The Macronutrients Chapter 1

Macronutrients Carbohydrates Lipids Proteins Provide energy Maintain structure

Atoms and Molecules Atoms 103 elements discovered Human body Nitrogen – 3% Hydrogen – 10% Carbon – 17% Oxygen – 65% Two or more atoms Molecules

Sodium Chloride

Carbon Organic compounds Component of all nutrients Exception – water, minerals Bonds with hydrogen, oxygen: CHO, lipids And nitrogen: Proteins Vitamins also carbon based

Carbohydrates Monosaccharides Basic unit Glucose, fructose and galactose Disaccharides Sucrose, lactose and maltose Oligosaccharides Short chains of monosaccharides (3-9) Mostly in legumes (peas, beans and lentils) Polysaccharides Long chains of primarily glucose

Monosaccharides Glucose Blood sugar, all other CHOs are converted to glucose by the liver Used by cells for energy Stored in muscle and liver as glycogen Converted to fat and stored Fructose Fruits and honey Galactose Component of milk sugar (lactose)

Disaccharides  Each disaccharide includes glucose as a principle component. Sucrose = Glucose + Fructose Found in most CHO containing foods Sugar, maple syrup, honey Lactose = Glucose + Galactose Found in milk Many are intolerant due to lack of Lactase Maltose = Glucose + Glucose Beer, cereals, seeds

Polysaccharides  Polysaccharides  10-to-thousands of monosaccharides linked together  Two forms: Plant and animal  Plant  Starch: Storage form of CHO in plants  Found in most complex CHOs  Pasta, potatoes, corn, grains, breads, cereals, rice  Animal  Glycogen: Storage form of CHO in animals  Why don’t we derive CHO from meat?

Starch (amylopectin)Starch (amylose) Glycogen A glycogen molecule contains hundreds of glucose units in highly branched chains. Each new glycogen molecule needs a special protein for the attachment of the first glucose (shown here in red). A starch molecule contains hundreds of glucose molecules in either occasionally branched chains (amylopectin; more easily digested) or unbranched chains (amylose).

Fiber Non-starch polysaccharide Cellulose (most abundant organic molecule on earth) Resist digestion Help digestive process forming Gels (cellulose, gums, pectin) Absorb water Gives “bulk” to stool Shortens transit time through GI tract Binding or diluting harmful chemicals Scraping action on cells of gut

Fiber Increased fiber intake May have certain health benefits Reduce serum cholesterol Fiber is fermented in large intestine “feeds” bacteria in the colon, keeping it healthy May reduce blood sugar in type II diabetics Types Water soluble: dissolve in water and form gels Water insoluble: do not dissolve in water, provide a sort of structure Sources Oats, barley, brown rice, peas, carrots, whole wheat, cabbage, beets, cauliflower, apple skin

Glycogen Most CHO energy stored as glycogen Vast majority stored in muscle This amount varies based on training status Still, small amount of energy Only enough for ~2hrs of activity

Glycogen  Glycogen is synthesized from glucose  Enzymatic process  Occurs following feeding  Particularly strong following exercise

CHO containing foods

Glycogen Dynamics  Hormones help to regulate blood sugar levels.  Insulin Signals cells to take glucose out of the blood and into the cell for use or storage  Glucagon stimulates the liver to break down glycogen (glycogenolysis) and form glucose from other compounds (gluconeogenesis) to raise blood glucose concentration.

Diabetes Type 1: Autoimmune disease Pancreas cannot make insulin Blood glucose rises to very high levels Dangerous to small blood vessels and nerves Can result in death if not controlled Diabetic coma How does this happen? Type 2: Insulin resistance Caused by obesity Cell fails to respond to insulin Blood sugar rises Easily treated

Diabetes

Type 2 diabetes Risk factors >45 yrs of age Overweight/obese (*) Family history Elevated blood pressure (>140/90) Elevated blood triglycerides (>250 mg/dL) Physical inactivity

Role of CHO in obesity Excessive CHO intake Elevated insulin Rebound hypoglycemia Makes you feel hungry Over eat Excess CHO Stored as fat Limited ability to store CHO as glycogen

Roles of CHO Energy source Primary fuel source for most types of activity Spares protein for structural purposes Low CHO diets cause proteins to be broken down to Amino acids Liver converts these amino acids to glucose Potential strain on kidney Prevents ketosis Low CHO prevents “normal” fat metabolism Fat is still mobilized from reserves Converted to ketone bodies for energy Fuel for central nervous system