Health Risks of Drinking Fruit Juice

Fruit Juice Increases Risk of Rectal Cancer

The effects of fruit and vegetable consumption on colorectal cancer (CRC) appear to differ by site of origin, according to a new study published in the October, 2011 issue of the Journal of the American Dietetic Association. Researchers found that within the proximal and distal colon, brassica vegetables (Brussels sprouts, cabbage, cauliflower and broccoli) were associated with decreased risk of these cancers. A lower risk of distal colon cancer was associated with eating more apples, however an increased risk for rectal cancer was found with increasing consumption of fruit juice.

"Fruits and vegetables have been examined extensively in nutritional research in relation to CRC, however, their protective effect has been subject to debate, possibly because of different effects on different subsites of the large bowel," commented lead investigator Professor Lin Fritschi, PhD, head of the Epidemiology Group at the Western Australian Institute for Medical Research, Perth, Western Australia. "It may be that some of the confusion about the relationship between diet and cancer risk is due to the fact that previous studies did not take site of the CRC into account. The replication of these findings in large prospective studies may help determine whether a higher intake of vegetables is a means for reducing the risk of distal CRC."

Researchers from the Western Australian Institute for Medical Research, University of Western Australia and Deakin University investigated the link between fruit and vegetables and three cancers in different parts of the bowel: proximal colon cancer, distal colon cancer, and rectal cancer. The case-control study included 918 participants with a confirmed CRC diagnosis and 1021 control participants with no history of CRC. The subjects completed extensive medical and nutritional questionnaires and were assigned a socioeconomic status based on their home address.

Consumption of brassica vegetables (e.g., broccoli, cabbage) was associated with reduced incidence of proximal colon cancer. For distal colon cancer, both total fruit and vegetable intake and total vegetable intake appeared to decrease risk. Distal colon cancer risk was significantly decreased in association with intake of dark yellow vegetables and apples, although there was an increased risk for rectal cancer with consumption of fruit juice. Risk of proximal colon cancer and rectal cancer was not associated with intakes of total fruit and vegetable, total vegetable or total fruit.

Previous studies on CRC have often failed to distinguish between the different sites of origin of cancers in the large bowel, even though it is now well established that tumors in the proximal colon develop along different pathways to those of the distal colon and rectum and that risk of cancer varies by subsite within the colorectum. The mechanisms for different effects of dietary components on different sites of the large bowel have not yet been determined.

The authors conclude that "from a public health point of view it is easier to translate food-based analyses into dietary recommendations, rather than using the intake of single nutrient."

The article is "Fruit and vegetable consumption and the risk of proximal colon, distal colon and rectal cancers in a case-control study in Western Australia" by Neeltje Annema, Jane S. Heyworth, Sarah A. McNaughton, Barry Iacopetta, and Lin Fritschi. It appears in the Journal of the American Dietetic Association, Volume 111, Issue 10 (October 2011) published by Elsevier.

Fruit Juice Increases Risk of Diabetes

Researchers in the Tulane School of Public Health and Tropical Medicine and the Harvard School of Public Health have found that one serving of fruit juice a day increased the risk of Type II diabetes in women. Fruit juices deliver a big sugar load in a liquid form that gets absorbed rapidly.

The researchers analyzed 18 years worth of diet and health data from 71,346 nurses who participated in the Nurses’ Health Study from 1984 to 2002. The women were all between 38 and 63 years old and diabetes-free when the study began. Approximately 7 percent of the participants developed diabetes over the course of the study.

Avoid grapefruit and other juices when taking certain drugs

Scientists and consumers have known for years that grapefruit juice can increase the absorption of certain drugs — with the potential for turning normal doses into toxic overdoses. Now, the researcher who first identified this interaction is reporting new evidence that grapefruit and other common fruit juices, including orange and apple, can do the opposite effect by substantially decreasing the absorption of other drugs, potentially wiping out their beneficial effects.

The study provides a new reason to avoid drinking grapefruit juice and these other juices when taking certain drugs, including some that are prescribed for fighting life-threatening conditions such as heart disease, cancer, organ-transplant rejection, and infection, the researcher says. These findings — representing the first controlled human studies of this type of drug-lowering interaction — were described at the 236th National Meeting of the American Chemical Society.

"Recently, we discovered that grapefruit and these other fruit juices substantially decrease the oral absorption of certain drugs undergoing intestinal uptake transport," says study leader David G. Bailey, Ph.D., a professor of clinical pharmacology with the University of Western Ontario in London, Ontario. "The concern is loss of benefit of medications essential for the treatment of serious medical conditions."

Bailey and colleagues announced almost 20 years ago the unexpected finding that grapefruit juice can dramatically boost the body's levels of the high-blood-pressure drug felodipine, causing potentially dangerous effects from excessive drug concentrations in the blood. Since then, other researchers have identified nearly 50 medications that carry the risk of grapefruit-induced drug-overdose interactions. As a result of the so-called "Grapefruit Juice Effect," some prescription drugs now carry warning labels against taking grapefruit juice or fresh grapefruit during drug consumption.

In the most recent research, Bailey's group had healthy volunteers take fexofenadine, an antihistamine used to fight allergies. The volunteers consumed the drug with either a single glass of grapefruit juice, water containing only naringin (substance in grapefruit juice that gives the juice its bitter taste), or water. When fexofenadine was taken with grapefruit juice, only half of the drug was absorbed compared to taking the drug with water alone, Bailey says. Loosing half of the amount of drugs taken into the body can be critical for the performance certain drugs, he points out.

They also showed that the active ingredient of grapefruit juice, naringin, appears to block a key drug uptake transporter, called OATP1A2, involved in shuttling drugs from the small intestine to the bloodstream. Blocking this transporter reduces drug absorption and neutralizes their potential benefits, the researchers say. By contrast, drugs whose levels are boosted in the presence of grapefruit juice appear to block an important drug metabolizing enzyme, called CYP3A4, that normally breaks down drugs.

"This is just the tip of the iceberg," Bailey says. "I'm sure we'll find more and more drugs that are affected this way."

To date, grapefruit, orange and apple juices have been shown to lower the absorption of etoposide, an anticancer agent; certain beta blockers (atenolol, celiprolol, talinolol) used to treat high blood pressure and prevent heart attacks; cyclosporine, a drug taken to prevent rejection of transplanted organs; and certain antibiotics (ciprofloxacin, levofloxacin, itraconazole). But additional drugs are likely to be added to the list as physicians become more aware of this drug-lowering interaction, Bailey says.

Orange and apple juices also appear to contain naringin-like substances that inhibit OATP1A2, Bailey says. The chemical in oranges appears to be hesperidin, but the chemical in apples has not yet been identified, the researchers notes.

Bailey advises patients to consult with their doctor or pharmacist before taking any medications with grapefruit juice or other fruits and juices. Unless it is known to be a problem, he recommends taking most medications only with water.