Protein requirements tend to cause confusion in most people but for those with kidney disease the confusion can be even greater. Do people with kidney disease need more protein? Or less protein? Do protein requirements change depending on your stage of kidney disease? Read on if you’d like to find out because I’m going to answer all of these questions and more.
Before we get to that though, there’s a few things we need to understand first.
What is protein?
Protein is considered the building block of life and is found in every cell of the body. It’s classified as a macronutrient because we need it in larger quantities in order for our body to function optimally. Protein is made up of ‘building blocks’ called amino acids that are attached to one another in long chains.
When we eat protein, our body breaks it down into these amino acids and then reassembles them in various ways to carry out various bodily functions. There are 20 different kinds of amino acids, and the sequence in which different amino acids are arranged helps determine the role of that particular protein. These amino acids can be classified as essential, non-essential or conditionally essential.
Essential amino acids are those that the body can’t make itself. This means that it’s essential that we get them from our diet. Essential amino acids are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine.
Non-essential amino acids can be made in our body, so we don’t need to consume them. Non-essential amino acids are alanine, asparagine, aspartate, glutamate and serine.
Conditionally essential amino acids are usually not essential, except in specific circumstances such as illness and stress. Conditionally essential amino acids are arginine, cysteine, glutamine, glycine, proline and tyrosine.
What does protein do?
When we hear the word protein, most people just think about its role in making muscle, but it does SO much more than that, in fact, it’s found in every cell of the body so it’s important for the health of muscles, bone, tissues and every organ (including the kidneys). Here are some of its key functions:
- Repair and maintenance – protein is vital for the repair and maintenance of body tissue. Hair, skin, eyes, muscles and organs are all made from protein.
- Production of hormones – for example insulin, the hormone that regulates blood sugar.
- Production of enzymes – enzymes are proteins that increase the rate of chemical reactions in the body. In fact, most necessary chemical reactions in your body wouldn’t efficiently proceed without enzymes and therefore without protein.
- Production of antibodies – protein forms antibodies that help prevent infection, illness and disease.
- Maintains proper pH – protein plays a vital role in regulating the concentrations of acids and bases in your blood and other bodily fluids.
- Balances fluids – proteins regulate body processes to maintain fluid balance. Albumin and globulin are proteins in your blood that help maintain your body’s fluid balance by attracting and retaining water.
- Transports and stores nutrients and other molecules – transport proteins carry substances through your bloodstream for example nutrients like vitamins and minerals, blood sugar, cholesterol and oxygen.
We can’t store protein in our body, so we need to consume it in the food we eat every day. Given all of the super important roles it plays in the body you would be forgiven for thinking that more = better. Not so, protein, like most things, only becomes a problem when we get too little or too much.
What happens if you eat too much protein?
A high protein diet is known to increase the risk of CKD development and progression through several mechanisms:
The kidneys are our filters for ridding the body of waste and toxic substances and returning vitamins, amino acids, glucose, hormones and other vital substances back into the bloodstream. If we eat more protein than our body needs, our kidneys have to deal with the excess, and this is where we start to run into problems.
Healthy kidneys normally keep protein within the bloodstream and out of urine partly because protein is such an important building block for the body, so it makes sense for the body to hold onto it and partly because protein molecules are too large to pass through the kidney (without causing damage).
Now, if the kidney glomeruli or tubules are damaged, or if there is an excessive amount of protein in the bloodstream (from high protein intake), the proteins will pass into urine, damaging the kidney as they go.
The other problem that occurs with a high protein diet is that it increases blood flow through the kidneys (hyperfiltration) to such a degree that further damage can occur- think of the difference between water from a garden hose compared to water from a high-pressure washer, that much blood flow through the kidneys is more than they can handle.
A higher protein intake also contributes to a higher acid load in the body. Most dietary proteins and particularly animal proteins are acid forming foods. This contributes to metabolic acidosis which is associated with a faster decline in kidney function.
Benefits of protein restriction in patients with CKD
Following a reduced protein diet reduces nitrogen waste products and decreases the kidney workload by lowering pressure within the kidneys. This has been shown to protect the kidneys of people with CKD, help with reducing symptoms and postpone the need to start dialysis treatment.
Now I don’t know about you, but if I’m going to change my diet, or make any changes for my health really, I’m much more likely to do it and stick to it if I understand the reasons behind why I’m doing it and how it’s actually going to help me so I wouldn’t expect you to be any different.
So let’s have a look at why reducing protein intake can be of benefit for people with kidney disease.
