Nutrition
Science of how living organisms
obtain & use food to support all the processes required for their
existence.
Nutrient
A substance present in foods used
by the body to serve one or more of the following purposes:
- Provide a source of energy
- Provide structural components
- Regulate chemical reactions in the body
Nutrient Density
Is a measure of the nutrients a
food provides relative to the energy it provides or /unit weight.
The absence of a nutrient from
the diet causes recognizable symptoms – deficiency disease
Non-nutritive substances
- Present in foods
- Phytochemicals
Plant derived non-nutrient
compounds which have biological activity in the body
- Zoonutrients
Present in animal foods &
provide health benefits beyond provision of essential nutrients & energy
- Functional foods
Foods that contain one or more
substances thought to have health benefits E.g. Nutrient, phytochemical or
zoonutrient
- Probiotic foods
Foods & dietary components
that contain beneficial live non-pathogenic bacteria
- Prebiotic foods
Foods that promote growth of non-pathogenic bacteria
- Added to foods
To give
flavour, colour, texture &/or freshness eg. Guar gum, colourants
A wholesome diet is needed for the maintenance of the body – Caraka
Samhitha (ca 1500 BC)
An adequate (balanced) diet
A diet (combination of foods) which provides energy and
all nutrients in correctproportions and in amounts adequate for each age
group, gender & physiological state
It should contain both:
Macronutrients and micronutrients
Macronutrients:
Water
Carbohydrate
Proteins
Lipids
(Minerals)
Micronutrients:
Vitamins
Trace
elements
Nutrient recommendations
- It is necessary to determine whether amounts of energy & nutrients consumed are likely to be adequate
- A set of dietary reference standards developed to assess adequacy of a person’s diet
- These standards referred to as “Dietary reference intakes - DRIs” encompass 4 sets of values: EARs, RDA, AIs, ULs
- These dietary standards are used to guide people on amounts to consume
Dietary reference standards: Dietary Reference
Intakes (DRIs)
Amounts
of energy, nutrients & other dietary components that best support health of
nearly all people
Estimated
Average Requirement (EAR)
Adequacy
of intake
- Recommended Dietary Allowances (RDA)
Goal
to assure adequacy of intake
Adequate Intake level (AI)
Adequate Intake level (AI)
Adequacy
of intake when no RDA is set for nutrient
Tolerable
Upper intake Level (UL)
Likelihood of excess or toxicity
Energy requirement of an individual
Adults:
Level
of energy intake from food that will balance energy expenditure when the
individual has a body size, composition & level of physical activity that
is consistent with long term good health
Children
& Pregnant or Lactating women:
Requirement
also includes energy needs for deposition of tissues or secretion of milk at
rates consistent with good health
What are the fuels in foods?
- Carbohydrate – 4 kcal/g
- Fat – 9 kcal/g
- Alcohol – 7 kcal/g
- Proteins – 4 kcal/g
Units of energy
Kilocalories (kcal or Cal)
Kilojoules (kj)
Megajoules (MJ)
1 kcal = 4.184 kj
1 MJ = 239 kcal
Energy
contribution of a food depends on:
- Its energy content
- Amount consumed (portion size)
- Bioavailability
Energy density = energy content/g of food
Why do we need energy?
Energy requirement depends on energy expenditure
Energy is needed for:
- 1 Basal metabolic activities – 50-65% of total energy expenditure
Body’s
activities at rest
- 2. Thermic effect of food – 10% of total energy expenditure
Energy
required to process food
- 3. Physical activities – 30-50% of total energy expenditure
Occupational &
leisure time activities
BMR
is affected by:
- Growth – children, pregnant & lactating women
- Lean body mass – lower in starvation, undernutrition
- Gender (lower in females)
- Climate
- Fever (12% increase in BMR for every 0C rise in body temperature above normal)
- Disease (eg. Thyroid hormones increase BMR)
Estimating average energy requirements
Energy
– Average requirements recommended, because excess energy:
- Cannot be excreted
- Is stored as fat
Estimated
Energy Requirements (EERs) (defined by IOM,USA) are:
Average energy intakes needed to maintain weight in
a healthy person of a particular age, sex, weight, height & physical
activity level consistent with good health
Two approaches
A.
WHO/FAO
1.
