Protein and Energy Requirements

Question 1

What is Protein-Energy Malnutrition (PEM)? Also name clinical features of PEM.

Answer 1

A range of conditions arising from a coincident lack of dietary protein and/or energy.
Clinical features associated with PEM are:
* Reduced body weight
* Muscle wasting and decreased strength
* Reduced respiratory and cardiac muscular capacity
* Skin thinning
* Decreased metabolic rate
* Hypothermia
* Apathy
* Edema
* Immunodeficiency

Question 2

Describe in a broad sence what happens to the body when there is inadequate protein and/or energy intake.

Answer 2

Inadequate protein and/or energy intake leads to reduced protein storage and reduced metabolic rate. These changes have their own consequences (e.g. decrease in muscle mass or bradycardia). The body is able to adapt to these changes, resulting in a zero protein and energy balance. However, when this inadequate protein and/or energy intake is long-lasting, this will result in e.g. metabolic stress and micronutrient deficiency. The body is no longer able to adapt, resulting in continuing protein and fat loss etc. This ultimately leads to death.

Question 3

What role do free fatty acids (FFAs) play in the muscles?

Answer 3

Muscles use free fatty acids (FFAs) as an important energy source, especially during periods of prolonged physical activity or when glucose availability is limited.

Question 4

When are ketones produced?

Answer 4

In the absence of sufficient glucose and with increased breakdown of fatty acids, the liver produces more ketones (alternative use for energy)

Question 5

Describe what happens in the body when:
* inbetween meals (interprandial)
* overnight
* early starvation
* prolonged starvation

Think of the brain, liver and muscles as the main players in this scheme.

Answer 5

• inbetween meals (interprandial): free fatty acids (FFAs) are used by the muscles and liver breaks down stored glycogen into glucose for the brain (glycogenolysis).
• overnight fasting state: the liver is still responsible for the glycogenolysis process (3/4), thus providing glucose to the brain by breaking down stored glycogen. The muscles mainly use FFAs, but ketones are also produced by the liver and some ketones are actually already used by the muscle (due to ‘fasting state’ of the body). For a small part (1/4), the muscle provides muscle-derived amino acids that can be used by the liver to stimulate gluconeogenesis, providing a small part of the glucose for the brain.
• early starvation: a larger part of the ketones produced by the liver are now used by the muscles and the muscle-derived amino acids are used to produce glucose (by gluconeogenesis).
• prolonged starvation: use of ketones for energy is minimized in muscles. Together with the liver still producing ketones, this results in higher levels of ketones in the blood. These ketones will be used for a large part (2/3) by the brain for energy. 1/3 of the energy is derived by gluconeogenesis in the liver by muscle-derived amino acids.

Question 6

Fill in: catabolic or anabolic

• Exercise is …
• Nutrition is …

Answer 6

• Exercise is catabolic
• Nutrition is anabolic

Question 7

Use the following words and put them in the correct order:
* Catabolic
* Nitrogen loss
* Anabolic
* Body protein
* Amino acids

Answer 7

Amino acids -> anabolic -> body protein -> catabolic -> amino acids (-> nitrogen loss)

Question 8

What is nitrogen loss in the context of protein turnover?

Answer 8

It refers to the elimination of excess nitrogen from the body (in the form of urea). When proteins are broken down or synthesized, they contain nitrogen in the form of amino acids. So protein synthesis results in loss of nitrogen (since nitrogen is taken up when amino acids are incorporated to form a protein) and protein degradation results in increase of nitrogen (since amino acids are released from the protein).

Question 9

What is anabolic resistance?

Answer 9

A reduced or impaired ability of the body to build new muscle protein in response to factors that would typically stimulate muscle growth (such as bedrest/inactivity or inflammation).

Question 10

There are certain guidelines for energy requirements. Why are these guidelines meant for healthy well-nourished people and not for malnourished patients?

Answer 10

Because the correction for malnutrition involves different energy requirements and dietary recommendations.

Question 11

What is basal metabolic rate based on?

Answer 11

Age and sex

Question 12

How much muscle loss is there with increasing age? And how much muscle loss is there as a result of hospitalization?

Answer 12

• Age: 0.2 kg/yrs
• Hospitalization: 0.2 kg/day

Question 13

What influences death rate in hospitals?

Answer 13

Whether someone has low or normal muscle mass. Low muscle mass is associated with increased risk of death during/after hospitalization.

Question 14

So if it is clear that hospitalization leads to loss of muscle mass. What can be linked to this decline in muscle mass compared to healthy people?

Answer 14

Anabolic resistance

Question 15

What factors influence protein turnover?

Answer 15

Age, illness, inactivity, nutrition.

Question 16

How much protein (g/kg/day) is recommended during critical illness?

Answer 16

1.3 g/kg protein per day

Question 17

More protein (or amino acids), less…

Answer 17

• muscle loss
• mortality
• better outcomes in general

Question 18

What is the effect of protein supplementation in obese older adults?

Answer 18

Protein supplementation in this group is associated with improvement of muscle mass and fat-free mass.

Question 19

Conclusions of this lecture:
* Inactivity, bedrest and disease induce muscle loss
* Adequate protein is important for muscle maintenance and survival in health and disease
* Protein requirements are increased in elderly, disease and sports.