AP headlines on diet not preventing cancer don't match corresponding story

Jul 18, 2007

As regular readers of this blog may have noted, I have an issue with misleading health headlines. Last night’s report titled: “No Cancer Benefit Found In Mega-Veggie-Diet Study” (WSJ) or “No Cancer Shield found in Fruit and Vegetable Diet” (NYtimes) is a perfect example of how a headline doesn’t tell the actual story.

Perspective from headline: eating lots of vegetables has no impact on any kind of cancer.

Better headline from blog posting reporting same article: “Fruit, Vegetables Don’t Prevent Breast Cancer Recurrence”

Now lets go into the real story:

Its tough to make people eat their vegetables and cut fat out of their diet. Although these people recorded ~10% fewer fat calories (or ~2-3% fewer overall) and significantly more fiber, there was no weight loss– which leads me to believe they didn’t actually change their diet much or food logs may not be telling the real story (as is the case with radio diary ratings)
This diet didn’t improve recurrence of breast cancer. This may not be surprising if you consider that diets high in fiber seem to reduce primary incidence of cancer, and you theoretically would expect colon cancer more so than breast cancer (discussed below)
Recurrence of cancer is very different from de novo development of disease

So lets talk about cancer biology.

Adult cancers generally occur due to a series of uncorrected cellular mutations accumulating over time in the same cell

“Recurrence” of cancer doesn’t mean that the cancer developed again. It means that although most of the cancerous cells were removed (and potentially incapacitated or held in check through the immune system), some were not, and those found a new way to multiply unchecked

Breast cancer appears to be mediated by hormones.

There is a hypothesis that reduction in hormone therapy has caused significant reduction in breast cancer incidence.
A corollary of that theory would indicate that the fattening of the population generates more of the enzyme aromatase (in the fat tissue), which increases body levels of estrogen– also raising breast cancer rates (careful, this link is pretty dense)

Nutritional approaches tend to either shore up deficiencies (i.e. immune function) or reduce cellular damage (through specific enzymes/proteins or through free radical reduction). These are control mechanisms to reduce/eliminate damaged pre-cancerous cells, but are less effective with a cell that has mutated enough to be cancerous

Dietary fiber appears to be theoretically most effective in colon cancer. One reason is that the bulk movement of fiber literally scrapes off cells and dilutes carcinogens– reducing the chance that cancerous cells form and persist. However, it isn’t clear which component of eating a lot of vegetables prevents colon cancer– but there is evidence that the top quartile of vegetable eaters does significantly better than the rest.

Takeaways:

Nutritional approaches to cancer are likely most effective in primary prevention over the course of a lifetime than secondary prevention (once someone has had a disease) over a few years

Breast cancer solutions likely track back to controlling hormone levels–diet and weight loss may be secondary parts of this– but the issue is an accumulation of change over time. Dietary intervention late in life may be the equivalent of turning the Titanic

People don’t really change their habits just because they are told to do so. Adherence to recommendations and programmatic change management haven’t entered the medical space to any significant degree