Below are two studies done on the benefits of grapefruit juice. The first study is done on the liver and the second study is on bone health.

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Carcinogenesis, Vol. 25, No. 2, 203-209, February 2004

MOLECULAR EPIDEMIOLOGY AND CANCER PREVENTION

Grapefruit juice intake does not enhance but rather protects against aflatoxin B1-induced liver DNA damage through a reduction in hepatic CYP3A activity

Masaaki Miyata1, Hiroki Takano, Lian Q. Guo, Kiyoshi Nagata and Yasushi Yamazoe

Division of Drug Metabolism and Molecular Toxicology, Graduate School of Pharmaceutical Sciences, Tohoku University, Aramaki, Aoba-ku, Sendai 980-8578, Japan

Influence of grapefruit juice intake on aflatoxin B1 (AFB1)-induced liver DNA damage was examined using a Comet assay in F344 rats given 5 mg/kg AFB1 by gavage. Rats allowed free access to grapefruit juice for 5 days prior to AFB1 administration resulted in clearly reduced DNA damage in liver, to 65% of the level in rats that did not receive grapefruit juice. Furthermore, rats treated with grapefruit juice extract (100 mg/kg per os) for 5 days prior to AFB1 treatment also reduced the DNA damage to 74% of the level in rats that did not receive grapefruit juice. No significant differences in the portal blood and liver concentrations of AFB1 were observed between grapefruit juice intake rats and the controls. In an Ames assay with AFB1 using Salmonella typhimurium TA98, lower numbers of revertant colonies were detected with hepatic microsomes prepared from rats administered grapefruit juice, compared with those from control rats. Microsomal testosterone 6ß-hydroxylation was also lower with rats given grapefruit juice than with control rats. Immunoblot analyses showed a significant decrease in hepatic CYP3A content, but not CYP1A and CYP2C content, in microsomes of grapefruit juice-treated rats than in non-treated rats. No significant difference in hepatic glutathione S-transferase (GST) activity and glutathione content was observed in the two groups. GSTA5 protein was not detected in hepatic cytosol of the two groups. In microsomal systems, grapefruit juice extract inhibited AFB1-induced mutagenesis in the presence of a microsomal activation system from livers of humans as well as rats. These results suggest that grapefruit juice intake suppresses AFB1-induced liver DNA damage through inactivation of the metabolic activation potency for AFB1 in rat liver.

[The complete research article]

http://carcin.oxfordjournals.org/cgi/content/full/25/2/203

Orange, Grapefruit Juice For Breakfast Builds Bones In Rats

07 Jun 2006

It may sound like Saturday cartoons: a strong-boned rat that can't be broken. But a couple of Texas researchers say the real hero is citrus juice.

Orange and grapefruit juice regularly given to lab rats prevented osteoporosis, long considered an unavoidable aging disease in which bones become more likely to break, according to a study by Texas A&M University's Vegetable and Fruit Improvement Center researchers. The article was published in Elsevier's Nutrition journal.

Osteoporosis affects about 2 million men and 8 million women in the United States, according to the National Osteoporosis Foundation. Nationally, about 1.5 million hips, vertebras and wrists break each year as a result, said Dr. Bhimu Patil, director of the center at Texas A&M in College Station.

"It's a silent disease of aging. But if we can maintain our bone strength, maybe we'll be able to prevent it," Patil noted.

For the study, 36 males rats were included for two months in the lab of Dr. Farzad Deyhim, professor of human and animal nutrition at Texas A&M- Kingsville. Half of the rats were a control group that continued life as usual. The others were castrated and then treated in one of three ways: no additional diet change; diet included orange juice; or, diet included grapefruit juice.

Castration was necessary, the researchers said, because the hormone testosterone is known to reduce antioxidants.

"This is a problem with aging men, because, the level of testosterone decreases as men age," said Deyhim, adding a similar study on female rats has begun.

Deyhim said fresh grapefruit or orange juice - mixed with sodium bicarbonate to neutralize acidity - was given to the rats each morning.

"They drank it with no problem, every morning," Deyhim said. "They drank more fresh juice than I did during that period."

Deyhim said the juice study was followed by a similar test with orange and grapefruit pulp, and although the results of that research has not been published yet, it too showed enhanced bone density.

He said the team will now examine the rats' bones at the cellular level "to see what caused that improvement in the bone." "A reduction in bone density is caused when there is an increase in oxidants. In these studies, both grapefruit juice and orange juice increased antioxidants in the rats' systems," Patil said. "So that is the benefit since oxidants damage bone cells.

"There are about 400 compounds in citrus," he said. "So we need to find out which compound in citrus caused this."

Patil suspects "limonoid,"a natural citrus compound, which has been increasingly studied for its potential to prevent various human diseases. Limonoids will be the next phase of the study, but there are at least 40 different ones, Patil cautioned.

"This study backs up our thoughts about the value of citrus," Patil said, noting that until researchers completely understand the interaction of grapefruit juice and certain medications, a person should ask a doctor.

"In general, people should eat a variety of all the colors (in food) to get all of the beneficial compounds," Patil added. "And eat fresh."

Kathleen Phillips
ka-phillips@tamu.edu
Texas A&M University - Agricultural Communications
http://agnews.tamu.edu/