(NDT) Chapter 4: Carbohydrates

What are carbohydrates?

One of the three macronutrient composed of carbon, hydrogen and oxygen. The preferred energy sources for the entire body.

Sources: Grains, fruits, veggies and milk.

Simple Carbohydrates

Carbohydrates that are composed of 1 (mono-) or 2 (di-) sugar molecules and are fast digesting.

Monosaccharide

A singular sugar molecule.

• Glucose (Most abundant in diet, preferred energy source for the brain)

• Galactose (Does not occur alone in foods (e.g) in lactose)

• Fructose (Sweetest natural sugar, also called fruit sugar/levulose)

Two main forms of bonds connecting Monosaccharides…

(1) a-glycosidic (alpha bond): (-OH) group below ring plane, easily digestible by human beings

(2) B-glycosidic (beta bond): (-OH) group on the anomeric carbon is above the ring plane, giving it a rigid structure therefore more difficult to digest (lactose and high fiber foods)

Disaccharides

Carbohydrate containing 2 sugar molecules

• Maltose (glucose+glucose): Product of breakdown of a larger molecule

• Sucrose (glucose+fructose): Natural sugar, brown, white, honey etc.

• Lactose (glucose+galactose): Milk sugar

Complex Carbohydrates

The second major classification of carbs, generally consisting of long chains of glucose molecules.

(Any carbohydrates with 3 or more monosaccharides, oligo, poly)

Oligosaccharides

Carbohydrates containing 3-10 monosaccharides, they cannot be digested by the human body and only broken down by the bacteria in the large intestine. (Gas producing)

• Raffinose (galactose+glucose+fructose): Brussel sprouts, beans, cabbage, whole grains

• Stachyose (galactose(2)+glucose+fructose: Beans and legumes

Polysaccharides

Most consists of hundreds to thousands of glucose molecules

• Starch: Storage form of glucose and plants (e.g., legumes, grains and tubers)

• Glycogen: Storage form of glucose in animals (stored in liver and muscles) (ND)

• Fiber: Forms support structure of plants

Starch (Food source and types)

Food sources: grains (wheat, rice, corn, oats, and barley), legumes (peas, beans, lentils), tubers (potatoes and yams)

• Amylose: Straight chain

• Amylopectin: Branched chain

• Resistant starch: type of fiber, highly indigestible

Fiber (Food sources and types)

ALL HAVE TO BE DIGESTED IN ORDER TO BE BROKEN DOWN IN LARGE INTESTINE

• Dietary fiber: Non-digestible parts of plants (skeleton)

• Functional fiber: Dietary fiber extracted from plants or made in lab for health benefits

• Total fiber: sum of dietary fiber and functional fiber

Soluble fibers

Easily digestible/fermented fibers that are viscous and dissolve in water

• Food sources: citrus fruits, berries, oat products, beans and bananas.

• Pectins, gums, mucilages

Insoluble fibers

Not digestible by bacteria in the colon and are not soluble in water .

• Food sources: Whole grains (wheat, rye, brown rice), vegetables

• Lignins, cellulose and hemicelluloses

Take note of… (fiber)

• Fiber rich foods: fruit, vegetables, whole grains

• Not ALL complete carbs are fiber rich (processing and such)

• 5g or more considered HIGH FIBER FOOD

Health Benefits of soluble fiber

• Promotes heart health and

• Regulates blood glucose by slowing down the processing of sugar

• Satiety (fullness)

Health benefits for insoluble fiber

• Helps move food through the digestive system faster (BULK to stool)

• Relieves constipation

• Aids the prevention of colon cancer

Recommended amounts of carbohydrates to consume based on AMDR and RDA

45-65% of entire diet and energy consumption. (225-325 g on a 2,000 kcal diet)

RDA: at least 130 g each day

Women: 28 g

Men: 35 g

Carbohydrate digestion in the mouth

• Chewing stimulates the secretion of saliva (salivary amylase)

