One in five Australians will be affected by depression at some stage in their lives. Karen Fittall speaks with the experts to discover how food can make a significant difference to this growing mental health issue.
You are what you eat – or so the saying goes. This is certainly evident in the physical sense, with obesity and heart disease being obvious indicators, but is it possible for your diet to influence your mental health as well, either positively or negatively? According to many experts – including Beyondblue’s Deputy CEO, psychologist Dr Nicole Highet – the answer is a very definite “yes”.
“There are two ways of looking at how diet plays a role in depression”, says Dr Highet. “First, there’s the preventative effect. While some people are genetically predisposed to depression, we know that being fit and healthy is going to give you the best chance of reducing the incidence of mental health problems. In terms of recovery, a healthy diet is able to provide a lot of good nutrients and vitamins that will increase the overall chance of recovery.”
Professor Michael Berk, Chair of Psychiatry for Barwon Health and The Geelong Clinic at the University of Melbourne, has published more than 200 papers on mood disorders and says the evidence shows there is a clear link between overall food intake and depression. “In fact”, he adds, “recent data suggests that people with the healthiest diets – ones that contain plenty of fruit and vegetables, wholegrains, low-fat dairy and lean meats – have the lowest risk of experiencing depression”.
The research Professor Berk refers to includes a 2010 University of Melbourne study which found that a diet high in processed foods and ‘junk’ puts women at an increased risk of depression and anxiety. Conversely, the study found that women who eat a ‘healthy’ diet are less likely to suffer either condition. Lead author of the study, Dr Felice Jacka says: “It seems that the diet that helps reduce your risk for heart and other medical diseases may reduce your risk for depression and anxiety, too”.
The nutrients that make a difference
It’s not only overall food intake which has been linked with depression. Professor Berk explains, “there is a lot of evidence surrounding a few individual nutrients and their role in protecting against depression”. The nutrients, he explains, are omega-3, folate, zinc and magnesium.
The long-chain omega-3 fatty acids found in oily fish provide a protective effect against depression. Dietitian Dr Dianne Volker, who released a study in 2006 which confirmed a link between high intake of long-chain omega-3 fatty acids (from fish) and an alleviation of depression, explains: “Long-chain omega-3s have an anti-inflammatory action – they inhibit the action of proteins produced by the immune system called pro-inflammatory cytokines, and high levels of these proteins are associated with an increased risk of depression”. Dr Volker adds that, “Omega-3s are also involved in maintaining levels of important neurotransmitters in the brain.”
How much? Dr Volker says the average Australian should consume 500mg of long-chain omega-3 fatty acids a day (or 3500mg a week). This translates to eating oily fish three times a week or using supplements to give your levels a ‘top up’. While it may sound like a lot, it’s not as hard as you think to meet your requirements – just 100g canned tuna contains 600mg omega-3.
Studies have found that people with the lowest folate levels may have as much as a 67 per cent increased risk of depression, say Japanese scientists. Conversely, those with the highest levels are 50 per cent less likely to have depressive symptoms. “We also know”, says Dr Highet, “that folate can help increase the effectiveness of antidepressant medication”. Folate can be found in some vegetables, fruits and fortified cereals.
How much? Adults should aim for 400µg folate a day. The amount for pregnant women will vary.
Japanese researchers confirmed the link between depression and zinc in a 2010 study, when they added a 7mg zinc supplement to participants’ diets. The increased zinc correlated to significant decreases in both anger and depression. Zinc is most readily found in red meat, fortified cereals, some nuts and some seafood.
How much? Adult women need 8mg of zinc each day, while adult males need 14mg.
In 2009, Australian researchers found that a diet low in magnesium may increase your risk of depression. The finding was given further weight by American researchers who found that magnesium was effective in treating major depression. They also concluded that it would be worth investigating the possibility that magnesium deficiency is the cause of most major depressions. Magnesium can be found in spinach, tofu, bananas, pumpkin and sunflower seeds, and some nuts (almonds and Brazil nuts).
