**3.4 Dietary advice for patients**

Before counselling patients with problematic fluid gains, it is essential to review their serum sodium. Patients with high IDFG who have normal pre-dialysis sodium levels are drinking in response to osmometric thirst and **must** be given advice on reducing their salt intake. Simply telling these patients to restrict fluid intake, as is common in many dialysis units (Lindley et al, 2005), will not succeed in reducing IDFG (Tomson, 2001).

Patients with high IDFG and low pre-dialysis sodium should be assessed for other reasons for fluid intake, such as high blood glucose or social drinking. These patients will probably benefit from salt restriction but they will also require individualised interventions.

The first step in reducing salt intake is to understand where the salt is coming from. In industrialized countries, 75-80% of salt consumed comes from manufactured foods including butter, cheese, biscuits, pastry, cereals, snacks, processed meats, sauces and readymade soups and meals. In Canada, bread is reported to account for 14% of total dietary salt intake (WHO, 2010). Mhurchu et al report that bread purchased in the UK contain over 1 g of salt per 100g on average (Mhurchu et al, 2011). Restaurant meals and fast foods are frequently high in salt. In more rural populations, salt used as a preservative and added in cooking (usually in sauces) is the major source of salt in the diet. Fresh foods (meat, fish, vegetables) contribute 10% or less to salt intake.

#### **Tips to reduce salt (sodium)**


Fig. 5. Tips on reducing salt intake based on the DASH brochure (US NHBLI, 2006).

The USA, Canada, UK, Australia and New Zealand are among the countries that consider a recommended daily allowance (RDA) of 6 g/day to be achievable and sustainable. A salt

The RDA for patients with kidney failure, as with all patients at high risk of cardiovascular disease, should probably be lower than for the general population. However, the practical and psychological benefit of having the same dietary restriction as family and carers, as well as the risk of malnutrition due to an unappetising diet, makes the national RDA a more

Before counselling patients with problematic fluid gains, it is essential to review their serum sodium. Patients with high IDFG who have normal pre-dialysis sodium levels are drinking in response to osmometric thirst and **must** be given advice on reducing their salt intake. Simply telling these patients to restrict fluid intake, as is common in many dialysis units

Patients with high IDFG and low pre-dialysis sodium should be assessed for other reasons for fluid intake, such as high blood glucose or social drinking. These patients will probably

The first step in reducing salt intake is to understand where the salt is coming from. In industrialized countries, 75-80% of salt consumed comes from manufactured foods including butter, cheese, biscuits, pastry, cereals, snacks, processed meats, sauces and readymade soups and meals. In Canada, bread is reported to account for 14% of total dietary salt intake (WHO, 2010). Mhurchu et al report that bread purchased in the UK contain over 1 g of salt per 100g on average (Mhurchu et al, 2011). Restaurant meals and fast foods are frequently high in salt. In more rural populations, salt used as a preservative and added in cooking (usually in sauces) is the major source of salt in the diet. Fresh foods (meat, fish,

**Tips to reduce salt (sodium)** Use fresh or frozen vegetables (if canned, look for low-sodium or no-salt-added on the label). If using food canned with salt, rinse the contents to remove as much as

 Try to use fresh poultry, fish and meat, rather than canned, smoked or processed products. Cheap processed meat often has salt added to make it absorb water and

Cook rice, pasta and noodles without salt and avoid instant or flavoured products as

 Make salad dressings and cooking sauces instead of buying them ready-made. Using other flavours (herbs, spices, lemon etc) may mean salt can be eliminated completely. Check nutrition labels on breakfast cereals, ready meals, soup and sauces to find products with lower salt/sodium. Food labelled as low in salt should contain less

Greater awareness of the need to reduce salt intake should increase the availability of low-salt products in the coming years, but always check that product labelled as low-

than 0.3 g of salt per serving, medium should mean 0.3 to 1.5 g per serving.

Fig. 5. Tips on reducing salt intake based on the DASH brochure (US NHBLI, 2006).

benefit from salt restriction but they will also require individualised interventions.

intake of 6 g/day is equivalent to a sodium intake of 2.3 g/day or 100 mmol/day.

(Lindley et al, 2005), will not succeed in reducing IDFG (Tomson, 2001).

realistic target for most patients.

