What does nutrition study the science behind?
- nutrients and substances that we ingest in food
- their actions, interaction and balance in relation to health and disease (how tissues use them)
- the process by which an organism ingests, digests, absorbs, transports, utilizes and excretes food substance
A futuristic look on nutrition
- looks at understanding the effects of over-nutrition
- understand the optimal levels of nutrients required for health and well-being
- people respond differently to the same thing - need for precision/personalized nutrition
What is an essential nutrient?
- a chemical that is required for metabolism that cannot be synthesized by our bodies or cannot be synthesized rapidly enough to meet the needs for one or more of our physiological functions
How can you determine of a nutrient is essential in our diet?
- removing the nutrient causes a deficiency and decline in health
- putting the nutrient back into the diet corrects the problem and health returns
What is a nutritional deficiency
- when a persons nutrient intake consistantly falls below the recommended requirement (not just for a day of 2)
Iron / Folate / Vitamin B12 deficiency
leads to anemia
- not enough red blood cells to transport oxygen around the body
- important at key stages of development (pregnancy and infancy)
Thiamine (Vitamin B1) deficiency
leads to Beriberi
- defective energy production
- abnormalities in the nervous system
Vitamin C deficiency
leads to scurvy
- defective collagen production
- causes haemorrhaging, bleeding of gums, etc.
Vitamin D deficiency
leads to rickets
- vitamin D is obtained from the diet and made in the body via UV radiation (sunlight)
- defective bone growth
What is the difference between nutrient deficiency and requirment
Deficiency: understand to prevention of disease
Requirement: understand to ensure optimal health
First approach at understanding nutritional requirements: WWI
- Stems from WWI and food rations - important for soldiers to function well on the battlefield
- limitations with the first recommendations included cost, gender (neglect female), age, physical activity, body size
Nutritional requirements: Daily values
- a simplified way for the government to provide consumers with info about the daily requirement for each nutrient
- based on a 2000-calorie-a-day diet
- only provide a guide for the general population, need tweaking based on the individual
Dietary reference intakes (DRIs)
- used to make daily values
- an umbrella term that refers to a set of values for nutrients (EAR, RDA, AI and UL)
Recommended dietary allowance (RDA) for different substances
Fat: women and men = 44-78g/day
Carbohydrate: men and women = 130g/day
Protein: men = 56g/day, women = 46g/day
Estimated average requirement (EAR)
- nutrient requirements meet the needs of 50% of the population (median)
EAR = RDA - 2SD
why is a range of nutrient intakes required
for individuals in a specific subset (e.g. age or gender) to achieve thee same endpoint of growth, storage or health
Recommended Dietary allowance (RDA)
- nutrient requirements meet the needs of ~ 97% of the population
RDA = EAR + 2SD
Tolerable Upper limit (UL) for RDA and EAR
- UL is the highest level of consistent daily nutrient intake that causes no risk of adverse effects
- too much of a good thing can be a problem (can mask other nutrients)
Adequate intake (AI)
- when sufficient scientific evidence is not available to establish an EAR and RDA then an AI is proposed
- based on less data, a “best guess”
- AI is determined based on the intake of healthy people who have an adequate nutritional status
- AI meets of exceeds the needs or most individuals
- lies between the RDA and the UL
Ancel Keys starvation experiment
characterized the physical and mental effects of starvation in 36 healthy men
- 3 months 3200kcal/day
- 6 months 1800kcal/day
- 3 months rehabilitation (took some 2 years to recover)
outcomes were weight loss, irritability, dizziness, tiredness, reduced sex drive, hair loss, depression
what are the 4 characteristics of a nutritious diet
adequate, moderate, balanced, varied
Adequate diet
provides enough calories, essential nutrients and fibre to keep you healthy
moderate diet
ensures you don’t consume excess calories or eat more of one food group recommended
balanced diet
making sure you eat nutrient-dense foods rather than nutrient-poor food