How much? Under the age of 30, men need 400mg magnesium daily and women require 310mg. Over the age of 30, that requirement jumps to 420mg and 320mg magnesium, respectively.
How do these nutrients work?
So how can specific nutrients make a difference to mental health? The answer is that scientists don’t know. “It’s complicated,” says Dr Volker, and there are still many questions to be answered. “For example”, she says, “we know that depressive symptoms are the most common neurological problem associated with a folate deficiency, but we also know that not everyone with a folate deficiency develops depression. So there’s a lot more to learn and understand about the mechanisms behind good mental health, and how and why nutrition plays a role”.
The other foods that make a difference
It’s not only specific nutrients which have been linked with a reduced risk of depression – other foods have too. Various studies have found that Mediterranean style diets, low-GI foods, carbohydrates and processed foods all play a significant role in easing or exacerbating depressive symptoms.
The Mediterranean diet
The prevalence of depression and other mental health issues is lower in Mediterranean countries, with experts pinpointing the diet native to the region as an explanation. In fact, according to Spanish research, people who closely adhere to the typical Mediterranean diet have a 30 per cent lower risk of depression than people who don’t follow the diet (or have a much ‘looser’ interpretation of it).
A Mediterranean diet involves a high intake of legumes, fruit and vegetables, nuts, cereals and fish; a low intake of meat and saturated fat; a moderate intake of low-fat dairy foods; and a high ratio of monounsaturated fatty acids to saturated fatty acids (ie. more healthy fats than bad fats).
Include low-GI foods
Low-GI foods may offer some protection against depression, say American researchers who found that people eating a high proportion of high-GI foods were more likely to experience mood changes and depression. One explanation could be that high-GI foods are more likely to cause blood sugar levels to fluctuate, which has been linked with increased depressive symptoms in people with type 2 diabetes.
This doesn’t mean you should exclude high-GI foods altogether – some fruits, vegies and cereals actually have a higher GI than ‘treat’ foods like biscuits (and of course you shouldn’t replace the former with the latter). Instead, aim to eat high-GI foods with lower-GI ones or with higher protein foods (like yoghurt) to lower the overall GI of the meal or snack. For a comprehensive list of the glycaemic indexes of foods, visit www.glycemicindex.com.
Steer clear of low-carb diets
While low-fat diets rich in healthy carbohydrates promote improvements in mood and protect against depression, fad diets that restrict carbohydrates have the opposite effect. Australian researchers compared a low-carb diet against a low-fat diet (both diets contained the same number of kiojoules overall) and found that those on the low-fat diet were less prone to anger and depression than those on the low-carb diet. While more research is required to understand the reasons for the difference, researchers believe it probably involves the effects of protein and fat intake on brain levels of serotonin – the chemical responsible for feelings of happiness. Stick to a diet which includes good fats and healthy carbohydrates, such as fruit, legumes and wholegrains, as these contain plenty of fibre, B vitamins and vitamin E.
Cut out the junk
People who eat a diet high in processed foods have a 58 per cent higher risk of depression than those who eat very few ‘man-made’ foods, according to a University College London UK study. The study also found that those who ate the most ‘whole’ foods had a 26 per cent lower risk of depression. Steer clear of processed, refined and fried foods, high-fat dairy products and sweets. Instead reach for more fruits, vegies, fish, wholegrains and lean meats.
The importance of exercise
Fitter people have significantly lower incidence of reporting depressive symptoms than unfit people, according to many studies, including research from the University of Carolina in the US. The study found that quantity counts, too – the more participants exercised, the more their risk of depression decreased.
Weight and depression
Research has uncovered a link between depression and being overweight, but does depression lead to becoming overweight, or does being overweight lead to depression? The answer seems to be ‘both’ – a type of ‘chicken-and-egg’. situation. As Dr Highet points out, “being overweight can make it harder to exercise, potentially eliminating the protective effect that physical activity can provide”.
