Rowan University



Chapter 1 The Macro-Nutrients

• This chapter is a review of basic nutrition, with some new twists that provides you with a foundation to advance your understanding of nutrition

Objectives of Chapter

• Carbohydrates, Fats, Proteins

o Know sources (quality and poor); Basic structures; Types; RDA’s; Function (specifically during exercise); Misconceptions

Carbohydrates

• All living cells contain carbs

• Primary food source comes from plants

o sugar, starch, fiber

• Small amount from animal sources

• lactose & glycogen

• Smallest units are: glucose, fructose, & galactose

Role of Carbohydrates

• Primary energy source for nervous system

o under normal circumstances ONLY fuel

▪ body has back up system (ketones)

o only structure to NOT need insulin

• Primary energy during high intensity exercise (>60% VO2max)

o role in lower intensities as well

o only fuel used anaerobically & aerobically

o lifting, sprinting, high intensity exercise

• Protein sparing effect

• “Metabolic primer” - “fats burn in flame of carbohydrates”

o w/o adequate carbs, fat can’t be completely metabolized producing “ketones”

• Limited stores will deplete quickly

o metabolic needs

o high intensity exercise

o low carb, low energy diets or skipping meals

o Practice/exercise day after day

• Should account for 55% of calories

o 4 kcals/gram

Monosaccharide (eval. sugar intake in diet)

• Basic unit of all carbohydrates

o only these 3 forms are absorbed

• Glucose (dextrose or blood sugar)

o all carbs ultimately converted to this form

o can be formed endogenously (inside body) via amino acids, lactic acid, glycerol through a process called “gluconeogenesis”

o semi-essential (need approx. 50-100 grams to prevent ketosis)

• Galactose - occurs lactating animals

• Fructose (levulose) - fruit sugar (sweetest)

o absorbed slower into bloodstream causing less of a rise in blood sugar (lower insulin response)

o slowly converted to glucose by liver after absorption

o may cause gastro-intestinal distress

Fate of Mono-Saccharides

Disaccharides

• 2 monosaccharides

o together with monosaccharides (called simple sugars)

o glucose is principle component

• Sucrose - most common; glucose & fructose

• 25% of total caloric intake in U.S. (if carbs need to be reduced it is here)

• Lactose - milk, least sweet; glucose & galactose

• large % of world pop. lacks “lactase” enzyme needed to breakdown (“lactose intolerant”)

Polysaccharides

• Many monosaccharide chains

• Classified into plant & animal categories

o “complex carb”

• Plant - starch & fiber

• Starch - storage form of carbs found in cytoplasm of cell

o energy source for plants

o veg., grains (bread, cereals, pasta, rice), peas, beans, etc.

o most important source of carbs in U.S. diet

• consumption has ( while simple sugar consumption (

Starches

• 2 forms of starch

o amount of each determines digestibility & thus insulin response

• Amylose - long straight chains; digested slowly

• Amylopectin - branched; digested & absorbed quickly

• **glycemic index

Glycemic Index vs Glycemic Load

• GI – numerical system measuring how quickly blood sugars rise b/c of a particular food

o ≥70 is high; 56-69 medium; ≤55 low

o if need blood sugar to ( quickly (during or recovery from exercise, diabetics who are hypoglycemic) high GI is good.

o if don’t want blood sugar to rise quickly (diabetics, those sensitive to sugars, control hunger cravings, most of time) low GI is good.

• GL –new way to asses impact of carbs

o GI tells us how quickly carbs are absorbed but nothing about total amount of carbs in food (limited info)

o GL tells us how much total ( blood sugars a food causes and how quickly

▪ ≥ 20 is high; 11-19 medium; ≤10 is low

• Example – watermelon has a HIGH GI but a low GL. Not bad in terms of how much it raises total blood sugar

Common Foods & Their Glycemic Load

Diabetics Should Pay Careful Attention to Foods Affect on Blood Sugar

Fiber

• Structural polysaccharide

o only in plants (cell wall)

o resists breakdown by digestive enzymes

• Cellulose (most common)

• Soluble – oats, legumes, fruits

o delays gastric emptying

o creates satiety

o delays small intestine emptying

o lowers serum cholesterol (binds bile)

• Insoluble – whole wheat, bran, vegetables

o normalizes transit time through large intestine

← risk of developing GI problems

o absorbs water

o colon cancer

Fiber (evaluate in project)

• Health links (25-30 g/day; 3:1 insoluble to soluble ratio)

← occurrence of obesity

o maybe because of satiety

o good for “snackers”

o May help with diabetes

▪ *slows rate of carb. digestion/absorption

▪ may be high in Mg+, improving insulin sensitivity

← hypertension rates

← intestinal disorders/colon cancer

← heart disease rates

← cholesterol levels

• Sources: p. 9 (9 servings F/V; 6-10 servings whole grains)

HMG-CoA reductase

o enzyme responsible for cholesterol synthesis

• Inhibiting this enzyme stimulates LDL receptors to uptake cholesterol from blood stream

• “Statin” medications work similarly just more potent

• Bacteria in large intestine feeding on fiber may ( HMG-CoA reductase

• Insulin ↑’s HMG-CoA reductase

Animal Polysaccharides (Glycogen)

• Major source of energy during exercise

• Muscle glycogen is immediately available

• Liver glycogen - broken down to dump glucose into bloodstream which then used by cells (“glycogenolysis”)

o controlled by “glucagon”

o “insulin” reverses process

• Gluconeogenesis production of new glucose from non-carb sources: A.A., glycerol, lactate

Glycogen

• Each gram of glycogen stores ( 2.7 g of water

o weight loss (~ 3 lbs of water weight)

o hydration for exercise

▪ carbohydrate overloading has potential to double glycogen storage (~ 6 lbs of water weight)

• Overnight fast greatly ( liver glycogen (by half) stores causing dehydration

o ~ 1-2 lbs of water weight loss overnight

▪ affect on morning exercise or practice?

Misconceptions of Carbohydrate

• Carbohydrates cause obesity

• Carbohydrates cause diabetes

• Carbohydrates cause excessive insulin responses associated with heart disease

• Protein intake is more important than carbohydrate intake for athletes

• Reducing dietary carb intake allows one to rely more on fat, so you will burn more fat during exercise & lose more fat weight

• Eating carbohydrates makes you hungry

• Energy & Carbohydrate Requirements

• Resting energy expenditure

o Teenage Females (12.2 x kg) + 746

o Teenage Males (17.5 x kg) + 651

o College Females (14.7 x kg) + 496

o College Males (15.3 x kg) + 659

• Activity factor b/t 1.3 - 2.1

o 1.3 – sedentary

o 1.6 – light exercise

o 1.7 – moderate exercise

o 2.1 – heavy exercise

Three Main Groups of Lipids

• Lipid is a general term for a group of compounds insoluble in water

• oils, fats, waxes, and related compounds

• Three Main Groups of Lipids

o Simple lipids

▪ Neutral fats – consist primarily of triglycerides

▪ 98% of dietary lipid

▪ Major storage form of fat in adipose cells

o Compound lipids

▪ Phospholipids and lipoproteins

o Derived lipids

▪ Formed from simple and compound lipids

▪ Fatty acids and steroids (ie cholesterol)

Role of Lipids in Body

• Ideal fuel (9 kcals/g)

• Primary fuel at rest & light exercise ( ................
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