How much did you drink at the weekend?

Fluids and Hydration Applying the Principles of Nutrition to a Physical Activity Programme

Learning outcomes Describe the main function of water List the ways in which the body loses fluid State how much water is needed per day Describe the potential consequences of dehydration Describe how to assess hydration levels Explain the effect of solute (sugar) and electrolyte (sodium) content on water absorption across the gut by osmosis Describe the composition of hypertonic, hypotonic and isotonic sports drinks and discuss their uses. Evaluate the effectiveness of different drinks as re-hydrators Discuss the diuretic effect of caffeine, alcohol and high-sugar drinks Describe current guidelines (Department of Health) for safe upper limits of alcohol per day State the energy value of alcohol

Functions of water Water accounts for 60-70% of our body Transport system for nutrients Removes waste products Temperature regulation Environment where chemical reactions occur

How is fluid lost from the body Water loss occurs continuously: Breathing Sweating Excretion of waste Typically 2.5 litres per day Water input needs to match water loss – otherwise dehydration occurs

Water intake Water can be derived from food and fluids consumed A well-balanced diet can provide 1 – 1.5 litres of water just from food. The rest must come from fluids Individual requirements vary depending on energy expenditure, temperature, body size, etc.

Consequences of dehydration Decrease in blood volume/blood pressure thus compromising distribution of nutrients and oxygen around the body. Decreased blood flow to the brain therefore headache, poor concentration and compromised motor fitness. Decrease in kidney function because of water retention Decrease in metabolic rate in all cells with consequences for metabolic efficiency and weight management Increased risk of poor digestion and constipation

How to assess hydration levels Urine colour hydration level Clear: Hydrated Very pale yellow (straw): Hydrated Pale yellow: Hydrated Yellow Mild: Dehydration Dark yellow: Dehydration

How fluids enter the blood Fluids move across the intestinal wall by osmosis – movement from a high to low concentration of molecules (sugar and salt) they contain Sugar = ‘solute’ Salt/sodium = ‘electrolyte’ Fluids can be categorised in relation to their ‘osmolality’ – depending upon their sugar and sodium content

Sports drinks Sports Drinks fall into three categories based on their osmolality: Hypertonic Isotonic Hypotonic Mainly depends on their sugar content

Hypertonic Contains more sugar than body fluids 8g(or more)/100mls Water moves into the gut to dilute it before it can be absorbed Useful in providing fuel for exercise Inefficient at providing hydration Fruit juice, fizzy drinks, energy drinks Over consumption can lead to tooth decay

Isotonic Contains the approximately the same concentration of sugars as body fluids Between 4 – 8g/100mls Absorption from gut is slightly faster than plain water, giving to fast hydration Useful during exercise as a small amount of energy is also supplied

Hypotonic Contains less sugar than body fluids 4g(or less)/100mls Absorption from gut is slightly faster than plain water, giving to fast hydration Less useful during exercise as only a very small amount of energy is supplied

Stimulates the kidneys to excrete more fluid Diuretics Stimulates the kidneys to excrete more fluid Caffeine (coffee, tea, cola, energy drinks, etc.) Alcohol High sugar content Can accelerate dehydration

Department of Health: ‘safe upper limits’ Recommended guidelines for safe alcohol consumption Department of Health: ‘safe upper limits’ Males Females Per Week 21 Units 14 Units Per Day 3 – 4 Units 2 –3 Units

½ pint of lager at 3.5% alcohol 25mls spirits at 40% alcohol Recommended guidelines for safe alcohol consumption You should not ‘save up’ your recommended units and consume them all in one day. What is a unit? ½ pint of lager at 3.5% alcohol 25mls spirits at 40% alcohol 125mls wine at 9% alcohol

Energy value of alcohol 1g (or 1ml) of alcohol contains 7kcal