Diet in chronic kidney disease in a Mediterranean African country

Tunisia is an emerging country with limited resources (https://​en.​wikipedia.​org/​wiki/​Emerging_​markets#cite_​note-2, https://​www.​theisn.​org/​images/​Membership/​Eligible_​Countries_​for_​Joint_​Membership_​Jan_​2016.​pdf, https://​datahelpdesk.​worldbank.​org/​knowledgebase/​articles/​378834-how-does-the-world-b). Chronic hemodialysis treatment begun in Tunisia in 1963 with a very strict selection. Only young people with social insurance, and without severe co morbidities (like neoplasia or severe heart disease) were treated with dialysis. End stage renal disease incidence rose from 81.6 per million people (pmp) to 137 in 2007 [1, 2]. This sharp increase could be linked to a political decision made in 1991 to treat all patients, regardless of their social insurance and comorbidities, but without significant increased number of renal transplantation which was at 14 pmp in 2007. Prevalence of renal replacement therapy (RRT) in December 2007 was 713 pmp [2]. Sfax is a southern Tunisian city, with one million population. According to the last regional registry data in 2014 RRT prevalence was 771 patients.

The main causes of end stage chronic kidney disease are unknown nephropathy [3]. Increase in the prevalence of ESRD treated with dialysis has led to an increase in costs of dialysis treatment, and dialysis expenditures represented 4.5% of Tunisian Health budget in 2000 [1]. Primary and secondary CKD prevention is therefore essential to our country which has limited resources. Primary prevention aims to decrease CKD incidence. Secondary prevention aims to slow renal function decline. They include not only therapeutic measurement such as control of hypertension, diabetes, but also lifestyle and dietary measures such as restricting sodium and protein intake.

Protein intake is still low in several Sub-Saharan African countries [4]. In Tunisia, protein intake appears to be adequate and similar to that observed in migrant Tunisian people living in France and local born French people [5]. In our center, we conducted a dietary intake evaluation prospective study of 100 consecutive CKD patients. Mean protein intake was 1.48 ± 0,4 g/kg/d (0.73-3 g/kg/d). We found that only 6 patients had a protein intake < 1 g/kg/d and 4 patients had a protein intake exceeding 2 g/kg/d [data not published].

Since the Brenner theories of increased workload on the remnant nephrons, and its prevention by decreasing protein intake [6], use of low protein diet for patients with renal damage in patients with CKD is a subject of controversy between supporters and adversaries [7, 8]. Complications of renal failure such inflammation and acidosis lead to hypercatabolism by activating enzymes that breakdown proteins. However, hypercatabolism is not stopped by protein intake increase. An increase in protein intake will worsen acidosis and accumulation of potential uremic toxins and development of uremic symptoms without increasing muscle mass [9, 10]. It has been shown that protein intake reduction in patients with moderate chronic kidney failure reduces blood chemistry abnormalities like acidosis, phosphorus and urea [11].

The main objective of any diet practice in patients with CKD is to slow chronic renal failure progression without inducing malnutrition. So before any prescription of protein diet, a nutrition assessment status should be performed. Regular nutritional assessment should be conducted every 2-3 months for non-dialysed out-patients with glomerular filtration rate (GFR) <20 ml/mn is recommended [12]. Screening for malnutrition should be more frequent when there is a malnutrition risk event. There are many methods for screening malnutrition, but the method selected should be simple, reproducible and not expensive [12].

The nutritional status assessment should be based on a group of clinicobiological parameters, which we employ in our center. These parameters should be inexpensive, reproducible and accessible in routine practice.

When prescribing protein intake, normal, low and high protein intake should be defined. However, normal protein intake definition is not clear. It should be a diet containing a minimum requirement to avoid deficit but also a not surpassing an ideal intake. The recommended protein intake is the daily intake level sufficient to meet the nutriment requirement of 97-98% of healthy people (https://​ods.​od.​nih.​gov/​Health_​Information/​Dietary_​Reference_​Intakes.​aspx) [27]. The recommended daily protein intake of healthy individuals is 0.83 g/kg/day [28].

An intake of 0.66 g/kg/day is accepted as average intake. The safe level of intake is equivalent to 0.83 of high quality protein [29].

In most studies restrictive protein and phosphorus diet delay glomerular filtration decline. But low protein diet < 0.6 g/kg is not recommended because their benefit is little and they increase malnutrition risk [30].

In our center we do not prescribe a restrictive diet below 0.6 g/day. A more restrictive diet needs a very strict monitoring of nutrition state and it has been shown not to have a significant benefit in many studies [31]. Moreover we have only one dietitian for 120 regular dialyzed patients and 2000 hospitalizations and 2000 consultations per year. In practice, after the second or the third nephrology consultation, patients with chronic renal failure, are referred to dietician for diet advice. Our dietician performs a nutritional status assessment using a anthropometric parameters (weight, height, and body mass index a dietary) and SGA. Following this, the patient is provided with diet advice and meal menu examples based on their Tunisian habits and lifestyle (Tables 1, 2 and 3). In general practice, for patients with middle and high socioeconomic status, the dietician will advise patients to eat animal protein (such as meat and fish) for either lunch, or dinner (Tables 1, 2 and 3).

