The study, which looked at data from almost 46,000 people, provides convincing evidence that dietary improvement significantly reduces symptoms of depression, even in people without diagnosed depressive disorders.

According to lead researcher, Dr Joseph Firth, an Honorary Research fellow at The University of Manchester and Research Fellow at NICM Health Research Institute at Western Sydney University, existing research has been unable to definitively establish if dietary improvement could benefit mental health.

But this new analysis published in Psychosomatic Medicine, brought together existing data from large clinical trials of diets for mental health conditions to help provide better insight

“The overall evidence for the effects of diet on mood and mental well-being had up to now yet to be assessed. But our recent meta-analysis has done just that; showing that adopting a healthier diet can boost peoples’ mood. However, it has no clear effects on anxiety.”

Linking food to mood

The study combined data from 16 randomised controlled trials that examined the effects of dietary interventions on symptoms of depression and anxiety. The majority of these examined people with non-clinical depression.

The study found that all types of dietary improvement appeared to have equal effects on mental health, with weight-loss, fat reduction or nutrient-improving diets all having similar benefits for depressive symptoms.

“This is actually good news” said Dr Firth; “The similar effects from any type of dietary improvement suggests that highly-specific or specialised diets are unnecessary for the average individual.

“Instead, just making simple changes is equally beneficial for mental health. In particular, eating more nutrient-dense meals which are high in fibre and vegetables, while cutting back on fast-foods and refined sugars appears to be sufficient for avoiding the potentially negative psychological effects of a ‘junk food’ diet.

Support for a lifestyle approach

Dr Brendon Stubbs, co-author of the study and Clinical Lecturer at the NIHR Maudsley Biomedical Research Centre and King’s College London, added: “Our data add to the growing evidence to support lifestyle interventions as an important approach to tackle low mood and depression.

“Specifically, our results within this study found that when dietary interventions were combined with exercise, a greater improvement in depressive symptoms was experienced by people. Taken together, our data really highlight the central role of eating a healthier diet and taking regular exercise to act as a viable treatment to help people with low mood.”

Interestingly in the studies examined, women derived the greatest benefit from dietary interventions for symptoms of both depression and anxiety.

The analysis was not able to pinpoint why but according to Dr Firth added: “It could be through reducing obesity, inflammation, or fatigue – all of which are linked to diet and impact upon mental health.”

The study, published in the scientific journal Nature Microbiology, is the first population-level study to look at this link. Population-level studies look at a group of individuals taken from the general population who share a common characteristic, such as age, sex, or health condition.

The first human data

The researchers from KU Leuven, a research university in Flanders, Belgium, set out to study the relation between gut bacteria and quality of life and depression. The authors combined faecal microbiome data with general practitioner diagnoses of depression from 1,054 individuals enrolled in the Flemish Gut Flora Project.

Lead researcher Jeroen Raes and his team found a clear link between gut bacteria and mental health as well as identifying specific gut bacteria linked to depression and providing evidence that a wide range of gut bacteria can produce neuroactive compounds.

Two bacterial genera, Coprococcus and Dialister, were consistently depleted in individuals with depression, regardless of antidepressant treatment. The results were validated by comparing the data to a second an independent group of 1,063 individuals from the Dutch LifeLinesDEEP study and to a study group of clinically depressed patients at the University Hospitals Leuven, Belgium.

Neuroactive microbes

Prof Jeroen Raes an expert in Gastroenterology, Microbiology and Systems Biology at KU Leuven, says: “The relationship between gut microbial metabolism and mental health is a controversial topic in microbiome research. The notion that microbial metabolites can interact with our brain – and thus behaviour and feelings – is intriguing, but gut microbiome-brain communication has mostly been explored in animal models, with human research lagging behind. In our population-level study we identified several groups of bacteria that co-varied with human depression and quality of life across populations.’

Previously, Prof Raes and his team have documented low microbial count and biodiversity among Crohn’s disease patients. They were, they say, surprised to find a similar community type linked to depression and reduced quality of life.

“Apparently,” said Raes, “microbial communities that can be linked to intestinal inflammation and reduced wellbeing share a set of common features.’

