Flashcards in 5) Fat, Carbohydrate, Water, Mineral, Electrolyte, and Vitamin Requirements in Adulthood (Part I) Deck (140)
What do omega-3 and omega-6 fatty acids compete for?
They compete for the same desaturase enzymes used in the elongation and desaturation of these fatty acids
What occurs if there is an excess of linoleic acid (omega-6) as compared to linolenic acid (omega-3)?
- Exhausts the desaturase enzymes to the detriment of a-linolenic acid
- Results in a greater production of arachidonic acid than DHA (pro-inflammatory effects)
What type of fatty acid does a high ratio of omega-6 to omega-3 fatty acids produce?
What type of fatty acid does a low ratio of omega-6 to omega-3 fatty acids produce?
What DRI is used to estimate the requirement for omega-6 and omega-3 fatty acids? How is it established?
- Adequate Intake (AI)
- Based on the median intake by US and Canadian adults, in which there is a lack of evidence for deficiency
How does the AI for omega-6 fatty acids fluctuate based on sex and age? Why?
- Omega-6 fatty acids are readily used for energy
- AI is higher in men
- AI is lower for people above the age of 50
Which fatty acids contribute to the requirement of omega-3 fatty acids, aiding in the reversal of omega-3 fatty acid deficiency?
EPA and DHA
In a post-absorptive state, which pathways produce glucose?
- 50% glycogenolysis in the liver
- 50% gluconeogenesis in the liver
In subjects adapted to starvation, what produces the brain's energy rquirement?
Keto acid oxidation produces around 80% of the brain's energy requirement
What two factors determine the EAR for carbohydrates? (2)
An adequate supply of glucose to provide the brain:
1) Without additional glucose production from protein or TGs
2) Without an increased quantity of ketones greater than observed after an overnight fast
What two factors does the EAR of carbohydrates assume? (2)
1) An energy-sufficient diet with AMDR of carbohydrates equal to 45 to 65%
2) Glucose is not limiting to the brain
What are the carbohydrate-dependent organs?
The ONLY carbohydrate-dependent organ is the brain
What are consequences of low-carbohydrate diets, observed in urbanized societies?
An increase in keto acids
What are the effects of a high concentration of keto acids?
May lead to bone mineral loss, high blood cholesterol, increased risks of kidney stones, urinary tract deposits
- Non-digestible carbohydrates and lignin that are intrinsic and intact in plants
- Not digested and absorbed in the small intestine
Define functional fiber.
Isolated, non-digestible carbohydrate shown to have beneficial physiological effects in humans
What are examples of functional fiber?
What does total fiber refer to?
Functional fiber and dietary fiber
There is a strong negative correlation between the intake of cereal fiber, and the risk of ________________.
How do fruits and vegetable fibers contribute to decreasing the risk of cardiovascular diseases?
- They do not (weak or non-existent correlation)
- Cereal fibers confer resistance to cardiovascular diseases
What are the four benefits of fiber? (4)
1) Amelioration of constipation and diverticular disease
2) Fuel for colonic cells
3) Decrease in blood glucose and lipids
4) Acting as a source of nutrient-rich low-energy foods (increases satiety and decreases obesity)
What makes determining an EAR for fiber difficult?
- The benefit of an increased total fiber intake is continuous across a range of intakes
- Defining a cut-off point is difficult
What DRI is used to estimate the requirement for fiber? How is it established?
- Adequate Intake (AI)
- Based on the intake of the population demonstrating a lower risk of cardiovascular diseases
Which types of fiber provide the greatest reduction in cardiovascular risk?
- Cereal fiber
- Proven functional fibers (psyllium and pectin)
How does fiber decrease cardiovascular risk?
Certain types of fiber bind cholesterol and prevent their absorption, decreasing cardiovascular risk and cholesterol
How does the requirement for fiber vary throughout the life cycle?
- There is no indication that fiber intake as a function of energy differs during the life cycle
- Thus, 14 grams of fiber per 1000 calories is applied to ALL life stages
What dictates fluid intake?
Behaviour, and NOT thirst
What mechanisms allow for the detection of thirst?
- Decrease in body water (detected by a low blood volume)
- Primarily sensed by an increase in sodium (detected by osmoreceptors in the brain)
What is the primary indicator of water status?
Plasma or serum osmolality