Grapefruit - Nutritional Properties

Nutritional Properties

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 shown to have strong antimicrobial properties against fungi. It is also believed to have antimicrobial properties for bacteria, however there are no known studies that demonstrate its efficacy. 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.