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