Eat more chocolate, take more naps and gorge on dandelion leaves trends now

In yesterday's Daily Mail, mind specialist Dr Richard Restak explored the importance of keeping memories alive in order to ward off the threat of dementia in old age. 

Here, in a second extract from his new book, The Complete Guide To Memory, he describes the ways you can boost your memory – and your chances of keeping Alzheimer's at bay.

Memory is the key to maintaining mental sharpness and speed of thought. 

A well-functioning memory virtually rules out degenerative brain diseases such as Alzheimer's and its dementia variants.

But memory is fragile; it needs nourishing. Here are some of the basic things you can do to maintain and even improve your memory.

Take a siesta to recharge your recollection 

Sleep is vital to maintaining your memory. 

During deep sleep, the synapses (structures that pass signals through the brain) transfer information from the hippocampus (the seahorse-shaped part of the brain that is the entry point for the formation of memory), along nerve pathways to the cortex, which is the outer layer of the brain where consolidation occurs – and short-term memory becomes long-term memory.

But short siestas, naps, snoozes, 40 winks – call them what you will – in the afternoon are also really good for you. 

A nap provides a great recharge and supercharge of your memory. I highly recommend it.

So, if you have been studying for an exam or an office presentation and would like to put what you know to the test, set aside time for a nap. 

Your ability to retrieve the necessary information will miraculously improve.

This is because sleep improves the quality of all types of memory but is especially beneficial to sensory information that is encoded – the process by which memories are stored in the brain – at a lower initial strength. 

The weaker the memory while awake, the greater the consolidation during sleep – and the more resilient the memory is to subsequent deterioration.

Naps lasting anywhere from 30 to 90 minutes have been shown to increase recall. In one study, participants were given a list of paired words to remember, then offered the choice of either napping or watching a television documentary. 

Those who napped showed a 21 per cent better recall than those who watched the documentary.

Studies also show that naps can compensate for poor night-time sleep. 

When nocturnal sleep is curtailed for some reason, a mid-afternoon nap reliably boosts memory performance, especially in adolescents and young adults.

So is napping advisable for you?

Not everyone finds it easy to fall asleep during the hours best suited for naps, which is between 1pm and 4pm, when your body clock goes into a natural dip. 

If you fit into this category, don't despair.

Lie down in a darkened, quiet room with no particular intention to fall asleep. 

The sooner after lunch the better, to take advantage of the natural drowsiness you feel after eating. 

After a few days of this, your brain will gradually shift into sleep mode based on similarities to night-time sleep.

If, when you wake up, you feel groggy or sleep-deprived, you have slept too long and will have a problem getting to sleep later that night. 

Over the years, I've learned to nap for exactly 30 minutes – but I know people who have trained themselves to drop off for just 15 minutes and then awaken refreshed and reinvigorated.

Don't hold back on the chocolate

The good news for chocoholics is that, according to research, dark chocolate enhances episodic memory – the memory of everyday events, including contextual information such as times, location and the emotions you experienced – especially in healthy young adults. 

One particular ingredient, cocoa flavonoids, improves memory function, probably via increased blood flow to the brain.

It works for older people too. Neuroscientists like me can now home in on a region of the hippocampus, the dentate gyrus, as the part of the brain responsible for memory improvement. With ageing, it declines in size and function.

In tests on volunteers aged 52 to 69, those who were put on a diet with a higher cocoa flavonoid content were found by MRI scanning and cognitive testing to have a much more active dentate gyrus, meaning that they were not losing their memories.

Read a good book (but fiction only)

Reading novels provides an especially helpful exercise in working memory. Why is fiction preferred over non-fiction? 

Because non-fiction works are often organised in ways that allow the reader to skip around according to personal interests and previous familiarity with the subject.

Fiction, on the other hand, requires the reader to proceed from beginning to end while retaining in working memory the various characters and plot developments. 

The fiction reader must remember when a character was first encountered along with all of their back story. 

Each time that character reappears, the reader, by means of working memory, has to recall the character's past actions, motivations and so on.

Incidentally, over my years as a neurologist and neuropsychiatrist I have noticed that one of the first signs of early dementia is that the person stops reading fiction. 

They can no longer keep the characters or plot development in their working memory.

Drink less booze - ideally none at all

Published opinions on alcohol consumption seem to vary from month to month, even day to day. 

For example, a study conducted by the French Institute of Health and Medical Research in 2018 found that a cohort of 9,087 people who didn't drink alcohol showed a higher risk of dementia compared to those who drank moderately.

So what does one conclude from something like that? Everybody should take up moderate drinking and outlive their teetotal neighbours? That doesn't make sense.

I have great difficulty thinking of alcohol – a known, albeit weak, killer of brain cells – as beneficial, or even just a neutral factor in the development of dementia. 

I've searched the world of literature on mild to moderate alcoholic consumption and the news is not supportive of continued drinking, no matter how small the amount.

To my knowledge, no evidence exists that alcohol impairs only memory while leaving other cognitive processes unscathed. 

Rather, it exerts harmful effects on cognition in general, resulting, in the final stages, in dementia.

In a recent study of more than a million dementia cases in France, excessive alcohol intake was found to be one of the greatest risk factors, even worse than high blood pressure and diabetes.

In a British study of 25,000

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