Filling, flavorful, and nutritious—it's easy to understand why grapefruits are no longer just an option for breakfast. Half a grapefruit provides more than 50% of the adult Recommended Daily Allowance (RDA) of vitamin ; it also has 325mg of potassium, 25mcg of folate, 40mg of calcium, and 1mg of iron. The pink and red varieties are high in beta carotene, an antioxidant that the body converts to vitamin A.
A cup of unsweetened grapefruit juice has 95mg of vitamin C, more than 150% of the RDA, and most of the other nutrients found in the fresh fruit. In the past many people shunned unsweetened grapefruit because of its tartness, but a naturally sweet juice can be made by using red or pink fruits, or by blending their juice with that of white grapefruits. Mixing orange and grapefruit juices also makes a refreshing drink that doesn't need sweetening.
Grapefruits are especially high in pectin, a soluble fiber that helps lower blood cholesterol. In addition, recent studies indicate that grapefruits contain other substances that prevent disease.
Pink and red grapefruits, for example, are high in lycopene, an antioxidant that appears to lower the risk of prostate cancer. Other protective plant chemicals found in grapefruits include phenolic acid which inhibits the formation cancer-causing nitrosamines, limonoids, terpenes, and monoterpenes, which induce the production of enzymes that help prevent cancer; and flavonoids which inhibit the action of hormones that promote tumor growth. Some people with rheumatoid arthritis, lupus, and other inflammatory disorders find that eating grapefruit daily seems to alleviate their symptoms. This is thought to stem from plant chemicals that block prostaglandins, substances that cause inflammation.
People who are allergic to other citrus fruits are likely to react to grapefruits, too. The sensitivity may be to the fruit itself or to an oil in the peel.