Transcript Week 3 CHO 2 notes

Basic Human Nutrition
Carbohydrates, Dietary Fibre, Lactose
intolerance, Milk allergy, Diabetes,
Glycaemic index, Artificial sweeteners
Lecture 3
Carbohydrates
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Simple carbohydrates
 Monosaccharides
 Disaccharides
Complex carbohydrates
 Polysaccharides
Simple Carbohydrates
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Monosaccharides
 Glucose
 Fructose
 Galactose
Disaccharides
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Maltose
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Sucrose
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Lactose
Complex
Carbohydrates
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Polysaccharides
 Glycogen
 Starches
 Fibres
Glycogen & Starch Molecules
Compared (small Segments)
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Complex
Carbohydrates
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Fibres
 Cellulose
 Hemicelluloses
 Pectins
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Complex
Carbohydrates
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Fibres
 Gums and mucilages
 Lignin
 Resistant starches
Complex
Carbohydrates
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Fibres
 Soluble fibres
 Viscous
 Fermentable
Complex
Carbohydrates
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Fibres
 Insoluble fibres
 Nonviscous
Recommended levels of Fibre:
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Between 25 to 35 g per day.
Ratio of insoluble to soluble of 3 to 1
and should be derived from natural
sources in foods rather than from
synthetic fiber supplements.
The average intake in adults is around
12 to 15 g per day.
Fibre health effects
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Heart disease
Diabetes
GI health
Cancer
Weight
management
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Viscous Fibers
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Nonviscous Fibers
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Can I have too much fiber?
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Excess fiber can cause problems:
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Obstruction of bowel
Reduction of the availability of some minerals.
Chelating agents link chemically with minerals,
iron, zinc, calcium etc, and carry them out of the
body.
Purified fibers are devoid of other nutrients.
Too much bulk in the diet can limit total amount of
food consumed—problem for children and elderly.
Digestion
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Mouth
 Salivary amylase
Small intestine
 Maltase, sucrase, lactase
Pancreas
 Pancreatic amylase
Carbohydrate
Digestion in
the GI Tract
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Digestion
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Large intestine
 Fermentation of viscous fibres
 Water, gas, short-chain fatty
acid production
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Absorption
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Lactose Intolerance
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Symptoms
Causes
 Lactase deficiency
Lactose Intolerance
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Prevalence
Symptoms
Dietary changes
 Does not require the elimination
of milk/milk products
 Acidophilus milk
Milk Allergy
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Lactose intolerance often confused with milk
allergy.
Milk Allergy always due to intolerance to
proteins not sugars.
Milk allergy – must avoid all sources of milk
and milk solids in the diet.
Calcium fortified Soya milk and juice and
calcium supplements can replace calcium lost
from dairy products.
Glucose in the Body
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Energy
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Glycoproteins
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Glycolipids
Body’s use of glucose
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In liver fructose and galactose are
converted to glucose.
The liver uses a small amount of
glucose for its activities then converts
the excess into glycogen –
glycogenesis.
Gycogen stores
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Glycogen makes up about 10% of
weight of liver or 100g.
Muscles hold about 325 g of glycogen.
Only about 15 to 20 g of CHO remains
unstored and circulates as blood
glucose.
Reconversion of glycogen to glucose
called glycogenolysis.
Carbohydrate
Metabolism
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Making glucose from protein
 Gluconeogenesis
 Process rapidly depletes muscle
 CHO is essential
 Protein-sparing action of
carbohydrates
Carbohydrate
Metabolism
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Converting glucose to fat
Fat cannot be converted to glucose
 Energetically expensive –glucose
must combine with fragments
before can be used as energy.
 Without CHO-ketosis develops
Carbohydrate
Metabolism
Making ketone bodies from fat
fragments
 Ketosis
 Acid-base balance
 Dehydration
 100g digestible CHO/day
needed to spare protein and
avoid ketosis
Regulation of blood glucose
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After a meal, blood glucose rises.
Hormone insulin released to assist
uptake of glucose by tissues.
Muscle and liver store the glucose as
glycogen. (Excess stored as fat)
When blood sugar drops, pancreas
secretes hormone glucagon.
