How diet can affect your mental wellbeing

As the world has changed drastically since the start of the pandemic, it may well be your diet has too. But does the food you eat really affect your mental wellbeing? We asked the experts.

Eat at regular intervals

By eating regularly, you will keep your blood sugar levels consistent. So why is this a good thing? When blood sugar drops, it leads to tiredness and irritability, and inconsistent blood-sugar levels have even been linked to mood disorders including depression and anxiety. If your blood sugar spikes, this will be followed by a dip and you’ll be hit by these issues. So eating erratically might be doing more harm than just leaving you with a rumbly tummy.

Nutritionist Sonal Shah explains, “If you get hungry often in the day and this affects your mood, concentration and energy levels, then eating at regular intervals is important. Eating every three to four hours is fine to prevent one’s energy levels dropping as a result of blood-sugar levels dipping”.

But the Nutritionist Resource member warns this doesn’t mean you should eat all the time: “It’s not ideal to continuously snack on foods throughout the day, as this grazing doesn’t allow the appetite and insulin hormones to regulate optimally”.

Drink plenty of fluids

Dehydration can impact your mental wellbeing by making it harder for you to think clearly and focus.

Shah says: “Dehydration is seen by the body as a stressor, leading to symptoms of low energy, poor focus, confusion and irritation. The brain cells require water just as the body does, and this explains why individuals who are dehydrated are more susceptible to mental stress. Water helps blood flow, so if there isn’t enough water to help clear the toxins out of the body, this leaves one feeling weak.

“Dehydration can also lead to cravings for unhealthy food like crisps, and refined carbohydrates and drinks containing alcohol and caffeine, which have diuretic effects on the body. Alcohol reduces cognitive function by dehydrating the body as it requires water to expel the alcohol from the bloodstream and this leads to the hangover symptoms the next morning. Fizzy drinks containing sugar may give a quick energy high, which mentally alerts you, but this is followed by sugar dip which leads to an energy low and mental tiredness”.

Eat a balanced diet

Felice Jacka, Professor of Nutritional Psychiatry and Director of the Food & Mood Centre at Deakin University, focuses on links between diet, gut health and mental and brain health.

She explains: “Extensive and consistent research tells us that healthier diets protect against depression. Given that depression is the leading cause of global disability, this is critical to understand.

“Indeed, these links are seen after taking into account important factors that can affect both diet and mental health, such as education and income, other health behaviours and body weight. More recently, evidence from randomised controlled trials tells us that helping people with depression to improve the quality of their diets can have a substantial benefit to their mental health and functioning. In these trials, the diet that had the major benefit was one designed to mimic a traditional Mediterranean diet, high in wholegrains, vegetables, fruits, fish and olive oil.”

Shah adds: “A balanced diet feeds the brain, providing it with the nutrients it needs to support a positive mood, and improve signalling pathways between brain cells for optimal brain function. The nutrients required to support a healthy mind and brain are so vast and it’s important to consume a varied diet and supplement nutrients that are low or missing in the diet.”

Try to avoid junk food when you’re tired

Recent science tells us there’s a reason why we’re tempted by those high-carb, sugar and fat products when we’re tired. If this is a short-term problem or one off, it’s not likely to cause issues in the long term, but if it’s ongoing it can become a chicken-and-egg situation.

“Certain foods can impact digestion and make you feel unwell, and this is intricately related to mood”, says Shah. She continues: “An example is feeling uncomfortably bloated, which leads to sluggish feelings accompanied by a brain fog, and this then impairs mental clarity. It swings both ways, so if you feel tired, with this low mental focus, anxiety, irritation and mood, you may reach for refined foods low in vitamins and minerals, which give you a quick high that is short lived.”

The same applies to comfort eating when stressed. “Comfort eating is emotional eating, and the triggers and reasons for it vary from individual to individual.... Food shouldn’t be used as a way to control emotions. Habits and eating behaviours take time to address, and I would recommend working with therapists to establish the reasons for them and heal them”, continues Shah.

Cut back on processed food

While there is a relationship between regular consumption of processed food and low mood, it’s hard to distinguish between cause and effect.

“Foods and drinks with added sugars, such as soft drinks, are very problematic to health. Many studies from around the world show that diets high in these types of foods – as well as those with added fats, salt and highly-processed flours – are linked to worse mental health as well as obesity, heart disease, diabetes and other conditions”, says Jacka.

Professor Jacka goes further: “In animal studies, sugar and ‘western diets’ lead to problems in both behaviour and cognition, at least partly through a detrimental impact on a part of the brain called the hippocampus. We’ve also shown that unhealthy diets are closely linked to a smaller hippocampus in humans, while a healthy diet is linked to a larger hippocampus. The hippocampus is a key part of the brain involved in learning and memory, as well as mental health, so this has important implications for people from childhood through to old age.”

Shah adds: “To break away from a processed food diet involves changing the taste buds so they become less tickled by junk food and begin to crave healthier foods.... So it’s a change of lifestyle and looking deeper into why the person is reaching for a certain food in the first place. Ask yourself: Is it work stress, anxiety, depression or lack of motivation?”

Eat a diverse diet for your gut microbes

There has been a lot of scientific focus on the role of the gut in fighting depression in recent years. A good diet, particularly one that is diverse and high in plants and seeds, has been linked to reduced levels of depression in a number of studies. Conversely, a diet low in variety and fibre has been linked to a greater risk of depression. “The link between food and mood has been confirmed by recent randomised clinical trials in humans”, writes Tim Spector, Professor of Genetic Epidemiology at King’s College London, in his book Spoon-Fed.

“There is a huge amount of effort going into research in this field around the world now”, says Professor Jacka. “Diet is one of the most important factors affecting the health of the gut and its bacteria (and it does this very quickly), whilst we also now know that the gut bacteria (microbiota) play a critical role in the health of our immune system, our metabolism, our gene expression, and our mental and brain health.”

Avoid binge drinking

One way we know that the gut is dramatically affected is through heavy drinking. “Excessive (binge) drinking appears to damage the lining of the gut, which can promote inflammation. Inflammation, in turn, increases the risk of a host of diseases, including depression.”

Can you improve your mental health by eating better?

Professor Jacka describes her work in treating people with depression through diet and lifestyle changes. “In our SMILES trial, which was the first randomised controlled trial of dietary improvement for people with moderate to severe clinical depression, we showed very large benefits to depressive illness of adopting a Mediterranean-style diet over a three-month period. We also showed that the more people improved their diets, the more their depression improved.

“We are now doing a lot of work to support changes to the healthcare system in Australia to ensure that people with depression have access to support to improve their health behaviours – particularly diet and exercise – as a fundamental part of their treatment.”

Should you make changes to your diet if you’re concerned about your mental health? “Seek a therapist to help with mental health, working alongside a nutritional therapist who can slowly help you transform your diet, educate you on why a balanced diet is important and unpeel areas of concern”, says Shah. “Changes to a diet cannot be made if the individual doesn’t have the mind-set or motivation to implement them step by step. Keeping a journal helps, as some days an individual may feel more motivated than other days, and logging this alongside a food diary can heighten awareness of areas that need to be worked on”, she concludes.

If you are concerned about your mental health, help and support is available.