This discovery builds on what is previously known. In 2015 research from Emory University School of Medicine and Winship Cancer Institute found that about one third of people with depression also have high levels of inflammation markers in their blood,

In this study, the authors were also able to identify gut bacteria that could potentially interact with the human nervous system. They studied genomes of more than 500 bacteria isolated from the human gastrointestinal tract according to their ability to produce a set of neuroactive compounds. This has allowed the authors to assemble a comprehensive guide to neuroactivity of gut species. Some bacteria were found to carry a broad range of these functions.

A new tool in the toolbox

Co-author Mireia Valles-Colomer, also from KU Leuven: ‘Many neuroactive compounds are produced in the human gut. Our toolbox not only allows us to identify the different bacteria that could play a role in mental health conditions, but also the mechanisms potentially involved in this interaction with the host. For example, we found that the ability of microorganisms to produce DOPAC, a metabolite of the human neurotransmitter dopamine, was associated with better mental quality of life.’

The researchers are now aiming to sample a larger group of people to confirm their findings.

• For more on the links between diet, gut bacteria and depression see our articles Dietary approach to major depression shows promise and Anti-inflammatory diet lowers depression risk

The benefits, the experts suggest, could be because heat restores the body’s natural temperature rhythm over the course of a day, which can be disrupted in depressed patients.

Scientists from the University of Freiburg in Germany tested the effects of thermal baths on 45 people with depression. The people in the study group (average age 48) all had moderate to severe depression, which was measured on the commonly used HAM-D scale.

On this scale a score of 19 or higher out of 50 indicates someone has severe depression – the average score among participants was 21.7.

Participants were randomly assigned to either twice-weekly spa bathing, or two sessions of moderate exercise a week over a two week period, after which time their depression retested.

The bath group were asked to sit in a 40°C (104°F) bath for 30 minutes, then relax with hot water bottles for 20 minutes. People in the exercise group had to do a moderate aerobic workout, such as running, dancing or swimming, for 40 to 45 minutes.

Better than exercise

Those in the bathing group saw an average drop of six points on the HAM-D scale within a fortnight, suggesting someone with severe depression could cut their symptoms to moderate depression, or somebody already on a moderate score could drop to mild by bathing. In contrast exercise patients only shaved three points off their score.

In addition, while 13 out of 23 people dropped out of the exercise group, only two out of 22 failed to complete the hot bath treatments.

Because baths are easy, enjoyable and have a fast acting effect, the team notes, people are more likely to keep up the habit over the long term.

Heat may rest the ‘clock’

Although the exact causes of depression are not clear, one theory is that it is linked to a disruption in our circadian rhythm – or body clock – which dictates our cycles of hormones, body temperature and sleep, among other things.

In those with depression, body temperature may not be well regulated and the heat from the baths and hot water bottles may have helped correct this. Results of this study, for instance, showed that the body temperatures of those in the bath group increased by around 2°C (3.6°F) after bathing.

• For more information on the benefits of baths see The health benefits of a hot bath. For more on the benefits of heat see Feel the heat – the benefits of a sauna

Natural Health News — Women may need a more nutrient-rich diet to support a positive emotional well-being, according to new research.

According to a team of US scientists, mounting evidence suggests that anatomical and functional differences in men’s and women’s brains influence susceptibility to mental health problems. However, little is known about the role of dietary patterns in gender-specific psychological wellbeing.

To find out more, a team of researchers led by Lina Begdache, assistant professor of health and wellness studies at Binghamton University, State University at New York, conducted an anonymous survey of 563 participants (48% men and 52% women) through social media to investigate this issue.

Writing in the journal Nutritional Neuroscience​, Begdache and her team found that men are more likely to experience mental well-being until nutritional deficiencies arise. Women, however, are less likely to experience mental well-being until a balanced diet and a healthy lifestyle are followed.

Gender differences go deep

“Evidence suggests that our ancestors’ diet, which was a high-energy-nutrient-dense diet, contributed significantly to brain volumes and cognitive evolution of mankind,”​ said Dr Begdache.

