Nutrition & Health Flashcards
What are the criteria for a nutrient to be classified as indispensable/essential?
- Must be required for growth, health or survival
- Absence/deficiency of substance in diet will lead to characteristic signs of deficiency disease
- Growth failure & signs of deficiencies can only be prevented by:
a. The nutrient itself
b. A precursor of nutrient - Not synthesised in the body & is required for critical function in body
- When intake is below a critical intake level - the growth response & severity of signs of deficiency is proportional to amount consumed
What are the exceptions to the criteria for nutrient classification as indispensable/essential?
- Some can be synthesized in the body from a precursor (e.g. VitA or Niacin)
- De novo synthesis in the body (Vit D from sunlight)
- Synthesis by microbes in the gut (Vit K)
What are examples of dispensable/non-essential nutrients?
- Non-essential Amino Acids
- Specific fats/CHO
- Alcohol
- Food additives
What are 2 non-essential nutrients that still have health benefits?
- Fluoride:
o Low dosages = prophylactic decrease in dental cavities
o Too much leads to fluorosis - Fiber:
o Insoluble (whole wheat, bran):
- NB for gastro-intestinal function
- Prevents constipation & colon cancer
o Soluble (oat bran):
- Fermentation leads to short chain fatty acids which :
• Provide energy for colonocytes
• Decrease plasma cholesterol
• V important in moderating the comp of microbiome
What are conditionally essential nutrients?
Essential in some populations but not in others
What are examples of populations with conditionally essential nutrient needs?
- Premature infants:
o Have immature metabolic enzyme systems
o They can’t synthesise/digest all the nutrients needed - Hyper-catabolic patients:
o Increased protein degradation
o Decreased protein synthesis
o i.e. Glutamine use > Glutamine production
What are Dietary Reference Intakes (DRIs)?
Is a collective term, including:
- Estimated Average Requirement (EAR) - Recommended Dietary Allowance (RDA) - Adequate Intake (AI) - Tolerable upper Intake Level (UL)
What is the Estimated Average Requirement?
- Intake that meets the estimated needs of a nutrient of 50% of individuals in a specified gender group, at the given life-stage.
- Includes an adjustment for an assumed bioavailability of respective nutrient
- Used for setting the RDA
- Insufficient scientific evidence for EAR -> no RDA set
What is the Recommended Dietary Allowances?
- Intake that meets the nutrient needs of almost all individuals in that gender group, at the given life-stage
- EAR + 2SD (standard deviations)
- RDA applies to individuals, not to groups
- Goal for dietary intake for the individual
What is Adequate Intake?
- Experimentally derived intake levels or approximations of observed mean nutrient intakes by a group of healthy people, who have normal circulating nutrient blood concentrations, growth, or other functional indicators of health.
- AI recommendation when scientific evidence is inadequate to set an EAR
- Indicates that substantially more research is needed to established EAR & RDA
What is the Tolerable Upper Intake Level?
- Max nutrient intake by an individual, which is unlikely to pose risks of adverse health effects in almost all individuals in a specified group.
- Set to protect the most sensitive individuals in the healthy general population
- Applies to chronic daily use
- Not a recommended level of intake
- Contains NOAEL & LOAEL
When did Tolerable Upper Intake Levels become necessary?
When food fortification occurred/became mandatory in many countries & Supplementation became available on the market (allowed people to meet these max levels).
What is a NOAEL?
- No-Observed-Adverse-Effect-Level (NOAEL):
o Highest intake/experimental oral dose of a nutrient at which no adverse effects have been observed in the individuals investigated
o This does not mean that there is no potential for adverse effects with such a high intake.
What is a LOAEL?
- Lowest-Observed-Adverse-Effect-Level (LOAEL):
o The lowest intake at which an adverse effect has been identified.
o If insufficient data to set a NOAEL - use LOAEL as guideline.
What are the applications of DRIs?
- Can use it to plan or assess a diet
- DRIs were purposefully developed for applying standards to groups & individuals - before they only had the RDA which was only for groups of people who were healthy and not any single individual.
- Food Labels
What are Dietary Goals?
- Quantitative dietary recommendations
- Intended for use by health professionals
What are Dietary Guidelines?
- Qualitative dietary guidance – in terms of food not nutrients
- Intended for use by the general public
- Public can use to assess/plan their own diet
- Express DRIs and dietary goals in terms of food
- Simple, practical advice for optimal food choices
- Each country has own set of guidelines
What do all diets emphasise limitation of?
- Refined starches
- Added sugars, sweets
- SSBs (Sugar-sweetened beverages)
- Bakery Foods
- Processed Meats
- Fast foods & takeaways
- Trans-fats, salts
What is nutritional genomics?
= [Genotype + Environment (Diet)] which form a functional phenotype
- Health-disease continuum is a player
- Is an overarching term for:
o Nutrigenetics
o Epigenetics
o Nutrigenomics
What is Nutrigenomics?