Calculate BMR from equations
2.
Multiply by physical activity factor
Eg.
Male: 18 – 30 years, weight 60 kg
BMR
= 15.3 x 60 + 678 = 1579 kcal/d
- Light activity: 1.53 x BMR
Energy
req./expenditure = 1579 x 1.53 = 2416 kcal/d
- Moderate activity: 1.76 x BMR = 2780 kcal/d
- Heavy activity: 2.25 x BMR
B.
Institute
of Medicine, Food & Nutrition Board, 2002
1.
Use
appropriate equation
Insert
age in years, weight (wt) in kg and height (ht) in m & physical activity
factor
2.
For
men >= 19 y
EER = [662 – (9.53 x age)] + PAL x [(15.91 x wt) + (539.6 x ht)]
3.
For
women >= 19 y
EER = [354 – (6.91 x age)] + PAL x [(9.36 x
wt) + 726 x ht)]
Physical activity
levels for EER equations
Classify
physical activity levels (PAL) depending on lifestyle
Ie.
Occupational and discretionary (leisure time) physical activities
Physical
activity factors (PAL)
Men
|
Women
|
Physical activity
|
|
Sedentary
|
1.0
|
1.0
|
Typical
daily living activities
|
Low
activity
|
1.11
|
1.12
|
+
30 – 60 minutes moderate activity
|
Active
|
1.25
|
1.27
|
+ >= 60 minutes
moderate activity
|
Very
active
|
1.48
|
1.45
|
+ >= 60 minutes
moderate activity & 60 minutes vigorous activity
Or
120
minutes moderate activity
|
Mod.
Activity is equivalent to walking at 3.5 to 4.5 mph
RDA’s
for Energy – Sri Lanka (source: MRI, 2007)
Energy
(kcal/d)
|
|
Infants
0-12 months
Children
1-6 y
Children
6-9 y
10-11 y (male)
10-11 y (female)
12-18 y (male)
12-18 y (female)
Adults
(male): 18-29.9 y
30-59.9 y
>60 y
Adults
(female): 18-29.9 y
30-59.9 y
> 60 y
Pregnancy
Lactation
|
560
– 720
875
– 1300
1775
2250
2100
2875-3375
2400-2500
2425-3375
(depending on activity)
2375-3325
1950-2350
2000-2750
1950-2750
1825-2125
+360
- +460 (2nd – 3rd trimester)
+675
(1-6 months), +460 (>6 months)
|
Energy distribution from nutrients –
Population recommendations
Nutrient
|
% of total
energy
|
Carbohydrates
|
55-75
|
Complex
CHO
|
50-70
|
Refined
sugars
|
0-10
|
Proteins
|
10-15
|
Fat
|
15-30
|
Nutrient
|
% of total
energy
|
Total fat
|
15-30
|
Saturates
|
<10
|
Monounsaturates
|
10-14
|
Polyunsaturates
|
3-8
|
Ratio of Omega 6: Omega 3
|
<5:1 (3:1)
|
Trans fats*
|
<1
|
Source: WHO,
1994, ICN 2009
Calculating the energy content of foods,
meals & diets
Total energy (kcal) = [carbohydrate (g) x 4] +
[protein (g) x 4] + [lipid (g) x 9]
Percent energy from CHO,
protein or fat = Calories
from CHO, protein or fat x 100
Total Cal
Carbohydrates
Simple Carbohydrates
Monosaccharides
(1 sugar unit)
Glucose
Fructose
Galactose
Disacchharides
(2 sugar unit)
Lactose
Sucrose
Maltose
Complex Carbohydrates
Oligosaccharides
(3-10 sugar units)
Raffinose
Stachyese
Polysaccharides
(>10 sugar units)
Starch
Glycogen
Dietary fiber
- Important source of energy
-
65
– 75% of total energy in Sri Lankan diet
- Food sources
-
Cereals
– Rice, Wheat, Kurakkan
-
Yams
– Potato, Manioc, Sweet potato
-
Starchy
fruits – Jak, Breadfruit
Provide digestible carbohydrates and fibre (if unrefined)
- Digestible carbohydrate
-
Monosaccharides
eg. Glucose, Fructose
-
Disaccharides
