The increase in the number of individuals living alone has implications for nutrition and health outcomes. The aim of this review was to investigate whether there is a difference in food and nutrient intake between adults living alone and those living with others. Eight electronic databases were searched, using terms related to living alone, nutrition, food, and socioeconomic factors. Forty-one papers met the inclusion criteria, and data of interest were extracted. Results varied but suggested that, compared with persons who do not live alone, persons who live alone have a lower diversity of food intake, a lower consumption of some core foods groups (fruits, vegetables, and fish), and a higher likelihood of having an unhealthy dietary pattern. Associations between living alone and nutrient intake were unclear. Men living alone were more often observed to be at greater risk of undesirable intakes than women. The findings of this review suggest that living alone could negatively affect some aspects of food intake and contribute to the relationship between living alone and poor health outcomes, although associations could vary among socioeconomic groups. Further research is required to help to elucidate these findings.

Loneliness or social isolation and food/eating behaviours have important health consequences and there are rationales for why they could interact. Loneliness and dietary behaviours are recognised as health determinants and targets for interventions at individual, group and population levels. However, there are currently no research reviews investigating associations between these areas. This scoping review synthesized evidence investigating loneliness or social isolation and food/eating behaviours in people aged over 16 years in high-income countries. A systematic search of five databases from 2000 was conducted using predetermined search terms. Dissertation database and backwards citation searches were also conducted. Full text screening of 254 articles/theses resulted in inclusion of three qualitative and 26 quantitative studies, with eight conducted in COVID-19 lockdowns. Almost all studies reported a relationship between loneliness/social isolation and eating behaviours usually considered harmful such as low fruit and vegetable intake and lower diet quality. Qualitative research also supports the detrimental influence of loneliness or social isolation on eating. Study quality was considered, and interpretation and comparison of results was complicated by use of varying methods. Better awareness and understanding of the relationship between these complex aspects of health is needed to inform the development of interventions and practice of nutrition and mental health practitioners, policymakers, researchers and end-users.

In our initial analysis of the Australian Vegan Study we estimated the mean daily intake of vitamin B12 of each participant and compared this to the Recommended Dietary Intake (RDI). However, the proportion of vitamin B12 that can be absorbed from large doses typically contained in oral supplements is considerably lower than the amount absorbed from food. In this analysis we took into account the estimated absorption from supplements in order to compare adequacy of vitamin B12 intake to the RDI. A cross-sectional online survey was used to obtain information from women (N = 1530) of reproductive age on a vegan diet in Australia. Vitamin B12 intake from food was estimated using a validated food frequency questionnaire and detailed questioning was used to estimate supplemental intake. We used published data on dose-dependent absorption rates to estimate amount of the vitamin absorbed to enable comparison to the RDI. Supplementation practices varied widely. Based on estimated amount absorbed, 39% of participants had an estimated total intake of vitamin B12 below RDI equivalency, compared to 26% based on mean daily intake. The potential absorption of vitamin B12 needs to be considered when estimating adequacy of intake and recommending supplementation.