Most people drink orange juice (OJ) for its vitamin C, but if you are trying to prevent a cold, other foods and fruits are more effective. On the other hand, OJ is an excellent source of the polyphenols hesperidin and diosmin. These chemical strengthen varicose veins and reduce bruising. You can drink up to a quart (approximately a liter) a day and absorb hesperidin. Drinking more than a quart a day will have no effect on vascular strength.
Juice from oranges also contains linalool, the calmative chemical in lavender. If you want to maximize linalool, however, squeeze the oranges yourself. Home-squeezed oranges (either by hand or with a household juicer) contain 40 times as much linalool as mechanically squeezed oranges used to make commercial juice, because hand- or home-squeezing bruises the peel.
If you don’t drink milk, OJ fortified with calcium and vitamin D is a relatively good food for maintaining bone strength, but you also need to eat at least some green vegetables for vitamin K. (Lettuce is an excellent source.) Calcium in the juice is absorbed as completely as calcium in milk, and calcium-fortified orange juice is appropriate for elderly people.
There is one health condition for which drinking juice from oranges raises risk, melanoma. In May 2003, researchers at Brigham and Women's Hospital and Harvard Medical School reported that vitamin C from food, and specifically vitamin C from orange juice, increased risk of melanoma, but the effect was not significant except in women who drank more than two glasses per day. If you have or have had melanoma, limit your daily OJ to one eight-ounce (225 ml) glass a day at most.
Also, if you take antibiotics, don’t drink OJ. A chelation reaction between orange juice and most antibiotics slows the absorption of the drug so that less is absorbed, and it also slows the metabolism of the drug so that any side effects are prolonged. In the case of amphotericin B, an antiobiotic given to people on chemotherapy and people who have HIV or AIDS, drinking the juice at the same time as taking the antibiotic reduces its effectiveness so much that microorganisms actually multiply rather than being killed.