Regulation of blood sugar
continued
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Glucagon stimulates conversion of
glycogen in liver to glucose
(glyconeogenolysis). Blood sugar rises.
Stress hormone Epinephrine does the
same thing when body in danger.
Blood sugar is tightly regulated by the
liver and insulin to a range called
normoglycemic.
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Maintaining Blood
Glucose
Homeostasis
Glycaemic Effect
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Some foods raise blood sugar more than others
Measured by how fast and how high the blood sugar
rises after a standardized portion of 100g of a food.
Fibre content, particularly soluble, cooking methods
and mixed foods affect glycaemic index of a food.
E.g., ice cream lower than potatoes. Baked potato
lower than mashed potato.
Glycaemic effect important to people with diabetes.
Constancy of
Blood Glucose
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Glycaemic response
 Glycaemic index
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Constancy of Blood
Glucose
Diabetes
 Type 1 diabetes 10-20% of all cases
 Failure of insulin production
 Cause: viral, genetics, disordered
immune system, other diseases,
environmental toxins.
 Type 2 diabetes
 Obesity
Type 2 diabetes; NIDDM
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90% of all cases
Characterized by insulin resistance of
body’s cells including fat cells.
Cells take up glucose too slowly; blood
sugar rises. Insulin also rises.
Pancreas loses supply of insulin and
may require supplementation with
exogenous insulin.
Causes of type 2 diabetes
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Genetics
Aging
Excess body fat
Excess alcohol
Uncontrolled diabetes…
High blood sugars destroy small
capillaries feeding organs. Can lead to:
Blindness
 Kidney disease
 Amputation of limbs (gangrene)
 Heart Disease, strokes
 Decreased resistance to infection
 Nerve damage
Diabetes is diagnosed..
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Fasting Blood test or glucose tolerance
test.
Glucose tolerance test:
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a 100g of glucose in a sugary drink taken
after fasting overnight. Blood sugar is
measured at set intervals to see how blood
sugar responds.
Management of diabetes…
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Diet and/or oral hypoglycaemic drugs or
insulin.
Diet: high in complex CHO, moderate in
simple sugars, high in fibre, low in
saturated fat, moderate in protein.
Exercise to regulate blood sugar and
weight.
Hypoglycaemia
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A symptom-low blood sugar
Postprandial hypoglycaemia – low
sugars after a meal.
Fasting hypoglycaemia
A blood test required to confirm low
blood sugar and observation of
symptoms.
Hypoglycaemia continued
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Symptoms: headache, mental dullness,
fatigue, confusion, amnesia, seizures
and unconsciousness.
Rare causes: pancreatic cancer,
infection of liver (hepatitis), advanced
alcohol-induced liver disease.
A few people are very sensitive to
insulin (may be pre-diabetic).
Hypoglycaemia continued
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Diet consists of:
regular small meals,
high in complex CHO and fiber
combined with protein to delay
absorption of CHO and slow release of
glucose into blood stream.
Sugars
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Added sugars
 Sucrose, invert sugar, corn
syrups, etc.
Sugars
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Health effects
of sugars
 Nutrient
deficiencies
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Sugars
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Health effects of
sugars
 Dental caries
 Dental plaque
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Accusations
Against Sugars
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Sugar causes
obesity
Sugar causes
heart disease
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Accusations
Against Sugars
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Sugar causes hyperactivity in
children
Sugar causes type 2 diabetes
DRI for CHO
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RDA for carbohydrate
 130 g/day
 45% - 65% total daily energy intake
Daily Value: 300 g/day
No more than 25% of total daily
energy intake from simple sugars
Artificial sweeteners
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Two types: sugar alcohols and
noncaloric sweetners.
Sugar alcohols: sorbitol, mannitol,
Isomalt, xylitol widely used in foods.
Provide 2 to 4 calories per gram.
Do not cause dental caries.
May cause diarrhea in large quanitities.
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Artificial sweeteners
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Saccharine,Cyclamate and cancer
Aspartame and PKU
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Do artificial sweeteners help with
weight control?
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Artificial sweeteners can assist with
weight control.
Beverages, particularly pop, coffee/tea,
contribute greatly to total calories.
Sugar –free is therefore beneficial.
Sugar-free snacks, pastries, cakes are
less popular which offsets benefit of
artificial sweetener.