“Males and females had different physical and emotional responsibilities that may have necessitated different energy requirements and food preference.” ​

Dr Begdache said that, as a result, gender-based differences in food and energy intake may explain the differences in brain volumes and connectivity between females and males.

The research suggests that polyphenols, omega-3 oils and folate are particularly beneficial for women. These nutrients are found in abundance, they note, in the Mediterranean diet.

“Beans (high in polyphenols) and fish (rich in omega-3 fats) intakes, specifically, associated with increased cortical thickness.” said Begdache who notes that  polyphenols have an active role to play in normal brain signalling and neurological health. ​

A study conducted by researchers from the US, Canada, France and Israel, has discovered that adults over the age of 60 are significantly cleverer at the start of autumn compared with spring. The difference between the autumn and spring equinox say the scientists, was equivalent to four years of ageing.

The study analysed data involving more than 3,000 people in North America and Europe, most of whom were over 70. They had each been given annual tests of memory and processing speed, with their testing spread randomly throughout the year.

Doctors had assumed that the month the testing occurred was irrelevant, but the paper in the online journal Plos Medicine found that the seasons did matter. In fact, cognitive performance was shown to be higher in the summer and autumn compared with winter and spring. It peaked at the autumn equinox then dropped off until the spring equinox six months later.

Important considerations for dementia testing

For some participants, the researchers also looked at levels of proteins associated with Alzheimer’s disease. This revealed seasonal rhythms in Alzheimer-disease-related proteins in the spinal fluid, and in the expression of specific genes in the brain, giving us a window into the underlying mechanisms.

They found a 30% greater chance of meeting diagnostic criteria for mild cognitive impairment or dementia if cognitive tests are carried out in late-winter or early-spring. “The difference in performance was enough to impact the clinical impression of what diagnostic category a patient was going to be in,” said one of the researchers Andrew Lim, from the University of Toronto.

The team could only speculate on the cause of such a change. Light, temperature, the body’s hormone levels or vitamin D consumption could be to blame, Lim said. But on the bright side, the study opens up the possibility that “good cognition” could be extended beyond that peak time to prevent or slow the onset of Alzheimer’s disease.

One theory is that our lifestyle and health habits vary with the season, we may for instance eat, sleep and exercise differently.

Lead researcher Philip De Jager, from Columbia University, said another theory was that during winter our brains experienced something akin to a mild hibernation. “The underlying rhythms are similar to those that regulate many other mammals and animals,” he said. “They probably help us minimise activity in months when fewer resources are available and take advantage of them at a time when they are abundant.”

• For more on the connection between weather and health see our article Must be the weather

The findings have implications for cities across the United States, where 15% percent of land is deemed “vacant” and often blighted or filled with trash and overgrown vegetation.

For the trial, published in JAMA Network Open, 541 vacant lots throughout Philadelphia were randomly assigned to one of three study arms: greening intervention, a trash clean-up intervention, or a control group with no intervention. The greening intervention involved removing trash, grading the land, planting new grass and a small number of trees, installing a low wooden perimeter fence, and regular monthly maintenance. The trash clean-up involved removing trash, limited grass mowing where possible, and regular monthly maintenance. The Pennsylvania Horticultural Society LandCare program performed the greening, trash clean-up, and maintenance.

The researchers then measured the mental health of Philadelphia residents 18 months before and after nearby vacant lots had been converted into green spaces, as well as residents living near untreated abandoned lots, and those that just received trash clean-up. Participants were asked to indicate how often they felt nervous, hopeless, restless, depressed, that everything was an effort, and worthless.

Clean, green and happy

They found that people living within a quarter of a mile radius of greened lots had a 41.5% decrease in feelings of depression compared to those who lived near the lots that had not been cleaned and greened. Those living near green lots also experienced a nearly 63% decrease in self-reported poor mental health compared to those living near lots that received no intervention.

Results were most pronounced when looking only at neighbourhoods below the poverty line, with feelings of depression among residents who lived near green lots decreasing significantly – by more than 68%.

The findings add to the growing body of evidence showing how revitalized spaces in blighted urban areas can help improve safety and health, such as reducing crime, violence, and stress levels. The most recent study, from the same team and published in February of this year, found up to a 29% decrease in gun violence near treated lots. This latest work is believed to be the first experimental study to test changes in the mental health of residents after nearby vacant lots were greened.

