Introduction

Watermelon, a popular tropical and subtropical fruit, is a vegetable crop that is huge, oval, round, or oblong in shape. Watermelon is abundant in vitamins phytochemicals, and commonly used for breakfast, appetizers and snacks. Watermelon is rich in carotenoid and lycopene, compounds that have cancer-fighting properties reduce inflammation. 

Watermelon is rich in citrulline, an amino acid that is utilized in the production of arginine. Additionally, it is characterized by numerous compacted seeds. Research on watermelon has mostly examined its nutritional, phytochemical, and antioxidant characteristics.

Citron watermelon, a resilient plant belonging to the Cucurbitaceae family, serves as a valuable source of food, feed, and pharmaceuticals in sub-Saharan Africa. It flourishes in dry conditions and exhibits tolerance to pests and illnesses. The crop possesses distinct nutritional and phytochemical components, which confer it with medicinal properties.

In Sudan, it is used for the treatment of conditions such as oedema, gout, and gastrointestinal diseases. In South Africa, it is used for the management of hypertension. Nevertheless, in Sub-Saharan Africa (SSA), it is widely disregarded and not fully utilized because of insufficient investment in research and development.

Consumers are replacing energy-dense snacks with antioxidant-rich fruits in response to the dietary suggestion to increase natural antioxidant intake. This tendency has generated a need in the food business for nourishing food, specifically derived from natural sources. Watermelon, a tropical fruit, is rich in vitamins B, C, and E, minerals, and antioxidants. It also possesses anti-inflammatory and antihypertensive characteristics and can protect against carbon tetrachloride-induced toxicity.

It is a hydrating fruit that is particularly enjoyable during the summer due to its abundant water content, appealing colour, and subtle flavour. Its chemical makeup increases its ability to scavenge HDL and LDL cholesterol from cell membranes, which is why it works so well for weight loss. It has been observed to enhance the aggregation of platelets, elevate the expression of growth factors, and bolster the proliferation and differentiation of cells in the kidney, heart, and other organs.⁶

Understanding kidney function

Before delving into the specific ways in which watermelon can enhance kidney function, it's crucial to grasp the role of these vital organs. The kidneys play a crucial role in regulating the composition and volume of bodily fluids. One in two Americans is predicted to acquire chronic kidney disease (CKD), a prevalent ailment that affects up to 13% of the US population.

It can result in kidney failure, heart failure, infection, acute renal damage, and death. Kidney function is evaluated through the utilization of albuminuria and/or glomerular filtration rate (GFR), which is the primary measure used in the clinical evaluation of kidney function. Decrease in GFR is associated with decline in renal function. The standard glomerular filtration rate (GFR) for men and women are 120 and 96 mL/min, respectively.¹⁰

Chronic renal failure (CRF) is a condition when the kidneys experience a gradual and permanent decrease in their ability to function properly. This leads to a reduction in the pace at which the kidneys filter blood and increase in the levels of creatinine in the blood plasma. Patients with proteinuria or hypertension experience a more rapid progression to chronic renal failure.

The consumption of lycopene in watermelon can help prevent kidney damage caused by biochemical and histo-pathological causes. A case report involving a 60-year-old man with chronic kidney disease (CKD) showed that the consumption of watermelon, without any changes to his diabetes therapies, resulted in a temporary decrease in serum creatinine levels and blood urea nitrogen (BUN) levels.⁷ 

Hydration: The key to kidney health

One of the simplest yet most effective ways to support kidney function is ensuring that a person is sufficiently hydrated. The kidneys flush out toxins and maintain proper function by relying on sufficient fluid intake and as watermelon is composed of over 90% water, it serves as a hydrating powerhouse. Consuming water-rich foods like watermelon not only helps meet daily fluid requirements but are also very important in providing essential electrolytes like potassium, which play a crucial role in kidney function.

Nutrient profile of watermelon

The tropical fruit watermelon is a rich source of phytochemicals, including minerals, vitamins, amino acids, phenolic, flavonoids, and pigments like lycopene and β-carotene. These phytochemicals can prevent disease and promote health. Lycopene, a pigment with a red hue, is a significant antioxidant contributor in the body and may provide protection against cardiovascular disease and cancer.

With a 60% bioavailability rate, watermelon is the most plentiful source of lycopene. Vitamin A and vitamin C are crucial minerals for maintaining healthy health, and watermelon is a rich source of these critical vitamins.

