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Week 4: Carbohydrates (Functions :check: (Main source of body fuel,…
Week 4: Carbohydrates
Functions :check:
Main source of body fuel
Forming bulk – promote healthy functioning of bowel
Storage of energy – Glycogen
Adequate CHO spares the proteins so that proteins are used for body’s growth and repair
Energy for brain
Description
Composed of oxygen, hydrogen and carbon
Most important energy-yielding macronutrient
Important part of a healthy and well-balanced diet
Abundant in a wide variety of foods
Have many various types
Polysaccharides: Many sugar units linked together
Starch:plant polysaccharide composed of glucose
Found in grains (wheat, rice), in root vegetable (yams, potatoes) and legumes (peas, beans)
Digestible by human body
Body hydrolyzes the starch to glucose and uses glucose as energy
Fiber: Non-digestible (for humans) structural carbohydrates of plants
Pass through the body, contribute no monosaccharides, and thus no energy
2 categories (both needed)
soluble
Dissolve in water
Form gels (vicous)
Fermentable (easily digested by bacteria in the colon)
Found in oats, legumes, barley, and fruits (apple, citrus)
Protecting against heart disease (by lowering blood cholesterol) and diabetes (by lowering blood glucose
non-soluble
Not dissolve in water
Do not form gels (non-viscous)
Less readily fermentable
Found mostly in whole grains, vegetables and most fruits
Promote bowel movement and alleviate constipation
Provide bulk and feelings of fullness, may help in weight manageme
Health benefits
Lower blood cholesterol
Prevent Heart disease
Prevent and control Diabetes
Promote gastrointestinal health
Prevent colon cancer
Weight management
Recommendation: 14g per 1000 kcal
Glycogen: animal polysaccharide composed of glucose
made and stored by liver and muscle tissues of human beings/ animals as a storage form of glucose for future use
(glucose) Glucose is made available when liver or muscle cells receives a hormonal message to “release energy”
Is not counted as one of the complex CHO in foods
Disaccharides: Pairs of sugar units liked together
Lactose (Glucose + Galactose)
The principal CHO of milk
Commonly known as milk sugar
Provides half of the energy (kcalories) provided by fat-free milk
Sucrose (Glucose + Fructose)
Commonly known as table sugar, beet sugar or cane sugar
Occurs in many fruits and some vegetables and grains
Maltose (Glucose x 2)
Also known as malt sugar
It produced whenever starch breaks down during digestion
Also occurs during the fermentation process that yields alcohol
Monosaccharides: Single sugar units
3 types
Galactose
A monosaccharide; naturally found in foods in small amounts
Fructose
Aka fruit sugar.
It is abundant in fruits, honey and juices.
Other sources can be soft drinks, ready-to-eat cereals and desserts with addition of high-fructose corn syrup
Glucose
Also called blood sugar or dextrose;
Serves as an important source of energy for all the body’s activities
Regulated by blood :check:
using hormones
Epinephrine: A hormone releases glucose from liver in stressful situations
Insulin: hormone that transports glucose from blood into cells to be used for energy (helps to lower blood glucose levels)
Glucagon: hormone that elicits release of glucose from storage in response to low blood glucose levels (helps to raise blood glucose levels)
CHO intake is insufficient to meet glucose demand in the body
gluconeogenesis: Body proteins are broken down to make glucose
Disrupting functions of proteins
Health Concerns Related to Carbohydrates Intake :check:
Very-High-Fiber Diets
Health Problems
Too much bulk, fill up too soon
Abdominal discomfort
Binds minerals, thus interfere absorption
May bind to some medications
if water intake is insufficient, Can cause constipation: hard, dry stools that are painful to eliminate
May cause haemorrhoids, rectal bleeding due to increased exertion and pressure
In severe cases, may cause intestinal obstruction, requiring surgery
Lactose Intolerance
Causes
Primary: Due to reduced amount of lactase produced in small intestine
Secondary: damage to the cells in the small intestine, leading to reduced lactase production (e.g. Crohn’s Disease)
Symptoms
Abdominal discomfort
Diarrhoea
Bloating
Flatulence
Omitting all milk products can lead to nutrient deficiencies, such as calcium, vitamin D and B vitamin riboflavin
Dietary changes
Increase the intake of milk products gradually
Consume with other foods in meals
Spread the intake throughout the day
Fermented milk products (e,g, cheese and yoghurt) may be better tolerated due to the reduced lactose content (bacteria digest lactose
Individualized lactose-free diet (lactose is also present in many non dairy foods such as bread, cereals, salad dressings, medications)
High Sugar Diets
Health problems
Increase the risk of weight gain and obesity
Obesity is a major risk factor for Type 2 diabetes mellitus
High intake of energy and sugar (especially fructose)
Associated with increased risk of cardiovascular diseases by raising the blood triglycerides and decrease HDL-cholesterol (aka “good” cholestereol)
Glucose Intolerance
Important to keep blood glucose level within normal range for body functions and prevent symptoms linked to the changes in blood glucose levels
Abnormal regulation of glucose levels can cause
Hyperglycemia (high blood glucose levels)
Hypoglycemia (low blood glucose levels)
Digestion and Absorption of Carbohydrates :green_cross:
Mouth
Stomach
Pancreas
Small Intestine
Large Intestine
Fiber passes intact through digestive tract to the large intestine
Fibre holds water, regulates bowel activity and binds substances such as bile, cholesterol and some mineral, carrying them out of the body
Brush border enzymes breakdown disaccharides into monosaccharides
Produces pancreatic amylase
breaks own large polysaccharides into maltose
Polysaccharides (starch & dextrins) Disaccharides (maltose)
. Mixing/ Churning
Starches and other simple sugars are swallowed and the amylase enzyme is deactivated once it comes into contact with the hydrochloric acid
. Stomach’s acid breaks down starch
But there is NO stomach amylase enzymes is produced to continue starch digestion
. Fibers linger in stomach delaying gastric emptying.