A positive impact

“Dilapidated and vacant spaces are factors that put residents at an increased risk of depression and stress, and may explain why socioeconomic disparities in mental illness persist,” said lead author Eugenia C. South, MD, MSHP, an assistant professor of Emergency Medicine and a member of the Center for Emergency Care and Policy Research at the University of Pennsylvania. “What these new data show us is that making structural changes, like greening lots, has a positive impact on the health of those living in these neighbourhoods. And that it can be achieved in a cost-effective and scalable way – not only in Philadelphia but in other cities with the same harmful environmental surroundings.”

Interestingly, analyses of the trash clean-up intervention only compared to no intervention showed no significant changes in self-reported mental health.

“The lack of change in these groups is likely because the trash clean-up lots had no additional green space created,” said co-author John MacDonald, PhD, a professor of criminology and sociology at Penn. “The findings support that exposure to more natural environments can be part of restoring mental health, particularly for people living in stressful and chaotic urban environments.”

The study shows that adding green space to neighbourhoods should be considered alongside individual treatments to address mental health problems in low resource communities. Additionally, greening is an affordable approach, costing about $1,600 (£1200) per vacant lot and $180 (£140) per year to maintain. For these reasons, the authors said, vacant lot greening may be an extremely attractive intervention for policy makers seeking to address urban blight and promote health.

“When total fibre intake was at approximately 21 grams per day, the risk of depressive symptoms reached a relatively low level, which has important public health implications,”​ the researchers wrote in their paper​​, published in the journal Nutrition​.

The average intake for most Americans, they note, is 15 grams of dietary fibre per day, while the recommended daily intake is around 30g per day.

The scientists, from the School of Public Health at Qingdao University in Cina, analysed data from the 2007 to 2014 National Health and Nutrition Examination Survey (NHANES) results, a publicly available data set of the dietary habits and nutritional status of more than 16,000 US individuals. They evaluated dietary fibre intakes of total cereal, vegetable, and fruit fibre intakes.

How does it work?

Just how dietary fibre helps to mediate symptoms of depression “remains poorly understood,” say the authors, but they suggest two possible mechanisms.

One is that dietary fibre acts as a ‘prebiotic’ selectively feed beneficial bacteria in the gut, and changing the balance of ‘good’ to ‘bad’ bacteria. This in turn influences brain function—a concept dubbed the ‘gut-brain’ axis.

Another proposal is that dietary fibre may lower glucose levels after a meal, inhibiting the inflammatory processes caused by a blood sugar spike.

They results build on previous research, for instance a 2016 study from Japan which suggested that higher fibre intake among Japanese employees may result in lower risk of depression.

Eating a high-fibre diet can balance blood sugar levels, help with digestion, lower cholesterol and potentially reduce the risk of diabetes  as well as heart disease and cancer.

In the UK as well as elsewhere most people do not eat enough fibre (the average intake is 17g per day for women and 20g per day for men). Although fibre supplements are available and can be helpful for some, nutritionists recommend getting the daily recommended amount of fibre from whole grains, fruits and vegetables, as well as pulses.

A new UK study has found that staying in sync with natural circadian rhythms – our daily sleep-wake and light-dark cycles – is linked to improvements in mood and cognitive functioning as well as a decreased likelihood of developing major depression and bipolar disorder.

Our internal body clock regulates multiple functions including body temperature and eating habits. Disruption of this clock, for instance through long-term night-shift work, has previously been associated with an increased risk of cancer, heart disease and obesity.

The observational study of over 91,000 people, aged 37 to 73, was conducted at the University of Glasgow and published in The Lancet Psychiatry.  It measured disruptions in sleep-wake cycles using a device called an accelerometer that is worn on the wrist and measures a person’s daily activity levels. Moods and mental well-being were measured using a standardised questionnaire.

Disruption leads to depression

Those with more circadian rhythm disruptions – defined as increased activity at night, decreased activity during the day or both – were significantly more likely to have symptoms consistent with bipolar disorder or major depression. They were also more likely to have decreased feelings of well-being and to have reduced cognitive functioning, based on a computer-generated reaction time test.

