Promoting Kidney Health With Raspberries

Could raspberries play a role in promoting kidney health?

Each roughly the size of a fist, the kidneys are crucial to health by removing waste products from the body. Additionally, they stimulate the release of various hormones involved in blood pressure (BP) management and red blood cell creation. Optimising kidney health is also important to preserving cardiac functions as the two systems are closely related.

There are many ways to keep the kidneys working as they should according to experts. Some common methods include avoiding processed foods (particularly those high in sodium), eating the correct amounts of fruits and vegetables, exercising routinely etc. In particular, certain components of raspberries have been found to have inhibitory effects on calculus formation in kidney stones and have natural antioxidant properties. For this article, we will focus primarily on raspberries’ properties and whether they indeed contribute to a healthier renal profile. Keep reading to find out how your kidneys work, the significance of a healthy diet, and how you might benefit from a few extra berries a day. 

Introduction

Importance of the renal system 

The renal system is comprised of the kidneys, ureter, and urethra. In the span of 24 hours, around 200 litres of blood flows through the kidneys where toxins and metabolic waste products are expelled. Alongside these excretions, tubular reabsorption allows for the regulation of water, solutes, and electrolytes in the blood via a passive process called ‘hydrostatic pressure’.¹

The renal system’s role in cardiovascular health

The renal and cardiovascular systems are tightly connected and therefore when one fails so does the other. Heart disease and renal disease share many common of the same risk factors such as high blood pressure and diabetes.² One example is the kidneys’ role in regulating sodium and water balance to maintain extracellular fluid (ECF) homeostasis. When there are complications concerning this system such as in chronic kidney disease (CKD) where there is an increased uptake in sodium and water, it causes increased ECF and in turn elevated blood volume. As a result, there is increased venous return to the heart causing arteries to stretch and increasing overall blood pressure.³

Diseases of the kidneys 

Chronic kidney disease (CKD)

Studies show that it is not easy to determine the true prevalence of CKD as it is difficult to detect in the first place.⁴ This is due to its asymptomatic nature in early/moderate CKD, however, it has been seen that it is present in approximately 10 to 14% of the population worldwide.⁴ In simple terms, many people may have developed CKD, but would not know until the disease progresses and does serious damage. 

Risk factors include:

• high blood pressure (straining of the kidneys’ blood vessels)
• diabetes (elevated levels of glucose affecting glomerular filtration)
• high cholesterol (building of fatty deposits in blood vessels)⁵

Kidney stones

One common, but less detrimental issue that can arise in the kidneys is the formation of renal calculi also known as kidney stones. In the world of medicine, it is termed ‘Nephrolithiasis’. According to recent studies, the prevalence of kidney stones is increasing affecting around 12% of the general population worldwide. Additionally, there seems to be an elevated risk in men as opposed to women for developing kidney stones.⁶

Risk factors include:

• history of diabetes, obesity, and high blood pressure 
• family history of kidney stones (reportedly doubles the risk of development)
• low fluid intake (e.g., water and electrolytes)⁶

Dietary implications for developing kidney disease

Protein

In the past decade, there has reportedly been a marked increase in protein intake in the general population. According to various studies, high dietary protein consumption can lead to a condition called intraglomerular hypertension. This is where high blood pressure interferes with the glomerulus’ ability to filter toxic byproducts out of the blood within the nephron.⁷ Furthermore, this can lead to hyperfiltration of the kidney, which could lead to the development of long-term CKD if unchecked. It is recommended that a human should not consume >1.2g of protein per kilogram of body weight per day to preserve kidney health.⁸

Sodium

Along with protein intake, dietary sodium consumption has been a big topic of discussion in recent years with the elevated emergence of the processed food industry. Various studies have reported that over 2g of sodium a day (5g of table salt) in adults has the chance to lead to long-term hypertension which adversely affects the kidneys according to the WHO.⁹   

Potassium

It is very important to include potassium in a healthy diet, however, it is important that one does not eat too much as this can have consequences on the kidneys' functions especially if one’s kidneys are already in a disease state. Hyperkalaemia happens when the kidneys cannot remove enough potassium from the bloodstream which can lead to cardiac arrhythmia.¹⁰ Current guidelines recommend that one does not exceed 2 to 4g of daily potassium intake. 

Lifestyle changes to help protect the kidneys 

Diet

Luckily, we live in a world where most food products need to advertise how much of various macro and micronutrients they contain. Therefore, one can simply take more care when going grocery shopping. According to various studies, the following measures can be considered to have a kidney-friendly diet: 

• To reduce sodium intake, you can cook with a variety of different spices rather than just using salt
• To manage protein consumption, take note of how much meat, poultry, eggs, fish, or milk you consume daily. You can easily do this by looking at the packaging and noting it down. At the end of the day tally up the amount of protein and check how this fits into your daily maximum (remember 1.2g per kg of body weight)⁸

Raspberries and kidney health

There have been various studies regarding the benefits of raspberries on general health. As it so happens, the kidneys are a crucial part of one’s general health. 

Antioxidants

Raspberries are high in antioxidants such as anthocyanins, quercetin, and ellagic acid.¹¹ Oxidative compounds are produced when tissue repair, inflammation, and defence reactions of the body. In conditions such as CKD, where there is a constant state of inflammation, oxidative compounds cause more stress and inflammation than normal.¹² Antioxidants are molecules that have the ability to give electrons without becoming unstable. In the case of free radicals, antioxidative molecules donate electrons to stabilise them thus rendering them unavailable to carry out any damaging chain reactions. 

Anti-inflammatory properties

According to in-vitro studies, raspberries have shown anti-inflammatory activity by reducing lipid oxidation, and DNA damage, and increasing antioxidant enzyme activity.¹¹ This is attributed to their polyphenol content. 

Nutritional Content 

Other than having important antioxidants and anti-inflammatory properties, raspberries contribute a lot to one’s nutrition. One such example is their high fibre content and low calorie and sugar content. However, there is an important distinction to be made. Research shows that raspberries in the form of purée and frozen provide 20% more dietary fibre than normal agriculturally grown ones.¹³

Alternative kidney-friendly foods

Blueberries and strawberries

Alternatively, blueberries and strawberries share the same attributes as raspberries being high in fibre, antioxidants, and low in calories and sugars. Specifically, a blueberry-enriched diet has been observed to be the best way to improve kidney function and reduce oxidative stress.¹⁴

Red grapes and apples

Outside the family of berries, there are various studies which recommend grapes and apples to be beneficial in improving kidney health. Different to berries, they contain compounds like quercetin which have been shown to reduce stimuli to systemic inflammation by regulating T-cell inflammatory responses.¹⁵

Summary

Key Points

In summary, according to various studies, incorporating raspberries into one’s diet is beneficial to kidney health. Experts believe that in patients with reduced kidney function such as in CKD, a raspberry-rich diet provides good protection against chronic inflammation. The renal system is a crucial component of our body that works 24/7. While humans can survive with just one, it is best not to get to that point and to think about your kidneys when planning your diet. 

Overview of raspberries 

Raspberries can provide important protection against oxidative free radicals to combat inflammation. They are also high in fibre and low in calories and sugar with lots of kidney-friendly nutritious compounds. 

Guidance

Incorporating raspberries into the diet is a great way to preserve kidney function, especially in patients with chronic illness. It should be noted that if one does suffer from kidney disease, they should follow their doctor’s advice and any prescribed medication. Berries can enrich kidney function, but not replace the qualities of important medications.