What is kidney disease?
Kidney disease occurs when your kidneys are damaged and can no longer filter blood as they should. Your kidneys are like two bean-shaped organs, the size of a fist, that filter out extra water and waste out of your blood. Kidneys can be considered to be blood purifiers as they filter out all the waste in your blood which you then excrete as urine. According to Kidney Care UK, around 10% of people living in the UK have Chronic Kidney Disease (CKD). If you are aged 80 and above, you are at greater risk of developing the condition.
There are different stages of CKD, and treatment is dependent on these stages:
- Stage 1 - Onset of kidney damage with normal function
- Stage 2 - Kidney function decreases mildly
- Stage 3 - Kidney function decreases moderately
- Stage 4 - Severe decrease in kidney function
- Stage 5 - Kidney failure
Symptoms of kidney disease
In the early stages of kidney disease, there are no apparent symptoms, and most people only find out through a blood or urine test. However, in more advanced stages, the following symptoms can occur:
- Swollen ankles, feet or hands
- Fatigue
- Nausea
- Haematuria (blood in your urine)
Causes of kidney disease
There are several causes of kidney disease; however, the most common causes are diabetes, high blood pressure, inflammation of the kidneys, a family history of kidney disease, and prostate cancer. According to the National Institute of Diabetes & Digestive and Kidney disease, individuals with diabetes or high blood pressure are at a greater risk of developing kidney disease.
Diabetes
Diabetes is a long-term disease that causes irregularities in an individual’s blood sugar levels. Blood sugar levels can either be high (hyperglycaemia) or low (hypoglycaemia). Your body naturally regulates the blood sugar levels in your body by producing insulin which breaks down sugars in your body. In some cases, this is not always possible as either the body is unable to produce sufficient insulin (Type 1 Diabetes); or the insulin produced is ineffective in breaking down the sugars (Type 2 Diabetes), thus resulting in diabetes. Diabetes can affect the kidneys by damaging the blood vessels in the kidneys and affecting the nerves in the kidneys due to the changes in blood sugar levels, which can result in kidney disease.
High blood pressure
High blood pressure or Hypertension occurs when there is an increased force or pressure against the blood vessel (arterial) walls when blood is being transported to other parts of the body. If left untreated, you can be at risk of developing a stroke and heart attack. The symptoms of high blood pressure are not always noticeable and can only be diagnosed following monitoring of your blood pressure by using a blood pressure machine. The increased blood pressure in the kidneys can affect kidney function and result in kidney disease.
How can diet help manage chronic kidney disease?
The kidney has many functions to help keep balance within the body and this is known as homeostasis. Functions include:
- Removal of excess fluids and waste.
- Maintaining acid balance by removing excess acid from the body as waste.
- Produces glucose
- Maintains blood pressure
Counteracting protein-energy wasting
When kidney damage occurs, the kidney is unable to carry out its functions effectively. This can then lead to a type of malnutrition known as protein-energy wasting (PEW). PEW is a defect in protein and energy stores in the body caused by the kidneys' inability to maintain acid balance and absorb glucose (sugars) and amino acids (building blocks of protein). People with PEW are at risk of developing nutritional deficiencies that can lead to muscle depletion, hypertension, anaemia and decreased quality of life.1
How can diet help?
Nutrition plays a huge role in managing the symptoms of PEW and kidney disease. Adopting a predominantly plant-based diet compared to an animal-based diet is preferred for people with kidney disease. For people not requiring dialysis (filtration of blood through a device), it is advised to restrict protein intake to 0.6 - 0.8g/kg per day (0.8 x how much you weigh). Whilst it is advised that people requiring dialysis should maintain a protein-rich diet (1.0 - 1.2g/kg/per day) in order to replenish lost protein and prevent further muscle breakdown. Research shows that maintaining a low-protein diet, in this case, can help prevent the development of PEW and provide adequate energy supplementation.2
A recent study highlighted that people with kidney disease will benefit from reducing their calorie intake to 25-35Kcal/kg/per day as opposed to the recommended 30-35Kcal/kg/per day.3
Preventing worsening of symptoms
Diabetes, diet and kidney disease
As previously mentioned, diabetes is caused by the body’s inability to regulate sugar levels in the blood. High glucose levels (blood sugars) can damage the blood vessels and tiny filters in your kidneys causing the kidneys to leak and not function properly. Long-term diabetes (>5 years) can increase your risk of developing kidney damage. Studies show that reducing carbohydrate intake to 50-60%, limiting protein intake and consuming adequate fat intake (30%) can help manage diabetes, thus reducing the risk of developing kidney disease.4,5
High blood pressure and kidney disease
High blood pressure can cause blood vessels to narrow, which eventually leads to damage to blood vessels in the body, including ones found in the kidney. Weakened blood vessels in the kidney prevent it from functioning properly, which leads to further complications. Limiting sodium intake (salt) to 2000mg/per day can help prevent increased blood pressure and therefore prevent kidney disease.6
Conclusion
Kidney disease manifests when your kidneys become defective and are unable to carry out their functions effectively. It is commonly caused by diabetes and high blood pressure and can lead to further complications such as protein-energy wasting, hypertension, anaemia and decreased quality of life. People with comorbidities, such as diabetes and high blood pressure, are at a greater risk of developing kidney disease. Nutrition plays a vital role in managing kidney disease. Adopting a predominantly plant-based diet and reducing carbohydrates and salt intake may help slow the disease's progression.
References
- Velasquez M, Andrews S, Raj D. Protein Energy Metabolism in Chronic Kidney Disease. Chronic Renal Disease. 2020;:225-248.
- Obi Y, Qader H, Kovesdy C, Kalantar-Zadeh K. Latest consensus and update on protein-energy wasting in chronic kidney disease. Current Opinion in Clinical Nutrition and Metabolic Care. 2015;18(3):254-262.
- Vidal A, Ríos R, Pineda C, López I, Raya A, Aguilera-Tejero E et al. Caloric Intake in Renal Patients: Repercussions on Mineral Metabolism. Nutrients. 2020;13(1):18.
- D’Alessandro C, Giannese D, Avino M, Cupisti A. Energy Requirement for Elderly CKD Patients. Nutrients. 2021;13(10):3396.
- Dyson P, Kelly T, Deakin T, Duncan A, Frost G, Harrison Z et al. Diabetes UK evidence-based nutrition guidelines for the prevention and management of diabetes. Diabetic Medicine. 2011;28(11):1282-1288.
- Kim H. Nutritional Intervention for a Patient with Diabetic Nephropathy. Clinical Nutrition Research. 2014;3(1):64.
