Les Jones

Science > Scientists Now Less Sure That Diet Prevents Cancer

Experts don't know if diet prevents cancer:

Michelson is one of a growing number of people who are turning to diets for protection from cancer. Cancer patients, doctors say, almost always ask what to eat to reduce their chances of dying. Diet messages are everywhere: The National Cancer Institute has an "Eat 5 to 9 a Day for Better Health" program, referring to servings of fruits and vegetables, and the Prostate Cancer Foundation has a detailed anti-cancer diet.

Yet scientists say they really do not know whether dietary changes make a difference. It is turning out to be much more difficult than anyone expected to discover if diet affects cancer risk.

I said earlier that I was now less convinced than when I was younger that science could guide policy. This sort of thing is a good example of why that is, though to be fair nutritional science is one of the worst case scenarios, since it's mostly based on long term statistics.

The best science - the stuff that gives science its reputation and authority - is based on repeatable, empirical studies where all conditions can be controlled and one variable can be changed. Want to know what's causing global warming? Why, that's theoretically easy - just take a statistically valid number of Earths, then vary the CO2 levels in one test set, then set up another solar system and vary the solar output in that test set, etc.

Except that you can't do that because we only have one Earth. Therefore the question of what's causing global warming is hard to answer because we have to fall back to ice cores, computer models, and other less-satisfying surrogates.