Diet and mental health: what is the

evidence?

Dr Simon Steenson

British Nutrition Foundation Tuesday, November 26, 2019

s.steenson@nutrition.org.uk

Overview

• Mental health – a global challenge

• What is depression?

• Diet and depression - why the interest?

• What does the evidence show?

• Issues with the evidence

• Biological mechanisms?

• Emerging studies

• What is next for this area of research?

Mental health – a global challenge

• Global Burden of Disease report (2017)1

- Data on 195 countries and territories worldwide

- Causes of years lived with disability (YLDs)

- Depressive disorders ranked 3rd leading cause (men and women)

• What about the UK?

- 1 in 6 adults in England had a common mental disorder (CMD) in 20141

- Anxiety, depression and other CMDs more common in women than men1

1 The Lancet 392: P1789-1858 2 Adult Psychiatric Morbidity Survey (NHS Digital, 2014)

What is depression?

• We all experience a low mood sometimes

• Clinical depression – symptoms for period of weeks/months

• Depression has become more common in recent years

• Different types and many different causes:

“Depression is a low mood that lasts for a long time, and affects your everyday life.” (Mind, 2019)

Figure 1: Trends in the percentage prevalence of depressive episodes among adult men and women aged 16-64 years living in England (Source: Adult Psychiatric Morbidity Survey 2014; NHS Digital)

Financial worries Bereavement

Alcohol and drugsFamily history

Long-term illness

Treatment of depression

• Diagnosed using a questionnaire (e.g. PHQ-9)

• Depression reoccurs in 50% of cases1

• Treatment depends on severity of symptoms

1 Burcusa SL & Lacono WG (2007) Clin Psychol Rev 8: 959-85; 2 Casacalenda et al (2002) American Journal of Psychiatry 159: 1354-60, 3 Berk et al (2019) JAMA 321: 842-843.

Mild depression

Self-help Exercise

Moderate/severe depression

Antidepressants CBT/counselling

• Treatments may only be effective in about half of cases2

• Need for alternative or adjunctive therapies to treat depression3

Dietary patterns and depression

• Eating a healthier diet may lower the risk of depression1

1 Li et al (2017) Psychiatry Res 253: 373-382.

• A ‘dietary pattern’ describes overall balance of foods eaten in the diet

• Information gathered using a diet diary or food frequency questionnaire (FFQ)

Associated with lower risk of depression

‘Healthy’ dietary pattern ‘Western’ dietary patternAssociated with higher

risk of depression

Dietary patterns and depression

• Recent meta-analysis of dietary patterns and depression risk

• Included 41 observational studies from 12 countries

Lassale et al (2019) Mol Psychiatry 24: 965-986.

Mediterranean Diet (MedDiet)

- Fruit, vegetables, legumes, cereals, olive oil, fish

- Meat, dairy, sweets, eggs

Healthy Eating Index (HEI) / Alternative Healthy Eating Index (AHEI)- Based on Dietary Guidelines

for Americans

Dietary Approaches to Stop Hypertension (DASH)

- Fruit, vegetables, legumes and nuts, wholegrains, low-fat dairy

- Sweet beverages, meat, sodium

Dietary Inflammatory Index (DII)- Inflammatory potential of the diet (45 foods)

• Studies used FFQ/food recall to ‘score’ adherence to 5 main dietary patterns:

Dietary patterns and depression

Lassale et al (2019) Mol Psychiatry 24: 965-986.

Dietary pattern No. studies

(cross-sectional)

Cohort estimate

(95% CI)

Cross-sectional

estimate (95% CI)

Overall estimate

(95% CI)

MedDiet 7 (3) 0.67 (0.55, 0.82) 0.66 (0.35, 1.24) 0.69 (0.59, 0.82)

HEI/AHEI 7 (4) 0.76 (0.57, 1.02) 0.53 (0.38, 0.75) 0.65 (0.50, 0.84)

DASH 4 (3) 0.89 (0.60, 1.31) 0.93 (0.72, 1.21) 0.90 (0.73, 1.12)

DII 9 (4) 0.76 (0.63, 0.92) 0.64 (0.45, 0.91) 0.71 (0.60, 0.84)

Other diets 18 (9) (general trend towards lower risk of depression)

• MedDiet studies provided strongest evidence for reduced risk of depression

• DASH diet not associated with lower depression risk (except single study)

• MedDiet and DII results not affected by age or depression type (self-reported or clinical)

• HEI/AHEI overall result no longer significant when excluding clinical depression

MedDiet = Mediterranean Diet; HEI/AHEI = (Alternative) Healthy Eating Index; DASH = Dietary Approaches to Stop Hypertension; DII = Dietary Inflammatory Index

Dietary patterns and depression

What are the limitations of the studies?

