Food for thought: the importance of nutritional well-being during COVID-19

Individuals with mental illness have poorer physical health, nutritional status, and lowered life expectancy. Optimising their physical and nutritional status has become an increasingly important therapeutic goal. Current experience with COVID-19 has further emphasised the susceptibility to physical illness and poorer outcomes amongst individuals with mental illness and those who are nutritionally compromised. Although life as we knew it has been suspended until the widespread roll-out of a vaccine, individuals can take immediate action to improve physical and mental health by attending to and optimising their nutritional well-being. Clinicians within mental health services have a crucial role to play in assisting such change, and reminding their patients of the importance of pursuing a healthy and balanced diet.


Introduction
Current life expectancy in Ireland, based on 2017 data, is 84 years for women and 80.4 years for men. (https:// www.gov.ie/en/publication/f1bb64-health-in-irelandkey-trends-2019/accessed August 29 2020). However, increased longevity has not necessarily led to increased quality of life for all. The cost of longevity brings about an increased incidence of, and time lived with, chronic illnesses such as cancer, diabetes, cardiovascular disease, cognitive, and mental health disorders. Furthermore, disparities exist and those with severe mental illness have a lowered life expectancy by 10-20 years compared to the general population, attributable to poorer diet, lack of physical activity, smoking, and substance abuse (Ringen et al. 2014). The independent adverse role of psychotropic medication on weight and nutritional status is also recognised as a factor (Mazereel. et al. 2020). Early and significant weight gain following the introduction of the first or second-generation antipsychotics is well recognised and thought to be due to increased central appetite (Foley & Morley, 2011). Weight gain is also associated with mood stabilisers (Sachs et al. 2006) and antidepressants (Serretti & Mandelli, 2010), and patients with lower BMI at baseline are not immune (Gebhardt et al. 2009). Morbidity and mortality in psychotropic medication users are further increased by the development of dyslipidemia and insulin resistance, both strongly related to medication-induced weight changes (Abosi et al. 2018).
Profound lifestyle changes have occurred over the recent years with industrialisation and technological advances, with more office-based, non-manual labour, longer commutes, and lower population-level energy expenditure related to work. More and more leisure time is spent on smart devices, computers, and watching television. A recent report by the World Health Organization concluded that 80% of children aged between 11 and 17 were not getting enough physical activity (Guthold et al. 2020). People with severe mental illness, especially those with schizophrenia and depression, are also known to be more sedentary than their healthy counterparts (Bort-Roig et al. 2020;Dipasquale et al. 2013). There is a clear relationship between a more sedentary lifestyle, for both youth and old, and weight gain, despite clinician's call to action (Manson et al. 2004). A recent Department of Health survey, from a representative sample of 7413 people living in Ireland, suggests that just over a third of adults, (37%) were of normal weight (http://tinyurl.com/yxuwotvu). Official OECD estimates place Ireland mid-table by international comparisons. Rates of obesity in children and adolescents have also increased. Indeed, the genesis of adult obesity is in childhood, and carries with it many risk factors for subsequent adult ill health, most notably cardiovascular, cancer, and diabetes. Poor dietary and activity habits established in childhood become engrained. Given that up to 60% of individuals with severe mental illness also have obesity, the additional medicationrelated dyslipidemia and insulin resistance, places them at additional cardiovascular risk (Abosi et al. 2018).
Despite being overfed, individuals with obesity have nutritional deficits in micronutrients, recognised to have anti-inflammatory, antioxidant, and antiviral properties, and have raised inflammatory markers such as C-reactive protein and fibrinogen, making them prone to infections and autoimmune disorders. Deficiencies in vitamins such as A, C, D, and E, along with lower levels of iron and zinc have also been reported. Consumption of high levels of fructose syrup, regulated by many European countries, has specifically been associated with lower levels of vitamin D and metabolic syndrome, even in the absence of increased body weight (Ferder & Inserra, 2010).
Vitamin D has been implicated in psychiatric illness for some time and receptors are prevalent in many parts of the brain associated with mental illness (Cuomo et al. 2019). Vitamin D is considered neuroprotective, reducing oxidative stress, modulating neuronal excitability via intracellular calcium homeostasis, and stimulating nerve growth. Low vitamin D levels have been associated with many childhood and adult disorders, such as mood disorders, psychosis, and autism, and might explain the seasonality of mood, with recommendations to monitor vitamin D levels in all psychiatric cohorts, especially the elderly, who are most at risk (Cuomo et al. 2019). Given the treatments of many patients with neuroleptic medication and the known associated risk of metabolic syndrome, this represents an increased risk. The association of low levels of vitamin D and the metabolic syndrome (Prasad & Kochhar, 2016) is of particular concern in a cohort of patients exposed to neuroleptic medications, which carry their own similar risk profile.

