We all intuitively appreciate that the foods we eat shape our thoughts, actions, emotions and behaviour. When you are feeling low, you reach for chocolate; when you are tired, you crave coffee. We all use food to soothe our moods and clear our heads without seeming to think much about it.

Yet the focus of most diets is on the way we look rather than the way we think. This is in part due to western society’s fascination with appearance, and medicine’s bias towards drugs and surgery. In fact, contemporary medicine often disregards the ways that our diet helps shape our cognitive health. Medical students are not trained in nutrition. And, for what it is worth, neither are scientists.

When I was a neuroscience student, I would marvel at how apparently simple substances such as sodium, potassium, magnesium and sugars determine whether our brain cells fire or not, grow or not, form new connections or wilt and die. It only became obvious in retrospect: the sodium, potassium, magnesium and sugars referenced were the same nutrients as in diet books or on food labels. To put it simply, the human brain is made of food.

In concrete terms, this means that whatever you just ate will be part of what you will think. For anyone lucky enough to use their brain for a living, this has immediate professional outcomes. In the long term, this affects every one of us, because food affects not just our moods and thoughts but also the way we age.

This has been the focus of my work as the associate director of the Alzheimer’s prevention clinic at the Weill Cornell medical college, New York City. For the last 15 years, we have been doing long-term studies to demonstrate the ways that diet prevents, delays or leads to cognitive conditions such as Alzheimer’s. The good news is that we have learned so much about what every one of us can do to optimise our brain health day to day.

Studies using next-generation imaging and genomic sequencing, both central to my work, have helped reveal that some foods such as vegetables, fruit, fish, wholegrains, nuts and seeds are neuro-protective. They not only shield the brain from harm, but also support cognitive fitness over the course of a lifetime.

It comes perhaps as no surprise that other foods such as fast food, fried food, excess fatty foods and refined sugar are downright harmful instead, slowing us down in general, making us feel sluggish and tired, while at the same time deeply increasing our risk of dementia.

These effects are particularly evident by looking at brain scans of people on different diets. For example, when we compared the scans of middle-aged people who had eaten a Mediterranean diet most of their lives with those of people of the same age who ate a western diet with processed food, processed meats, sweets and fizzy drinks, we saw the way the latter group’s brains had shrunk prematurely. Subsequent studies provided even more alarming evidence that people on the western diet had started developing Alzheimer’s plaques already in their 40s and 50s. These are all signs of accelerated ageing and increased risk of future dementia.

The bottom line is this: the more processed, packaged and refined foods that you consume on a regular basis, the higher your risk of cognitive decline further down the line.

In terms of the food that helps, there is no single miracle food or supplement that will keep us young, healthy and bright-eyed with a perfect memory (and beware anyone who tells you there is). There are, however, some important and urgent best practices that we need to get into people’s kitchens.

My top five brain foods:

• Fatty fish (salmon, mackerel, bluefish, sardines, anchovies) contains a blend of nutrients that are perfect for the brain, including omega-3 fats (a brain-must), choline (a B vitamin needed to make memories), vitamins B6 and B12 (needed to support the nervous system), minerals such as iron and magnesium (needed for healthy blood and tissues) and a good amount of protein. Research shows that consuming fish only once a week is associated with a 70% reduced risk of Alzheimer’s in old age. Of all the nutrients present in fish, the omega-3s seem to be particularly protective against dementia. For those who do not eat seafood, alternative sources of omega-3s include flax seeds, olive oil, almonds, avocados and other plant-based foods.

• Dark leafy greens (spinach, swiss chard, kale and all sort of greens) and cruciferous vegetables (broccoli, cauliflower, cabbage) are all full of vitamins, minerals, fibre and disease-fighting nutrients that are crucial for a healthy nervous system. Large-scale studies show that people who consume one or two servings of these vegetables every day experience fewer memory problems and cognitive decline than people who rarely eat greens. Simply eating a salad every day keeps your brain 11 years younger.

• Berries (especially blackberries, blueberries, strawberries, raspberries but also dark cherries, goji berries, mulberries) are packed with antioxidants that help keep memory sharp as you age. They are also a great source of fibre and glucose, the main energy source for the brain. They are sweet but have a low glycaemic index so they help regulate sugar levels.

• Extra virgin vegetable oils, especially olive oil and flaxseed oil. These are loaded with anti-ageing nutrients, such as omega-3s and vitamin E. Olive oil is also rich in monounsaturated fat, a kind of fat that is good for the heart. What is good for the heart is good for the brain.

• Complex carbohydrates, such as wholegrains, legumes and sweet potatoes, are packed with brain-supportive nutrients from protein to B vitamins to a bounty of antioxidants and minerals. They are also a good source of glucose combined with a high fibre content to stabilise blood sugar levels. The more fibre, the lower the food’s effects on insulin. As a result, these foods enhance your metabolism, support a healthy digestion and boost the immune system too.

