Dietary Guidelines for Kidney Disease (An Update)
Hi Friends,
Once a month we hold an interdisciplinary journal club. For those who don’t know: a journal club is kind of like a book club for health professionals. Except instead of reading and reviewing a book, we read and review a research article from an academic journal. This helps to keep us updated with the newest scientific developments in our field, it helps us to align our practices with other disciplines of health professionals and helps us advocate for our patients and for our own professional knowledge and expertise.
This month we read an article to update our knowledge about renal nutrition (AKA nutrition guidelines for people with kidney disease). This article was shared with the doctors, physios and audiologists in our referral network. This means that all of us understand the importance of nutrition and dietetics care for these patients and that none of us are giving contradictory nutrition advice to said patients. Pretty neat huh?
Okay, so if you are interested in knowing what the latest guidelines are with regards to nutrition for people with kidney disease, I’m going to give you a quick simplified summary. Please just bear in mind that this guidance is specifically for people with kidney disease. So, if you don’t have kidney disease, it does not apply to you.
The information in this blog post is a adapted from an article published in the Journal of Renal Nutrition, July 2020, entitled: Keeping the Diet Simple and Natural in Chronic Kidney Disease: A South African-Based Dietary Infographic. The article was written by Zarina Ebrahim , Nazeema Esau , Lynette Cilliers and can be accessed via https://doi.org/10.1053/j.jrn.2019.11.007
Dietary changes have been shown to delay the progression of kidney disease and help minimize + manage disease symptoms. In other words, diet is important!
Traditionally, dietitians have used complicated calculations and dietary prescriptions for renal patients with long lists of foods to avoid and/ or include. This approach takes many hours of education from the dietitian and is possibly overcomplicated. It might not be necessary to restrict all these foods.
Several studies have found that healthier diets lead to slower decline in kidney function in patients with kidney disease. Western diets are associated with progression of kidney dysfunction. Whereas, dietary patterns that are richer in fruits, vegetables and whole-grains tend to slow down disease progression and lower risk of death in those with kidney disease. Some authors have suggested that we stop overly focusing on single nutrients and foods for people with kidney disease but rather focus on healthy diets as a whole. Makes sense, right?
Traditional renal diets are extremely challenging to follow. Studies have found that these diets are unpalatable, very restrictive, and expensive. Patients feel frustrated, demotivated and experience a loss of autonomy. Because of this, many patients don’t follow the guidelines and end up relying on convenience and fast foods. Unpalatable diet, loss of appetite, depression, and difficulty implementing the diet all lead to inadequate energy intake and weight loss in renal patients. Not sticking to dietary prescriptions can lead to progression of kidney disease and ultimately higher risk of death and disease. One study found that a simplified renal diet with 6 key dietary messages was better followed because it was more flexible in terms of types of foods and amounts. This led to better disease outcomes for these patients. Basically, making diet advice simple, flexible and enjoyable for renal patients is key to them sticking to their diet and therefore managing their disease progression.
“One study found that a simplified renal diet with 6 key dietary messages was better followed because it was more flexible in terms of types of foods and amounts. This led to better disease outcomes for these patients. Basically, making diet advice simple, flexible and enjoyable for renal patients is key to them sticking to their diet and therefore managing their disease progression.”
Now let’s talk more about the actual guidelines and what we should be telling patients with kidney disease:
1. Protein: Limiting protein intake in the diet is important for delaying disease progression in kidney disease. Protein intake should be kept to 0.6-0.8g/kg/day. This is actually the recommendation for the general population so this is not in fact a low protein diet. However, most Westerners eat much more protein than this: over 1.3g/kg/day. So, most people will need a bit of education on how to cut down their protein intake (usually by eating smaller portion sizes and focusing more on lower protein foods). Those on dialysis will need to eat more protein: 1-1.2g/kg/ day. This is almost the same amount of protein as the general population eats so it shouldn’t feel like much of a restriction and patients shouldn’t have to overly “count” their protein intake.