Western diet
The increase in obesity has been attributed to the increased consumption of a Western diet, and there has been a steady and consistent shift from fresh home-grown and home-cooked foods to a diet high in fat, salt, and sugar content. Up to 15% of calories consumed are from 'added' sugars, often in the form of fructose syrup. These sugars are viewed as 'empty calories', with minimum essential nutrients or dietary fibre, leading to overweight but undernourished individuals. These highly processed foods, additive-rich but nutritionally poor, are often cheap, palatable, and easily stored with long shelf lives, making them popular choices in the lower socio-economic classes or those with poorer adaptive daily living skills. Poor dietary choices and resultant higher BMIs, in those economically more disadvantaged, may well be driven by lower cost; it is also influenced by other lifestyle habits such as smoking and excess alcohol consumption and lower physical activity, behaviours also found in those with severe mental illness (Bort-Roig et al. 2020; Dipasquale et al. 2013) . Furthermore, the co-occurrence of depression in females provided the main pathway linking lower SES and BMI (Beydoun & Wang, 2010). In contrast, a healthy diet consists of the ingestion of a wide variety of fresh fish, fruit, and vegetable, nuts, and unsaturated fats, giving a balance of essential fats, fibre, and macronutrients, and consumed at a rate commensurate with energy expenditure. Poorer planning and functioning in activities of daily living, more prevalent in individuals with mental illness, might pose an additional impediment to home cooking and sourcing of foods, and promote the adoption of a Western-style diet, and consumption of higher proportions of processed foods.
The type and diversity of food eaten also shapes, and is driven by, millions of microorganisms lining our digestive tract. These microbes in turn can lead to food preferences, and independent of calories consumed, alterations in body weight, blood sugar, and cholesterol (Patterson et al. 2016). Both beneficial and harmful microbes exist, playing a role in inducing cytokines and other anti or pro-inflammatory/immunity cells, synthesising certain vitamins and neurotransmitters, and playing a role as part of the larger gut-brain axis. The end result is an individually specific microbiome either promoting or hindering physical, cognitive, and mental health.

Relationship of diet and mental health
It is, therefore, not surprising that a consistent relationship between the quality of diet and health in adults has been found, over and above other potential confounders of social-economic class, education, and even BMI (O'Neil et al. 2014). These apply to both physical and mental health. Cross-sectional and prospective studies show a relationship between baseline quality of diet and subsequent depression, with poorer diet at baseline predicting poorer mental health and quality of life, and a protective effect linked to good baseline diet (Jacka et al. 2011). There was no evidence of reverse causality, in that poorer mental health did not shift dietary habits. This is also true in the adolescent population, highlighting the long-term impact of early dietary choices and the potential preventative role of nutritional advice and education.
A systematic review concludes that changing from a Western-style diet to a traditional Mediterranean diet confers an advantage against depression (Lassale et al. 2019). Such is the evidence base in depression, that omega-3-polyunsaturated fatty acids, or Ω-3-PUFA, are recommended in international guidelines for the treatment of depression in adults, children, pregnant women, and the elderly (Guu et al. 2019). The recognised beneficial effect of removing additives and food colourings in diets of youth with ADHD has been expanded to youth with other behavioural difficulties (Stevenson, 2010), with other recent studies questioning a causal role of the Western diet in ADHD development (Ríos-Hernández et al. 2017).
With nutritional modifications becoming part of mainstream treatments, the industry is also shifting from exclusively focussing on new drugs towards a search for nutritional supplements and the healthy food industry has become lucrative. Regrettably, many 'miracleproducts' are just that, with little evidence, benefits and indeed if not carefully monitored, at risk of adverse effects. At the same time, advances in nutritional science indicate that optimal intake levels of vitamins, minerals, and fibre, and adherence to a Mediterranean diet, may protect against these long-term diseases.
Personal behavioural change also plays a major part. In the Irish Survey of Lifestyle Attitudes and Nutrition (SLAN) completed by 10,364 adults, the health-related effects of adopting various healthier lifestyle choices showed that those who were able to incorporate four such behaviours (being physically active, consuming five or more fruit and vegetable servings daily, not smoking, and moderate alcohol intake) were significantly more likely to report better general and mental health (Harrington et al. 2010). Despite health-related behavioural changes being recognised as difficult in adolescents, it is never too early or too late to endeavour to facilitate a positive motivating environment, targeting family, peers, and social networks, initiated from the clinicians' office.

