I've read with interest a new study, from the University of Southern California and the University of Hawaii, which was just published in the British Journal of Cancer. This study of 50,000 women states that eating Grapefruit can increase the risk of breast cancer. The fruit is believed to boost blood levels of estrogen, the hormone associated with increased risk of the illness.
The researchers claim that post-menopausal women who eat as little as one quarter of a grapefruit per day could see their chances of a certain breast cancer increase by 30 per cent. (Perhaps you remember the popular "Grapefruit Diet" that made the rounds years ago--most dieters would have been eating at least six times this amount!)
Previous studies have shown that a molecule called cytochrome P450 3A4 (CYP3A4) is involved in metabolising estrogen hormones. Grapefruit may boost blood estrogen levels by inhibiting this molecule, allowing the hormones to build up.
Grapefruit has had other health cautions over the years. You may remember the Grapefruit warning a few years ago when scientists found that Grapefruit can dramatically affect the way that drugs are metabolized in the body. There were strong cautions at the time to avoid taking Grapefruit juice with prescription medicine. The same thing could be going on here with estrogen.
It's clear that there is a lot we don't understand yet about fruit and vegetables; while they provide us with life-enriching vitamins, minerals and fiber, they also are delivery vehicles for powerful phytochemicals, an understanding of which hasn't been clearly developed by scientists.