Lead researcher Professor Daniel Smith, professor of psychiatry at the university, noted: “It’s widely known that a good night’s sleep is a good thing for well-being and health. That’s not a big surprise. But I think what’s less well-known and what comes out of this work is that not only is a good night’s sleep important, but having a regular rhythm of being active in daylight and inactive in darkness over time is important for mental well-being.”

Aim for better sleep hygiene

Smith also says that it is still not certain whether an out-of-kilter body clock causes mental health problems, or if the mental health problems are causing disturbances to people’s daytime and night-time cycles.

However, findings from this study – the largest of its kind so far – are consistent with research indicating a link between sleep disruptions and mood disorders. Another British study in, for example, showed that men who worked night shifts for four years or more were more likely to have anxiety and depression than those who work during the day.

There is also evidence that the body clocks of people who suffer from depression are ‘out of sync’.

He adds that better sleep hygiene is key. ‘There are a lot of things people can do, especially during the winter, such as getting out of the house in the morning to get exposed to light and take exercise, so that by evening they are tired.

‘You can also turn off your mobile phone around 10pm because the light in it is telling your brain it’s daytime. But it is hard for some people, such as shift workers, because of their job or because of their family circumstances.’

Again this advice links to recent findings that taking a more mindful approach to using our phones, computers and tablets can make us happier.

• For more on circadian rhythms see our article The ancient clock that rules our lives – and determines our health

In a small study published in the journal Phytomedicine, researchers at the Mashhad University of Medical Sciences in Iran, found that the 30 new mothers supplemented with 15 mg of saffron daily showed greater improvement in their symptoms compared to the same number of new mothers who took a placebo.

The intervention period lasted eight weeks, during which study participants were not allowed to receive any other behaviour therapy.

Symptom severity was judged, based on responses to what is known as the Beck Depression Inventory questionnaire, the most widely used psychometric test measuring severity of depression.

The researchers noted that in Iran, as elsewhere some degree post-partum depression is normal.

“Numerous adverse effects of antidepressants as well as the attitudes of breastfeeding mothers, who prefer to consume herbal medicine rather than chemical drugs, encouraged us to assess the effects of saffron (Crocus sativus L) on mothers suffering from mild-to-moderate postpartum depressive disorder,”​ they write.

Saffron’s mental health benefits​

Most saffron supplements available are aimed at assisting weight loss and satiety. Recently there has been research to suggest that antioxidants in saffron could help protect ageing eyes. But there is also emerging science to suggest mental health benefits.

A meta-analysis by researchers at the University of Florida, Gainesville included five studies in which saffron was compared to placebo (two studies) or to conventional anti-depressant treatment (three studies). ​

Results suggested that saffron (the dosage was 30 mg per day of powdered saffron) is significantly better than placebo in improving symptoms of depression and more or less equivalent to standard pharmaceutical antidepressants (i.e., imipramine or fluoxetine).”

This latest study adds on to the existing evidence for the benefits of saffron for people suffering from mild to moderate depression.”

One of the most expensive spices

Saffron is derived from derived from the stigma of the flower Crocus sativus, commonly known as the saffron crocus. It is one of the world’s most expensive spices because the stigmas of each flower need to be collected by hand and there are only a few per flower. A pound of saffron can cost $1,500 (£1,100). By comparison, a pound of organic turmeric root powder can sell for around £8).

This might seem to put the remedy outside the reach of many mothers. But commenting on the various studies of saffron benefits Stefan Gafner, chief scientific officer of the American Botanical Council noted that, “Not all studies were carried out with saffron stigma (which is the rather expensive saffron plant part used as a spice), but quite a few were done with the saffron petals, which are much less costly”.​

He adds that even if the stigma are used, the dosage of 30 mg per day (twice what was used in the current study) is so low that it is possible to manufacture an affordable saffron supplement.

It’s worth noting that there is no evidence yet on the safety or effectiveness of saffron for post-partum depression breastfeeding mothers, nevertheless the early results from these small trials are encouraging.