**3.4 Dietary advice for patients** 

vegetables) contribute 10% or less to salt intake.

increase in weight.

they usually have added salt.

possible. Don't add salt to the water used for cooking.

Use ketchup, barbeque, soy and other sauces very sparingly.

salt do not contain potassium-based salt substitutes.

The importance of salt restriction for the whole population means that advice on lowering salt intake and recipes for low salt meals are widely available on the internet. The only modification required in dialysis patients is the need to be very careful of salt substitutes as they often contain potassium. Unfortunately the potassium content of processed food is often not clearly labelled. Figure 5 shows the tips for lowering salt intake from the 'Dietary Approaches to Stop Hypertension' brochure (US NHBLI, 2006) adapted for dialysis patients by a renal dietitian.

Patients who can tolerate only very limited fluid removal, and those who are hypertensive in the absence of fluid overload, may need to take further steps to reduce their salt consumption. This will include switching to unsalted butter and bread. If salt-free bread is not available, ways to substitute unsalted rice or pasta for bread should be sought. As these more stringent restrictions are difficult to implement, it is essential to prevent sodium loading during dialysis in these patients. Consideration should be given to lowering the dialysate sodium to 133-135 mmol/l and minimising infusion of normal saline (which contains 154 mmol/l sodium) at the end of dialysis (Penne et al, 2010).

Dialysis patients may have impaired taste sensitivity (Middleton 1999). If salt restriction leads to weight loss because the patient finds their food unappetising, they should be referred to a dietitian to look into the use of acceptable alternative flavourings. The need to check for weight loss and provide individual dietetic counselling is especially important in patients who need a very restricted salt intake as described above.

### **3.5 Implementing salt restriction: Staff education**

There is a sound physiological basis for restricting intake of salt rather than fluids to control IDFG in most patients, though there are few published comparisons of the different approaches. Rupp et al compared patients on a traditional sodium and fluid restricted diet with those given a diet that just restricted sodium and found a significant decrease in IDFG only in the group on the simpler low-sodium diet (Rupp et al, 1978). Kayikcioglu et al compared cardiac function and blood pressure control in two units, one of which practiced a salt restriction strategy while the other relied on the use of anti-hypertensives (Kayikcioglu et al, 2009). The use of salt restriction not only reduced the requirement for antihypertensive medication (7% vs. 42%), but led to significantly lower IDFG (2.29 vs. 3.31 kg) and fewer episodes of intradialytic hypotension (11% vs. 27%).

With such clear benefits, it is surprising that there is not more emphasis on salt restriction in haemodialysis units. Patient information currently available via the internet tends to focus on fluid restriction, with advice such as using smaller cups, sipping slowly, sucking ice cubes or lemon wedges and keeping a fluid journal. The popularity of fluid restriction may be because fluid intake is relatively easy to monitor, while salt is hidden in manufactured foods and cutting out the 'visible' added salt has a disappointing impact on IDFG.

Dialysis staff can change the focus from fluid to salt restriction and establish a culture of sharing advice for reducing salt intake within the unit. With pressure from the World Health Organisation and national food safety bodies, we should see more low-salt products and increased disclosure of salt content. Tables of salt content in foods that can be used in educational material and quizzes are available from organisations such as the US Department of Agriculture (USDA, n.d.) and the Australian Healthy Eating Club (Healthy Eating Club, n.d.). Staff aiming to reduce their own salt intake to < 6 g/day will be able to swap tips rather than impose rules. How long does it take to get used to unsalted butter? Which breakfast cereals have the lowest salt content? How easy is it to make low salt bread? Haemodialysis patients with little or no residual renal function can get feedback on the impact of any dietary modification simply by monitoring their fluid gains. As a rough

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guide, every kilogram gained between dialysis sessions corresponds to an intake of 8 g of salt. So a 0.5 kg decrease in IDWG over the short break shows they have managed to reduce their salt intake by 4 g (2 g/day). Staff will need to carry out 24 hour urine collections to check their own salt consumption.

The link between low IDFG and poor survival is well established (Sezer et al, 2002) and haemodialysis patients are often at risk of malnutrition, so it is essential to ensure that what appears to be a successful intervention to reduce salt intake does not lead to undiagnosed weight loss and fluid overload.
