Reading: Firth, Ganswich, Borsini, Wootton & Mayer (2020) - Food and Mood: How do Diet and Nutrition Affect Mental Wellbeing?

Question 1

Causality in the food and mental health link

Answer 1

Hard to determine causality in this link though: is it that diet is causing changes to mental health or that mental health is causing changes to diet? Or are they both influencing each other?

Question 2

In what ways might mental health be causing changes to diet?

Answer 2

-Comfort eating’

• Changes in appetite due to mood
• Appetite inducing effects of psychiatric medications

Question 3

Mediators in the diet and mental health relationship

Answer 3

Barriers to maintaining a healthy diet may also disproportionality affect people with mental illness e.g. financial, environmental determinants

Question 4

Glycemic index

Answer 4

Ranking of a carbohydrate in terms of the speed at which it is digested, absorbed, metabolized, and ultimately affects blood glucose and insulin levels (high GI goods are things like sugar, sugary soft drinks, white bread, potatoes etc.)

Question 5

Link between glycemic index and mood

Answer 5

• Relationship between progressively higher dietary glycaemic index and incidence of depressive symptoms.
• Experimental exposures to diets with high glycaemic load in controlling setting increases depressive symptoms in healthy volunteers, with a moderately large effect.

Question 6

Potential mechanism to explain the link between glycaemic index and mood

Answer 6

• The compensatory responses that lower plasma glucose concentrations after high glycaemic load foods could trigger secretion of hormones like cortisol, adrenaline, growth hormone and glucagon.
• These ‘counter hormones’ than cause changes in anxiety, irritability, and hunger.

-Explains why reoccurring hypoglycemia is associated with mood disorders as same hormones released.

Question 7

Link between diet and inflammation

Answer 7

Sustained adherence to Mediterranean dietary patterns reduces markers of inflammation in humans while high calory meals high in saturated fat trigger immune response.

Question 8

Mood disorder and inflammation link evidence

Answer 8

• People with depression score significantly higher on measures of dietary inflammation ( which means they consume more foods that are associated with inflammation like trans fats and refined carbohydrates, and lower amounts of food that would combat this such as omega-3-fats.
• A randomised control trial of anti-inflammatory agents showed they significantly reduced depressive symptoms while medications that stimulate inflammation induced depressive states.

Question 9

More research is needed to show the link between diet, inflammation and mood

Answer 9

• More research is needed on the complex interrelations between diet, mood and inflammation as research has shown that stressors experienced in the previous day or a history of major depressive disorders cancels out the positive benefits of healthy food choices on reducing inflammation and improving mood.
• Only some clinically depressed individuals present with the ‘inflammatory phenotype’ and so this type of dietary intervention wouldn’t work for everyone.

Question 10

Gut microbiome

Answer 10

broad term that refers to the trillions of microbial organisms, including bacteria, viruses, and archaea, living in the human gut.

Question 11

Evidence to support a link between the the gut microbiome and mental health

Answer 11

• Emotion-like behaviour in rodents changes with changes to gut microbiome.
• Major depressive disorder in humans is associated with alterations of the gut microbiome
• Transfer of faecal gut microbiota from humans with depression into rodents appears to induce animal behaviours that are hypothesized to indicate depression like states.
• Ingestion of probiotics by the healthy individuals alters the gut microbiome and the brains response to a task that requires emotional attention, even reducing depressive symptoms.

Question 12

Things that alter the gut microbiome

Answer 12

• Genetics
• Exposure to antibiotics
• Diet e.g. a diet low in fibre and high in saturated fats, refined sugars and artificial sweeteners = bad. A Mediterranean diet can promote gut microbial taxa which can metabolize these food sources into anti-inflammatory metabolites

Question 13

Stigma and dietary choices

Answer 13

Findings should never be used to stigmatism dietary choices i.e. mentality that an individual should just simply change their diet and that will be a ‘fix all’ is flawed and may contribute to further mental health problems.

Question 14

Is the link between diet and mental health simple?

Answer 14

• The causes of mental health are many and varied and will often present and persist independently of nutrition and diet.
• The new research is still in its establishing phases and it will take a while to get to the stage where large scale interventions are significantly and consistently improving the lives of those with mental health difficulties.

Question 15

Well established link between diet and mental health?

Answer 15

• Important not to forget some of the information/ big picture stuff that is already known about the link between diet and mental health e.g. diabetes and obesity already associated with poorer mental health.