A team of researchers from the Department of Food Science and Nutrition at the Illinois Institute of Technology has reviewed the preclinical and clinical trial evidence to assess intake of the watermelon (Citrullus lanatus) on cardiovascular and metabolic outcomes and to identify future directions important for establishing dietary guidance and therapeutic recommendations actionable by health care professionals, patients, and the general public.
Watermelon is a unique fruit loved for its sweet juicy flesh and strong ties to hot summer days, picnics, and family gatherings. Image credit: Andrea Petra Fogas.
Watermelon, a member of the family Cucurbitaceae, is a commercially important horticultural crop in the United States and many parts of the world.
Watermelons are aptly named due to their high water content serving early dwellers of Africa a source of water in drought-ridden desert regions.
Historical tracings over 1,000s of years suggest ancient breeders in Egypt reshaped the watermelon and likely started the improvement process of the flesh from bitter to the sweeter melon we enjoy today.
Ancient Romans and Greeks are thought to have introduced the idea of using watermelon for its medicinal properties.
Watermelon was cultivated in India, China, and Iberia, and by the 17th century widely grown in Europe.
Watermelon made it to the United States by the late 1500s, but it was not until the 20th century when the U.S. Department of Agriculture funded a watermelon breeding project at its South Carolina location leading to increased production in the United States.
Watermelon flesh contains various nutrients including proximates, vitamins, minerals, carotenoids, and amino acids.
Its sweet taste is due to soluble sugars such as sucrose, fructose, and glucose, while malic, citric, and oxalic acids are the predominant organic acids that impart characteristic watermelon flavor.
The red, yellow, and pink colors of watermelon flesh are due to the presence of carotenoids such as beta-carotene and lycopene, which vary by cultivar, maturity, and origin. Lycopene is famed for its singlet oxygen quenching capacity and potential role in prostate cancer.
Watermelon also contains various phenolic compounds including phenolic acids, lignans, coumarins, iridoids, and flavonoids.
Most notably, however, watermelons are unusually high in citrulline and arginine, non-proteinaceous amino acids. Citrulline and arginine contents of watermelon vary according to variety and geographical region and in different parts of the watermelon.
“Research is unveiling the health-promoting potential of watermelon,” said lead author Dr. Britt Burton-Freeman and colleagues.
“The current literature review provides evidence that watermelon intake and citrulline supplementation lower blood pressure in human trials.”
“Although more research is needed, favorable effects on lipids/lipoprotein metabolism are emerging based on the data we reviewed and reported in preclinical models.”
This figure summarizes research findings from animal and human literature between 2000 and 2020 on cardio-metabolic health benefits of watermelon. The unique phytochemical and amino acid composition of watermelon works across multiple mechanisms to induce biological effects. Central to these effects may be the provision of citrulline/arginine unusually abundant in watermelon and precursors of nitric oxide signaling molecule. Collectively the data indicate watermelon intake and citrulline supplementation lower blood pressure in human clinical trials. Favorable effects of watermelon intake on lipids/lipoprotein metabolism are emerging based on human data, and consistently reported in animal research. A role in body weight control, possibly through satiety mechanisms, is also suggested. Glucose control in chemically and diet-induced animal models of diabetes is apparent, though data in humans are limited presently. Image credit: Burton-Freeman et al., doi: 10.1007/s11883-021-00978-5.
In their review, the authors analyzed the preclinical and clinical trial evidence published from 2000 to 2020 to assess watermelon intake and citrulline on cardiovascular and metabolic outcomes.
They explored studies related to the whole fruit as well as citrulline supplementation, focusing on key cardio-metabolic risk factors.
They concluded that watermelon provides a combination of nutrients and phytochemicals working across multiple mechanisms to induce biological effects.
According to the team, citrulline and arginine are central to these cardio-metabolic effects, and polyphenols, lycopene, potassium and magnesium contribute as well.
“Our review provides evidence that watermelon intake and citrulline supplementation lower blood pressure in human trials,” the scientists said.
“Favorable effects on lipids/lipoprotein metabolism are emerging based on human data and consistently reported in animal models after watermelon intake.”
“A role in body weight control, possibly through satiety mechanisms, is also suggested and warrants further research. Likewise, glucose control in chemically and diet-induced animal models of diabetes is apparent, though limited data are available in humans.”
“Emerging areas include brain and gut health indicated by nitric oxide bioavailability in all tissues and evidence showing improved gut barrier function and altered microbial composition after watermelon intake.”
“Overall, watermelon provides a combination of nutrients and phytochemicals that work across multiple mechanisms to induce biological effects.”
“Central to these effects may be the provision of citrulline/arginine; however, when combined with several other notable components such as (poly)phenols, lycopene, potassium, and magnesium, effects of watermelon intake on cardio-metabolic endpoints may be expected.”
“Three grams and possibly as low as one gram citrulline per day may be sufficient to induce cardio-metabolic benefits.”
“Evidence supporting an amount of watermelon to reliably influence outcomes of interest is less mature.”
“Continued research on the whole fruit and its products (i.e., juice) to obtain sufficient intake data (amount and frequency) relative to clinical outcomes in different populations is required to advance preventative and therapeutic strategies with watermelon for optimal health and disease risk reduction.”
The review paper was published in the journal Current Atherosclerosis Reports.
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B. Burton-Freeman et al. 2021. Watermelon and l-Citrulline in Cardio-Metabolic Health: Review of the Evidence 2000-2020. Curr Atheroscler Rep 23, 81; doi: 10.1007/s11883-021-00978-5
Source link: https://www.sci.news/medicine/watermelon-cardio-metabolic-health-10492.html