Salivary amylase is secreted in the saliva and begins to break down starch only, not simple sugars.
The longer the starch remains in the mouth, the more digestive action that takes place by the amylase enzyme
Acceptable Macronutrient :check:
Distribution Range: 45 – 65% of total calories requirements
Added sugar should contribute to no more than 10% of dietary energy.
approximately 40 - 55g (8-11 tsp) daily.
This limit includes sugar added to beverages, desserts, cakes, candies, etc.
Diet high in Added Sugars :check:
Health Problems
Increase calorie intake → Obesity
Alter blood lipid profile → Heart Disease
Uncontrolled Diabetes
Nutrient deficiencies by supplying energy without providing nutrient
Dental carries
Decreasing Added Sugar Intake
Using the food label, compare the number of sugar grams to number of carbohydrate grams
If the difference in number is small, the food is likely to be high in added sugars
Choose fruits when desiring something sweet
Opt for non- presweetened breakfast cereals
Add fruit to yogurt rather than buying varieties with fruit added
Alternatives to sugars :check:
artificial sweeteners
Advantages
Low or non-caloric alternative of sugars
Provides virtually no energy
Less concerns in tooth decay
A substitute for people with diabetes
Only a very small amount needed
Disadvantages
Controversies in
Aspartame
: Contains 2 amino acids → aspartic and phenylalanine
FDA approved it as safe use
Not suitable for a genetic disease called Phenylketonuria (PKU)
People with PKU are unable to dispose phenylalanine (amino acid) which is toxic to nervous system and can cause brain damage
Some may exhibit vague but not dangerous symptoms (e.g. headache, dizziness, nausea) due to sensitivity
Controversies in
Saccharin
Approved for use in > 100 countries
Taken off market when high doses caused cancer in lab animals. Risk increases in individuals who are smokers
Removed from the list of suspected cancer-causing substances in year 2000. Warning labels are no longer required
Controversies in
Sucralose
::
a structure like sugar and a sugar-like taste, it is not natural
Sold under the trade name of Splenda
Has been approved for used
The digestion and absorption of sucralose is not clear due to a lack of long-term studies on humans. The majority of studies were done on animals for short lengths of time
Includes
Stevia leaves or monk fruit
Long been used by people of South American and china, respectively
Used to sweeten foods and beverages
Granted by FDA as “generally recognised as safe” (GRAS)
Can be used as additives in foods and beverages
sugar alcohols: “polyols”, meaning that the sugar molecule has multiple alcohol groups attached. neither sugar or alcohol
Occurs naturally in plants, especially fruits
Only half the calories of sugar, 2-3kcal/g instead of 4kcal/g
Example: sorbitol, mannitol, xylitol
Eat in Moderation
Glycaemic Response :check:
Glycaemic Load (GL):Considers the GI and the amount of carbohydrate consumed
Foods with high GL will lead to high secretion of insulin
Chronically high insulin outputs lead to
high blood triglycerides
Increased fat deposition in the adipose tissues
Increased fat synthesis in the liver
More rapid return of hunger after a meal
Glycaemic Index (GI):Ratio of the blood glucose response of a given food compared with the standard (typically, glucose or white bread)
Description
GI is a method of classifying foods according to their potential for raising blood glucose
GI measures how much blood sugar increases in the 2 or 3 hours after eating
The lower the GI, the better the impact on glucose level
Benefits of Food with low GI
Improve glucose control
Improve blood lipids
Reduce risk of heart disease
Help with weight management
Disadvantages of Method
Influenced by:
Food’s starch structure (amylose vs amylopectin)
Fiber content
Food processing
Physical structure (small vs large surface area)
Temperature
Amount of protein and fat
Based on a serving of food that would provide 50g of carbohydrates
This amount may not reflect the amount typically consumed
