Could Grapefruit Diets increase breast cancer in women?

Yet again, Grapefruit is in the news again

A report from the Universities of Southern California and Hawaii, published in the British Journal of Cancer, states that eating it can increase the risk of breast cancer by nearly a third. The fruit is believed to boost blood levels of oestrogen, which is a particular problem if you're pre-disposed or have a family history of oestrogen receptive breast cancer
Researchers claim that post-menopausal women who eat as little as one quarter of a grapefruit per day (or juice equivalent) could see their chances increase by 30 per cent. Most dieters would have been eating at least six times that amount.
This is not the first time grapefruit has been implicated in a health scare.
We know that grapefruit contains substances called naringin, bergamottin and dihydroxybergamottin which can speed up or slow down how drugs are metabolised in the body by inhibiting an enzyme (CYP3A4) in the stomach.
Anyone taking immuno-suppressant drugs knows to avoid grapefruit; other drugs known to be affected include anti-depressants such as Seroxat, statins such as simvastatin; sedatives such as Valium; antihistamines such as Claritin; blood pressure tablets such as Felodipine; and even Viagra.
CYP3A4 is also known to influence the metabolism of oestrogen and the American researchers had wanted to see if this resulted in higher levels of oestrogen and therefore an increased risk of breast cancer. Even so, their findings surprised them.
''We think of all fruit as benign,'' says Catherine Collins, chief dietician at St George's Hospital in London. ''But it's much more complicated than that. Fruit and vegetables provide us with vitamins, minerals and fibre but they also deliver plenty of phyto-chemicals, the power of which we just don't understand yet."
Collins explains that the bitter taste of raw cruciferous vegetables such as broccoli or sprouts is caused by a minute quantity of cyanide in the cells, released when we crunch them. ''The cyanide travels to our liver which it stimulates to produce detoxifying enzymes.
These clean up the cyanide cells but also any other toxic substances present at that time in our bodies.''
Collins says that the substance in grapefruit responsible for increasing levels of oestrogen in the blood will be just such a chemical, and one of thousands of biological active substances in the fruit. ''It might be harmful to some but it might be useful to others - it could even act as a sort of natural HRT, as soya does.''