Hyperphosphataemia is an ineluctable consequence of chronic renal failure with serious complications at short, middle and long term outcomes. Hence, it is a veritable challenge of the nephrologist in the follow up of his patients. Some authors have emphasized the importance of early and effective control of phosphate load before hyperphosphataemia develops to prevent the increase in PTH and FGF23 and maintain near-normal phosphorus levels for longer as CKD progresses [32].

Dietary measure are crucial in hyperphosphatemia, even if drugs are needed.

In this approach, patient, nephrologist and dietician together form an equilateral triangle with the apex as the patient. Collaboration with dietician improves dietary compliance. Restriction of food containing phosphorus is not prescribed until hyperphosphatemia is present [28, 32]. It has been shown that dairy intake significantly increased the serum phosphorus concentration at different DFG levels [29, 32, 33], so they must be consumed with moderation. However, some aliments are prohibited, because of the high content of phosphorus, potassium and sodium like soft drinks, and canned foods. Some other foods have high phosphorus and sodium content (such as processed and melted cheese, delicatessen and aliments with phosphorus additives) should be also avoided.

Our experience of diet management is based on a preliminary upkeep with the nephrologist who explains the risk of hyperphosphataemia to the patient, and that the main treatment is the reduction of aliments rich in phosphorus (e.g. dairy, legumes, meat, complete cereals, dried fruit, and soda drinks). The patient is then referred to department dietician. As mentioned previously, our department has only one dietician for 120 dialyzed patients and 2000 hospitalizations and 2000 consultations per year. For external consultation the dietician provides weekly consultations for CKD and hypertensive patients The dietitian begins with a food consumption survey in order to detect the patient’s excess. (The phosphorus intake should be 800 -1000 mg/d). They explain to the patient that some food products must be avoided because of their high phosphorus and sodium content, such as octopus and particularly cuttlefish, which is consumed excessively in our local area, as many coastal towns in this region have high fish consumption. Some food products should be taken in moderation, such as dairy, legumes, meat, complete cereals and dried fruit (Table 4).

It is common in our region that men and elderly people don’t cook for themselves when they do not live alone. If the patient confirms that they will not be preparing their own food, our dietician will ensure that they discuss diet changes and the new recipes with the person who will be preparing the patients’ food, again, to help improve adherence to the new diet. These recipes should be adapted to the patient's socio-demographic characteristics. For example, the rural patient does not have the same meal habits as those living in towns or cities. In fact, in our geographic region, eating meals prepared outside of the home is more common in in cities where there is greater animal product consumption, while vegetable staples and full grain are generally consumed more in rural regions. It is therefore very important that the dietician works closely with the patient and their family to obtain a clear understanding of their meal habits so that they can create meal examples that cater to the patient’s habits and lifestyle. If the patient is provided with a diet plan that has been tailored to their lifestyle, then the patient is more likely to adhere to these changes.

In Tunisia, a Mediterranean diet is predominant, and as such, a high amount of vegetables and fruits are consumed which leads to a high potassium intake. If such a diet is recommended for cardiovascular protection, in the very high cardiovascular risk CKD patient, it becomes problematic. When serum potassium levels are at high normal range, we recommend patients to avoid dates, the highest potassium content product, largely consumed as a fruit in Tunisia. For the others, we recommend a diet with a reduced intake of specific high potassium foods, such as bananas, dried fruits, almonds, vegetables and chocolate (Table 5). Our advice is not to soak vegetables in water, which is not effective at reducing potassium levels, but instead double cook them (for example, boil, rinse and boil again). This process leaches more potassium from the vegetables than normal cooking methods [37].

For raw vegetables used in salads, it is advised to use original Tunisian salad containing tomatoes, cucumber, onion and peppers. Other vegetables, such as cabbage, should be avoided in salads.

Our main objective of diet prescription in CKD is to slow chronic renal failure progression and to prevent its metabolic complications such as hyperphosphatemia and hyperkaliemia. Dietary restriction covers three principal components: potassium, phosphorus and sodium.

Potassium restriction needs to avoid certain fruit and vegetables. Phosphorus restriction that needs protein intake restriction should be carefully prescribed to avoid malnutrition. Dietary salt should also be reduced.

The role of the dietician is therefore pivotal in helping to create such a diet. For each patient, the dietician must determine their nutritional state, and take into consideration the patient’s individual lifestyle habits. This also involves providing guidance and support to the patient, and their family if required. Nutritional advice should be general but it is important to also adapt the diet to each patient’s eating habits to improve adherence rates.

The diet itself must offer an adequate quantity of animal protein, which will provide the body with the essential amino acids for tissue repair, hormone synthesis without inducing phosphorus, and balance the level of sodium or potassium consumption. It’s a veritable calculation which must also integrate the patient’s requirement for calories, vitamins, amino acids and hormones.

Given the low number of dieticians working in our hospital settings, local authorities need to be made more aware of crucial role played by dieticians. Prevention is far better than treatment. In this perspective, dietary measures must be at the core of our intervention.