Outcome (depression)

• Wide range of causes of depression

• How many people develop depression?

• Clinical diagnosis or self-reported?

Exposure (diet)

• How is diet defined?

• Which questionnaire is used?

• Does diet change over time?

• Recall bias

• Observational studies

Confounding factor

(e.g. weight)

Direction of the relationship?

What are the biological mechanisms?

• Dietary quality may affect pathways associated with mental illness:

- Low-grade inflammation

- Oxidative stress

• MedDiet reduces C-reactive protein (CRP) and interleukin 6 (IL-6) vs. low-fat control diet1

• Increased CRP and IL-6 associated with depressive symptoms2

• Depressed patients have higher levels of free radicals and oxidative damage products3

• Can a healthier dietary pattern protect against oxidative stress/inflammation?

1 Estruch et al (2010) Proc Nutr Soc 69: 333-40; 2 Valkanova et al (2013) J Affect Disord 3: 736-44; 3 Liu et al (2015) PLoS One 10: e0138904

The HELFIMED trial

• 85 adults with self-reported depression (18-65 years; 2:1 women to men)

3 months• Higher MedDiet score

• Greater reduction in depressive symptoms (45%) than controls (28%)

• 1.68 times greater improvement vs. controls

InterventionFood hampers and MedDiet cooking workshops every two weeks for 3 months and fish oil supplements for 6 months

• Differences between groups maintained

6 months

Parletta et al (2017) Nutr Neuroscience 22:474-487

ControlSocial group sessions every two weeks for 3 months

The SMILES trial

• 12 week RCT of 67 adults (71% female) with moderate/severe depression (adjunctive treatment)

• 7 sessions with dietitian to promote MedDiet (diet support group) vs. ‘befriending social support’ visits (control)

• Diet support group showed significantly greater improvement in depressive symptoms at 12 weeks

• Greater proportion in remission (score <10 on MADRS scale) in the diet support group (32%) vs. control (8%)

Jacka et al (2017) BMC Med 15: 23

Fig. 2 MADRS scores for dietary support and social support control groups at baseline and endpoint. Effect size: Cohen’s d = –1.16 (95% CI –1.73, –0.59). Baseline data n = 67; 12 week data n=56; p<0.001 for between groups.

The SMILES trial

• Researchers conducted an economic assessment of the trial ($ AUD)

• Lower health sector and societal costs

• Due to lower health care costs and costs of unpaid productivity

• Supports cost-effectiveness of dietary therapy

Chatterton et al (2018) BMC Public Health 18: 599

$856 lower (95% CI: -1247, -160)

$2591 lower (95% CI: -3591, -198)

What is next for research in this area?PREDI-DEP trial

• Large clinical RCT in 4 research centres in Spain1

• Effect of MedDiet (with olive oil) on risk of recurrent depression and improvement of symptoms (vs. no intervention)

• Dietary intervention delivered by trained dietitians

• Depressive symptoms assessed by psychiatrists and clinical psychologists through clinical evaluations

• Based on PREDIMED trial intervention2

1 Sánchez-Villegas et al (2019) BMC Psychiatry 19: 63; 2 Estruch et al (2018) NEJM 378: e34.

Lower risk of major cardiovascular event with MedDiet + extra-virgin olive oil (HR 0.69 [95% CI: 0.53 to 0.91])

Takeaway messages

• Mental health is a global problem

• There is a need for additional therapies for mental health problems

• Observational studies indicate healthier dietary patterns (e.g. MedDiet) may lower risk of depression

• Emerging RCTs also support diet as potential treatment for depression and appear to be cost-effective

• More RCTs needed with well defined dietary exposure and methods of assessing depressive symptoms (e.g. PREDI-DEP study) to establish strength and direction of association

• Are interventions feasible at a population level?

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Disclosure of interests

Thank you!

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