Archive 2005 2006 2007 2008

Citrus: It Only Begins With C

You may eat oranges and other citrus fruits and drink their juice because of their vitamin C, but they also contain other important nutrients. In addition, scientists have been discovering an array of interesting and potent phytochemicals (plant chemicals) in citrus fruit. For example, at least 170 phytochemicals have been identified so far in orange juice. Citrus fruits contain carotenoids and fiber—notably pectin, which helps lower cholesterol. They are also rich in polyphenols, which include a wide range of flavonoids and related compounds, many with beneficial effects and nearly all with tongue-twisting names.

Several recent studies have suggested that citrus fruits and juices have the following potential benefits:

• A study in the Journal of the American Medical Association found that consuming just one extra daily serving of certain fruits and vegetables, including citrus fruits or juices, reduces the risk of stroke by about 20%. Earlier research had also suggested that flavonoids such as those in citrus can lower the risk of stroke.

• An Israeli study linked orange juice with a reduction in oxidation of LDL ("bad") cholesterol. Oxidation increases artery-damaging deposits and thus promotes atherosclerosis.

• A Canadian study last year found that orange juice boosts HDL ("good") cholesterol. This study was odd, however, since this effect occurred only in people drinking at least three glasses of juice a day. No other food is known to have a significant effect on HDL, so further studies will be needed to confirm this finding.

• A Dutch study found that citrus fruit, probably because of its supply of the B vitamin folic acid, lowers blood levels of homo-cysteine, a substance that may increase the risk of heart disease.

• Citrus skin contains D-limonene and coumarins, which leach into the juice. D-limonene may help detoxify potentially cancer-causing compounds while reducing the activity of proteins that trigger abnormal cell growth, according to laboratory studies. Coumarins help reduce blood clotting and may also have anti-cancer capacity. Certain compounds that give citrus fruit their bitter or tart taste are also believed to have antioxidant and anti-cancer effects.

• A study presented at last year's conference of the American Institute for Cancer Research showed that animals fed orange juice had a reduced incidence of colon cancer. Of course, the same effect may not occur in humans.

• Oranges contain the following carotenoids: beta cryptoxanthin, which may help reduce the risk of certain cancers; and zeaxanthin and lutein, which may help keep eyes healthy. Besides beta carotene, pink and red grapefruit provide lycopene, another carotenoid, which may help prevent prostate cancer.

To get the most from your juice

The amount of vitamin C in eight ounces of OJ can range from about 80 to 140 milligrams. The exact amount depends on many factors: the variety of oranges, their ripeness, the climate and season in which they grew, and how the juice was handled, processed, and stored (heat, including pasteurization, reduces vitamin content). Vitamin C deteriorates when in contact with oxygen, so the longer juices sit around exposed to air, the less vitamin C. Loss of flavor parallels loss of nutrients.

Fortunately, because oranges are so rich in vitamin C, you can assume that, as long as it tastes good, eight ounces of any type of orange juice supplies 100% of the daily RDA (recently raised to 75 milligrams for women, 90 for men). Still, here are some pointers:

• Fresh-squeezed juice has the highest vitamin C content initially.

• Unopened canned and bottled juices are next best: stored at room temperature, they retain more than 75% of their vitamin C for a year or longer.

• Chilled cartons, especially if the juice has been reconstituted, and unrefrigerated mini-boxes usually contain slightly less vitamin C and have a shorter shelf life.

• When buying a chilled carton, check the date on it, which indicates the last day it can be sold. If the date is close or has passed, there may have been a significant loss of vitamin C—and of taste.

• Store juices properly to protect vitamins (and probably some phytochemicals). At home, a refrigerated carton can last two to four weeks (depending on its date) before there's a serious loss of vitamin C and taste. The same is true of frozen juice once it is reconstituted, and of canned juice once it is opened. To protect the vitamin C from air, store the juice in a tightly closed glass container and keep it at 40°F. or below.

Grapefruit juice and drugs

The potent compounds in fruits and vegetables can also have less desirable effects. Grapefruit juice, for example, can greatly boost the concentration of many drugs in the bloodstream. This increases the risk of side effects and, in a few cases, serious reactions. It's theorized that a chemical in grapefruit—possibly naringin, one of the flavonoids that give grapefruit its tart taste—affects enzymes in the body needed for drug metabolism.

The problem doesn't occur in all people, doesn't happen with all grapefruit juice (oddly enough), and is most likely to occur when the drugs are taken with the juice. Whole grapefruit may or may not have the same effect as the juice. If you're on medication and drink grapefruit juice, check with your pharmacist about the possible interaction. You may be advised to avoid eating grapefruit and drinking its juice.

The drugs affected include some of the "statin" cholesterol-lowering drugs, notably lovastatin and simvastatin; certain calcium channel blockers (taken for high blood pressure and angina), such as felodipine (Plendil), nifedipine (Procardia, Adalat), amlodipine (Norvasc), and vera-pamil (Calan, Verelan); certain tranquilizers (benzodiazepines such as Halcion); and at least one AIDS drug (the protease inhibitor Crixivan). The toenail-fungus drug Sporanox may also be affected.