|Year : 2014 | Volume
| Issue : 1 | Page : 11-18
Nutrition in chronic kidney disease
Manisha Sahay1, Rakesh Sahay2, Manash P Baruah3
1 Department of Nephrology, Osmania Medical College and General Hospital, Hyderabad, Andhra Pradesh, India
2 Department of Endocrinology, Osmania Medical College and General Hospital, Hyderabad, Andhra Pradesh, India
3 Excel Hospitals, Guwahati, Assam, India
|Date of Web Publication||24-Dec-2013|
Department of Nephrology, Osmania Medical College and General Hospital, 6-3-852/A, Ameerpet, Hyderabad - 500 016, Andhra Pradesh
Source of Support: None, Conflict of Interest: None
Malnutrition is common in patients with chronic kidney disease (CKD) and is an important cause of morbidity and mortality. Assessment of nutritional status is mandatory for all CKD patients. Many tools are available for assessing the nutritional status. Patients with CKD need to follow a healthy diet plan to maintain normal protein stores and to avoid metabolic complications. This article deals with the practical aspects of nutrition in patients with CKD.
Keywords: Calories, chronic kidney disease, diet in chronic kidney disease, nutrition assessment, protein
|How to cite this article:|
Sahay M, Sahay R, Baruah MP. Nutrition in chronic kidney disease. J Med Nutr Nutraceut 2014;3:11-8
| Introduction|| |
Chronic kidney disease (CKD) is defined as renal disease lasting for equal to or more than 3 months duration and characterized by either a fall of glomerular filtration rate (GFR) to less than 60 mL/min/1.73 m 2 or even with GFR more than 60 mL/min/1.73 m 2 it is defined by the presence of abnormalities in urine analysis, blood biochemistry, imaging or on histopathology.  CKD has five stages as defined by kidney disease outcome quality initiative. 
Malnutrition is an important feature of CKD. Malnutrition occurs in varying degrees depending on the stages of CKD.  Depending in part upon the method used and the population studied, from 40% to 70% of patients with end-stage renal disease are malnourished.
It may result from various factors, which include
- Loss of appetite
- Impaired digestion and absorption
- Metabolic acidosis
- Emotional stress.
Malnutrition is seen in patients on hemodialysis  as well as in those on peritoneal dialysis.  Many studies have shown that malnutrition is associated with increased mortality.  Many guidelines exist regarding assessment of nutrition and management of nutrition in patients with CKD and on dialysis. ,,,,
| Assessment of Nutritional Status in CKD|| |
There is no single measurement that can be used to determine the presence of malnutrition. Therefore, a panel of measurements is recommended. ,,,
A food diary is very useful, especially if the patient weighs the portions of food. The intake of protein, fat and carbohydrate can then be calculated from standard food tables. 
Patient recall should cover a relatively short period of time, such as 3 days and should include dialysis and non-dialysis days. This should be performed every 6 months. 
Subjective global assessment
The SGA score includes three patient-reported components (weight loss, appetite, vomiting) and three evaluator-performed components (muscle wasting, presence of edema, loss of subcutaneous fat). ,
| Anthropometry|| |
Standard body weight
The ideal body weight is given by the formula-height in cm - 100. Patients who are less than 90% of normal body weight are considered to be mildly to moderately malnourished and those who are less than 70% of normal body weight are considered severely malnourished. Undernourishment is associated with high mortality in dialysis patients. , Individuals who are 115% to 130% of SBW are considered mildly obese, those between 130% and 150% are moderately obese and those above 150% of SBW are considered to be severely obese. It is recommended that a target body weight for maintenance dialysis patients is between 90% and 110% of SBW. Weight change is assessed by evaluating the patient's weight during the past 6 months. A loss of 10% of body weight over the past 6 months is severe, 5% to 10% is moderate and less than 5% is mild.
In children with CKD malnutrition is one of the factors causing stunting of growth. Height and height - weight charts are useful in determining the ideal height and weight for height in children. 
