I was told over the dinner table a hundred times when I was a kid that carrots can make you see in the dark, and loads of people swear orange juice will stave off a cold. But aficionados of the US internet newspaper the Huffington Post, and umpteen other blogs, are now mulling over a guide to food and drink options that purportedly boosts your brain, lowers your blood pressure or staves off cancer. A link to the Foodproof site brings up the "top 100 foods to improve your productivity".

A few of the suggestions might give pause for thought. Cake sounds unlikely to do much for the digestion, though I'm willing to believe it may be good for inducing sleep. More likely it will pile on the pounds. And diet soda as a "low-fat filling food"? Cheese and milk also reside in this category - but surely only the tasteless low-fat version.

On the whole, though, what these type of lists give you are intrinsically good foods, such as fish, chicken, watermelon, pineapple and almonds, which have been in some way, at some time, linked, however tenuously, to particular benefits, or protection against certain diseases. Eating these things is not proven to stop you getting cancer or improve your eyesight, but as part of a varied and balanced diet, they may do you some good.

The benefits we do know about generally come from groups of foods rather than single items, according to nutritionist Glenys Jones from the Human Nutrition Research unit in Cambridge, which advises the government on its anti-obesity strategy. "It is very hard to pin it down to one specific food. That's because we have lots of other things affecting us," she says. "It may be that the people eating more fruit and veg are the people who go to the doctor and get treatment earlier, or don't smoke." Exercise is an important factor too. "We won't find one miracle food that will compensate for an unhealthy lifestyle."

There has been much hype over cancer-preventing foods, says Ed Yong, health information manager at Cancer Research UK.

"In some cases there is scientific evidence to support this, but usually this comes from studies of small numbers of people or of cells grown in Petri dishes. Also, researchers may test molecules that are present in only small amounts in food, so you would have to eat an unmanageable amount of the original food to get the supposed benefits ... Tomatoes, green tea, pomegranates, blueberries and vitamin C have all been trumpeted as our dietary saviours over the years. But to date, none of this evidence is compelling enough to single out any of these as a 'superfood'."

So there you have it. Don't eat one or two of these foods, but a mixture of all of them. Maybe go steady on the cake though.