The effect of the environment (nutrients) on gene expression
- Nutrients can influence production of hormones
- Hormones can influence signal transduction & production of transcription factors
- These can increase/decrease transcription
What is the nutrigenomic effect of Vitamin A, D and poly-unsaturated fatty-acids?
- They interact with intracellular receptors which influence transcription factors -> influence transcription via promoter area
What is the nutrigenomic effect of Vitamin C?
(An anti-oxidant) It prevents oxidative damage of RNA
What is the nutrigenomic effect of Zinc?
Necessary for certain transcription factors in the promote area & influences DNA binding.
What is the nutrigenomic effect of Vitamin K?
Important for post-translational mods of certain proteins in order to become biologically active.
What is Epigenetics?
- Heritable, but reversible changes in the expression of a gene or trait
- Don’t involve mutations/SNPs - i.e. no changes in DNA sequence
- Examples:
o Histone Modification
o Methylation
What is Nutrigenetics?
The study of the environmental (dietary) effects on phenotype outcomes.
o Studies the effect of genotype x diet on a phenotype indicator
What is Precision Nutrition?
- Dietary changes/recommendations based on genotype
- Pursues development of comprehensive & dynamic nutritional recommendations based on shifting, interacting parameters in a persons internal & external environment throughout life
What are some ethical issues related to Nutrigenetics?
- Direct-to-consumer marketing (DTC): Cutting out the health professional, needs consumer education
- Discrimination: Loss of privacy, employment, social discrimination
- Children: Testing for adult onset disorders?
- ‘unintended information’ - Finding out about Alzheimers etc.
- Cost: Accessible for all?
- Trigger unhealthy quests for health
What is a monogenic disease?
- High penetrance
- Single gene involved
- E.g. cystic fibrosis
What is a polygenic disease?
- Low penetrance
- Many genes (polymorphisms) involved
- E.g. Diabetes, cancer, CVD
What type of evidence is needed for genotype based nutrition?
Evidence should:
1. Predict a robust increase or decrease in disease risk or improvement in treatment outcome in relation to a specific dietary pattern, food or nutrient intake
- Confirm causality – subsequent genotype-based intervention must decrease disease risk or improve treatment outcome
o Associations from observational studies need to be verified in dietary intervention studies to provide evidence of causality
Types of Genetic screening for genotype based Nutrition
- Susceptibility screening for prevention
a. Screen healthy people at risk (due to family history, other indicators) for a disease
b. Screen healthy people in general for alleles associated with common multifactorial diseases (obesity, CVD, etc.) - Screening individuals to optimize treatment outcomes
a. Remember contribution of a single SNP to disease risk is small
b. A SNP can be good or bad
What is the Candidate Gene Approach to Nutrigenetics?
- Hypothesis driven
- Relies on current understanding of biology & physiology of disease
- Known/presumed biological function/metabolic pathways
What is the Genome Wide Association Approach to Nutrigenetics?
- Investigates the entire genome
- No prior assumptions
- Identify previously unsuspected loci associated with disease
- Can narrow down locus more accurately
- BEWARE of incidentalomics:
o Unexpected incidental findings (false +’s)
What are some contributors to chronic inflammation?
o Autoimmune effects o Excess body fat o Genomics & epigenetics o Infection o Smoking o Inflammatory diet o Microbiome o Physical trauma o Antigens o Lack of sleep o Emotional upsets/stress
What are some biomarkers associated with chronic inflammation?
o Mediators involved in or produced as a result of inflammatory process
o NB to use valid markers – reflect inflammatory status & be predictive of future health status
o No consensus as to which markers best represent low-grade I or differentiate between acute & chronic I
o Ongoing research
What is an inflammatory score (IS)
- IS of -1 = Max anti-inflammatory effect
- IS of +1 = Max pro-inflammatory effect
Example of a pro-inflammatory dietary pattern
Wester Type diet:
- Increased: Red meat, fat dairy products, refined grains, sugars
- Decreased: Fruit, veg, legumes
- Energy dense, nutrient poor
- 0 < IS < +1
- Core Mechanisms:
o Excess Energy:
• Results in weight gain -> central obesity -> activates inflammatory pathways
o Increased Saturated Fats:
• Increased SF -> increased weight & adipose tissue
• Changes in membrane & lipid raft comp -> altering cell signalling
• Activates inflammatory paths in cells
• Contributes to metabolic stress
o Carbs:
• Lack of fiber -> increased energy density & decreased nutrients
Example of anti-inflammatory dietary pattern
Mediterranean & DASH diets:
- Increased: Fruit, veg, whole grains, fish
- Moderate: Alcohol, olive oil, chicken, legumes
- Decreased: Red meat, high fat dairy products, refined grains, salt, added sugar
- -1 < IS < 0