• Breaks down polysaccharides into shorter polysac. and disaccharides

In the Stomach

• Salivary amylase is destroyed by stomach acids

• No carbohydrate digestion occurs

In Small Intestine

• Where most of the digestion and absorption of carbohydrates occur

• Pancreatic amylase breaks down remaining starch into maltose

• Specific enzymes breaking down di- into mono- (maltase, lactase, sucrase)

• Mono absorbed by small intestine INTO bloodstream

Pancreas

• Release digestive enzymes + bicarbonate

• Released into small intestine via pancreatic duct

In the Liver

• Converts most non-glucose mono- into glucose

• Converts fructose and galactose into GLUCOSE

• Stored as glycogen in muscles and liver (provides energy to muscles and maintains blood glucose levels through the liver

in the Colon (Large Intestine)

• Not enough digestive enzymes in order to break down fiber

• Bacteria ferments soluble fibers (producing gas

• Insoluble fiber will add to the bulk in the stool and be secreted

Major sources of sugar in the American Diet

• Most american eat too much added sugar (diet should consist of les than 10% of added sugar)

• Largest source: sweetened soft drinks

• Diets HIGH in simple sugars can lead to health problems

Diabetes

Chronic disease in which the body cannot regulate glucose within its normal limits (hyperglycemia occurs)

• Hyperglycemia: higher than normal levels of blood glucose

• if not tended to: kidney failure, stroke, blindness, CVD

Type 1 Diabetes

• 5-10% of those with diabetes

• autoimmune condition where pancreas fail to produce enough insulin (destroys insulin producing cells)

• usually diagnosed within 10-14 years of age (genetic link)

• requires the administration of insulin (daily)

Type 2 Diabetes

• Accounts for most diabetes cases (90-95%)

• Progressive disorder in which the body becomes more unresponsive to insulin (insulin resistance/ insensitivity)

• Linked to lifestyle factors, eventually pancreas will stop producing

Type 2 Diabetes (Signs)

• High blood insulin levels

• High glucose after meals

Type 2 Diabetes Treatments

• Weight loss, physical activity and regular exercise

• Healthy choices in diet

• Associated with an aging population, poor diet and obesity

Hypoglycemia

• Low blood glucose: weakness, shakiness and anxiety

• condition where blood sugar drops below 70 mg/dL

• Reactive hypoglycemia: pancreas produce too much insulin

• Fasting hypoglycemia: insulin production too much even after not eating

Insulin

Hormone produced by the pancreas which is released to reduce blood glucose levels and typically rises after the consumption of a meal.

• stimulates the liver and muscle cells to take up glucose and store it as glycogen (glycogenesis)

• stimulates glucose transporters to carry glucose molecules across the cell membrane (remove from blood stream)

Glucagon

Hormone released from pancreases to increase blood glucose levels typically after their is not food entering the body for over 3 hours. (IN LIVER)

• Stimulates the liver to breakdown stored glycogen into glucose

• Gluconeogenesis: process of the body making its own glucose by breaking down body proteins (amino acids cannot be used for their regular function)

Other hormones that increase blood glucose level…

• Norepinephrine and epinephrine (responsible for our fight or flight responses)

• Cortisol and growth hormone (increased usage of gluconeogenesis) acts on adipose tissue

Ketoacidosis

Carbohydrates spare protein and prevent ketoacidosis which is chemical imbalance in which there is a excessive build up of acids (ketones) because the body has broken down fats for energy instead to glucose (due to a lack of insulin)

• ketosis: inadequate intake of carbohydrates will lead to the break down of fats for energy which produce ketones (possibility for acidic blood)

Nutritive sweeteners

Sugars that provide energy (kcal)

• Includes sugars and syrups: Sucrose (table sugar), glucose, fructose, lactose, maltose.

• Syrups + concentrates: High fructose corn syrup, honey, molasses, maple syrup, agave nectar, fruit juice concentrate.

• Sugar alcohols as well

Non-nutritive sweeteners

Sugars that provide few to no calories, limited use is not considered harmful (within Acceptable Daily Intake)

• Saccharin, sucralose, acesulfame, aspartame, neotame, stevia, advantame, monk fruit extract, splenda

• Aspartame ADI= 50 mg/kg/day