Naringenin and hesperitin in orange juice may counteract the rise in free radicals and nuclear factor-kB binding caused by sugar consumption.

University of Buffalo - Orange juice, in spite of its high content of simple sugars, seems to be a healthy food for diabetics due to its abundant flavonoids, naringenin and hesperitin, a study by endocrinologists at the University at Buffalo has shown. The study appeared in the June 2007 issue of Diabetes Care.

Flavonoids suppress destructive oxygen free radicals - also known as reactive oxygen species, or ROS. An overabundance of free radicals can damage all components of the cell, including proteins, fats and DNA, contributing to the development of many chronic diseases, including heart disease and stroke as well as diabetes.

“Many major diseases are associated with oxidative stress and inflammation in the arterial wall, so the search for foods that are least likely to cause these conditions must be pursued,” said Paresh Dandona, M.D., Ph.D., head of the Diabetes-Endocrinology Center of Western New York and senior author on the study.

“Our previous work has shown that 300 calories of glucose induces ROS and other proinflammatory responses,” said Dandona, who is Distinguished Professor of Medicine in the UB School of Medicine and Biomedical Sciences.

“We hypothesized that 300 calories-worth of orange juice or of fructose would induce less oxidative stress and inflammation than caused by the same amount of calories from glucose.”

The resulting study involved 32 healthy participants between the ages of 20 and 40, who were of normal weight, with a body mass index of 20-25 kg/m2. Participants were assigned randomly and evenly into four groups, who would drink the equivalent of 300 calories-worth of glucose, fructose, orange juice or saccharin-sweetened water.

Fasting blood samples were taken before the test and at 1, 2 and 3 hours after a 10-minute period to consume the drinks. Results showed a significant increase in ROS within 2 hours in samples from the glucose group but not in those from the fructose, orange juice or water group.

“We were intrigued by the fact that there was no increase in ROS or inflammation following orange juice consumption, even though its glucose concentration was the same as in participants in the glucose group,” said Dandona. “This raised the question of what in the juice was responsible for suppressing ROS generation: flavonoids and vitamin C or fructose?”

An additional round of test on the samples showed that neither fructose nor vitamin C suppressed the oxygen free radicals. However the two types of flavonoids in orange juice - hesperetin and naringenin - inhibited ROS generation by 52 percent and 77 percent, respectively.

“Our data are relevant to patients with diabetes,” said Dandona, “because stress from ROS and inflammation are increased significantly in this population and may contribute to development of atherosclerosis. Clearly the choice of foods that either don’t increase or actually decrease oxidative and inflammatory stress is important.”

“The search for safe non-inflammatory foods and diets must continue,” Dandona stressed, “especially since obesity, being overweight and type 2 diabetes are associated with oxidative stress and inflammation, and more than 60 percent of U.S. population is affected by these conditions.”

Editorial note - This very neat research article on orange juice used an up-to-date method of measuring free radicals that looks at ROS generation from those white blood cells that are involved in causing damage to arterial walls in atherosclerosis. Similarly, the measure of inflammation looked at NF-kB binding in those same white blood cells. The reason I mention these details is that some older research into flavonoids and antioxidant effects used methods that may not be that relevant to how atherosclerotic damage actually occurs in people’s blood vessels.

While it is possible that the two flavonoids studied - hesperitin and naringenin - are responsible for the health-saving effects of orange juice, it should be noted that this part of this study was done “in vitro” and with concentrations of flavonoids that probably cannot be achieved or sustained in people via normal food consumption (50 micromolar is quite high compared to a practical maximum of about 1 micromolar serum concentration for any polyphenols obtained from food). This concentration issue always raises the question of whether or not nutritional supplements or extracts might have health benefits.

In the conclusion of this study we also find interesting details. Alcohol at a 300 calorie dose does not result in increased ROS generation or NF-kB binding. The sugars in orange juice are about 30 percent each of glucose and fructose, and 40 percent sucrose (which breaks down to glucose and fructose). Orange juice seems to be cause a slightly higher insulin response than plain glucose, and that may also account for some of the decrease in free radical generation and inflammatory NF-kB binding seen in this study following orange juice ingestion. More studies will clarify the value of the flavonoids - Dr. Z.