Common knowledge is often based on good science. It is thus reassuring that most of our fellow citizens accept the well-researched idea that diet influences health.

Discussions of exactly what diet produces what health effect can get cantankerous, though, so two recent publications are welcome additions to the debate.

It’s been known for some time that calorie-restricted diets prolong life and lead to fewer cancers. Researchers from MIT now tell us why this is so (Nature 458 [9 April 2009], 725–731).

If the cellular enzyme phosphatidylinositol-3-kinase is highly active, then dietary restriction does not provide protection from cancer formation. PI3K is involved in insulin-mediated signaling, so this is the likely target for nutrient restriction’s beneficial effects.

Best of all, therapeutic or preventative strategies might be able to take advantage of this pathway without the unappealing prospect of actually getting people to eat less.

The other discovery comes from the Medical College of Georgia (Cancer Research 69 [1 April 2009], 2826–2832). Thangaraju et al. offer a molecular explanation of why high fiber diets provide protection from colon cancer.

It turns out that bacteria in the colon eat roughage and produce the simple organic molecule butyrate. The butyrate in turn activates the uncolorfully named receptor GPR109A, which triggers programmed cell death (apoptosis). Voila, cancer cell expires.

So the overall lesson is to cut calories and eat more fiber. You’ve probably already heard this in the common knowledge category, but now it is buttressed by science.

But I’ve always wondered: if you truly are what you eat, why would anybody eat nuts?