Sports Nutrition Exam #1

Nutrition

the total processes of ingestion, digestion, absorption, and metabolism of food and the subsequent assimilation of nutrient materials into the tissue.

Nutrient

substance found in food that performs one or more specific functions in the body.

Functions of Nutrients

1. Promotion of growth and development

-proteins

-calcium and phosphorus as building blocks of the skeleton

2. Provision of energy

-carbohydrates and fats

3. Regulation of metabolism

-vitamins, minerals, and protein.

Functions of Carbohydrates

1. Energy to the muscle

2. Energy to the brain

3. Storage form of energy

Functions of Fiber

-Insoluble fiber decreases the transit time of fecal matter through the intestines.

-Soluble fiber lowers blood cholesterol concentration and normalizes blood glucose.

Carbohydrate intake and Health Effects

-Sugar intake is associated with obesity, although this conclusion is debated.

-Concern has been raised about the dramatic increases in the intake of added sugar over the past 30 years.

Fiber intake and Health Effects

-associated with reduced risk of various chronic diseases.

Lipids

compounds that are soluble in organic solvents such as acetone, ether, and chloroform.

-derived from Greek word meaning "fat"

-general name for fats, waxes, and related compounds.

-Oils are liquid at room temperature, whereas fats are solid.

Functions of Lipids

-fuel to most cells and an important fuel for contracting muscles.

-fat protects vital organs such as the heart, liver, spleen, kidneys, brain, and spinal cord.

-the intake of fat soluble vitamins A, D, E, and K and carotenoids is dependent on the daily fat intake, and fats provide the transport medium in the body.

- phospholipids and cholesterol are important constituents of cell membranes.

-Cholesterol is also an important precursor in the formation on bile and is itself an important component of bile.

Lipids as Fuel

-Only some of the lipid forms can be used as fuel- fatty acids, intramuscular triaclglycerols (IMTG), and circulating plasma triacylglycerols (chylomicrons and VLDLs)

Fat intake in Western Countries

-Few people in western countries have a fat intake below 20%, and the average daily intake is 100 to 150 g/day, or roughly 34% of the daily caloric intake.

Protein Characteristics

-20 different amino acids are commonly found in proteins.

-each amino acid consists of a carbon atom bound to four chemical groups: a hydrogen atom; an amino group called a side chain, which varies in length and structure.

-different side chains give different properties to the amino acid.

Functions of Protein

-provide structure to all cells in the human body

-integral part of the cell membrane, the cytoplasm, and the organelles.

-muscle, skin, and hair are largely composed of protein, bones and teeth of minerals embedded in protein framework.

-many proteins are enzymes that speed up chemical reactions.

-amino acids are the building blocks of all proteins.

Protein as a building block

-amino acids are bound to each other in a protein by so called peptide bonds.

-Small proteins are often referred to as peptides of polypeptides.

Protein Intake

-Recommended protein intake varies worldwide from 0.8 to 1.2 g/kg b.w.

-Protein intake in the western world is usually averages 80 to 100 g/day. 100 grams of protein is roughly equal to 400 kcals of energy, so for a 2,000 kcal diet, that is 20%.

-Unlike carbs and fat, protein has not been associated with negative health effects.

-Some amino acids are described as essential because they cannot be synthesized in the body and so must be obtained from food.

Functions of Water

-Transports nutrients in solution.

-Provides protection (lubrication, cleansing, and cushioning)

-Helps regulate body temperature (sweating)

-Participates in biochemical reactions

-Provides the medium in which these reactions take place (by the transport in the blood of nutrients and oxygen to the tissues and the transport of carbon dioxide and waste products away from the tissues)

-Helps get rid of waste products (urine)

Water Intake

-Water intake of an adult is typically 2.0-2.8 L/day

-Rule of thumb: fluid requirements are 1 ml for every 4 kJ of energy expended or 1 ml/kcal.

-Of the daily 2.0-2.8 L consumed, 1.0-1.5 L is usually in the form of fluids and the rest obtained from foods.

-Athletes training and competing in the hot conditions may have fluid requirements greater than 15 L/day.

Vitamins, Minerals, and Trace Elements

-vitamins are organic compounds

-minerals and trace elements are inorganic compounds.

-collectively known as micronutrients, these essential compounds have many biological functions.

-all 13 known vitamins have important functions in most metabolic processes in the body.

-vitamins must be obtained from the diet, except Vitamin D, which can be synthesized from sunlight, and vitamin K, which is synthesized by bacteria in the intestine.

Functions of Vitamins and Minerals

-they serve as regulators and links in the processes of energy release from food.

-they are important cofactors in various chemical reactions and as such are important in maintaining homeostasis.

Essential Nutrients terminology:

essential=indispensable

nonessential=dispensable

Dietary Reference Intake (DRI)

-the new standard for nutrient recommendations that can be used to plan and assess diets for healthy people. Think of DRI as the umbrella term that included the following values.

Estimated Average Requirement (EAR)

-nutrient intake value that is estimated to meet the requirement of half of the healthy individuals in a group.

-used to assess nutritional adequacy of intakes of population groups.

-EARS are used to calculate RDAs.

Recommended Dietary Allowance (RDA)

-goal for individuals and is based on the EAR.

-daily dietary intake level that is sufficient to meet the nutrient requirement of 97-98% of all healthy people in a group.

-If an EAR cannot be set, no RDA value can be proposed.

Adequate intake (AI)

-used when a RDA cannot be determind.

-a recommended daily intake level based on an observed or experimentally determined approximation of nutrient intake for a group (or groups) of healthy people.

Tolerable Upper Intake LEvel (UL)

-the highest level of daily nutrient that is likely to pose no risks of adverse health effects to almost all individuals in the general population.

-as intake increase above the UL, the risk of adverse effect increases.

Daily Values (DV)

-term used in food labeling that is based on a daily energy intake of 2,000 kcals and for the food labeled.

-gives the percentage of the RDI and the DRV recommended for healthy people in the U.S.

Practical guidelines for a balanced healthy diet

-there are over 40 essential nutrients. The concept of a balanced diet refers to eating a wide variety of foods in moderation to support normal or optimal functioning.

-mypyramid was developed by the U.S. department of agriculture (USDA) and represents the 2005 dietary guidelines for americans.

Cellular and Subcellular skeletal muscle structure

- Thick and thin filaments

-sarcomere

-sarcolemma

-t-tubules

-sarcoplasmic reticulum

-mitochondria

sarcomere

functional unit of skeletal muscle

sarcolemma

plasma membrane of a skeletal muscle cell

T-tubules

invaginations of the cell membrane of the muscle cell which increases the surface to volume ratio of the cell.

sarcoplasmic reticulum (SR)

-storage depot for calcium

-important for the process of release and uptake of calcium for muscle contractions.

Force generation in skeletal muscle

-action potential across cell membrane

-stimulates the release of calcium from intracellular stores in the SR.

-calcium floods the cytosol (in muscle this is called sarcoplasm)

-calcium binds to troponin-tropomyosin complex

-tropomyosin moves out of the way of the myosin binding site on actin allowing crossbridge cycling to proceed provided there is sufficient ATP for muscle detachment and activation of the crossbridges.