You are what you eat, so if your diet is poor, you may be dealing with stress, anxiety or even depression. Dietitian Brooke Longfield explains what it really means to have food on the brain.
Most of us can recall a time (or three!) when food, whether it was chocolate, cake or even coffee, improved our mood. When we’re under stress or feeling blue, a sweet treat peps us up, at least temporarily, and this is largely thanks to our brain chemicals. Certain foods excite the brain, lifting its levels of feel- good neurotransmitters, such as serotonin, a chemical that experts link to elevated mood.
Still, we know that a diet packed with fatty, sugary foods certainly doesn’t keep us feeling good, so what’s the difference between these short-term pleasures and lifelong mental wellbeing? Well, we’re actually starting to find out.
Researchers have only recently (over the past six years) begun to explore the way food can affect our emotions. Leading the way is Felice Jacka, PhD, Principal Research Fellow in the School of Medicine at Victoria’s Deakin University and President of the International Society for Nutritional Psychiatry Research.
“We’re only just beginning to understand that depression’s underpinnings involve multiple systems within the body, most notably the immune system and the gut, and that these systems are strongly influenced by what we eat,” explains Jacka.
In other words, our food may be a cause of stress, anxiety and depression, but it might also help treat such conditions, potentially reducing our reliance on drugs such as antidepressants.
The mental rewardsof eating well
In 2010, Jacka studied the diets of more than 1000 Australian women aged from 20 to 93 to see whether she could establish a relationship between food and poor mood. Women who ate well by following a wholesome diet of fruit and vegies, meat, fish and wholegrain foods (such as grainy bread and brown rice) experienced less anxiety and depression. In direct contrast, women who ate large amounts of processed, fried and sugary foods (such as cakes, biscuits, takeaway and even alcohol) were more likely to suffer from mood disorders.
“In short, a healthy diet appears to protect against depression in particular,” says Jacka, “whereas an unhealthy diet increases the risk of these disorders.”
Similar findings emerged from a 2011 Norwegian study of more than 5700 adults. Subjects who had a better-quality diet were less likely to be depressed or anxious. (This large study also took variables such as age, physical-activity levels, income and alcohol consumption into consideration.)
“The make-up of a healthy diet differs depending on where you live,” adds Jacka, “but the diets in these studies have a common core: more fruit and vegetables, and less junk food.”
Food for thought
So what is it about our modern diet that’s making us not only fatter, but also miserable, stressed and anxious? “We have good reason to believe that foods high in saturated fat or refined carbohydrates, or both, have a very negative impact on our brains and immune systems,” explains Jacka. These fatty, sugary foods trigger systemic inflammation — an ongoing low-level immune response throughout the body — whereas fruit, vegetables and omega-3 fats work against it.
Unhealthy lifestyle factors, such as stress, smoking and obesity, also provoke this inflammation, which is a risk factor for several illnesses of both the body and mind. Experts now link systemic inflammation with brain changes that can cause major depression.
The soothing sea-change diet
The good news is that one easy-to-follow, sustainable eating plan has proved to have the reverse effect, reducing inflammation and strengthening immunity. Studies also show that its health-boosting foods can improve mood.
As you may have guessed, it’s the Mediterranean diet. This way of eating focuses on vegetables, fruit, nuts, legumes (which include beans, lentils and chickpeas), oily fish and olive oil, along with only small amounts of both red meat and dairy products.
An ongoing 1999 European study, which continues to track the dietary habits of more than 10,000 people, strongly suggests that an eating plan comprised of Mediterranean foods can help prevent depression. When people ate Med-style meals for a 2014 study at Melbourne’s Swinburne University of Technology, they felt a lot more alert and content after just 10 days on the plan.
One of the Mediterranean diet’s distinguishing features is that it provides little red meat. In one of Jacka’s studies, women who ate either less or more than 500g of cooked red meat each week (the recommended intake) were twice as likely to suffer from depression or anxiety compared with those who ate the recommended 500g.
Developing the antidepression diet
In the past, most of the research on the connection between diet and mental health has been in the form of observational studies. This means researchers simply record what people eat without intervening in their diets. In an exciting step forward, Jacka is currently running the very first intervention study, tweaking the diets of people who have major depression and eat a poor diet.
“This intervention diet is a modified Mediterranean diet that includes plenty of fruit and vegetables as well as legumes, nuts, olive oil and vinegar,” says Jacka. “It also provides slightly more red meat than a traditional Med-style diet does.
“This very important study is the first worldwide attempt to answer this question: ‘If I improve my diet, will my depression also improve?’ — and we hope to have the results before the end of this year,“ says Jacka. “If we discover that having a better diet improves the mental health of people with depression, we’ll have a whole new way of thinking about how to treat it, and that’s exciting.”
Indeed, the fascinating global work of Jacka and her colleagues is giving us a new understanding of the ways in which food affects the brain. Some foods can have a positive impact on our state of mind; others do the opposite.
Help! I want sugar… I need coffee… I crave chocolate!
Whichever food you crave when you’re feeling flat or stressed, relying on sugary treats or coffee to power through the day is a risky move. When you overindulge in such foods and drinks, their stimulants flood your brain, making it less sensitive to their pleasurable effects. This creates a vicious cycle: You need to consume more and more to achieve that same boost in mood.
