Do healthy diets help reduce anxiety and depression?

According to one expert, most Americans are overfed in calories yet starved of the vital array of micronutrients their brains need

Finding balance: studies suggest that people who eat a greater variety of vegetables are happier (iStock)

The patient, a 48-year-old real-estate professional in treatment for anxiety and mild depression, reveals that he has eaten three dozen oysters over the weekend.

His psychiatrist, Dr Drew Ramsey, an assistant clinical professor of psychiatry at Columbia University, is impressed: “You’re the only person I’ve prescribed them to who came back and said he ate 36!”

Dr Ramsey, the author of several books that address food and mental health, is a big fan of oysters. They are rich in vitamin B12, he says, which studies suggest may help to reduce brain shrinkage. They are also well stocked with long-chain omega-3 fatty acids, deficiencies of which have been linked to higher risk of suicide and depression.

But shellfish are not the only food he is enthusiastic about. Dr Ramsey is a pioneer in the field of nutritional psychiatry, which attempts to apply what science is learning about the impact of nutrition on the brain and mental health.

Dr Ramsey argues that a poor diet is a major factor contributing to the epidemic of depression, which is the top driver of disability for Americans aged 15 to 44, according to a report by the World Health Organisation. Together with Samantha Elkrief, a chef and food coach who sits in on many of his patient sessions, he often counsels patients on how better eating may lead to better mental health.

The irony, he says, is that most Americans are overfed in calories yet starved of the vital array of micronutrients that our brains need, many of which are found in common plant foods. A survey published in 2017 by the Centres for Disease Control and Prevention reported that only one in 10 adults meets the minimal daily federal recommendations for fruit and vegetables – at least one-and-a-half to two cups per day of fruit and two to three cups per day of vegetables.

Nutritional psychiatrists like Dr Ramsey prescribe antidepressants and other medications, where appropriate, and engage in talk therapy and other traditional forms of counselling. But they argue that fresh and nutritious food can be a potent addition to the mix of available therapies.

Americans routinely change what they eat in order to lose weight, control their blood sugar levels and lower artery-clogging cholesterol. But Dr Ramsey says that it is still rare for people to pay attention to the food needs of the most complex and energy-consuming organ in the body, the human brain.

The patient Dr Ramsey is seeing credits the nutritional guidance, including cutting down on many of the processed and fried foods and fatty meats that used to be part of his diet, with improving his mood and helping him overcome a long-term addiction to alcohol.

“It’s one part of the whole package that helps alleviate my depression and helps me to feel better,” he says.

Only one in 10 adults meets the minimal daily federal recommendations for fruit and vegetables

Research on the effect of diet on mental functioning is relatively new, and food studies can be difficult to perform and hard to interpret, since so many factors go into what we eat and our general wellbeing. But a study of more than 12,000 Australians published in the American Journal of Public Health in 2016 found that individuals who increased the number of servings of fruits and vegetables that they ate reported that they were happier and more satisfied with their life than those whose diets remained the same.

Another study of 422 young adults from New Zealand and the United States showed higher levels of mental health and wellbeing for those who ate more fresh fruits and vegetables. Interestingly, the same benefits did not accrue to those who ate canned fruits and vegetables. “We think this is due to the higher nutrient content of raw fruits and vegetables, particularly B vitamins and vitamin C, which are vulnerable to heat degradation,” said Tamlin Conner, a study author and senior lecturer at the University of Otago.

One of the first randomised controlled trials to test whether dietary change may be effective in helping to treat depression was published in 2017. In the study, led by Felice Jacka (a psychiatric epidemiologist in Australia), participants who were coached to follow a Mediterranean diet for 12 weeks reported improvements in mood and lower anxiety levels. Those who received general coaching showed no such benefits.

A Mediterranean diet, rich in wholegrains, legumes and seafood as well as nutrient-dense leafy vegetables that are high in the fibre, promotes a diverse population of helpful bacteria in the gut. Research suggests that a healthy gut microbiome may be important in the processing of neurotransmitters like serotonin that regulate mood.

“Our imaging studies show that the brains of people who follow a Mediterranean-style diet typically look younger, have larger volumes and are more metabolically active than people who eat a more typical western diet,” says Dr Lisa Mosconi, the director of the Women’s Brain Initiative at the Weill Cornell Medical Centre in New York. Such brain benefits may be protective against the onset of dementia, she says.

Dr Mosconi notes that “there is no one diet that fits all” but advises patients to cut out processed foods, minimise meat and dairy and eat more wholefoods like fatty fish, vegetables and wholegrains and legumes to cut the risk of developing degenerative brain diseases associated with ageing.

She and Dr Ramsey both recommend “eating the rainbow”, that is, consuming a wide array of colourful fruits and vegetables like peppers, blueberries, sweet potatoes, kale and tomatoes. Such foods are high in phytonutrients that may help to reduce harmful inflammation throughout the body, including the brain, and promote the growth of new brain cells throughout our adult years, they say.

Dr Emily Deans, a clinical instructor in psychiatry at Harvard Medical School, cautions that a plant-only diet may carry some risks. Some large observational studies suggest, for example, that strict vegetarians and vegans may have somewhat higher rates of depression and eating disorders than those who eat a more varied diet. Those on a meat-free diet may also need to take supplements to provide missing nutrients. “Some of the key nutrients for the brain, like long-chain omega-3 fatty acids and vitamin B12, are simply not found in vegetable-only diets,” says Dr Deans.

Samantha Elkrief, the food coach who assists Dr Ramsey, adds that it’s not just what we eat but the attitudes that we bring to our food that contribute to mental wellbeing. “I want to help people find the foods that give them joy, that make them feel good,” she says. “It’s about slowing down and becoming more mindful, noticing your body, noticing how you feel when you eat certain foods.”

© New York Times