Healthy Fruit: Grapefruit

The grapefruit (Citrus × paradisi), is a subtropical citrus tree known for its bitter fruit, an 18th-century hybrid first bred in Barbados. When found it was named the "forbidden fruit"; it has also been misidentified with the pomelo or shaddock (C. maxima), one of the parents of this hybrid, the other being sweet orange (C. × ​sinensis).

These evergreen trees are usually found at around 5–6 metres (16–20 ft) tall, although they can reach 13–15 metres (43–49 ft). The leaves are dark green, long (up to 150 mm, or 6 inches) and thin. It produces 5 cm (2 in) white four-petaled flowers. The fruit is yellow-orange skinned and largely an oblate spheroid; it ranges in diameter from 10–15 cm. The flesh is segmented and acidic, varying in color depending on the cultivars, which include white, pink and red pulps of varying sweetness. The 1929 US Ruby Red (of the Redblush variety) has the first grapefruit patent.

The fruit has become popular since the late 19th century; before that it was only grown as an ornamental plant. The United States quickly became a major producer of the fruit, with orchards in Florida, Texas, Arizona, and California. In Spanish, the fruit is known as toronja or pomelo.

Grapefruit comes in many varieties, determinable by color, which is caused by the pigmentation of the fruit in respect of both its state of ripeness. The most popular varieties cultivated today are red, white, and pink hues, referring to the internal pulp color of the fruit. The family of flavors range from highly acidic and somewhat bitter to sweet and tart. Grapefruit mercaptan, a sulfur-containing terpene, is one of the substances which has a strong influence on the taste and odor of grapefruit, compared with other citrus fruits.

Grapefruit is an excellent source of many nutrients and phytochemicals that contribute to a healthy diet. Grapefruit is a good source of vitamin C, contains the fiber pectin, and the pink and red hues contain the beneficial antioxidant lycopene. Studies have shown grapefruit helps lower cholesterol, and there is evidence that the seeds have antioxidant properties. Grapefruit forms a core part of the "grapefruit diet", the theory being that the fruit's low glycemic index is able to help the body's metabolism burn fat.

Grapefruit seed extract (GSE) has been claimed to have strong antimicrobial properties, with proven activity against bacteria and fungi. However, no studies have demonstrated any efficacy by GSE as an antimicrobial for either bacteria or fungi. Additionally, although GSE is promoted as a highly effective plant-based preservative by some natural personal care manufacturers, studies have shown that the apparent antimicrobial activity associated with GSE preparations is merely due to contamination with synthetic preservatives.

Since grapefruit juice is known to inhibit enzymes necessary for the clearance of some drugs and hormones, some have hypothesized that grapefruit juice may play an indirect role in the development of hormone-dependent cancers. A 2007 study found a correlation between eating a quarter of grapefruit daily and a 30% increase in risk for breast cancer in post-menopausal women. The study points to the inhibition of CYP3A4 enzyme by grapefruit, which metabolizes estrogen. However, a 2008 study has shown that grapefruit consumption does not increase breast cancer risk and found a significant decrease in breast cancer risk with greater intake of grapefruit in women who never used hormone therapy.

Grapefruit contains large quantities of a simple polyamine called spermidine, which may be related to aging. It is known to be necessary for cell growth and maturation, and as cells age their level of spermidine is known to fall. Scientists have shown that feeding spermidine to worms, fruit flies and yeast significantly prolongs their lifespan. In addition, adding spermidine to the diet of mice decreased molecular markers of aging, and when human immune cells were cultured in a medium containing spermidine, they also lived longer.

A number of studies have found a risk for kidney stones from drinking grapefruit juice. In one study, just one 8-ounce cup of grapefruit juice per day increased the risk for forming stones by 44%. Grapefruit peel oil is used in aromatherapy and it is historically known for its aroma.

In Costa Rica, especially in Atenas, grapefruits are often cooked to remove their sourness, rendering them as sweets; they are also stuffed with dulce de leche, resulting in a dessert called toronja rellena (stuffed grapefruit). It is also known as pomelo in the Philippines.

Grapefruit has also been investigated in cancer medicine pharmacodynamics. Its inhibiting effect on the metabolism of some drugs may allow smaller doses to be used, which can help to reduce costs. Grapefruit is used as a natural laxative, as it stimulates defecation (especially true for pink grapefruit).

Grapefruit, raw, white, all areas : Nutritional value per 100 g (3.5 oz)

Energy 138 kJ (33 kcal) | Carbohydrates 8.41 g

Sugars 7.31 g | Dietary fiber 1.1 g

Fat 0.10 g | Protein 0.69 g | Water 90.48 g

Thiamine (Vit. B₁) 0.037 mg (3%)

Riboflavin (Vit. B₂) 0.020 mg (1%)

Niacin (Vit. B₃) 0.269 mg (2%)

Pantothenic acid (B₅) 0.283 mg (6%)

Vitamin B₆ 0.043 mg (3%) | Folate (Vit. B₉) 10 μg (3%)

Vitamin C 33.3 mg (56%) | Calcium 12 mg (1%)

Iron 0.06 mg (0%) | Magnesium 9 mg (2%)

Manganese 0.013 mg | Phosphorus 8 mg (1%)

Potassium 148 mg (3%) | Zinc 0.07 mg (1%)

Percentages are relative to US recommendations for adults.

Source: USDA Nutrient database

Source, Images: http://en.wikipedia.org/wiki/Grapefruit