eg. Sucrose, Lactose, Maltose
-
Polysaccharides
eg. Starch
- Indigestible carbohydrates – Dietary fibre (NSPs)
·
Not
digested by human digestive enzymes, May be acted upon by bacterial enzymes
(non-carbohydrate lignin also included under fibre)
Recommended dietary intake 27-40 g/d (WHO) (high in soluble fibre)
·
Insoluble
fibre
Cellulose, Hemicelluloses, Lignin
·
Unrefined
cereals, Vegetables
·
Soluble
fibre
Pectins – Fruits
Gums – Legume seeds
Food
|
Serving size
|
Insoluble Fiber (g)
|
Soluble Fiber (g)
|
Total Dietary Fiber (g)
|
Fruits
Guava
Orange
Banana
Mango
|
100 gm
1 medium
1 medium
1 medium
|
0.7
1.4
|
1.3
0.6
|
4.7
2.0
2.0
3.7
|
Vegetables
Carrots
Tomato
Potato
|
1 large
1 small
1 medium
|
1.6
0.7
0.8
|
1.3
0.1
1.0
|
2.9
0.8
1.8
|
Dark green leafy vegetables 1 cup
|
approximately 4-5
|
|||
Cereal Products
All-Bran® cereal
Oat bran
Cornflakes® cereal
Rolled oats
Whole-wheat bread
White bread
Macaroni
|
½ cup
½ cup
1 cup
¾ cups
1 slice
1 slice
1 cup cooked
|
7.6
2.2
0.5
1.7
1.1
0.1
0.3
|
1.4
2.2
0
1.3
0.3
0.3
0.5
|
9.0
4.4
0.5
3.0
1.4
0.4
0.8
|
Legumes
Green peas
Kidney beans
Dhal
Lentils
|
2/3 cup
½ cup
½ cup
1/3 cup
|
3.3
4.9
4.7
3.9
|
0.6
1.6
1.2
0.6
|
3.9
6.5
5.9
4.5
|
See also Box 8 in the FBDG for Sri Lanka
Additional information from www.nal.usda.gov/fnic/foodcomp/data
Fats
- Include visible or hidden fats
- Concentrated form of energy (9 kcal/g)
- Improves taste & texture of food
- Supply essential fatty acids
·
Linoleic acid (cis 9,12: C18, omega 6)
· Alpha-linolenic acid (cis
9,12,15: C18, omega 3)
- Provide a vehicle and aid absorption of fat soluble vitamins
- Visible fats
·
Butter, Margarine, Cream, Oil
·
Curries, Sauce
·
On meats
- Hidden fats
·
Biscuits, Cakes, Chocolates
·
Cheese, Pastry, Some snacks
·
Nuts, Avocado
Fats can divide into three
categories
- 1. Phospholipids – FA, Glycerol, P, N base
Glycolipids – FA, Sphingosine, CHO
- 2. Triglycerides – FAs + Glycerol
- 3. Derived lipids
Sterols – Cholesterol, chol. ester- Chol. + FA
Prostaglandins, Thromboxanes, Leukotrienes
Fatty acids can divide into two
categories
Saturated
fatty acids
·
Palmitic,
Stearic
Unsaturated
fatty acids
·
Monounsaturated (one cis double bond)
Eg. Oleic, Palmitoleic
·
Polyunsaturated (>one cis double bond)
Eg. Linoleic acid (omega 6), Alfa-linolenic acid (omega 3)
·
Trans fatty acids (trans double bonds)
Unsaturated fatty acids
Fatty Acid composition of some common oils & fats
Margarine - SFA - 17%, MUFA - 50%, PUFA - 33%
Cholesterol content of some common foods
Chicken giblets - 1 cup - 650 mg
Beef liver - 3 oz. - 325 mg
Egg - 1 - 275 mg
Shrimp - 3 oz. - 150 mg
Salmon - 3 oz. - 125 mg
Crab - 3 oz. - 110 mg
Chicken - 3 oz. - 110 mg
Pork - 3 oz. - 100 mg
Beef - 3 oz. - 90 mg
Lamb - 3 oz. - 80 mg
Oysters - 3 oz. - 70 mg
Ice cream - 1/2 cup - 60 mg
Turkey - 3 oz. - 50 mg
Plant foods do not contain cholesterol
Proteins
·
Thousands of proteins present in the body play
many roles
-
Enzymes, Hormones, Receptors, Antibodies,
Transporters, Structural proteins etc.
