The
secret slimming effect of sweet potato waste

Proteins in wastewater from sweet potato
processing reduce fat levels, weight in mice

Date:

December 7, 2016

Source:

Elsevier

Summary:

The sweet potato pie you eat during the
holidays might not be good for your waistline, but according to a new study,
the starchy water left over from cooking the sweet potato could have slimming
effects — at least in mice.

The sweet potato pie you
eat during the holidays might not be good for your waistline, but according to
a new study published in the journal Heliyon, the starchy water left
over from cooking the sweet potato could have slimming effects — at least in
mice.

In
the new study, mice on a high fat diet had significantly lower body weight
after one month if they were also fed sweet potato peptide, which was produced
by enzyme digestion of proteins in the water wasted during processing. This
suggests the peptide plays a role in digesting fats, but more research is
needed to determine whether this also happens in humans.

More than 105 million
metric tons of sweet potato are produced globally every year, according to the
International Potato Center (CIP), making it the world’s fifth most important
crop. About 15 percent of sweet potato is used to produce starch materials,
processed foods, and distilled spirits in Japan. The resulting wastewater is
usually discarded, potentially causing serious environmental problems.

In the new study, Dr.
Koji Ishiguro from National Agriculture and Food Research Organization in Japan
and colleagues wanted to find a new way to use this waste, so they investigated
the effect of proteins found in the water on digestion in mice.

“We throw out huge
volumes of wastewater that contains sweet potato proteins — we hypothesized
that these could affect body weight, fat tissue and other factors,”
explained Dr. Ishiguro. “Finding alternative uses for the sweet potato
proteins in wastewater could be good for the environment and industry, and also
potentially for health.”

The researchers fed three
groups of mice high fat diets, giving one group the protein digest — sweet
potato peptide (SPP) — at a high concentration and one group at a lower
concentration. After 28 days they weighed the mice and measured their liver
mass and fatty tissue. They also measured the levels of the fats cholesterol
and triglyceride, as well as leptin, which controls hunger, and adiponectin,
which regulates metabolic syndrome.

Mice that were given SPP
had significantly lower body weight and liver mass. Mice fed SPP also had lower
cholesterol and triglycerides, and higher levels of the hunger and
lipid-controlling hormones. The results suggest that SPP helps activate
appetite suppression and control lipid metabolism in mice fed high fat diets.

“We were surprised
that SPP reduced the levels of fat molecules in the mice and that it appears to
be involved controlling appetite suppression molecules,” commented Dr.
Ishiguro. “These results are very promising, providing new options for
using this wastewater instead of discarding it. We hope SPP is used for the
functional food material in future.”

Story Source:

Materials provided by Elsevier. Note:
Content may be edited for style and length.

Journal Reference:

1.    Koji Ishiguro, Rie
Kurata, Yoshikazu Shimada, Yoto Sameshima, Takashi Kume. Effects of a
sweetpotato protein digest on lipid metabolism in mice administered a high-fat
diet. Heliyon, 2016; 2 (12): e00201 DOI: 10.1016/j.heliyon.2016.e00201