Body mass index
This is derived by dividing body weight in kilograms by the square of height in meters BMI is a measure of body fatness. Recommended BMI for men is 23.6 while for females it is 24 kg/m 2 . Obesity is defined as BMI > 30 kg/m 2 . ,
Skin fold thickness
It is a rough measure of body fat. About 50% of body fat is located in the subcutaneous tissues. SFT should be measured at 4 sites-biceps, triceps, sub-scapular and supra-iliac region. SFT should be measured by skin fold calipers. SFT is used to determine the body fat percentage by the formula of Durnin and Wormersley. ,
Mid arm circumference
It is measured at the midpoint between the acromion and the olecranon. It should be measured by non-stretchable tape measure.  Muscle mass can be derived from SFT and MAC. About 60% on the body's protein is present in the skeletal muscles. Hence MAC is a good measure of body proteins.  Protein-energy wasting can be diagnosed if three characteristics are present:
- Serum albumin of less than 3.8 g/L, serum pre-albumin of less than 30 mg/dL and serum cholesterol less than 100 mg/dL
- Reduced body mass (low or reduced body or fat mass or weight loss with reduced intake of protein and energy)
- Reduced muscle mass (muscle wasting or sarcopenia, reduced mid-arm muscle circumference).
Serum albumin is a measure of visceral protein.  Hypoalbuminemia may be due to poor intake, uremic milieu, urinary and dialysis albumin losses.  Low albumin levels predict mortality.  Most laboratories utilize a colorimetric method for the measurement of the serum albumin concentration esp the bromcresol green (BCG) assay. Other methods available are bromocresol purple, nephelometry and electrophoretic methods. BCG is reliable, quick and inexpensive and is reasonably accurate. It may overestimate the value at higher levels and vice versa. Nephelometry and Electrophoresis are expensive and time consuming and are not for routine use. In maintenance hemodialysis (MHD) pre-dialysis albumin is used.
Positive acute-phase proteins (e.g., C-reactive protein, alpha-1 acid glycoprotein, ferritin and ceruloplasmin) are not nutritional parameters but may be used to identify the presence of inflammation in individuals with the low serum albumin or prealbumin. 
This is a good measure of visceral protein stores. It has a shorter half-life than albumin (2-3 days vs. 21 days). Low levels (<30 mg/dL) predict mortality. However prealbumin levels are affected by altered GFR thus in renal failure albumin is a better marker of nutritional status than prealbumin. ,
Retinol binding protein. This is also thought to be a good marker of nutritional status. 
It was supposed to be a better marker of nutritional status than albumin as it has a relatively shorter half-life (8 days vs. 21 days). However like albumin, it is also a negative phase reactant. In addition, Iron deficiency increases serum transferrin levels; hence, it is not a good marker of nutritional status.
Individuals with low, low-normal, or declining serum cholesterol levels should be investigated for nutritional deficits.  The relationship between serum cholesterol and mortality has been described as either ''U-shaped'' or ''J-shaped,'' with increasing risk for mortality as the serum cholesterol rises above 300 mg/dL or falls below approximately 100 mg/dL.
A low pre-dialysis or stabilized serum urea level may indicate a low intake of protein or amino acids. 
In individuals with negligible urinary creatinine clearance, the nutritional status of individuals undergoing MHD or chronic peritoneal dialysis who have a pre-dialysis or stabilized serum creatinine of less than approximately 10 mg/dL should be evaluated. ,
Measurement of protein equivalent of nitrogen appearance
Dietary protein intake can also be estimated by calculating the protein catabolic rate (PCR), also called the protein equivalent of nitrogen appearance (nPNA), utilizing kinetic modeling. PCR is a reflection of protein intake only if the patient is in neutral nitrogen balance. ,
Estimating protein intake
Compliance with dietary protein restriction can be estimated from a 24-h urine collection, providing daily intake is relatively constant and the patient is in a steady state (as evidenced by a stable blood urea nitrogen and body weight). In this setting, urinary nitrogen excretion is roughly equal to nitrogen intake. During steady-state conditions, nitrogen intake is equal to or slightly greater than nitrogen assessed as total nitrogen appearance (TNA).
TNA is equal to the sum of dialysate, urine, fecal nitrogen losses and the post-dialysis increment in body urea-nitrogen content. Because the nitrogen content of protein is relatively constant at 16%, the PNA can be estimated by multiplying TNA by 6.25. Each gram of nitrogen is derived from 6.25 g of protein. In the clinically stable patient, PNA can be used to estimate protein intake. Because protein requirements are determined primarily by fat-free, edema-free body mass, PNA is usually normalized (nPNA) to some function of body weight (e.g., actual, adjusted, or standardized [NHANESII] body weight [SBW] or body weight derived from the urea distribution space [Vurea/0.58]).
