Sweet potatoes are rich in carotenoids and are an excellent source of vitamin A , which is good for eye health, has antioxidant properties and also counteracts aging . This vitamin is also associated with cancer prevention. 
They contain a variety of B vitamins, including thiamine , riboflavin and niacin, as well as B5 and B6. According to the National Institutes of Health in the United States, vitamins from this group help the body process the food consumed and convert it into energy. These vitamins are also important for the formation of red blood cells
The aim of the Japanese scientists who conducted the study is to find a way to reuse the water in which sweet potatoes are boiled in industrial production. Therefore, experts decide to check its nutritional value and effects. 
During a laboratory study, researchers tested the effects of high and low protein concentrations in sweet potato water. 
The data indicate that at high concentrations, a significant decrease in body weight and liver size is observed . In addition, cholesterol and triglyceride levels are lowered, and levels of the metabolic hormones leptin and adiponectin are increased. 
These data suggest that sweet potato protein has the ability to suppress appetite and control lipid metabolism
As these effects have not been observed in the human body, further studies should be performed.
The results were published in the journal Heliyon .