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 processOccurs 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