-
Proteins can also provide energy
·
Consist of amino acids linked together by
peptide linkages
·
20 AAs commonly found in proteins of which 9 are
essential & these must be provided in the food
·
Essential/Indispensable AA
Valine, Histidine,
Isoleucine, Leucine, Lysine, Methionine, Phenyl alanine, Threonine, Tryptophan
Cannot be synthesized in
the body, Must be taken in food
·
Non-essential/Dispensable AA
Alanine, Aspartic acid,
Asparagine, Glutamic acid, Serine, Arginine, Cysteine, Glutamine, Glycine,
Proline, Tyrosine
Normally not essential,
May become essential or requirement may increase in some disease states
Conditionally essential AA
·
Cysteine
& Tyrosine in hepatic disease
·
Glycine,
Glutamine, Serine & Cysteine in inflammatory states
·
Glutamine
– required for GI tract, tissue trauma
·
Arginine
– intestinal, metabolic dysfunction & endothelial dysfunction
Protein turnover
·
Continuous synthesis & degradation
·
Rate of turnover relate to the function
E.g. Enzyme proteins –
fast
Structural proteins – long lifetime
Healthy adults who are
not gaining or losing weight
I.e. In a steady state
with no growth or protein loss are in zero N balance or N equilibrium
N consumed as protein in
diet = Amounts lost in urine, faces, other routes
Negative N balance: N
Intake < N Output
Positive N balance: N
Intake > N Output
Negative N balance in starvation, injury, infection, cancer
(loss of body protein)
Chronic illness & trauma
Most protein loss is
from skeletal muscle
With preservation of
viscera & other proteins
No adaptation
Starvation
Loss of protein affects
most tissues similarly
Priority to restrict
loss of protein by minimising need for glucose
Brain adapts to use
ketone bodies, with decreased protein synthesis in most tissues
Quality
of protein
· Essential AA content compared with required
pattern/g protein (limiting AA – lowest amount)
·
High quality: animal proteins eg. Eggs, milk,
fish, meat (exception collagen & gelatin)
·
Moderate or low quality: most plant proteins
·
Infants & children need more essential AA
/kg body weight than adults
I.e. Essential AA
ratio is higher
Total AA
Supplementary action of proteins
If a
protein deficient in an essential amino acid is mixed with another protein
having the same AA the quality of the diet increases – supplementary action
E.g.
Rice is deficient in Lysine
Pulses
contain Lysine but moderate or low quality
Lysine
deficit in rice overcome by taking pulses/fish, milk products or eggs in same
diet
E.g.
Soya, Dhal, Mung etc. + Rice,
Fish/Egg/Curd + Rice,
Macaroni & Cheese
RNI
for protein
Recommended
intakes of high quality reference proteins for normal humans (MRI, 2007)
Age (yrs)
|
RDA (g/d)
|
0 –
0.5
|
21
|
7 –
10
|
19
|
Male Female
| |
10
– 11
|
48 50
|
12
– 15
|
69 65
|
19+
|
57 57
|
Pregnancy
|
+
10 g/d
|
Lactation
(1-6 months)
|
+
20 g/d + 14 g/d (> 6 months)
|
Protein requirement of adults
·
Estimated
to be:
0.75 g of high quality, digestible protein/kg body weight
for both sexes
·
Requirement
of mixed protein:
Approximately 1 g/kg body weight
·
Regular
physical activity increases protein requirement to:
1.2 – 1.6 g/kg body weight
Increased requirements usually covered by increased food
intake
Fluid & Electrolytes
Water constitutes approximately 60% of adult body weight &
higher % of a child’s weight
-
Carries
nutrients & waste products throughout the body
-
Participates
in metabolic reactions & serves as a solvent
-
Aids
in maintaining blood pressure & temperature
-
Maintains
blood volume
-
Acts
as a lubricant
To support these vital functions, body’s water balance is
actively regulated
To maintain water balance intake from liquids, foods
& metabolism must balance losses from kidneys, skin, lungs & faeces
Water balance