Watermelon also has citrulline, a non-essential amino acid that may have antioxidant and vasodilator properties and it also contains polyphenols, total phenolic compounds, and flavonoids that possess antioxidant qualities, as well as anticancer and anti-inflammatory benefits.⁹

Watermelon and chronic kidney disease (KD)

Diabetes, hypertension, and other disorders can induce chronic kidney dysfunction, which can develop into CKD and ESRD (End-stage renal disease). The primary focus of treatment is on dialysis or a kidney transplant prior to the onset of uremia symptoms.

The five stages of CKD are damage to the kidneys with a nearly normal GFR, moderate GFR decline, average GFR drop, and severe GFR reduction. It has been recommended that kidney patients consume watermelon, as it can help reduce kidney damage and advancement, potentially slowing down the progression of CKD.³

Reducing kidney stone risk

Kidney stones, crystallized deposits that form in the kidneys, can impair renal function and cause excruciating pain if left untreated. Fortunately, watermelon may offer a natural solution for reducing the risk of kidney stone formation. Studies suggest that watermelon consumption can increase urine volume and promote the excretion of waste products, thus reducing the concentration of stone-forming substances in the urine.

Furthermore, watermelon contains citrulline, an amino acid that may help prevent the formation of certain types of kidney stones by inhibiting the accumulation of calcium oxalate crystals. The findings indicated that a duration of 24 hours was enough to transform calcium oxalate crystals into an amorphous state.⁵

Anti-inflammatory and antioxidant effects

Watermelon is a widely consumed fruit throughout the summer season that contains antioxidants such as carotenoid lycopene and phenolic antioxidants. The substance includes cucurbitacin E, a phytonutrient with anti-inflammatory properties, as well as amino acids. Watermelon contains high levels of vitamins C, A, potassium, and magnesium.

The chemical constituents of this substance enable it to remove LDL and HDL from cell membranes, hence promoting weight loss and reducing the likelihood of cardiovascular disease. Lycopene can be found in concentrated form in watermelon pomace.¹

Another investigation was undertaken to examine the anti-inflammatory and antioxidant properties of watermelon lycopene. To find out how strong the antioxidants were, different tests were used, such as the FRAP assay, which measures ferric reducing antioxidant power, and the DPPH radical scavenging activities.

The antioxidant activities of watermelon lycopene were much higher than those of tomato lycopene, and its superoxide anion scavenging activity was comparable to that of Trolox. INOS and COX-2 mRNA and protein levels in lipopolysaccharide-stimulated HaCaT cells were dose-dependently reduced by watermelon lycopene, showing its substantial anti-inflammatory effect. Watermelon lycopene was discovered to be a beneficial provider of antioxidant and anti-inflammatory substances.⁴

Precautions for watermelon consumption

The extensive utilization of pesticides gives rise to apprehensions regarding both the safety of food and the potential consequences on the ecosystem. Vegetables and fruits in Thailand are not thoroughly monitored for pesticide residual levels.

A study revealed that 91.7% of watermelon samples had 5 different pesticides, whereas 90% of durian samples contained 3 pesticides. The amounts observed were much below the specified Minimum Risk Level (MRL) standards.

Despite the fact that there is a small danger connected with pesticide exposure from ingesting watermelon and durian in Thailand, the study came to the conclusion that particular efforts should be made in order to decrease the overall exposure to these harmful pesticides.¹¹

Summary 

In conclusion, watermelon emerges not just as a delectable summer treat but as a formidable ally in nurturing kidney health with its high water content that replenishes hydration levels, which are essential for efficient kidney function.

Moreover, its nutrient-rich composition, not only boost vitamins, but also antioxidants, and diuretic elements like potassium, and which enhances the strength and resistance of the kidneys. By incorporating watermelon into our diet, a natural arsenal against inflammation, oxidative stress, and kidney stone formation can be accessed.

Each succulent bite promotes the vitality of our kidneys and mitigates the risks of renal ailments and becomes a gesture of self-care. So, as you relish the juicy sweetness of watermelon, revel not only in its flavour but also in its potential to safeguard and enhance the intricate workings of your kidneys. Embrace watermelon as more than just a fruit it is also a conduit to vibrant renal health and overall well-being.