It's a cruel fact of life: our brains shrink as we get older. Many experts reckon that the average brain decrease 2% during each decade of adulthood.

So as a man in his early forties, I've lost just over 4% of my brain. By the time I'm 60, I'll have lost 8%. And if I get to 80, I'll have lost a whopping 12% of my brain. I feel dizzy even writing it down.

Worse still, the neurotransmitters in your brain begin to go on the blink as you get older. This means that messages travel a lot more slowly through the tissues of your brain. Poorer circulation also means that your brain doesn't receive vital nutrients as efficiently. The result is that your brain cells don't function as well as they used to.

So far, so bad.

But did you know that, despite all this, memory lapses and confusion are NOT an inevitable result of ageing? Or that there is a diet that could help your brain function improve?

Why your brain should be fat

It might surprise you to learn that the human brain is 60% fat. To keep its complex networks of fibres working properly, the brain needs good supplies certain types of fats, known as omega-3 fatty acids. Found in fish, animal meat and eggs, these fats are essential if you want to keep your brain healthy. They can also help you ward off depression, memory loss, aggression and learning difficulties.

A low-fat brain means that millions of vital fatty brain connectors begin to malfunction. As Dr Andrew McCulloch, chief executive of the Mental Health Foundation, says: "we are only just beginning to understand how the brain as an organ is influenced by the nutrients it derives from the foods we eat, and how diets have an impact on our mental health."

The problem is, we just aren't getting enough of the good natural stuff these days. We eat two thirds less fish than 30 years ago. We eat fewer vegetables and, when we do, they've often travelled for thousands of miles, coated in pesticides.

Some experts believe the decline in our diet has opened the doors for dozens of mental health problems. Poor diet could has be linked to depression, schizophrenia, and attention deficit hyperactivity disorder. Now clinical trials are underway to find out whether omega-3 supplements could reduce problems such as depression, dementia and schizophrenia.

There are other fats your ageing brain needs, too…

3 ways to give your brain a boost

* Phosphatidylserine (PS) helps your brain cells do their jobs properly. You can give your PS levels a boost with supplements like soybean lecithin.

* Acetyl-L-Carnitine (ALC) can improve your mood and memory while protecting the nerve cells in your brain. You can ask for these supplements at your local health store.

* Coensyme Q10 gives your brain energy, while also protecting your brain from the side-effects of that energy production: dangerous free radicals. Domestically farmed meat doesn't have enough of this fat, so you'll need daily supplements instead.

A fatty brain is good for your mood, memory and mental health. So try and eat high quality protein every day. Ideally, that means good organic meats and fish. Or you can top yourself up with the supplements I mention above.