Water The most critical nutrient but usually the most overlooked.

The Vital Functions of Water  Facilitates Chemical Reactions  Transports Nutrients and Waste Products  Lubricates Surfaces  Regulates Body Temperature

Facilitates Chemical Reactions  Most chemical reactions in the body require water, like breaking down carbohydrates, fats, and proteins for energy.  Water is a reactant in many chemical reactions in the body. Water is needed to split the bonds in the starch chain and the elements of the water molecule become part of the separate glucose molecules. Water is needed to split the bonds in the starch chain and the elements of the water molecule become part of the separate glucose molecules.

Transports Nutrients and Waste Products  Water is a solvent. a liquid in which substances can be dissolved a liquid in which substances can be dissolved  Water can dissolve most substances: Amino acids from proteins Amino acids from proteins Glucose from carbohydrates Glucose from carbohydrates Minerals Minerals Water-soluble vitamins Water-soluble vitamins  Blood is primarily made of water and is responsible for transporting nutrients through the body as well as carrying dissolved wastes away from the cells  Water helps remove waste from the body through perspiration, exhaled water vapor, feces, and urine.

Lubricates Surfaces  Water is a lubricant. A substance that reduces friction between surfaces. A substance that reduces friction between surfaces.  The water in saliva lubricates food as you swallow it.  Water acts as a lubricant throughout the digestive system to assist the easy passage of nutrients.  Tears lubricate your eyes.  Fluids surround your joints to keep bones from rubbing together.  Cushions vital tissues and organs

Regulates Body Temperature  Normal body temperature is near 37 o C. Temperatures that are above or below this can cause serious health problems.  Heat from your body is released when blood flows near the surface of your skin.  Sweat glands produce perspiration. The evaporation of water in perspiration helps cool your body.  When your body gets too cold, your blood vessels constrict to restrict the amount of blood flowing near your skins surface.

Fluid balance  Throughout the body, there needs to be a balance between water intake and water excretion.  Cells are like balloons. Burst or collapse?  Intracellular water: the water inside the cells.  Extracellular water: the water outside the cells.  Water can move freely across the cell membranes.  The concentration of sodium, potassium, and chloride determines the movement of water.

The Source of the Body’s Water Supply  Most people need about 2-3 liters a day to replace body fluids.  While water is the best source of this nutrient, milk, pop, juice, broth, tea, and other liquids have a high water content.  As food contains some water, it also acts as a source of water. Example: orange juice is 87% water, while summer squash is 96% water.  12% of your water needs are met by metabolism.

Bottle Water vs. Tap water  c3MSY c3MSY c3MSY  The cost of bottle water can be several hundred times higher than the cost of tap water.  Bottle water is no healthier than safe, clean, pure tap water.  f9EM

Can you drink too much water?  Yes! The result is water intoxication.  Drinking large quantities of plan water can dilute the concentration of electrolytes in the extracellular fluid. This can cause headaches and muscle weakness. Severe cases of water intoxication can cause death.  Infants are at a high risk of water intoxication when experiencing diarrhea or vomiting.  When fluid losses are excessive, both fluids and electrolytes must be replaced.

How Is Body Water Lost?  Water loss happens in one of three ways: Urine Urine Sweat Sweat Breath Breath  Factors that increase water losses: Hot or warm temperatures Hot or warm temperatures Dry climates Dry climates Using diuretics – increase urine production Using diuretics – increase urine production Caffeine, alcoholCaffeine, alcohol Illness Illness Exercise Exercise

Effects of Water Loss  Because fluids make up a high percent of your body weight, when you lose water, you lose weight. Water weight is quickly regained when body fluids are replenished. Water weight is quickly regained when body fluids are replenished.  When you lose 2% or more of body weight in fluids, you will become thirsty.  If you do not replace water losses, you may dehydrated (body contains lower than normal amount of body fluids). Urine, sweat decreases, concentration of sodium in blood increases. Urine, sweat decreases, concentration of sodium in blood increases.  Athletic performance will go down with a 3% fluid loss.

Guidelines for Fluid Replacement  Drink ounce glasses (1.5-2 liters) of water a day.  If you feel thirsty, drink liquids.  When the weather is hot, you should make an effort to increase fluid intake.  Begin drinking before you start to exercise.  Healthy urine output is a minimum of 2 ½ cups a day.  Use the color of your urine to gauge your water input: Light-coloured urine is what you are aiming for, almost clear.

People with above average needs for water  Infants  Older adults  Pregnant women  Lactating women  People on high-protein diets