The measurement of total nitrogen losses in urine, dialysate and stool is inconvenient and laborious; regression equations to estimate PNA from measurements of urea nitrogen in serum, urine and dialysate have been developed. The urinary nitrogen excretion can be estimated from:
Urinary nitrogen excretion = Urine urea nitrogen + Non-urea nitrogen
Non-urea nitrogen excretion is relatively constant and equals 30 mg/kg/day.
Thus, estimated protein intake = 6.25 (Urine urea nitrogen + 30 mg/kg)
If, for example, 24-h urine urea nitrogen excretion is 8.2 g in a 60 kg man excreting 3.5 g of protein per day, then:
Estimated protein intake = 6.25 (8.2 + 1.8) =62.5 g.
Some amount of urinary protein loss can be ignored, but each gram excreted above 5 g/day should be added to the above formula. Thus, protein intake is approximately 1 g/kg/day in this individual.
Since creatinine is produced from non-enzymatic creatine metabolism in skeletal muscle, estimating the rate of creatinine production has been used to assess lean body mass in stable patients on maintenance dialysis. Estimated lean body mass was below normal in 47 and 66% of hemodialysis and peritoneal dialysis patients, a presumed reflection of inadequate nutrition. ,,
DEXA ,, was variably found to be useful for estimating the nutritional status.
Biometric impedance analysis
BIA is an attractive tool for nutritional assessment of individuals undergoing dialysis because it is relatively inexpensive to perform, non-invasive and painless, requires minimal operator training and is correlated with several aspects of body composition. However, body water variations affect the measurements of lean body mass hence BIA is not a very useful measure for assessment of nutritional status. 
| Diet Recommendation in CKD|| |
The diet recommended for CKD patients as described in guidelines , is as follows:
It should be about 35 kcal/kg/day. In obese individuals 30 kcal/kg/day is recommended. It should consist of 20-30% calories from proteins, 20-30% from fats and 40-60% from carbohydrates. In children the calorie intake varies with the age of the child. ,,
Proteins should be restricted to 0.6 g/kg body weight in non-dialyzed CKD patients. 2012 KDIGO guidelines suggest the use of a lower high quality protein diet of 0.8 g/kg/day among select pre-dialysis patients who are highly motivated to follow such a diet. Low protein diet is helpful in controlling hyperphosphatemia, metabolic acidosis and hyperkalemia. Dietary protein restriction may protect against the progression of CKD by hemodynamically mediated reductions in intraglomerular pressure and by changes in cytokine expression and matrix synthesis.  The hemodynamic effects of protein-induced hyperfiltration may be due to changes in hormones (such as glucagon and insulin-like growth factor-1), alterations in the renin-angiotensin system and intrarenal effects, including tubuloglomerular feedback. The ideal protein intake recommended in CKD patients was highlighted in the modification of diet in renal disease (MDRD) study.  The MDRD study included 255 patients with GFR 13-24 mL/min/1.73 m 2 who were randomly assigned to either a low protein diet or a very low protein diet (0.3 g/kg/day) with a keto acid-amino acid supplement. Among patients assigned to the very low protein diet, no benefit was observed in either the time to end-stage renal disease or overall mortality at a mean follow-up of 2.2 years. A follow-up of the MDRD study at 12 years also showed no benefit to the very low protein diet in delaying the progression of kidney disease However unlike in non-dialysis CKD, in patients on dialysis the protein intake needs to be increased. In patients on hemodialysis the protein intake should be 1.5 g/kg/day while in patients on continuous peritoneal dialysis the protein intake should be 2 g/kg/day.  Patients on hemodialysis lose significant quantities of amino acids during the dialysis.  The losses are even more on continuous ambulatory peritoneal dialysis (CAPD). In patients on dialysis the appropriate dialysis dose (dialysis adequacy) prevents protein catabolism. ,,
Protein should be high biological value (BV) protein. Vegetable proteins are better than animal proteins. Soy protein and whey proteins are good. The BV of whey protein is very high. Besides whey, the only other food that contains very high levels of BV protein is whole eggs as well as egg whites. The key difference between whole eggs and whey protein is that whey protein does not contain high levels of fat like that of the eggs. Whey protein is also low in phosphorus. Soy Proteins contain high quantities of protein similar to the protein found in animals. They also contain much less cholesterol and many important amino acids. The Food and Drug Administration has stated that 25 g of soy protein in a person's daily diet can help reduce the likelihood of developing or advancing heart disease. Furthermore, soy proteins stimulate the thyroid and promote weight loss. They are helpful in preventing hormone related diseases and osteoporosis. Fish, lean meat and egg whites are good sources of protein. Red meat should be avoided as it is rich in phosphates.