When you down a coffee, for example, your body secretes the hormone adrenaline. In response, your brain suppresses the adrenaline’s effects, driving you to seek out more coffee.
Remember: The more you rely on these sorts of quick fixes to make yourself feel good, the more of them you need, and the less effective they become at helping manage your mood.
The brain is about 60 per cent fat, so our grey matter is strongly influenced by what we eat.
Saturated fat, for example, the unhealthy fat in many fried and processed foods, actually makes brain-cell membranes less flexible. Tellingly, a 2013 Australian study shows that depressed people’s brains are more rigid, making it harder for them to learn, remember and pick up new motor skills. As Jacka says, the concept of brain plasticity is just one of the biological factors in depression.
A whole third of the brain’s fat (20 per cent of that 60 per cent) is made up of the essential fatty acids omega-3 and omega-6. These fats are essential because the body can’t make them, so we have to eat foods rich in healthy fats, such as oily fish and olive oil, to support brain function.
Omega-3 fats are especially important in battling depressive symptoms because they strengthen our neural connections, ensuring smooth communication among brain cells.
In a 2002 study from New Zealand, people who ate the most fish reported improvements in mood and overall mental health. Other research reveals lower rates of depression in countries such as Norway and Japan, where most people have a diet full of oily fish.
Unfortunately, the Aussie diet is generally low in omega-3 fats, particularly when compared with the Mediterranean way of eating. With its healthy amounts of fish, olive oil and nuts, the Med diet has many aspects worth adopting, not only for better brain function, but also for good heart health.
Your state of mind doesn’t begin and end with your head. Think of the way unwelcome news causes that sinking feeling in the pit of your stomach, or of how feeling nervous brings on the butterflies. Your gut can clearly sense stress and even fear, so what’s behind this intestinal intelligence?
For starters, the digestive tract is home to millions of nerve cells that constantly communicate with the brain by sending messages back and forth. What’s more, gut bacteria can make chemicals that promote feelings of either calm or stress, depending on the foods we’ve eaten. In fact, these bacteria produce about 95 per cent of the body’s serotonin, the ‘happiness hormone’ that so many drugs are designed to elevate.
So what kinds of food keep our gut bacteria healthy? “It’s a simple message that comes down to consuming plenty of fibre,” says Jacka. “If you eat lots of fruit, veg, whole grains and legumes, and stay away from processed foods that are high in sugar and fat, your gut microbes will be happy.”
Scientists are also discovering that probiotics, substances that encourage the growth of ‘good’ gut bacteria, may help lift mood. When people in a 2011 US study took probiotics for just one month, they experienced less anxiety and depression. Yoghurt is a source of probiotics, but “fermented foods and vinegar are also good for gut health”, adds Jacka.
Add these foods to your weekly menu
Of course, enjoying a few bites of one or two foods can’t lead to long-term happiness — food is fuel, not a magic bullet. Still, studies show that some nutrients, including B-group vitamins, zinc, omega-3 fats, folate, magnesium and selenium, can help lift mood.
To create a well-balanced diet, focus on your foods as a whole — eat more fruit, vegetables and whole grains, along with other natural foods, and cut back on highly processed junk food and alcohol. The following foods play vital roles in supporting optimal physical and mental health, so make sure they feature regularly on your weekly menu.
Oily fish: Boost your levels of healthy omega-3 fats by putting oily fish, such as fresh or canned salmon, tuna and sardines, on the menu two to three times a week.
Whole grains: Replace refined and processed cereals, biscuits and fluffy white bread with high-fibre carbohydrates, such as brown rice, soy-linseed bread, rolled oats and quinoa.
Nuts: Nibble on two to three Brazil nuts (and score all your selenium for the day) or snack on a small handful of unsalted raw or roasted walnuts, cashews or almonds.
Berries: Pop fresh or frozen berries into smoothies or onto yoghurt. Juicy blueberries and strawberries are bursting with immunity-boosting vitamin C.
Leafy green veg: Add more filling fibre to meals with spinach, Asian greens, broccoli and Brussels sprouts, all of which are rich in folate. Toss them into salads and stir-fries with a splash of extra-virgin olive oil.
Baked beans: Start your day with a healthy breakfast of baked beans on wholegrain toast to boost your intakes of fibre and magnesium. Opt for reduced-salt or no-added-salt beans; they taste as good as the regular variety.
Legumes: Think of tasty ways to add more chickpeas, lentils and beans to lunches and dinners. These pulses are nutritional powerhouses full of B-group vitamins, folate, magnesium and fibre.
Lean red meat: Top up your stores of iron, zinc and vitamin B12 with a 100 to 120g portion of (raw) red meat, which is about the size of your palm, three to four times a week.
Yoghurt: Promote the growth of your ‘good’ gut bacteria with a probiotic-rich yoghurt. Look for plain and unsweetened varieties, and add natural sweetness with chopped fresh fruit.
Our current understanding of the complex interaction between food and mood is incomplete because research into the link is still in its early stages — we can’t yet attribute the association to simple cause and effect.
Despite this, Jacka is optimistic that the emerging evidence will result in diet-based approaches becoming leading therapies for anxiety and depression. “My hope is that dietary intervention becomes a mainstay treatment within a couple of years. But in the meantime, eating healthy, unprocessed foods is a good preventive strategy to improve overall health and wellbeing.”