NRVs and the Digestive System

Question 1

What are the ADGs? How are they developed? Whom are they addressed too?

Answer 1

ADGs give advice on eating for health and wellbeing. They have been developed from the most current scientific evidence and are targeted at the general healthy Australian population.

Question 2

What is the goal of the ADGs?

Answer 2

To prevent chronic and deficiency diseases

Question 3

What is the AGHE?

Answer 3

A food selection guide which provides a visual representation of the food proportions we should be consuming from the 5 food groups

Question 4

How much does one need to consume of each of the 5 groups? (e.g. Adults). What is an “alternative” in the dairy group?

Answer 4

Varies depending on age, sex and life stage. 5-6 veggies, 2 fruit, 3-6 grain, 2-3 lean meat, 2.5-4 dairy, 0-3 additional/discretionary.

1 serve = 150g fruit/ 75g veggies/ 500kJ grain/ 5-600kJ meat, dairy and discretionary

Alternatives = soy

Question 5

What is a serve of discretionary food based on?

Answer 5

Energy content (5-600kJ)

Question 6

What is the nutrition information panel (NIP)? What does it must contain?

Answer 6

Provides the average quantity of energy (kcal or kJ) of a product. Also provides the amount of protein, carbs, fats, sat fats, sugars and sodium. Also provides any info on product claims

Question 7

What is the difference between the “per serve” and “per 100g” columns? When would you use each?

Answer 7

Per serve varies based on the product type – can be used when consuming a certain portion size

Per 100g to compare between products

Question 8

What is the difference between total and “sugars” under carbohydrate?

Answer 8

Total = sugars + other
Sugars = sugars

Question 9

Does the “Sugars” row relate to added sugar or naturally contained sugar?

Answer 9

Both

Question 10

Where do you find out whether a product has added sugar or not?

Answer 10

The ingredients list

Question 11

What does the NIP not tell you?

Answer 11

Quality of the food – e.g. types of AA in protein, types of FA in fat

Question 12

Explain why there is not an RDI for all nutrients. (Only 10 nutrients have an RDI)

Answer 12

Not all nutrients contain a functional biomarker of deficiency

Question 13

How are each of the NRVs determined and what do they represent?

Answer 13

EAR = 50% of the population will be deficient with this level of intake. Calculated when there is a functional biomarker of deficiency

RDI = 2-3% of the population will be deficient. Based on the EARx1.2, or 2stdev to the right

AI = Median intake of apparently healthy populations (per age/sex etc.) as determined via surveys. Should cover the needs of more than 97-98% of people and is a set value. When unable to determine biomarker of deficiency

UL = Highest nutrient intake likely to pose no adverse effects or risks in almost all healthy individuals. Set when biomarker of toxicity is known

Question 14

What are the AMDR for each macronutrient? Why this proportion of each?

Is this breakdown of macronutrients the only way to eat “healthy”? Why?

Answer 14

AMDRs provide ranges of macronutrient intake to maximise general health outcomes. They only apply to individuals 14 and over. They are determined in order to meet micronutrient EAR via consuming foods from the core food groups. They are not individualised and not the only way to eat healthy

20-35% fat with saturated and trans limited to 10%. Long chain n-3 0.2% EER

15-25% protein

45-65% CHO from low GI sources. Limit sugar and increase fibre

Question 15

Explain the difference between food allergies and food intolerances, highlighting the key points. Can you think of some specific examples

Answer 15

Food allergies are dose independent and initiate and immune response. Food intolerances are dose dependent, with higher doses causing more severe symptoms

Peanut allergies vs lactose intolerance

Question 16

Describe the processes and location in the GIT involved in digestion and absorption

Answer 16

Oral cavity - chewing increases SA (mechanical). Food mixed with saliva = becomes a bolus (chemical). Components of saliva include mucous (lubricates food), salivary amylase, lingual lipase and lysozymes (break down bacteria)

Bolus travels down the oesophagus and into the stomach via the lower oesophageal sphincter.

In the stomach, the bolus is mixed with stomach secretions to create chyme.

These secretions include Gastrin, (G cells, hormone controls HCl and pepsinogen release), HCl (parietal cells, denatures proteins, destroys bacteria and viruses, aids in mineral absorption and activates pepsinogen), Pepsinogen (chief cells, pepsin digests proteins), Gastric lipase (chief cells, fat digestion), Mucus (goblet cells, protects stomach from being digested).

Chyme passed into the duodenum via the pyloric sphincter. Its release is controlled by gastric inhibitory peptide (GIP).

Secretions in the duodenum break down the nutrients further. CCK stimulates release of pancreatic enzymes and bile. Secretin stimulates release of pancreatic bicarbonate. Bicarbonate neutralises the chyme. Bile emulsifies fat droplets. GIP signals the stomach to limit release of chyme and slows gastric motility. Sphincter of Oddi

Most digestion and absorption occurs in the small intestine. Lined by villi and microvilli.

Ileocecal sphincter

Large intestine

Question 17

What is the difference between digestion and absorption?

Answer 17

Digestion is the process of breaking down food components into molecules that can be absorbed by enterocytes and delivered into blood or lymphatic circulation. Macronutrients are turned into monomers, micronutrients are freed from larger food particles

Absorption is the uptake of monomers and micronutrients from the lumen of the GIT through the absorptive cells (enterocytes), into the blood or lymph for transport to organs/cells. Adequate absorption processes are key for nutrition: nutrients don’t contribute to overall health until they are inside the body

Question 18

What is the difference between peristalsis and segmentation?

Answer 18

Peristalsis is the sequential contraction of GIT wall muscles to facilitate movement of bolus and chyme. Is triggered by the autonomic nervous system. Hydration and bulk of faeces play a roll – stretching of intestinal wall promotes peristalsis

Segmentation is the

Question 19

Outline the various absorption pathways, and their mechanisms, for nutrients to be
delivered to cells

Answer 19

Passive, facilitated, active, endocytosis

Water soluble nutrients absorbed via the CVS – enter directly into the portal vein

Fat soluble nutrients absorbed via the lymphatic system. Packed as chylomicrons and transported via lacteals into lymph vessels to the thoracic duct where the enter the CVS circulation

Question 20

What is the difference between probiotics and prebiotics?

Answer 20

Probiotics are live bacteria, identical to those found in the gut. Populate the gut with good bacterial species. Consumed as supplements or via foods (yoghurt, seaweed, sauerkraut)

Prebiotics are non-digestible carbohydrates that feed the gut bacteria and promote their growth via acting as substrates. Fermentation results in SCFA