For vegetarians' tofu instead of paneer, soyabeans and groundnuts are rich sources of proteins. Lentils (daals) or legumes (rajma, channa, blackeyed beans) prepared with only a small amount of oil are an excellent source of protein and soluble fiber. Pulses roughly contain 20 g protein/100 g, cereals have 10 g/100 g. CKD patients may lose proteins in urine. While calculating the dietary intake the urinary protein losses should be added to the protein requirement if the daily urine protein loss exceeds 1 g.  Many protein supplements are available in Indian market. Each gram of protein provides 4 kcal of energy. Approximate Protein content of some food categories are shown in [Table 1].
These should be mostly complex carbohydrates, i.e., those with a high glycemic index.  Refined or simple sugars should be avoided. Good sources of complex carbohydrates are wheat, unpolished rice, oats and barley etc., White bread should be replaced with brown bread. Brown rice is healthier than white rice. Sago is a good source of carbohydrates, which is poor in protein. Each gram of carbohydrate provides 4 kcal of energy. Six servings should be taken per day 50% of which should be whole cereals. Approximate carbohydrate content of some food categories are shown in [Table 1].
In patients on CAPD a significant amount of carbohydrates is absorbed from the dialysate fluid in the abdomen. This should be taken into account when calculating the carbohydrate requirement for the patient.
Fats are an important source of energy. Each gram of fat gives 9 kcal of energy. Approximate fat content of some food categories are shown in [Table 1].
The diet should contain an appropriate proportion of mono and polyunsaturated fatty acids and cholesterol, i.e., in 1:1:1 ratio.
Monounsaturated fat (omega-9) is considered "good" fats because they may lower low-density lipoprotein (LDL) cholesterol and may help raise high-density lipoprotein cholesterol. Good sources of monounsaturated fats are: Olive oil, canola oil and peanut oil. Groundnut and mustard oil have less polyunsaturated fats, but good monounsaturated fatty acids (MUFA). Avocados, olives (high in sodium), nuts: Almonds, peanuts, pistachios and hazelnuts also have a good amount of MUFA.
Polyunsaturated fat are considered "good" fats because they help lower LDL cholesterol when used in place of saturated fat. Good sources of polyunsaturated fat (omega 6) are: Corn oil, safflower oil, sunflower oil and sunflower seeds. Good sources of alpha linolenic acid (plant omega 3) are: Canola oil, ground flax seeds, flaxseed oil, walnuts and soybean oil. Among animal foods fish is rich in omega 3.
Trans-fats are can raise LDL cholesterol. Trans-fats are primarily man-made from vegetable oils as a result of food processing, which changes vegetable oils into semisolid fats, e.g., partially hydrogenated fats. Trans-fats are also produced when oil is re-used. Trans-fats are also found naturally in meat, cheese, butter and dairy products. Sources of trans-fat are: Baked goods: Pastries, cakes, cookies; Fried foods: French fries, fried chicken, onion rings, Indian snacks cooked in re-used oil, e.g., chevda, bhel, dalda (vanaspati). Frying should be discouraged and instead boiling, grilling or baking is recommended.
Saturated fat: Full cream milk dishes should be avoided as they contain saturated fats. Avoid coconut and coconut milk (high in saturated fat).
In addition to the quality the quantity consumed is also important. An ideal combination of oils may be (i) rice bran oil or (ii) sunflower with mustard oil or ground nut oil. Non-vegetarians can include fish in their diet. The CKD patient should consume approximately ½ L of oil in a month. Dyslipidemia should be treated in early stages of CKD. 
A daily intake of 20 g of fiber is recommended. Fruits, vegetables, cereals and legumes are good sources of fiber. High fiber foods (>10 g/100 g) include wheat, bajra, rice, millets, legumes, ragi, maize, pulses and fenugreek. Moderate fiber foods (1-10 g/100 g) include fruits and vegetables while processed and refined foods contain <1 g/100 g while milk, oils, meat do not contain any fiber. 
