An orange a day keeps the doctor away — or will at least help prevent high blood pressure, abnormal cholesterol levels and excess body fat.

A natural compound commonly found in citrus, called nobiletin, strengthens the body clock and improves metabolism, according to research from a team of biochemists from The University of Texas Health Science Center at Houston (UTHealth) and other scientists from Baylor, UT Southwestern Medical Center in Dallas and the Kyoto Prefectural University of Medicine in Kyoto, Japan.

The body clock, also known as the circadian clock, is what controls a person’s’ sleep cycle. It tells your body when it is ready to sleep and wake up.

The study’s lead author and assistant professor of biochemistry and molecular biology at UTHealth, Zheng “Jake” Chen, said that there is plenty of evidence that shows there is a relationship between the body clock and health. If the clock malfunctions, many disorders, such as metabolic syndrome, could occur.

Metabolic syndrome is a group of conditions that increase the risk of heart attack and stroke. It occurs in about a third of adults in the United States.  

The team screened thousands of chemical compounds from food in search of one that could improve the function of the circadian clock. After months of searching, they found that nobiletin, a chemical found in citrus peels, had the effect they were looking for.

“Our finding that [nobiletin] targets the circadian clock is completely novel,” Chen said. “We are very excited about that.”

Chen said that although people have been using citrus peels in traditional medicines to increase digestion and relieve intestinal bloating, scientists never understood how they worked.

To test the effects of the compound on obesity, the team gave nobiletin to groups of overweight mice.

The mice with normal body clocks exhibited a 40 percent reduction in excess bodyweight; their bodies handled glucose better, and they increased their energy use. The mice became much more active and their health greatly improved overall. 

Chen said that this is what the team hoped they would find. If nobiletin works the same way in humans as it does in mice, it could be used to treat obesity and metabolic disorders.

“Now we are gaining more insight on the physiological processes that are controlled by the biological clock,” Chen said. “And now it’s time to apply that knowledge to actual health. That is my motivation.”