Well yes, food itself does, because you need nutrition for your brain to function properly! “Eat food, mostly plants” as the saying goes – that’s the long and the short of it. Anything you could say that has psychoactive effects is not considered food, on the whole, just according to basic safety definitions. If we have declared that something is safe to eat, then it is not going to be something that has an effect on the brain.
Sugar, for example, is often seen as affecting behaviour, but actually it doesn’t. You might get a pleasure reaction from it – it’s enjoyable to eat sugar – but it certainly doesn’t dramatically affect your behaviour. No study of children has ever found that it makes them act differently, although it does appear that if parents are told their children have had sugar, they will rate their behaviour as worse. The perception is entirely based on expectation, not on a real effect.
"No study of children has ever found that it makes them act differently, although it does appear that if parents are told their children have had sugar, they will rate their behaviour as worse."
There is some interest in tryptophan, which is present in some foods – things like cocoa – that has some psychoactive influence, and some people with bipolar disorder claim that they can control some elements of mania with it, but the jury’s out there. If you have tryptophan in large enough amounts, it can certainly be used clinically, but there’s no proof it’s available enough in foods to have an effect.
Fish oils are supposed to be 'brain food' but sadly there’s no evidence at all they influence brain function either – other than inasmuch as they are good for your heart and thus good for you generally. That is actually very important if you’re talking about brain function. It is utterly reliant on your heart, and if you’ve got cardiovascular problems your brain will be one of the first parts of the body that suffers. Seen that way round, then yes, healthy eating does help your brain, because it will help your heart. The same is true of exercise: it’s great for the brain, because it’s great for your heart.
As for drugs: it depends whether you talk about improving function, or affecting behaviour, which is slightly different. Amphetamines are the big one. Along with other related stimulants, that's what people prescribe in America for ADHD. It may go by different brand names, but essentially children are getting speed. A huge number of children are taking this, and of course college-age kids too, who are getting hooked on it because it makes them feel they can study better: but actually all it’s really doing is helping them stay awake so they can spend more time studying. There’s no evidence that it’s actually making their brain work better. Again, it’s about expectations. It leads you to believe you’re doing to be able to study more, but there’s no evidence whatsoever that you’ll do any better, in fact quite possibly you’ll do slightly less well.
"You give coffee to someone who’s completely drug-naive – who’s not used to it – and it shows no improvement at all."
Caffeine, too: people think it’s sharpening them up, improving their function, and in fact you can find studies that show it doing this. But the problem with all these studies – and my colleague Susan Michie has written about this – is that they’re all done with people who are in caffeine withdrawal. They take people, take them off caffeine for a couple of weeks, give them tests and find they’re functioning less well without caffeine than they do with it. But in fact these people are still in full-on withdrawal, which is actually awful. It takes months to get through caffeine withdrawal. So if you think a coffee is making you concentrate better, maybe it is, but that’s purely because the withdrawal was affecting your concentration adversely before you had it. You give coffee to someone who’s completely drug-naive – who’s not used to it – and it shows no improvement at all.
There are some studies going on with people with impaired function, for example old people with strokes, that suggest that stimulants can give small improvements there, although the jury is still out here – but if it is there, it would seem to be a non-linear improvement, so if your brain is already functioning pretty well, it doesn’t seem that easy to get any boost beyond that. If you have a young, healthy, educated, well-looked-after brain, on the whole it’s probably working flat out anyway, so it may just be that if your brain’s not somehow impaired, then it’s not possible to improve cognition as such.