Potassium

Question 1

How is potassium absorbed?

Answer 1

90% absorbed in small and large intestines by either passive diffusion or Na/K pump

Question 2

Where is potassium stored?

Answer 2

95% stored inside cells

Uptaken by active transport

Question 3

How is potassium excreted?

Answer 3

Mostly in urine and small amounts in faeces and sweat

Regulated by aldosterone

Question 4

What are the functions of potassium?

Answer 4

• major cation in intracellular fluid
• contractility of smooth, skeletal and cardiac muscle
• excitability of nerve tissue
• high potassium intake reduces serum calcium excretion
• High potassium intake promotes sodium + water excretion, resulting in reduced blood volume, and
  reduced blood pressure (main mechanism of DASH)
• responsible for changing the membrane potential during depolarisation of the cell

Question 5

What is caused by a deficiency of potassium?

Answer 5

Hypokalemia:

• cardiac arrhythmia and cardiac arrest
• muscle weakness
• fatigue
• irritation
• glucose intolerance

Usually due to profound fluid loss rather than lack of intake

Question 6

What is caused by a toxicity of potassium?

Answer 6

Hyperkalemia:

• cardiac arrhythmia/ cardiac arrest
• muscle weakness
• temporary paralysis
• gastrointestinal ulceration

Does not occur through diet alone, use of supplements and potassium chloride

Question 7

How does chronic kidney disease effect potassium intake?

Answer 7

Chronic kidney disease results in poor excretion of potassium so intake must be severely limited, which restricts many foods

Question 8

What are good sources of potassium?

Answer 8

• potato with skin
• beans
• salmon
• milk
• banana

Question 9

What is the DASH diet and what does it involve?

Answer 9

Dietary Approach to Stop Hypertension

• Sodium: 2300mg
• Potassium: 4700mg
• Calcium: 1250mg
• Magnesium: 500mg
  all of these are higher than the NRVs (except Na)

Fibre: 30g

Question 10

What does the DASH diet promote a high potassium to sodium ratio?

Answer 10

The aim of the high K:Na ratio is to promote the excretion of sodium, which in turn will cause water excretion, leading to decreased blood volume, and thus decreased blood pressure

Question 11

What are the roles of magnesium and calcium in the DASH diet?

Answer 11

Calcium acts as a smooth muscle relaxant, so relaxes the smooth muscles of the arterial walls

Magnesium also acts as a vasodilator

Question 12

What is the role of fibre in the DASH diet?

Answer 12

Fibre acts to bind cholesterol for excretion, to reduce the overall CVD risk

Also assists in appetite control which can help reduce weight and reduce hypertension