Water sources
|
Amount (ml)
|
Water losses
|
Amount (ml)
|
Liquids
|
550 – 1500
|
Kidneys (urine)
|
500 – 1400
|
Foods
|
700 – 1000
|
Skin (sweat)
|
450 – 900
|
Metabolic water
|
200 – 300
|
Lungs (breath)
|
350
|
GI tract (faeces)
|
150
|
||
Total
|
1450 - 2800
|
Total
|
1450 - 2800
|
Water needs depend on:
-
Foods
a person eats
-
Environmental
temperature & humidity
-
Activities
levels & many other factors
AI for total water (drinking water & beverages &
foods):
-
Men
3.7 l/d
-
Women
2.7 l/d
DRI committee
Electrolytes
·
Major
minerals from salts that dissolve in body fluids (electrolytes) & cells
direct where these salts go
·
Are
vital to life of cells & must be closely regulated to maintain appropriate
distribution of body fluids
·
Help
to hold water in compartments where it is needed
·
Help
to maintain appropriate distribution of body fluids & acid base balance
Major minerals
- Calcium and Phosphorus are the most prevalent minerals in the body
- Although all major minerals influence fluid balance, Na, K & Cl are most noted for this role
- Na – principal electrolyte in extra cellular fluid and primary regulator of extra cellular fluid volume
- Cl – the major negative ion in extra cellular fluid, salt is a major food source
- K – major cation in cells & plays a major role in maintaining fluid & electrolyte balance & cell integrity
- Diets rarely lack Na
- When intake are low, body adapts by reducing losses in urine & sweat – deficiency unlikely
- Na intake should be < 2000 mg/d
- Processing increases Na content
K recommendations and food
sources
Abundant in all living cells
Fresh foods (intact cells), specially fruits &
vegetables contain adequate K
Processing leads to decreased K
K intake should be at least 90 mmol/d (3.51 g/d)
Food dietary guidelines Sri Lanka - 2011
Serving Sizes
1 cup = 200ml tea cup
Cereals and Starchy foods
Cooked rice ½ cup – 60g
Bread 1
slice (50 g)
Vegetables
Cooked vegetables
(fruit vegetable or leafy vegetable) 3 tbsp (1/2 cup)
Raw salads
1 cup (200 ml)
Fruits
Medium size fruits 1
(1 banana/1 orange)
Cut fruit/fruit salad ½ cup
Dried fruits
2 tbsp (20-30 g)
Fish, pulses, dried
fish, egg, poultry and meat
Cooked fish/poultry/meat 30 g
Cooked pulses 3 tbsp
Eggs 1
Dried fish
15 g
Milk & dairy
products
Milk
1 cup (200 ml)
Yogurt/curd
1
cup (100 ml)
Milk powder
30 g (2 tbsp)
Nuts & oil seeds
1 tbsp (15 g)
Cooked items/quantities measured without gravy
Approximately 8 glasses of water
The diet of a Sri Lankan
Business Man
Mr. Perera is a busy man who owns
his own prosperous business as a building contractor. His typical daily meals
are as follows.
Breakfast
4 slices white bread with pol
sambol, lunu theldala
Tea with 3 teaspoons sugar and full
fat milk
Lunch
4 cups white rice with chicken
curry, parippu, papadams, & 1 egg cooked in coconut milk
Afternoon
Tea with full fat milk and 3
teaspoons sugar
Dinner
4 white flour rotis and chicken
curry, ala thel dala
Evaluate his diet using the Food
Based Dietary Guidelines for Sri Lankans and the following chart
What suggestions would you have for
Mr. Pereira about improving his diet?
Evaluation of a diet
Food Group
|
# of servings consumed
|
# servings recommended
|
Within range?
|
Recommendations for
change
|
Rice, bread, cereals
|
||||
Fruits
|
||||
Vegetables
|
||||
Milk products
|
||||
Fish, pulses, meats, eggs
|
||||
Nuts, oils, sugar
|
References:
- 1. Essentials of nutrition & diet therapy Williams & Schlenker (Latest edition)
- 2. Understanding nutrition E Whitney, S R Rolfes 11th Edition, USA
- 3. Nutritional Sciences from Fundamentals to food, M Mcguire & K A Beerman, Thomson Wadsworth, USA, 2005
- 4. Food Based dietary guidelines for Sri Lankans, Ministry of Health, 2011
No comments:
Post a Comment