As a society, we are used to the idea that we feed our bodies, and that our diet shapes our waistlines. But many of us forget that the same diet also feeds our brains, and that the food we give our brains shapes our thoughts and actions. I invested many years formally studying neuroscience and neurology, and have spent many more years as a scientist in those fields. Back when I started, most of my time was spent with medical journals. But 15 years into my research, much of my time is spent with cookbooks.

These books are essential to contemporary brain science. The recipes become food, and that food shapes our brains just as surely as it builds our bodies. Day after day, the foods we eat are broken down into nutrients, taken into the bloodstream and carried up into the brain. Once there, they replenish depleted storage, activate cellular reactions and become the very fabric of our brains.

The brain is the hungriest organ in the body, consuming more than 20% of your body’s total energy haul. At the same time, our brain cells are irreplaceable. Unlike the rest of the body, where cells are continuously replaced, the vast majority of brain cells stay with us for our entire lives – which means they are in need of extra care and nourishment.

Next-generation medical imaging and genomic sequencing studies, including work from my lab at the Alzheimer’s Prevention Clinic at Weill Cornell Medical College, New York, have helped us understand that some foods play a neuro-protective role, shielding the brain from harm. It’s no surprise that, conversely, other foods are harmful for the brain, slowing us down and increasing the risk of cognitive decline. So, what does this mean for your daily menu in terms of optimising for brain health? It means lots of the following:

Fatty acids

A specific kind of fats called polyunsaturated long-chain fatty acids, such as the famous omega-3s. Fatty fish, such as salmon, mackerel, anchovies and sardines, is the best natural source of the only kind of fat the brain needs throughout a lifetime. Where fish isn’t an option, flax and chia seeds are good alternatives.

Glucose

A specific kind of carbohydrate called glucose. Glucose is the only energy source for the brain, so it’s crucial that the brain gets enough of it. Foods that are naturally rich in glucose and that at the same time contain enough fibre to stabilise your blood-sugar levels are beetroot, kiwi fruit, whole grains, sweet potatoes, onions and spring onions. Raw honey, maple syrup and coconut sugar are also good sources.

Vitamins and minerals

All sorts of vitamins and minerals, especially those with antioxidant effects such as vitamin A, vitamin C, vitamin E and selenium – but also iron, copper and zinc. Fruit and vegetables are the best natural source of these: go for berries, oranges, grapefruit and apples, which are sweet but have a low glycemic index. Leafy green or cruciferous vegetables (broccoli, cabbage, spinach, kale, dandelion greens), as well as other vegetables such as onions, carrots, tomatoes or squash are also full of vitamins, minerals, fibre and disease-fighting nutrients that are needed for a healthy nervous system. Make every meal a rainbow.

Extra-virgin olive oil

Last but not least, extra-virgin olive oil is a brain-must, as it is loaded with anti-ageing nutrients such as omega-3s and vitamin E. Vitamin E is particularly important to protect ourselves against dementia. Large studies in the US and Europe have found that elderly people who consumed more than 16mg a day of vitamin E had a 67% lower risk of developing dementia compared with those who consumed little to none. Dementia risk was further reduced by taking vitamin E in combination with vitamin C. Both these vitamins protect brain cells from the harmful effects of toxins and free radicals, while vitamin E has the added benefit of increasing oxygen delivery to the brain.

Now for the no-nos

At the same time, some foods are a big no-no. These include fast food, fried food such as fish and chips, fatty foods such as red meat, pork and high-fat dairy, and, most of all, processed foods: baked goods loaded with trans fats and refined sugar such as cakes, biscuits, crisps, ready meals and frozen pizza, as well as many snacks. Then there are all of the margarines and commercial cheeses, along with other spreadable or “creamy” products. Ditto for processed meats such as salami, bologna and frankfurters. The more of these processed foods you consume on a regular basis, the higher your risk of cognitive decline and dementia. Across multiple studies, people who consumed as little as 2g a day of trans fats had twice the risk of those who ate less than 2g. It’s disheartening to discover that most people in those studies ate at least 2g a day, with the majority of participants eating more than double that dose on a regular basis.

Genes aren’t destiny

Beyond thoughts, moods and memory, diet plays a clear and determinant role in brain ageing and the risk of developing Alzheimer’s, the most common form of dementia, which affects 46 million people worldwide (and is projected to affect 130 million by the year 2050). When I started working in the field, most people understood Alzheimer’s as the inevitable outcome of bad genes, ageing or both. In 2018, it is clear that genes aren’t destiny, and ageing isn’t a linear path to unavoidable dementia.

Most people don’t realise that less than 1% of the Alzheimer’s population develops the disease due to a genetic mutation. These mutations are very rare and so is their outcome: an early-onset and particularly aggressive form of Alzheimer’s that develops when people are in their 30s, 40s and 50s. But the majority of the population doesn’t carry those mutations, and so the real risk for the rest of us is simply not determined by our genes.

While the blueprints for an individual brain do depend in part on DNA, recent discoveries have led neuroscientists to understand that genes load the gun, but lifestyle pulls the trigger. In fact, there is consensus among scientists that at least one third of all Alzheimer’s cases could be prevented by improving our lifestyle, from ameliorating cardiovascular fitness, to keeping our brains intellectually stimulated and, of course, eating better.

The human brain has evolved over millions of years to absorb specific nutrients and to function on a relatively specific diet. Now our society must also evolve, to attend to what our brains need to be fed. On a personal level, that’s for anyone pursuing a long life and a youthful brain to enjoy it. On a global level, that is millions of people who will have a chance to age gracefully with their mental capacities intact.

Brain Food: How to Eat Smart and Sharpen Your Mind by Lisa Mosconi is published by Penguin Life.