• In addition, I always recommend drinking water as the main source of fluids. Even though water is not usually considered a food, it is definitely a major source of nutrition for our thirsty brains. More than 80% of the brain’s content is water. Every chemical reaction that takes place in the brain requires water, especially energy production. The brain is so sensitive to dehydration that even a minimal loss of water can cause symptoms such as brain fog, fatigue, dizziness, confusion and, more importantly, brain shrinkage. Why is this important? Because people often do not realise that the “water” they are drinking is not actually water. Purified water, fizzy water – all these beverages were stripped of the precious nutrients and natural electrolytes the brain needs to stay hydrated and work efficiently. The brain needs more than something wet; it needs the essential nutrients that real water carries with it.

These foods and nutrients are valuable at all stages of life. While the dietary needs of the rest of the body vary somewhat with age (more protein is needed when we are younger; more calcium and vitamin D when we are older), this does not seem to be the case for the brain. However, like every diet, the effects and efficacy of these foods will vary massively from individual to individual. My current research is looking at the differences between the ways that male and female brains need and metabolise specific nutrients. Of note in the research thus far: women’s brains seem to need more antioxidants, especially vitamins A, C and E (which can all be found in the plant-based foods listed above), as well as the anti-inflammatory omega-3s found in fish, nuts and seeds.

In the end, a brain-healthy diet optimises your capacity for keeping a healthy, sharp and active brain over a lifetime – while reducing the risk of developing age-related cognitive impairments and dementia. As individuals and as a society, we must refocus attention on how our food choices shape our brains, as surely as they shape the rest of us.

So, what are you going to have for dinner tonight?

Recipes for a brain-healthy day

Breakfast: Yoghurt parfait

Total time: 5 minutes

Ingredients (serves 2)
1 cup plain yoghurt
2 tablespoons toasted wheat germ
2 teaspoons ground flax seeds
½ cup blueberries
½ cup raspberries

Directions
In a bowl, mix together yoghurt, wheat germ and flax meal. Transfer to small jars. Top with blueberries and raspberries or your favourite fresh fruit. Feel free to sweeten with a little honey or maple syrup if needed.

Lunch: Vegetable soup served with brown rice

Prep: 20 minutes (less than 10 minutes if using an electric chopper)

Cook: 25 minutes

Ingredients (serves 6 or more)
450g broccoli, finely chopped
1 cup red cabbage, finely chopped
1 small onion, chopped
6 medium carrots, finely chopped
6 green onions, finely chopped
4 stalks of organic celery, finely chopped
4 cloves of garlic, finely chopped
2 cups sweet peas (frozen are good)
1 cup shelled edamame (eg soybeans)
3cm piece ginger root, grated
3 litres of vegetable broth (no added salt)
2 tablespoons extra virgin olive oil
Brewer’s yeast, 1 teaspoon per person

Directions
1. Put all the veg in a large pot. Add broth and bring to a boil. Cover and simmer for 20 minutes or until tender. (Personally, I prefer to cook these al dente as I like the consistency better than mushy vegetables and I believe it preserves the veggies’ ability to better deliver nutrients).

2. Turn off the heat, add olive oil and let cool for a few minutes.

3. Distribute in bowls. Sprinkle brewer’s yeast over the soup. Add brown rice for extra texture.

Dinner: Scandinavian salmon, served with a salad of mixed baby greens, broccoli sprouts and cherry tomatoes with a lemon vinaigrette dressing

Scandinavian salmon

Prep: 5 minutes

Cook: 15 minutes

Ingredients (serves 4)
½ cup of dry white wine
½ cup of water
4 salmon fillets (about 80g each)
1 tablespoon butter, softened
1 teaspoon chopped parsley
1 small garlic clove, minced
Salt to taste
4 teaspoons of salmon roe (optional)

Directions
Heat wine and water over medium high heat in a large non-stick pan (approx 5 minutes)

Slide salmon pieces into poaching liquid and dot with butter. Sprinkle with dried parsley, garlic, and salt to taste. Bring to a slow boil, reduce heat to medium and poach until salmon flesh is firm, about 10 minutes. Plate and sprinkle with salmon roe (optional).

Lemon vinaigrette dressing and salad

Ready in: 5 minutes

Ingredients (serves 4)
Juice of 1 lemon
4 tablespoons extra virgin olive oil
2 tablespoons balsamic vinegar
1 tablespoon maple syrup (optional)
Selection of baby greens, broccoli sprouts and cherry tomatoes

Directions
Put all ingredients into a small jar and mix to combine. Pour over the mixed salad.

• Lisa Mosconi is the author of Brain Food: How to Eat Smart and Sharpen Your Mind, published by Penguin Life at £14.99