Diet in Renal Disease

A short tutorial on the kidney and diet. 20 mins. 

Read in conjunction with the comprehensive EdRen patient information pages on diet – they need to be full if it’s your diet for years. They also have more photos and cartoons.

• Sodium
• Protein
• Energy
• Phosphate
• Potassium
• Fluid
• Transplantation
• Malnutrition

Then test yourself on the RENAL DIET QUIZ

Sodium (salt)

Plays vital role in regulation of fluid balance and blood pressure, as the major anion of extracellular fluid. Restriction is essential for compliance in fluid restricted patients.

Guidelines for general population = max 6g (100 mmol*) NaCl per day – but this is much more than is essential. An estimated 75% of salt intake comes from processed foods. All renal patients advised on a ‘No Added Salt’ (NAS) diet: 80-100mmols/day.

• Avoid adding salt at the table
• Use small amount in cooking or none at all
• Reduce intake of salty foods (e.g. cheese, smoked food, savoury snacks)
• Limit intake of packet, processed & convenience foods
• But avoid salt replacements (e.g. Lo Salt) because of their potassium content
• Encourage use of pepper, herbs and spices as alternative flavourings

See, all that Chemistry was useful.  Recommended: the Royal Society of Chemistry’s interactive periodic table (also as a free phone app)

Extracellular fluid and sodium

It might be useful to go back to our fluid therapy tutorial (EdRen textbook)
The perils of salt (history of nephrology; optional further reading)

Protein

Essential for the growth and repair of body tissues.

Protein-rich foods include: Meat, chicken, fish, eggs, cheese, yoghurts, nuts, pulses, meat substitutes. But note that some high protein foods contain high levels of phosphate and potassium.

Recommendation for protein varies according to stage of renal disease/ type of renal replacement therapy. High intake is probably harmful to those with reduced renal function.

Pre-dialysis/ Conservative Management
Controlled protein intake (0.8-1g/kg/IBW) (IBW = Ideal body weight)

• Helps to reduce phosphate load
• Prevents acidosis
• May reduce uraemic symptoms
• But must maintain nutritional status
• Use of low protein diets is controversial

Haemodialysis
Moderate protein requirements (1-1.2g/kg/IBW)

• Haemodialysis is a catabolic process
• Aim to replace protein lost during dialysis (~4g per session)

Peritoneal Dialysis
Higher protein requirements (1.1-1.5g/kg/IBW)

• Average peritoneal losses of 5-15g protein per day
• Increased losses in peritonitis

Energy

Adequate energy intake essential to optimise nutritional status.

Pre dialysis/ Conservative Management
High energy requirements (30-35 kcal/kg/IBW)

• Can have raised metabolic rate

Haemodialysis
High-energy requirements (30-35 kcal/kg/IBW)

• Catabolic process raises metabolic rate

Peritoneal Dialysis
Moderate energy requirements (25-30/kg/IBW)

• Account for calories absorbed from dialysis fluid (can be 70-270kcal/day

Phosphate

Phosphate control essential for prevention and management of hyperparathyroidism, renal bone disease; and less certainly, arterial stiffening and vascular calcification.

Phosphate in the diet generally associated with intake of protein: Meat, fish, chicken, eggs, yoghurts, cheese, milk.

Typical UK intakes of phosphate: – Men: 47mmol/day – Women: 36mmol/day

When GFR deteriorates to 25-30ml/min, phosphate retention can occur. Level of restriction depends on treatment mode, residual renal function, dietary intake, and biochemistry. Phosphate not very well dialysed – relatively large ion, with small gradient as plasma concentration low (1-2mmol/l).

Aim to maintain serum phosphate <1.8mmol/l. Control can be achieved via combination of:

Low phosphate diet

• Limit high phosphate foods (Cheese, yoghurt, eggs, nuts, milk, oily fish)
• May have to restrict phosphate intake to approx 30mmol/day.
• However, must maintain adequate protein intake

Phosphate binding medication:
Works in the stomach by binding the phosphate in foods – so should not be taken without food as will have no benefit

• Calcichew, Phosex (Calcium containing)
• Renagel, Alucap, Fosrenol, Lanthanum carbonate (Non-calcium containing)

Potassium

Average intakes in the UK: – Men 84mmol/day -Women 66mmol/day

Restriction often required in renal patients for prevention and management of hyperkalaemia. Level of restriction based on treatment mode, dietary intake and biochemistry.

• Aim approx 1mmol per kg/IBW (e.g. 5ft 8in male ~68mmol)
• Often no restriction required in peritoneal dialysis
• MUST RULE OUT NON-DIETARY

High Potassium Foods (more info on high potassium foods)

• Milk
• Potatoes and green vegetables (boiling reduces K+ content) , Potato crisps (Maize/corn better)
• Fruit (limit all fruit, fruit juice, dried fruit) and nuts
• Salt substitutes
• AND unfortunately: milk chocolate, coffee, toffee, liquorice, wine, beer, cider. But spirits are low in K+.

Fluid

Restriction may be needed to prevent excessive fluid retention, depending on urine output. Impossible if salt intake high. Must count foods with a high fluid content (e.g. soup, ice cream, custard, gravy, jelly) in allowance. Difficult; aim to give practical tips: using smaller cups, sucking ice-cubes.

Pre-dialysis

• Ensure adequate fluid intake (2-2.5L per day)
• May require restriction when nearing ESRF

Haemodialysis

• Varies depending on residual renal function
• Usually 500mls + PDUO
• Intradialytic weight gains of >2kg indicate excessive fluid intakes

Peritoneal Dialysis

• Varies depending on residual renal function and ultra filtration
• Tends to be less restricted than in haemodialysis

Transplantation

Post-op

• Ensure adequate nutritional intake post-op
• Ensure adequate intake of fluid and electrolytes during polyuric phase
• Dietary restrictions can usually be relaxed as function improves

Education on discharge

• Healthy eating
• Food safety, drug interactions
• Adequate calcium for bone preservation
• Potential to develop obesity, hyperlipideamia and steroid induced diabetes.

Malnutrition

Now do the Renal Diet Quiz