COVID-19 and nutrition
Following the declaration in March 2020 by the World Health Organization of the global COVID-19 pandemic, governments across the world imposed unprecedented restrictions, shutting schools, businesses, and travel in an effort to protect society and slow down the spread of the virus. At the start of lockdown, the initial nutritional concern was that of food availability, especially for the elderly who were advised to cocoon. A shift from fresh to frozen or processed foods was feared should food trade deliveries dry up, accompanied by some anecdotal media reports of bulk buying. This did not happen and fresh food remained plentiful, as did written and video media broadcasts on how to spend lockdown experimenting with cooking. For certain groups, such as those with an eating disorder, the presence of readily available and potentially threatening food, with restrictions on exercise and outdoor access, caused intense anxiety, and deterioration in symptoms (Schlegl et al. 2020). For others, the opportunity to constantly 'graze' led to weight gain, and obesity, with all the aforementioned risks. A poorer prognostic risk in obese individuals has been suggested with COVID-19 (Alberca et al. 2020) and a higher rate of obesity in older adults in Italy was proposed as a putative explanation to account for the excess deaths in patients with COVID-19 when compared to China (Dietz & Santos-Burgoa, 2020). In addition, more and more evidence is emerging linking vitamin D deficiency to increased infectivity, morbidity, and mortality in COVID-19 (Aygun, 2020). Interventional studies emerged as to the beneficial effects of treatment with the active form of vitamin D, calcifediol (Castillo et al. 2020). Given levels of vitamin D are recognised to be low both in Ireland (Cashman et al. 2013), particularly now in winter months, and low amongst those with mental illness (Cuomo et al. 2019), this places patients attending Mental Health Services in Ireland at double jeopardy.
Level 5 restrictions, about to recommence in January 2021, will limit access to outdoor activities, team sports, and gyms, and could potentially lead to poorer physical health and weight gain. Studies that have investigated activity levels during earlier lockdowns have shown both the benefit of increased activity and the negative effect of increased sedentary time on physical and mental health (Cheval et al. 2020). Working from home can further increase sedentary behaviour, and unfettered access to readily available snacking foods. Limited social engagement limits mood-boosting experiences and can increase the risk of loneliness, isolation, and lead to despondency and poor self-care. Elderly persons, fearful of the resurgence of disease and those with pre-existing mental illness may be most at risk of poor nutritional care.

Clinical assessment and nutritional advice
Scientifically robust studies in mental health have now caught up with nutritional medicine and attest to the importance of quality and diversity of diet and microbiome in physical and psychiatric illness. The greater prevalence of obesity and poorer physical health amongst those with mental illness has been well documented. Nutrition is increasingly being considered as a crucial and potentially modifiable factor in the aetiology and maintenance of many illnesses, in both young and old, and one that clinicians should incorporate into their usual practice. However, at odds with the growing evidence of the importance of a healthy and balanced dietary intake, its role in mainstream clinical practice or indeed medical training is less developed. Routine primary care clinical assessments do not typically enquire about the adequacy of dietary intake or physical activity, weight, and BMI infrequently calculated. The recognition of medication-related metabolic effects amongst patients on anti-psychotics has led to monitoring of weight in many, and pharma-sponsored healthy lifestyle programmes. The presence of a dietician or nutritionist as a core member of the multidisciplinary team is not yet common practice. Studies suggest that when such nutritional advice is offered, patients do try to follow it.
Given physical health is often poor amongst mental health services users, coupled with difficulties in self-motivation and self-care, psychiatrists could play a crucial role in reviewing and advising about healthy lifestyle choices, Food for thought 3

Conclusion
There has been a seismic shift in the understanding of the importance of a balanced diet to our health and longevity. There is very good evidence of the role of nutritional manipulation going beyond calorie restriction and weight loss. Equally, there has been ample evidence of the negative effect of the Western-style diet on populations. As we emerge from the Christmas period, with the excess of food, drink, and more sedentary behaviour, and as we enter the period of new resolutions, clinicians are well poised to assist in behavioural change.
Each consultation offers the clinician the opportunity to enquire about the quality of dietary intake, and advise patients to incorporate freshly cooked fruits and vegetables as part of standard daily intake, limit the amount of processed fast foods consumed and take a daily walk to search perhaps for the Irish sun. Supplementation with vitamin D is particularly important during the winter months. It may well be that behind this COVID-19 cloud, better eating and lifestyle approaches will shine through, and not a moment too soon.
Suggested advice a clinician might give to their patients during the consultation is listed in Tables 1 and 2. A more detailed leaflet is available from the authors upon request.

Conflict of interest
Louise Bourke-Furey has no conflict of interest to declare. Fiona McNicholas has no conflict of interest to declare.

Ethical standards
The authors assert that all procedures contributing to this work comply with the ethical standards of the relevant national and institutional committee on human experimentation with the Helsinki Declaration of 1975, as revised in 2008.

Financial support
This research received no specific grant from any funding agency, commercial, or not-for-profit sectors.