But the limit on exercise is only one part of the equation, with recent research showing that the relationship between obesity and depression is even closer than initially thought. A recent study conducted at the Leiden University Medical Center in the Netherlands showed that depression increases the risk of becoming overweight. They also found that the reverse is true – obesity can increase the risk of depression. Having suffered from depression for the majority of her adult life, Ingrid Ozols, 45, says she learned to use food as a source of comfort as a child.
“As I grew older, I was never sure whether I was eating because I was depressed, or whether it was the more poor food choices I made and the heavier I got, the more depressed I became – and so the more I ate!” Ingrid adds, “It’s not only a chicken-and-egg situation – where I’m not always aware of what occurs first, the eating or the emotions – but it can become a vicious circle”.
Through experience and treatment, Ingrid has learned how important it is to manage lifestyle factors by exercising regularly, avoiding alcohol, getting enough sleep, having a healthy diet and managing her weight to keep her depression under control. “Which is not to say I get it right all the time”, she says, “I continue to be a work in progress! But I know that eating well and cutting out sugary drinks and junk food, and replacing them with water and healthy meals, is healthy for me – it’s good for both my general health and my mental health”.
We’ve put the advice into practice with an action plan designed to help you prevent or manage depression.
Step 1 – Purge the pantry
Start by clearing out the pantry of all the sugary, high-fat and fried snacks, and any other highly processed foods. Once that’s done, restock it with dried fruit, fortified cereals, wholegrain breads and snacks and lighter versions of your favourite ‘treat’ foods. Remember, it’s not about getting rid of high-carb foods, it’s about choosing low GI carbs where you can. Including the right type of carbs in your diet is essential to good mental health.
Next, clear out the bacon and other processed meats from your fridge and fill it with lean meats, low-fat dairy, and plenty of fresh fruits and vegies.
Step 2 – Make sure you are getting your nutrients
Omega-3: Oily fish is the best source of long-chain omega-3s; try sardines, mackerel and salmon. It’s not hard to meet your 500mg requirement: add a 100g canned tuna to salads (600mg); serve 85g canned sardines on toast (1700mg); or have a 150g fillet of fresh salmon (824mg). For non-fish eaters, try omega-3-enriched eggs (about 100mg per egg) or walnuts (about 1800mg per 30g serve).
Folate: To help you get your 400µg a day, make an omelette with 2 eggs, 75g rocket and 1/2 cup each cooked asparagus and spinach. Serve it with two slices wholegrain bread and an orange. Other sources include lentils (1/2 cup has 179µg) and fortified breakfast cereals (100g can provide as much as 330µg).
Zinc: A 100g serve lean beef has about 4mg zinc, 3 1/2 tablespoons cooked crab contains 8mg and just a single medium-sized oyster contains 12mg. Pour yourself a bowl of fortified cereal – some cereals contain as much as 6mg per 100g.
Magnesium: Two tablespoons of almonds provide 79mg magnesium; 1/2 cup cooked spinach has 70mg; 1/2 cup tofu contains 127mg; and a medium banana provides 33mg. Other good sources include pumpkin seeds, sunflower seeds and Brazil nuts. So pack a snack of almonds, Brazil nuts and sunflower seeds; swap the chicken in your stir-fry for tofu; or stir cooked spinach through pasta sauce.
Step 3 – Opt for a more Mediterranean diet
The essential components of a Mediterranean diet include lots of fresh fruit and veg, low-GI carbohydrates, wholegrains, healthy fats, oily fish and low-fat dairy. It also means lowering your intake of meat and saturated fats. When starting any new diet, it’s best to consult with an Accredited Practising Dietitan first.
Omega-3: 500mg/day (350mg/week)
Zinc: 8mg/day for women, 14mg/day for men
Magnesium: 310-320mg/day for women, 400-420mg/day for men