2. Phosphate: I won’t go into the physiological details, but basically too much phosphate can cause havoc in people with kidney disease. Traditional advice in renal disease was all about teaching patients lists upon lists of high vs. low phosphate foods to restrict. This made renal diets really difficult and complicated. Nowadays we know that there are different types of phosphates found in foods and that some are absorbed more than others. Therefore, just focusing on the right types of foods can make a huge difference to phosphate intake. Phosphates found in animal foods are absorbed at a rate of 40-80%. In Western diets, more than half of the phosphate in the diet comes from animal protein sources. Plant-based phosphate sources (beans, pulses, nuts and grains) are only absorbed at a rate of 20-40%. Lastly, inorganic phosphates are types of phosphates used as an additive or preservative in processed foods. These types of phosphates have an absorption rate of over 90%. It’s very difficult to know how much phosphates are included in processed foods as the quantity is not required to be reported on the nutrition label. However, they are reported in the ingredient list as an “E” number or as the full name of the additive. Certain cooking methods such as boiling, slicing and pressure cooking can reduce the phosphate content of foods by up to 50%. Bottom line: we don’t need to be giving renal patients complicated lists of high vs. low phosphate foods. We can simply tell them to focus more of their protein intake on plant protein sources, to boil or pressure cook higher phosphate foods and to avoid processed foods which have phosphate-derived additives. These simple changes should be sufficient to limit their phosphate intake enough to manage their kidney disease.
3. Fibre: Kidney disease negatively affects gut health. Traditionally, all the dietary restrictions we have imposed on renal patients have often led to lower fibre diets which further worsen gut health. High fibre diets have been shown to reduce inflammation and risk of death in these patients. Basically, we want patients with kidney disease to eat enough fibre and not have to restrict their diet to the point of inadequate fibre intake as this won’t be good for their overall health and disease risk.
4. Sodium: Again, without going into too much detail, high sodium intake in the diet can cause havoc for renal patients. Most renal patients have high blood pressure and restricting sodium intake can help to manage blood pressure and actually decrease reliance on blood pressure medications. Sodium intake should be restricted in renal patients as long as this doesn’t compromise their general nutrition (by making their diet too bland perhaps). We only need to limit sodium to around 2.3-2.5g/day in renal patients which again is the same guidelines as the general population. So, not technically a sodium restriction. Again though, most Westerners eat lots more than this with most of their dietary sodium coming from processed and preserved foods. We don’t need to give extensive lists of high vs. low sodium foods. We can simply advise patients to focus on more unprocessed foods, cook with less salt and to read and assess the sodium content of their packaged foods.
5. Fluids: Most patients with kidney disease need to restrict their fluid intake to some extent. These guidelines are a little more complicated as they change depending on the patients’ disease progression, treatment and urine output. But, sodium or salt intake affects the way the body manages fluid and affects thirst, making it more difficult to drink less. So, one thing we do want to tell all renal patients is to limit their sodium intake in order to manage their fluid balance better.
6. Potassium: At times, renal patients get high levels of potassium in their blood. High blood potassium is life threatening and is most often caused by various medical factors related to the disease state. Traditionally, diet advice for kidney patients used to focus on long lists of high potassium foods to avoid. However, there is not much evidence to show that potassium in the diet has much affect on blood potassium levels in renal patients or that restricting dietary potassium even helps to reduce blood potassium levels. Most high potassium foods are very healthy and help to prevent heart disease (a common health condition in kidney patients). Potassium found in processed foods might affect blood levels differently and potassium-derived salt replacements have very large amounts of potassium. Overall, we want to be advising renal patients to eat plenty of healthy plant foods (even if they are high in potassium) but to avoid processed foods where possible and to avoid salt replacements. Some kidney patients on dialysis with high blood levels of potassium may need to restrict their dietary potassium intake further with the guidance of a dietitian.
7. General diet: Diets rich in plant-based protein provide additional benefits for heart health, blood pressure, cholesterol and progression of kidney disease. High fibre plant foods like whole-grains, fruits, vegetables, legumes and nuts should be advised. Processed, preserved, ready-made or convenience foods should be limited. We should educate patients on how to read food labels to identify additives with sodium, potassium and phosphate and using appropriate cooking techniques to lower potassium and phosphate content in food. We want to make dietary advise for renal patients practical to follow and empowering taking into account their overall health and wellbeing- this includes their enjoyment of food, heart health, kidney health, gut health, mental health and so much more!