Nutrition for Fitness Leaders

Nutrients

Tracey Kobayashi

50 Phelan Ave, NGYM
San Francisco, CA 94112
(415)452-7311
tkobayas@ccsf.edu

Tracey's Home

    PE 9A: Fit or Fat
    College & Career Ed
    PE 50: Fitness Center

CCSF Home

PE Department

SFHA Computer Class

Lectures

Old Courses

IM Me!

    AIM - TKatCCSF
    Yahoo - tkobico
    ICQ - 155909399

[ Intro ] [ Nutrients ] [ Energy ]
[ Apps ] [ Commercial Diets ]

Nutrient Classification

Nutrients are absorbed substances which provide some sort of benefit to the body. During the digestive process, food is broken down into its base nutrients. There are two major classifications of nutrients:

• Micronutrients: vitamins and minerals. Assist in metabolic reactions and in fluid balance. Micronutrient absorption may occur in the small or large intestine, depending on the nutrient.
• Macronutrients: or calorie-yielding nutrients. Macronutrients include carbohydrates, lipids (fats) and proteins. Macronutrient absorption occurs in the small intestine.

Micronutrients

Vitamins tend to act as enzymes, assisting with different reactions. They have two major classifications:

• Water-soluble vitamins (B & C): need to be ingested regularly, since excess amounts are excreted in the urine.
• Fat-soluble vitamins (A, D & E): can be stored in the body, and therefore can be toxic if ingested in large amounts.

Vitamin K has characteristics of both water and fat-soluble vitamins, but is typically categorized as a fat-soluble vitamin.

Minerals are elements which play roles in bodily functions. Sodium and Potassium concentrations help to regulate fluid levels, as well as play a role in generation of action potentials.

Macronutrients

Macronutrients (carbohydrates, proteins and fats) are calorie-yielding nutrients.

• Carbohydrates: 2 hours mouth to absorption.
  Digestive Tract
  • Chemical digestion begins in mouth with salivary amylase and continues in the stomach and small intestine. Carbohydrates digest down into glucose.
  • Glucose is absorbed by active transport in the small intestine. It is believed the carrier protein responsible for absorption needs a sodium ion present to work.
  Circulation and Storage
  • Blood glucose levels control insulin and glucagon release. High blood glucose stimulates insulin, which causes rapid cell uptake, usage and storage (as glycogen or converted into tricglyceride if glycogen storage capabilities are exceeded). Low blood glucose stimulates glucagon, which works to restore circulating levels by releasing liver glycogen, and manufacturing glucose from other constituents (most notably, protein). The brain is ALWAYS permeable to glucose. Unlike other cells, it can only use glucose for energy, so needs to be guaranteed a constant supply.
• Proteins: 4 hours mouth to absorption.
  Digestive Tract
  • Chemical digestion begins in stomach, where HCl breaks down selected proteins, and continues in the small intestine, where other enzymes come into play. Proteins digest into amino acids.
  • Amino acids are absorbed by a sodium co-transport mechanism similar to glucose absorption. 98% of ingested protein is typically absorbed as amino acids, and 2% is excreted into the feces.
  Usage: Amino acids are manufactured into proteins, which act as enzymes and structural blocks. They can also be deaminated to form lipids when excess protein is ingested at one time, or glucose when there are insufficient levels. Average daily protein requirements:

  Group	Recommendation
  Average, Moderately Active Adult	RDA = 0.8 g/kg body mass ADA = 1.0-1.5 g/kg body mass
  Strength/Speed Athlete	1.2-1.7 g/kg body mass
  Endurance Athlete	1.2-1.4 g/kg body mass

• Fats: 8 hours, mouth to absorption.
  Digestive Tract
  • Chemical digestion begins in the stomach with gastric lipase, but 95% of fat digestion occurs in the small intestine. Most ingested fats are in triglyceride form, and they break down into fatty acids and monoglyceride.
  • Fatty Acids and Monoglycerides combine with bile salts from the liver to form micelles, which carry them to the brush borders of the epithelial cells where they are absorbed via diffusion, leaving the bile salts in the chyme. Normally 97% of ingested fat is absorbed. Without bile acids, only 40-50% are absorbed.

  Storage: FFAs reform into triglycerides in adipose tissues and liver for storage.

  Usage:

  • Adipose triglycerides convert into FFAs, and move through the circulatory system to the target cells for usage.
  • Liver triglycerides, transformed from excess glucose and amino acids, are transported through the cirulation to target cells on Very Low Density Lipoproteins (VLDLs). Once the triglyceride is released to the target cell, the VLDL converts into Low Density Lipoprotein (LDL -- the "bad" cholesterol).
  Lipids protect and insulate vital organs, make up cellular membranes, help transport certain nutrients, and act as energy substrates.

For more information on recommended nutrient intakes, check with the Food and Nutrition Board of the National Academy of Science.

[ Intro ] [ Nutrients ] [ Energy ]
[ Apps ] [ Commercial Diets ]