Too much salt increases blood pressure. Salt can be replaced with other spices to preserve the taste. Roughly not more than 1 tsp of salt should be consumed per day. American heart association has recommended 1500 mg salt in the diet per day. Renal failure patients should not use Lo Na salt as though it is low in sodium it has a high K content.
Potassium should be restricted. High K foods mean K more than 200 mg/portion. One portion is ½ cup. High K foods include apricots-dried, banana, dates, grapefruit, figs, kiwi, mango, orange, prunes, raisins, fruit juices: Grapefruit juice, orange juice and prune juice. Low K fruits include apple, apricots, blueberries, black berries, grapes, strawberries, raspberries, cherries, peaches, plums, pineapple, pears and watermelon.
Vegetables: Starchy vegetables potato, baked, potatoes, mashed, sweet potato, baked, other beans, dried, vegetable juice/sauce, carrot juice, tomato juice, lentils, artichoke, raw carrots, spinach, tomatoes, pumpkins, broccoli, beetroots and cabbage. Asparagus, beets, peas (dried) and Brussels sprouts.
Cooked carrots, green or red cabbage cauliflower, corn, cucumber, lettuce, eggplant, onions, green peas and radish have low K.
Meat-fish, red meat and poultry are K rich.
Dairy milk, yogurt, Molasses and chocolate have high K content.
All cereals have low K except bran have low K. Pasta, noodles, tea (<16 oz) and coffee (<8 oz) have low K. Nuts are rich in K. Salt substitutes have high K.
To reduce K content slice bigger vegetable into 1/8 inch thick pieces, rinse in warm water for a few seconds, soak for a minimum of 2 h in warm water. Use 10 times the amount of water to the amount of vegetables. If soaking longer, change the water every 4 h. Rinse under warm water again for a few seconds. Cook vegetable with 5 times the amount of water to the amount of vegetable.
Daily recommended intake of calcium is 1000 mg. Calcium content from calcium containing P binders should also be taken into consideration. Calcium carbonate contains 40% elemental calcium while calcium acetate has 33%. 
Phosphorus has to be restricted in CKD to prevent cardiovascular morbidity and mortality. High phosphorus is associated with vascular calcification. High P foods include bran and whole wheat cereals, beans, milk and milk products (cheese, ice-creams, custards, cottage cheese, pudding, yoghurt, nuts, beverages (colas, cocoa, beer) and non-vegetarian diet esp red meat. P content can be minimized by using non-dairy creamer and broken wheat. Double jeopardy - high potassium and high phosphorus containing foods are milk, dairy products, nuts and seeds, chocolate and whole grain products. 
High protein foods contribute to metabolic acidosis of uremia along with reduced GFR. Bicarbonate levels should be maintained above 22 meq/L. Bicarbonate supplementation retards the progression of CKD. ,
Iron-about 6 mg/kg of oral iron is recommended instead of 2 mg/kg/day. Intravenous iron may be given at a dose of 1500 mg/year. Zinc supplementation may be needed. Other minerals are given in usual recommended doses.
The CKD patients need supplementation of vitamin D. The levels of 25 hydroxy cholecalciferol should be above 30 ng/mL. This should be measured and corrected. The patients may be treated with 60,000 units of vitamin D weekly for 12 weeks and subsequently with 600,000 units/month. Other fat soluble vitamins do not need supplementation. Patients on hemodialysis or CAPD lose water soluble vitamins during dialysis; hence, these should be supplemented. ,
| Nutritional Supplementation|| |
Many nutritional supplements are available in the market. These may be in the form of powders, which are low in K and phosphate. These can provide 7-10 kcal/kg calories and 0.3-0.4 g/kg protein. Some patients may need gavage or tube feeds. In younger patients feeding jejunostomy may be needed. Patients on dialysis may be given intradialytic parenteral nutrition. , Patients on peritoneal dialysis may benefit from amino acid based dialysis solutions. 
| Conclusion|| |
Proper nutrition is essential to reduce morbidity and mortality in CKD patients. Nutrition is often neglected in CKD patients while more focus is placed on modalities of dialysis and on transplant. A proper diet history, nutritional assessment and counseling are an important cornerstone of CKD therapy. Some patients tend to over-eat unhealthy foods while at other extreme others restrict almost all food stuffs. CKD diet does not mean a restricted diet. In fact most patients even with CKD can adopt a healthy diet with minor modifications esp those highlighted above.
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