Background
Problem drinking is an important problem among the homeless population in developed countries. Estimates range from 8 to 58 %, with the prevalence increasing in more recent years [
1,
2]. In the UK, 35 % of the homeless drink twice per week or more with around 63 % of the homeless drinking more than the recommended limit every time [
3,
4]. Official estimates for the number of rough sleepers in England vary between about 2500 and 8000, with this figure on the rise [
5,
6]. However, some form of homelessness applies to a much wider population. This is difficult to measure, with the ‘hidden homeless’ staying with friends or family, in hostels or bed and breakfasts or in other vulnerable housing situations [
7].
Problem drinkers who are homeless tend to obtain a large proportion of their energy intake from alcohol, and as a result, they are rarely underweight [
8,
9]. However, this alcohol-rich diet is likely to lack a variety of important nutrients including micronutrients such as vitamins and minerals as well as macronutrients such as protein [
10,
11]. Alcohol causes damage to the gastrointestinal tract, reducing effective absorption of consumed nutrients such as sodium, carbohydrates, water, proteins and fats [
12]. This damage often results in gastrointestinal motility issues and digestive disorders. These in turn cause problems, such as loss of appetite, nausea, vomiting, diarrhoea, abdominal pain, maldigestion and malabsorption of nutrients, all of which may contribute to malnutrition [
12]. Thiamine deficiency in particular can impair cognitive function and make behaviour change, such as abstinence from drinking, much more difficult to achieve [
13]. If untreated, malnutrition in heavy drinkers can lead to serious complications such as brain damage (Wernicke’s encephalopathy and Korsakoff’s psychosis), liver disease, impaired immunity and infections [
14‐
16].
People experiencing homelessness are at risk of being malnourished due to a low income and lack of ways to store and cook nutritionally beneficial foods, leading to a reliance on cheap, ready-prepared foods [
17]. They may also lack knowledge of how to achieve a healthy diet in their situation. Provided food sources (e.g. soup kitchens) make an important contribution to energy intake and nutritional health [
17], but may not be optimised to improve users’ diets. Limited resources and staff training preclude the provision of fresh, high-quality food sources [
10,
11,
18]. Often, the goal of charitable food providers is to provide filling meals to stave off hunger rather than improving nutritional health [
19]. Persons who are both homeless and problem drinking simultaneously are at a particularly high risk of malnutrition as difficulties in accessing nutritional food are compounded by excessive alcohol consumption. Severely dependent drinkers with a low income might choose to spend their available money on alcohol instead of food [
20]. Additionally, homeless people do not receive the benefit of household members (e.g. family) who can influence the eating behaviours of housed heavy drinkers [
21‐
23]. Given the combined effects of homelessness and heavy alcohol drinking upon the risk of malnutrition, homeless problematic drinkers are likely to have different nutritional needs from non-homeless individuals.
Improving the nutritional status of homeless heavy drinkers might be achieved by adapting the dietary intake of participants to be more nutritionally beneficial, either through informing or encouraging participants to change their dietary choices or by improving the nutritional quality of the food available to them. Interventions to achieve this may include distribution of a specific fortified food product or supplement; interventions delivered through soup kitchens (e.g. menu changes, fortification of food, etc.); advice to care providers or food providers on how to tackle deficiencies; or peer support interventions related to nutrition. Specific interventions proposed in the literature include a chocolate spread fortified with micronutrients specifically developed for the homeless population in Paris [
24], nutrition classes delivered to homeless mothers and cafeteria staff [
25], leaflets for the homeless aimed at improving nutritional literacy [
8] and guidelines for a daycare centre providing food to the homeless [
26].
Why it is important to do this review
The aim of this review is to bring together existing evidence of the effectiveness of nutritional interventions in homeless drinkers, in order to understand how the nutritional status of this population could be improved. This review will inform the development of effective interventions that can be implemented in the community to improve health of the target population.
Systematic reviews ascertaining the effectiveness of interventions to improve health in the homeless have been undertaken. The focus of these reviews was on interventions that tackle either the housing problem or substance abuse [
27‐
29], rather than nutrition. The current review will identify whether there are effective and affordable ways to improve nutrition directly or indirectly by increasing the likelihood of complex behaviour change such as alcohol detoxification. Thiamine deficiency in particular can impair cognitive function and make behaviour change much more difficult to achieve [
13]. Similarly, reviews addressing nutrition in problem alcohol drinkers exist [
30,
31], but problem drinkers who are homeless or otherwise in vulnerable housing represent a special case. Intervention to address problematic drinking will not necessarily be applicable to problematic drinkers who are also homeless. Studies regarding the non-alcohol-drinking homeless, while still relevant, will also not necessarily apply to the alcohol-drinking homeless. This review aims to bring these two elements together and look at the interventions aimed at improving nutritional status of problem drinkers that can be successfully delivered to the homeless population.
Objective
The objective of this review is to assess the effectiveness and cost-effectiveness of interventions for preventing or correcting micronutrient deficiencies and other forms of malnutrition and related comorbidities in problem drinkers who are homeless or vulnerably housed.
Discussion
This review aims to summarise the available evidence base of the effectiveness and cost-effectiveness of interventions to address malnutrition in the homeless or vulnerably housed and problem drinking population.
It is likely that the quantity of evidence for nutrition-based interventions in the target population will be limited. In particular, we do not expect studies of randomised controlled trials to be numerous. This is partly due to inherent problems with conducting trials in the homeless population, which is by nature transient and thereby creating difficulties with collecting follow-up data. As a result, we are not limiting our search to RCTs but including a range of study designs. A limitation of this review may be that results of the studies cannot be combined in a meta-analysis.
Given the expected scarcity of evidence, the absence of language restrictions and extensive grey literature search are particularly advantageous for this review. Additionally, a scoping search and pilot screening have been undertaken to refine the selection procedure, and these indicate that the number of hits to be screened should be manageable.
Another strength of this review lies in its broad scope, without strict constraints imposed on the types of outcomes or interventions considered. This will allow an exploration of the range and diversity of interventions that have been evaluated. The results of this review should help to inform the implementation of similar interventions in the community to improve the health of the problem drinking homeless.
Acknowledgements
We thank Adrian Bonner for the useful discussion regarding the effects of malnutrition in heavy alcohol drinkers.
This research is supported by the National Institute for Health Research (NIHR) Collaboration for Leadership in Applied Health Research and Care West (CLAHRC West) at University Hospitals Bristol NHS Foundation Trust. The views expressed are those of the authors and not necessarily those of the NHS, the NIHR or the Department of Health.
Competing interests
The authors declare that they have no competing interests.
Authors’ contributions
KP, CF, JS, EM and HT designed the study. HT is the lead reviewer and drafted the manuscript. JK and TJ are secondary reviewers and contributed to the pilot screening and refinement of the selection criteria. AR developed the search strategy and conducted the scoping search. All authors have critically revised the manuscript and approved the final version.