Phosphorus and phosphate
Hyperphosphataemia contributes to renal bone disease. The most recent KDOQI best practice guidelines recommend a reduced intake of phosphorus to 800-1000mg when serum phosphorus levels are 1.5mmol/l at CKD stages 3 and 4 and 1.8mmol/l at stage 5 or when intact PTH plasma levels are increased above acceptable levels.

Phosphate binders are needed if dietary phosphorus intake cannot be maintained at acceptable serum phosphorus levels, but the combined intake of calcium intake from food and phosphate binders should not exceed 2000mg/day (5).

Potassium
Severe hyperkalaemia is life threatening and with progressive kidney disease potassium retention is common. The intake of foods with high potassium content, drugs such as ACE inhibitors and potassium-sparing diuretics, and the metabolic acidosis caused by hyperglycaemia, all contribute to hyperkalaemia.

It is common practice not to reduce dietary potassium to less than
1mmol/kg/ibw, to maintain an acceptable quality of dietary intake.

Vitamin supplements
Water-soluble vitamins are recommended to supplement losses during dialysis. A potassium-restricted diet also restricts foods that are high in these vitamins.

There is, as yet, no specific agreement on recommendations for kidney patients but patients with a poor nutritional intake are bound to have a reduced intake of vitamins and routine supplementation may outweigh the hidden risks.

Nutritional intake may be compromised as these patients are prone to co-morbid disease (cardiovascular disease), disability (amputations), retinopathy with partial blindness, and neuropathy (gastroparesis). Psycho/socio-economic factors contribute to quality of life as well as nutritional intake and need to be investigated with appropriate support.

Further Reading
The Nutrition Sub-Committee of the Diabetes Care Advisory Committee of Diabetes UK. (2003) The implementation of nutritional advice for people with diabetes. Diabetic Medicine 20 786-807 www.diabetes.uk

Geoffrey Boner and Mark E Cooper (eds). (2003) Management of Diabetic Nephropathy. Martin Dunitz. London and New York.
ISBN 1 84184 076 9. www.dunitz.co.uk