Fear in a fruitbasket

The grapefruit industry thought it was going to make a “comeback” this year. Many of the groves that were destroyed several years ago by hurricanes have recovered, and this year’s harvest is looking like the best one in awhile. And then this news came out:

“Grapefruit may raise breast cancer risk”

Of course, like most headlines, it’s a little more complicated than that. This finding arose from a study conducted by a group of researchers from the University of Southern California and the University of Hawaii. They found that women who ate the equivalent of about 1/4 of a grapefruit each day had a 30 percent higher risk of breast cancer than women who ate less.

That’s not a lot of grapefruit for such a big increase. But there are some key details that may help explain the link a little further — and may even help exonerate grapefruit.

The researchers attribute the increased breast cancer risk to grapefruit’s effect on a substance called cytochrome P450 3A4 (CYP3A4). Apparently, the fruit inhibits CYP3A4, which, in turn, inhibits the metabolism of estrogen in the body. And, as the researchers stated “Since it is well-established that estrogen is associated with breast cancer risk, it is plausible that regular intake of grapefruit would increase a woman’s risk of breast cancer.”

I see their train of thought, but take a look at how easily it can be derailed:

First of all, this is the only study that has ever suggested such a link — and women have likely been eating grapefruit for centuries. If it really had such a substantial impact on breast cancer risk, wouldn’t that have come to light before now?

Second, if you’re a regular Nutrition & Healing or Health eTips reader, you know just how inaccurate that blanket “estrogen causes breast cancer” statement is. (And if you’re a new reader or just need a refresher course, check out the upcoming December issue of Nutrition & Healing — also available on www.nutritionandhealing.com — for a complete breakdown of how estrogens work in the body.)

But the sweeping generalization these researchers made also left out another important piece of information. Estrogen metabolism isn’t the only thing CYP3A4 is responsible for in the body. According to a study published in 2005 in the journal Trends in Biochemical Sciences, “cytochrome P450 3A4 (CYP3A4) catalyzes the initial step in the clearance of many pharmaceuticals and foreign chemicals.”

And while grapefruit does indeed block its action, so do some common patent medications, including certain antidepressants and calcium channel blockers.

So I don’t think it’s unreasonable to hypothesize that maybe some sort of medication may have blocked CYP3A4 from clearing another medication from at least some of the women’s systems. And perhaps those lingering “space alien molecules” (as Dr. Wright calls them) played some part in the increased breast cancer risk.

Obviously, all I can do is play devil’s advocate here. But it seems to me that placing all the blame on a fruit that has always been considered to be a good source of valuable nutrients is a bit more of a stretch than, at the very least, considering the role of substances that really have no place in the human body.

If you’re concerned, by all means, go ahead and toss the grapefruit from your holiday fruit basket. There’s certainly no reason that you have to eat it. All I’m saying is that I wouldn’t expect giving it up to be the answer to your fears.

Sources:

“Grapefruit may raise breast cancer risk — study,” NutraIngredients (www.nutraingredients.com), 7/16/07

“Prospective study of grapefruit intake and risk of breast cancer in postmenopausal women: the Multiethnic Cohort Study,” British Journal of Cancer 2007; 97(3): 440-445

“Structures of cytochrome P450 3A4.” Trends Biochem Sci. 2005; 30(1): 5-7