Download energy-yielding nutrients

Nutritional and metabolic
diseases
By
Dr.Dlair Maroof
MB.CH.B , D.I.M , F.I.C.M
NUTRIENT AND ENERGY REQIUREMENTS
Macronutrients
ENERGY-YIELDING NUTRIENTS
• Carbohydrates, Lipids, Proteins
• Functions:
– Energy
– Structure
– Function
Three dietary components can provide fuel for oxidation in
the mitochondria to generate energy as (ATP).
These have different energy densities: carbohydrates (4
kcal/g), lipids (9 kcal/g) and protein (4 kcal/g).
Carbohydrates
• Free sugars
monosaccharide glucose , fructose
disaccharides
sucrose , maltose and lactose
• Short chain CHO
oligosaccharides maltodextrins
Carb. Form
Example
Monosaccharide
Glucose
Fructose
• Starch
Galactose
• Non starch polysaccharide
fibrous
cellulose
Disaccharide
Sucrose
Lactose
Maltose
viscous
pectins
Polysaccharide
Starch
Cellulose
Glycogen
Sugars
Classified into
 intrinsic (part of the cellular structure of fruit ,milk …etc ) more acceptable
nutritionally and less harmful metabolically because of association with other
natural nutrients
 Extrinsic( concentrated or refined )

goals
Reduce intake to minimum as possible
refined sugar is the major factor for dental carries
Sugars also lead to hyperinsulinemia which associates with hyperlipidemia
,atherosclerosis and tumors like colon cancer
Starches
• In cereals(wheat, rice );in root foods (potato) and in legumes
• Provides the largest proportion of calories
• Some digested by salivary amylase others by pancreatic amylase , absorbed to
increase blood sugar
• A small % escape digestion to pass to colon to be fermented there by resident
bacteria thus ,behaves like dietary fibers
• Glycemic index :is the incremental area under the 2
hr glucose curve after eating the amount of food
that contains 50 gm carbohydrates
Non starch polysaccharide=
dietary fibers
They are parts of food not digested by human GIT enzymes
Classficaton
 Fibrous NSP :cellulose ,hemicelluloses and lignin .increase
the water holding capacity colonic contents and bulk of
feces
 Relieve simple constipation , reduces incidence of
diverticulosis and colon cancer
 Viscous NSP :pectins and gums more effective in upper
intestine
 Slow gastric emptying ,contribute to satiety , flatten GTT
curve and reduce plasma cholesterol
Proteins
•
•
•
Dietary protein consists of both essential and other amino acids that are required for
protein synthesis.
Are main structural components of human body cells, adequate intake is essential for life as
their constituents of essential amino acids(9 of 20 that can not be synthesized in the body)
The nine essential amino acids are histidine, isoleucine, leucine, lysine, methionine/cystine,
phenylalanine/tyrosine, threonine, tryptophan, and valine.
• All amino acids can be used for energy, and certain amino acids (e.g.,
alanine) can also be used for gluconeogenesis.
• When energy intake is inadequate, protein intake must be increased,
since ingested amino acids are diverted into pathways of glucose
synthesis and oxidation. In extreme energy deprivation, proteincalorie malnutrition may ensue
• Current recommendations for a healthy diet call for at least 10–14%
of calories from protein.
• Biologic value tends to be highest for animal proteins, followed by
proteins from legumes (beans), cereals (rice, wheat, corn), and roots.
• Combinations of plant proteins that complement one another in
biologic value or combinations of animal and plant proteins can
increase biologic value and lower total protein requirements.
• Protein needs increase during growth, pregnancy, lactation, and
rehabilitation after malnutrition
Fats
• High energy density (9kcal /gm) contributes to
obesity in sedentary people
Classification
Saturated :increases LDL and total cholesterol
Monounsaturated (oleic acid )
Poyunsaturated
w6 /lenolenic ,lenoleic [essential fatty acids ,precursor of
prostogandins and leukotriens& arachidonic acids .
w4/docosahexanoic acid[in fish oil are antagonists of thromboxane
A2 & inhibitors of thrombosis])
Recommendations depending on individual’s risk for CHD ,
obesity &cancer Vs energy requirements