- Reduced Glomerular Hyperfiltration- reduces the amount and increased pressure of blood flow through the kidneys (turning down the high-pressure washer) which protects the kidneys from further damage.
- Reduced proteinuria- protein loss in urine causes damage to the filtering units of the kidneys and lowers protein levels in the body. Following a low protein diet has been shown to lower proteinuria by 20% to 50% in people with CKD.
- Reduced uraemic toxins– uraemic toxins come from the metabolism of partially digested protein by our gut bacteria. These uraemic toxins are absorbed into the bloodstream to be cleared by the kidneys. When the kidneys aren’t functioning optimally, these uraemic toxins then build up in the bloodstream causing symptoms like nausea, itchy skin, loss of appetite, fatigue, high blood pressure, anaemia and heart disease and cause damage and scarring to the kidneys.
- Reduced oxidative stress- by reducing levels of oxidative stress, we can help to prevent further injury and damage to the kidneys.
- Reduced metabolic acidosis- the more acidic your body is, the more damage occurs to your kidneys and the faster your rate of kidney decline. In order for your body to repair damaged tissues and be able to heal, it needs to be in a slightly alkaline state.
- Reduced phosphorus levels- as kidney disease progresses, the kidneys start to lose their ability to excrete phosphorus which means levels in the body increase. High phosphorus levels can cause damage to the body, weaken bone and increase the risk of heart attack, stroke and death.
- Reduces insulin resistance- insulin resistance occurs when your cells stop responding to the hormone insulin. This causes higher insulin and blood sugar levels and can eventually lead to type 2 diabetes. Insulin resistance is a common feature of CKD that can impair blood sugar control.
How much protein should I be eating?
So, the next obvious question is- how much protein should I be eating if I have kidney disease? The following recommendations come from the 2020 Kidney Disease Outcomes Quality Initiative (KDOQI) nutrition guidelines.
Stages 1 & 2 CKD (eGFR of 60 to 90+)
Protein: 0.8 grams protein per kg of body weight
(eg. 48 grams for a 60kg (132 pound) adult)
Stages 3 to 5 CKD (eGFR below 60) without diabetes
Low Protein Diet: 0.55 grams to 0.60 grams protein per kg of body weight
(eg. 33 grams to 36 grams for a 60kg (132 pound) adult) OR
Very Low Protein Diet: 0.28 grams to 0.43 grams protein per kg of body weight
(eg. 16.8 grams to 25.8 grams for a 60kg (132 pound) adult)
* When a very low protein diet is followed this must include keto acid/amino acid analogs to meet protein requirements and only be undertaken under close clinical supervision*
Very low protein diets typically are only recommended to people in stages 4 & 5 of CKD
Stages 3 to 5 CKD (eGFR below 60) with diabetes
Protein: 0.60 grams to 0.8 grams protein per kg of body weight
(eg. 36 grams to 48 grams for a 60kg (132 pound) adult)
Stage 5 CKD on dialysis
Protein: 1.0 grams to 1.2 grams protein per kg of body weight
(eg. 60 grams to 72 grams for a 60kg (132 pound) adult)
These amounts are guidelines only and actual protein requirements may differ from person to person so it’s important to discuss your own protein requirements with your doctor, dietitian or naturopath. These recommendations are for people who are ‘metabolically stable’ which means the absence of any active inflammatory or infectious diseases, without poorly controlled diabetes, absence of diseases like cancer and without significant short-term weight loss.
Concerns over low protein diets
One of the concerns when someone is following a low protein diet and particularly a very low protein diet is protein energy malnutrition which occurs when you’re not getting enough protein for your body’s demand. I spoke earlier about the many important roles that protein plays in the body so it makes sense that problems can arise when we get less than our body needs to function.
Maintaining adequate energy intake is necessary to prevent protein energy malnutrition and evidence from studies indicates that energy intake ranging from 30 to 35 kcal per kg per day (eg. 1,800 to 2,100 kcal per day for 60kg adult) prevents protein energy malnutrition in people following a low protein diet.
I just wanted to highlight that the type of protein you consume is also important, not just the amount. It is well established that following a primarily plant-based diet is protective to the kidneys and can help prevent the development and progression of CKD so most of your protein should be coming from vegetarian sources and if eating animal protein choose chicken, fish, seafood or eggs.
So there you go, a deep dive into all things protein and kidney disease. If you’ve found this article useful, I’d really appreciate it if you let me know by clicking the ‘SHARE’ button below and feel free to share it with family and friends.