Eating carbohydrates makes you stupid Cognition
The potato might not seem a likely source of brain power, but carbohydrates overall appear to improve memory and brain function. A study at the University of Toronto found that people who had the greatest percentage of carb calories in their diet performed best on tests. Don't overestimate the power of carbs, though, because for some people the reverse could be true: "If your blood glucose levels are erratic or difficult to control, eating simple carbohydrates such as sugary snacks and white bread, can make you feel sluggish and stupid," says registered nutritionist Carina Norris. "People with diabetes, 'pre-diabetes' or even those who are just particularly sensitive to feeling their sugar levels rising and falling, could be negatively affected."
Verdict: Whatever you eat, the important thing is to maintain your blood sugar levels. "Nutrients that release energy slowly will help keep your mind and body alert. So that includes carbs, especially complex carbohydrates such as oats, wholegrain bread and fruit," says Norris. "That said, healthy unsaturated fats and proteins also help ensure glucose levels in your blood are kept steady, helping you to avoid an energy/brain slump."
You can learn a new language during sleep
It's a nice idea. You put on a foreign-language CD, nod off and – hey presto! – several nights later you're almost fluent in Mandarin. And with only one third of Brits being bilingual, this kind of nocturnal training would provide a huge boost to our education system, not to mention international political relations. Unfortunately, though, there is no evidence to back up this idea. According to the National Sleep Foundation, you cannot simply add information to your brain while you sleep. What's more, that CD could even make it harder to learn a language normally if it disturbs your slumber because you'll be less able to concentrate when you're awake.
Verdict: Buy a foreign-language CD by all means, but stick to sleeping at night and learning by day. And take comfort in the fact that learning a new language is an excellent way to give your brain a workout, according to a study at University College London.
Constant repetition is key to memorising facts
Mindlessly repeating a phrase or number isn't necessarily the best way to ensure that morsel of information remains embedded in your brain. In fact, several studies have shown that spaced repetition, leaving a day between reviewing some text, for example, is the best way to ensure it stays in your long-term memory.
Verdict: Write foreign words, great quotes or birthdays you'd like to remember on a piece of paper and put it on the fridge so you can read it once a day. After about five days, the information should have sunk in.
You can't grow new brain cells
Scientists once thought that our brains were in peak condition in our twenties. From then on it was all downhill – neurons were lost, never to be found again. But now they know different. Parts of the brain such as the hippocampus where memories are made and the olfactory bulb, which deals with your sense of smell, make new brain cells regularly. "We no longer believe that there is a dramatic loss of neurons as people age, but there are other structural, neurochemical and physiological changes that do occur in the older brain," says neuroscientist and memory expert Dr Adam Gazzaley, of the University of California.
Verdict: Your brain is capable of more than you realise, so give it regular workouts (see below).
Crosswords are the best way to keep your mind sharp
Not if you've been doing that same cryptic crossword for years. Once you've figured out how something works, it becomes easier. "Crossword puzzles are probably not the number one thing to do to keep your mind sharp as you age, although they are likely not to be harmful," says Dr Gazzaley. "I'd recommend engaging in activities that really challenge your mind, or as I like to think of it, 'stepping out of your comfort zone'. Travel, social events and learning a new language or musical instrument are good things to try."
Verdict: Keep doing crosswords but also try your hand at a simple French or Spanish word game to keep your grey matter fresh (www.languagegames.org has some good ones). Then take a holiday and put your new language skills to the test.
You only use 10% of your brain
What's the other 90% for, then? Good question. This statement is misused – it's true we may only use a small part of our brain for each particular task and so at any one time the rest of the brain could be 'out of use', but it would be impossible to function if you lost 90% of your grey matter.
Verdict: Put this myth out of your mind and clear some room for some useful information.
As you get older, your memory gives out
Your muscles are weaker, your joints hurt and your hair is turning grey, so surely your brain will deteriorate as drastically? Not as much as you'd expect: "While it is true that memory will decline to some degree with normal ageing, severe changes in cognition (memory, attention, multitasking, planning, organisation, language...) are associated with diseases, such as Alzheimer's," says Dr Gazzaley. "Other parts of cognition, such as vocabulary and knowledge of the world (semantic memory) are better preserved. From our research using functional brain imaging we've found that older adults exhibit a decrease in the ability to effectively filter distracting, irrelevant information and this impacts their memory performance (http://gazzaleylab.ucsf.edu)."
Verdict: Losing your memory doesn't have to be a part of getting older. To maximise your ability to recall all-important birthdays, eat well, exercise your brain, and keep distractions such as music or TV off while learning new information. And sign up for classes: a study published in Neurology found that people with higher levels of education were less likely to display as severe symptoms of Alzheimer's as those who didn't.