 1 or more EAA are lacking, the use of all other EAA decreases in the same proportion

Nitrogen (protein) balance: DIAAS-score

= Digestible Indispensable (= essential) Amino Acid Score

• Developped to better reflect the digestibility of individual dietary indispensable AA

• AA pattern for reference protein is taken from

  • breastmilk

  • pattern for 0,5 year old infants

  • pattern for 3 to 10 year old children

• Devided in 3 categories

  • Not to be used as single protein source

  • good quality

  • excellent quality

Water homeostasis: The water balance

• 50 - 70% of body weight is water

  • 60 % intracellular water

  • 40% extracellular water: blood, interstitial fluid

• Importance for supply and excretion

• Homeokinesis = dynamic equilibrium

  • determined by movement of water and electrolytes

  • dependent of 4 processes

    • filtration

    • diffusion

    • osmosis → most dominant regulating system

    • active transport

Minimal intake (ml/d) = minimal secretion (ml/d)

• Metabolic water

  • 1 g carbohydrate = 0,6 g H2O

  • 1 g protein = 0,41 g H2O

  • 1 g fat = 1,07 g H2O

• Essential water

  • needed to remove endproducts from the metabolism (urea, sulphates, phosphates)

Water homeostasis: The water balance: osmole, osmolarity, osmolality

• osmole = 1 mole/n (n = number of particles in 1 mole)

  • Eg. 1 mole NaCl => 2 osmoles

  • Eg. 1 mole CaCl2 => 3 osmoles

• osmolarity = osmole/l solution

• osmolality = osmole/l solvent

Water homeostasis: The water balance: electrolyte composition

• K+ mostly intracellular

• Na+ mostly extracellular

Water homeostasis: Regulation of thirst and urine production

• Thirst → hypothalamus is stimulated

• Urine production = control of water balance → nephron (kidney)

  • formation and composition of urine is based on

    • 1) glomerular filtration

    • 2) tubular secretion of the nephrons: H+ and K+

    • 3) tubular reabsorption: Na+

• GFR = glomerular filtration rate = 180 l/d

• net filtration pressure = blood pressure - pressure in the capsule of Bowman - colloid osmotic pressure of blood plasma

Water homeostasis: Regulation of water and Na balance

Based on active Na-reabsorption preceeding a passive water reabsorption

Examples:

Lack of water	blood volume ↓ → osmotic pressure ↑ → secretion of ADH (= anti-diuretic hormone = vasopressine) by hypothalamus → reabsorption of water ↑
Excess of water	reverse mechanism of lack of water
Lack of Na+	osmotic blood pressure ↓ → GFR ↓ → Na+ excretion↓→ renin ↑ + aldosteron ↑→ reabsorption Na+ ↑
Excess of Na+	osmotic blood pressure ↑ → reverse mechanism → Na+ loss in urine + large water loss Water loss without Na loss is possible Na loss without water loss is not possible (drinking seawater)

Water homeostasis: Regulation of water and Na balance: tubular reabsorption

• reabsorption by diffusion: water, PO4(3-), glucose, Na+ and K+

• reabsorption by active transport: eg. sugar

Steps

1) Loop of Henle

• Descending limb: Na+ comes in → limb is permeable to water and water is lost by osmosis → filtrate gets concentrated (up to 1400 mosmol/l)

• Ascending limb: impermeable to water but actively pumps Na+ out → filtrate gets diluted→ creates high osmolality → hyptertonic environment (= higher osmotic pressure)

2) Collecting duct

• water is drawn out by osmosis → concentrates the urine to match the omsolality of the deep medulla, allowing the body to conserve water

• dependant of ADH (no ADH = water is removed out of CD; ADH = water stays in CD)